TMS320C6000 Assembly Language Tools v8.2

TMS320C6000 Assembly Language Tools
v8.2.x
User's Guide
Literature Number: SPRUI03B
May 2017
Contents
Preface....................................................................................................................................... 10
1
Introduction to the Software Development Tools .................................................................... 13
1.1
1.2
2
Introduction to Object Modules ............................................................................................ 17
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
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3.2
3.3
3.4
3.5
3.6
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Loading ......................................................................................................................
3.1.1 Load and Run Addresses ........................................................................................
3.1.2 Bootstrap Loading .................................................................................................
Entry Point...................................................................................................................
Run-Time Initialization .....................................................................................................
3.3.1 _c_int00.............................................................................................................
3.3.2 RAM Model vs. ROM Model .....................................................................................
3.3.3 Copy Tables........................................................................................................
Arguments to main .........................................................................................................
Run-Time Relocation ......................................................................................................
Additional Information ......................................................................................................
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Assembler Description ........................................................................................................ 39
4.1
4.2
4.3
4.4
2
Object File Format Specifications ........................................................................................
Executable Object Files ...................................................................................................
Introduction to Sections ...................................................................................................
2.3.1 Special Section Names ...........................................................................................
How the Assembler Handles Sections ..................................................................................
2.4.1 Uninitialized Sections .............................................................................................
2.4.2 Initialized Sections ................................................................................................
2.4.3 User-Named Sections ............................................................................................
2.4.4 Current Section ....................................................................................................
2.4.5 Section Program Counters .......................................................................................
2.4.6 Subsections ........................................................................................................
2.4.7 Using Sections Directives ........................................................................................
How the Linker Handles Sections ........................................................................................
2.5.1 Combining Input Sections ........................................................................................
2.5.2 Placing Sections ...................................................................................................
Symbols .....................................................................................................................
2.6.1 External Symbols ..................................................................................................
2.6.2 Weak Symbols .....................................................................................................
2.6.3 The Symbol Table .................................................................................................
Symbolic Relocations ......................................................................................................
2.7.1 Dynamic Relocation Entries......................................................................................
Loading a Program .........................................................................................................
Program Loading and Running ............................................................................................ 32
3.1
4
Software Development Tools Overview ................................................................................. 14
Tools Descriptions.......................................................................................................... 15
Assembler Overview .......................................................................................................
The Assembler's Role in the Software Development Flow ...........................................................
Invoking the Assembler ....................................................................................................
The Application Binary Interface .........................................................................................
Contents
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4.5
4.6
4.7
4.8
4.9
4.10
4.11
4.12
4.13
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Assembler Directives .......................................................................................................... 74
5.1
5.2
5.3
5.4
5.5
5.6
5.7
5.8
5.9
5.10
5.11
5.12
6
Naming Alternate Directories for Assembler Input .....................................................................
4.5.1 Using the --include_path Assembler Option ...................................................................
4.5.2 Using the C6X_A_DIR Environment Variable .................................................................
Source Statement Format .................................................................................................
4.6.1 Label Field..........................................................................................................
4.6.2 Mnemonic Field ....................................................................................................
4.6.3 Unit Specifier Field ................................................................................................
4.6.4 Operand Field ......................................................................................................
4.6.5 Comment Field ....................................................................................................
Literal Constants ...........................................................................................................
4.7.1 Integer Literals .....................................................................................................
4.7.2 Character String Literals..........................................................................................
4.7.3 Floating-Point Literals .............................................................................................
Assembler Symbols ........................................................................................................
4.8.1 Identifiers ...........................................................................................................
4.8.2 Labels ...............................................................................................................
4.8.3 Local Labels........................................................................................................
4.8.4 Symbolic Constants ...............................................................................................
4.8.5 Defining Symbolic Constants (--asm_define Option) .........................................................
4.8.6 Predefined Symbolic Constants .................................................................................
4.8.7 Registers ...........................................................................................................
4.8.8 Register Pairs ......................................................................................................
4.8.9 Register Quads (C6600 Only) ...................................................................................
4.8.10 Substitution Symbols ............................................................................................
Expressions .................................................................................................................
4.9.1 Mathematical and Logical Operators ...........................................................................
4.9.2 Relational Operators and Conditional Expressions ...........................................................
4.9.3 Well-Defined Expressions ........................................................................................
4.9.4 Legal Expressions .................................................................................................
4.9.5 Expression Examples .............................................................................................
Built-in Functions and Operators .........................................................................................
4.10.1 Built-In Math and Trigonometric Functions ...................................................................
4.10.2 C6x Built-In ELF Relocation Generating Operators .........................................................
Source Listings .............................................................................................................
Debugging Assembly Source .............................................................................................
Cross-Reference Listings .................................................................................................
Directives Summary........................................................................................................
Directives that Define Sections ...........................................................................................
Directives that Initialize Values ...........................................................................................
Directives that Perform Alignment and Reserve Space ...............................................................
Directives that Format the Output Listings ..............................................................................
Directives that Reference Other Files ...................................................................................
Directives that Enable Conditional Assembly ...........................................................................
Directives that Define Union or Structure Types .......................................................................
Directives that Define Enumerated Types ..............................................................................
Directives that Define Symbols at Assembly Time ....................................................................
Miscellaneous Directives ..................................................................................................
Directives Reference .......................................................................................................
Macro Language Description
6.1
6.2
6.3
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............................................................................................. 155
Using Macros .............................................................................................................. 156
Defining Macros ........................................................................................................... 156
Macro Parameters/Substitution Symbols .............................................................................. 158
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6.4
6.5
6.6
6.7
6.8
6.9
6.10
7
Archiver Overview ........................................................................................................
The Archiver's Role in the Software Development Flow.............................................................
Invoking the Archiver .....................................................................................................
Archiver Examples ........................................................................................................
Library Information Archiver Description ...............................................................................
7.5.1 Invoking the Library Information Archiver .....................................................................
7.5.2 Library Information Archiver Example .........................................................................
7.5.3 Listing the Contents of an Index Library ......................................................................
7.5.4 Requirements ....................................................................................................
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Linker Description ............................................................................................................ 178
8.1
8.2
8.3
8.4
4
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Archiver Description ......................................................................................................... 171
7.1
7.2
7.3
7.4
7.5
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6.3.1 Directives That Define Substitution Symbols.................................................................
6.3.2 Built-In Substitution Symbol Functions ........................................................................
6.3.3 Recursive Substitution Symbols ...............................................................................
6.3.4 Forced Substitution ..............................................................................................
6.3.5 Accessing Individual Characters of Subscripted Substitution Symbols ...................................
6.3.6 Substitution Symbols as Local Variables in Macros ........................................................
Macro Libraries ............................................................................................................
Using Conditional Assembly in Macros ................................................................................
Using Labels in Macros ..................................................................................................
Producing Messages in Macros ........................................................................................
Using Directives to Format the Output Listing ........................................................................
Using Recursive and Nested Macros ..................................................................................
Macro Directives Summary ..............................................................................................
Linker Overview ...........................................................................................................
The Linker's Role in the Software Development Flow ...............................................................
Invoking the Linker........................................................................................................
Linker Options .............................................................................................................
8.4.1 Wildcards in File, Section, and Symbol Patterns ............................................................
8.4.2 Specifying C/C++ Symbols with Linker Options .............................................................
8.4.3 Relocation Capabilities (--absolute_exe and --relocatable Options) ......................................
8.4.4 Allocate Memory for Use by the Loader to Pass Arguments (--arg_size Option) .......................
8.4.5 Compression (--cinit_compression and --copy_compression Option) ....................................
8.4.6 Compress DWARF Information (--compress_dwarf Option) ...............................................
8.4.7 Control Linker Diagnostics ......................................................................................
8.4.8 Automatic Library Selection (--disable_auto_rts and --multithread Options) .............................
8.4.9 Do Not Remove Unused Sections (--unused_section_elimination Option) ..............................
8.4.10 Linker Command File Preprocessing (--disable_pp, --define and --undefine Options) ................
8.4.11 Error Correcting Code Testing (--ecc Options) .............................................................
8.4.12 Define an Entry Point (--entry_point Option) ................................................................
8.4.13 Set Default Fill Value (--fill_value Option) ...................................................................
8.4.14 Define Heap Size (--heap_size Option) ......................................................................
8.4.15 Hiding Symbols .................................................................................................
8.4.16 Alter the Library Search Algorithm (--library Option, --search_path Option, and C6X_C_DIR
Environment Variable)...........................................................................................
8.4.17 Change Symbol Localization ..................................................................................
8.4.18 Create a Map File (--map_file Option) .......................................................................
8.4.19 Managing Map File Contents (--mapfile_contents Option) ................................................
8.4.20 Disable Name Demangling (--no_demangle) ...............................................................
8.4.21 Merging of Symbolic Debugging Information ...............................................................
8.4.22 Strip Symbolic Information (--no_symtable Option) ........................................................
8.4.23 Name an Output Module (--output_file Option) .............................................................
8.4.24 Prioritizing Function Placement (--preferred_order Option) ...............................................
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8.5
8.6
8.7
8.8
8.9
8.10
8.11
8.12
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8.4.25 C Language Options (--ram_model and --rom_model Options) ..........................................
8.4.26 Retain Discarded Sections (--retain Option) ................................................................
8.4.27 Scan All Libraries for Duplicate Symbol Definitions (--scan_libraries) ...................................
8.4.28 Define Stack Size (--stack_size Option) .....................................................................
8.4.29 Enforce Strict Compatibility (--strict_compatibility Option) ................................................
8.4.30 Mapping of Symbols (--symbol_map Option) ...............................................................
8.4.31 Generate Far Call Trampolines (--trampolines Option) ....................................................
8.4.32 Introduce an Unresolved Symbol (--undef_sym Option)...................................................
8.4.33 Display a Message When an Undefined Output Section Is Created (--warn_sections) ...............
8.4.34 Generate XML Link Information File (--xml_link_info Option) .............................................
8.4.35 Zero Initialization (--zero_init Option) ........................................................................
Linker Command Files ...................................................................................................
8.5.1 Reserved Names in Linker Command Files..................................................................
8.5.2 Constants in Linker Command Files ..........................................................................
8.5.3 Accessing Files and Libraries from a Linker Command File ...............................................
8.5.4 The MEMORY Directive ........................................................................................
8.5.5 The SECTIONS Directive .......................................................................................
8.5.6 Placing a Section at Different Load and Run Addresses ...................................................
8.5.7 Using GROUP and UNION Statements ......................................................................
8.5.8 Special Section Types (DSECT, COPY, NOLOAD, and NOINIT).........................................
8.5.9 Configuring Error Correcting Code (ECC) with the Linker..................................................
8.5.10 Assigning Symbols at Link Time ..............................................................................
8.5.11 Creating and Filling Holes .....................................................................................
Linker Symbols ............................................................................................................
8.6.1 Using Linker Symbols in C/C++ Applications ................................................................
8.6.2 Declaring Weak Symbols .......................................................................................
8.6.3 Resolving Symbols with Object Libraries .....................................................................
Default Placement Algorithm ............................................................................................
8.7.1 How the Allocation Algorithm Creates Output Sections ....................................................
8.7.2 Reducing Memory Fragmentation .............................................................................
Linker-Generated Copy Tables .........................................................................................
8.8.1 Using Copy Tables for Boot Loading ..........................................................................
8.8.2 Using Built-in Link Operators in Copy Tables ................................................................
8.8.3 Overlay Management Example ................................................................................
8.8.4 Generating Copy Tables With the table() Operator .........................................................
8.8.5 Compression .....................................................................................................
8.8.6 Copy Table Contents ............................................................................................
8.8.7 General Purpose Copy Routine ................................................................................
Partial (Incremental) Linking.............................................................................................
Linking C/C++ Code ......................................................................................................
8.10.1 Run-Time Initialization .........................................................................................
8.10.2 Object Libraries and Run-Time Support .....................................................................
8.10.3 Setting the Size of the Stack and Heap Sections ..........................................................
8.10.4 Initializing and AutoInitialzing Variables at Run Time ......................................................
Linker Example ............................................................................................................
Dynamic Linking with the C6000 Code Generation Tools ..........................................................
8.12.1 Static vs Dynamic Linking .....................................................................................
8.12.2 Bare-Metal Dynamic Linking Model .........................................................................
8.12.3 Building a Dynamic Executable ...............................................................................
8.12.4 Building a Dynamic Library ....................................................................................
8.12.5 Symbol Import/Export ..........................................................................................
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Object File Utilities ............................................................................................................ 275
9.1
Invoking the Object File Display Utility ................................................................................. 276
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9.2
9.3
9.4
10
Invoking the Disassembler............................................................................................... 277
Invoking the Name Utility ................................................................................................ 278
Invoking the Strip Utility .................................................................................................. 278
Hex Conversion Utility Description ..................................................................................... 279
The Hex Conversion Utility's Role in the Software Development Flow ............................................
Invoking the Hex Conversion Utility ....................................................................................
10.2.1 Invoking the Hex Conversion Utility From the Command Line ...........................................
10.2.2 Invoking the Hex Conversion Utility With a Command File ...............................................
10.3 Understanding Memory Widths .........................................................................................
10.3.1 Target Width .....................................................................................................
10.3.2 Specifying the Memory Width .................................................................................
10.3.3 Partitioning Data Into Output Files ...........................................................................
10.3.4 Specifying Word Order for Output Words ...................................................................
10.4 The ROMS Directive .....................................................................................................
10.4.1 When to Use the ROMS Directive ............................................................................
10.4.2 An Example of the ROMS Directive ..........................................................................
10.5 The SECTIONS Directive ................................................................................................
10.6 The Load Image Format (--load_image Option) ......................................................................
10.6.1 Load Image Section Formation ...............................................................................
10.6.2 Load Image Characteristics ...................................................................................
10.7 Excluding a Specified Section...........................................................................................
10.8 Assigning Output Filenames ............................................................................................
10.9 Image Mode and the --fill Option .......................................................................................
10.9.1 Generating a Memory Image ..................................................................................
10.9.2 Specifying a Fill Value .........................................................................................
10.9.3 Steps to Follow in Using Image Mode .......................................................................
10.10 Controlling the ROM Device Address ..................................................................................
10.11 Control Hex Conversion Utility Diagnostics ...........................................................................
10.12 Description of the Object Formats......................................................................................
10.12.1 ASCII-Hex Object Format (--ascii Option) .................................................................
10.12.2 Intel MCS-86 Object Format (--intel Option) ...............................................................
10.12.3 Motorola Exorciser Object Format (--motorola Option)...................................................
10.12.4 Extended Tektronix Object Format (--tektronix Option) ..................................................
10.12.5 Texas Instruments SDSMAC (TI-Tagged) Object Format (--ti_tagged Option) .......................
10.12.6 TI-TXT Hex Format (--ti_txt Option) ........................................................................
10.1
10.2
11
Sharing C/C++ Header Files With Assembly Source .............................................................. 304
11.1
11.2
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Overview of the .cdecls Directive .......................................................................................
Notes on C/C++ Conversions ...........................................................................................
11.2.1 Comments .......................................................................................................
11.2.2 Conditional Compilation (#if/#else/#ifdef/etc.)...............................................................
11.2.3 Pragmas .........................................................................................................
11.2.4 The #error and #warning Directives ..........................................................................
11.2.5 Predefined symbol _ _ASM_HEADER_ _ ...................................................................
11.2.6 Usage Within C/C++ asm( ) Statements.....................................................................
11.2.7 The #include Directive .........................................................................................
11.2.8 Conversion of #define Macros ................................................................................
11.2.9 The #undef Directive ...........................................................................................
11.2.10 Enumerations .................................................................................................
11.2.11 C Strings........................................................................................................
11.2.12 C/C++ Built-In Functions .....................................................................................
11.2.13 Structures and Unions ........................................................................................
11.2.14 Function/Variable Prototypes ................................................................................
11.2.15 C Constant Suffixes ..........................................................................................
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11.3
11.4
A
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Symbolic Debugging Directives .......................................................................................... 312
A.1
A.2
B
11.2.16 Basic C/C++ Types ...........................................................................................
Notes on C++ Specific Conversions ...................................................................................
11.3.1 Name Mangling .................................................................................................
11.3.2 Derived Classes ................................................................................................
11.3.3 Templates ........................................................................................................
11.3.4 Virtual Functions ...............................................................................................
Special Assembler Support ..............................................................................................
11.4.1 Enumerations (.enum/.emember/.endenum) ................................................................
11.4.2 The .define Directive ...........................................................................................
11.4.3 The .undefine/.unasg Directives ..............................................................................
11.4.4 The $defined( ) Built-In Function .............................................................................
11.4.5 The $sizeof Built-In Function ..................................................................................
11.4.6 Structure/Union Alignment and $alignof( ) ..................................................................
11.4.7 The .cstring Directive ...........................................................................................
DWARF Debugging Format ............................................................................................. 313
Debug Directive Syntax .................................................................................................. 313
XML Link Information File Description................................................................................. 314
B.1
B.2
XML Information File Element Types ..................................................................................
Document Elements ......................................................................................................
B.2.1 Header Elements ................................................................................................
B.2.2 Input File List .....................................................................................................
B.2.3 Object Component List ..........................................................................................
B.2.4 Logical Group List ...............................................................................................
B.2.5 Placement Map ..................................................................................................
B.2.6 Far Call Trampoline List ........................................................................................
B.2.7 Symbol Table .....................................................................................................
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C
Glossary .......................................................................................................................... 323
D
............................................................................................................... 323
Revision History ............................................................................................................... 328
D.1
Recent Revisions ......................................................................................................... 328
C.1
Terminology
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List of Figures
TMS320C6000 Software Development Flow
2-1.
Partitioning Memory Into Logical Blocks ................................................................................ 19
2-2.
Using Sections Directives Example ...................................................................................... 24
2-3.
Object Code Generated by the File in
2-4.
Combining Input Sections to Form an Executable Object Module................................................... 27
3-1.
Bootloading Sequence (Simplified) ...................................................................................... 34
3-2.
Autoinitialization at Run Time ............................................................................................. 36
3-3.
Initialization at Load Time ................................................................................................. 37
4-1.
The Assembler in the TMS320C6000 Software Development Flow
4-2.
Example Assembler Listing ............................................................................................... 71
5-1.
The .field Directive ......................................................................................................... 82
5-2.
Initialization Directives ..................................................................................................... 83
5-3.
The .align Directive......................................................................................................... 83
5-4.
The .space and .bes Directives
5-5.
Double-Precision Floating-Point Format ............................................................................... 105
5-6.
The .field Directive ........................................................................................................ 114
5-7.
Single-Precision Floating-Point Format ................................................................................ 115
5-8.
The .usect Directive
7-1.
The Archiver in the TMS320C6000 Software Development Flow .................................................. 173
8-1.
The Linker in the TMS320C6000 Software Development Flow
8-2.
8-3.
8-4.
8-5.
8-6.
8-7.
8-8.
8-9.
10-1.
10-2.
10-3.
10-4.
10-5.
10-6.
10-7.
10-8.
10-9.
10-10.
10-11.
8
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1-1.
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..........................................................................................
.....................................................................................................
....................................................
Section Placement Defined by .........................................................................................
Run-Time Execution of ..................................................................................................
Memory Allocation Shown in and ......................................................................................
Compressed Copy Table ................................................................................................
Handler Table .............................................................................................................
A Basic DSP Run-Time Model ..........................................................................................
Dynamic Linking Model ..................................................................................................
Base Image Executable ..................................................................................................
The Hex Conversion Utility in the TMS320C6000 Software Development Flow .................................
Hex Conversion Utility Process Flow...................................................................................
Object File Data and Memory Widths ..................................................................................
Data, Memory, and ROM Widths .......................................................................................
The infile.out File Partitioned Into Four Output Files .................................................................
ASCII-Hex Object Format................................................................................................
Intel Hexadecimal Object Format .......................................................................................
Motorola-S Format ........................................................................................................
Extended Tektronix Object Format .....................................................................................
TI-Tagged Object Format ................................................................................................
TI-TXT Object Format ....................................................................................................
List of Figures
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List of Tables
4-1.
TMS320C6000 Assembler Options ...................................................................................... 42
4-2.
C6000 Processor Symbolic Constants .................................................................................. 57
4-3.
.................................................................................................... 57
........................................................................ 62
Built-In Mathematical Functions .......................................................................................... 65
Symbol Attributes........................................................................................................... 73
Directives that Control Section Use ...................................................................................... 75
Directives that Gather Sections into Common Groups ................................................................ 75
Directives that Affect Unused Section Elimination ..................................................................... 75
Directives that Initialize Values (Data and Memory) ................................................................... 75
Directives that Perform Alignment and Reserve Space ............................................................... 76
Directives that Format the Output Listing ............................................................................... 76
Directives that Reference Other Files ................................................................................... 77
Directives that Affect Symbol Linkage and Visibility ................................................................... 77
Directives that Control Dynamic Symbol Visibility ..................................................................... 77
Directives that Enable Conditional Assembly ........................................................................... 77
Directives that Define Union or Structure Types ....................................................................... 78
Directives that Define Symbols ........................................................................................... 78
Directives that Create or Affect Macros ................................................................................. 78
Directives that Control Diagnostics ...................................................................................... 79
Directives that Perform Assembly Source Debug ...................................................................... 79
Directives that Perform Miscellaneous Functions ...................................................................... 79
Substitution Symbol Functions and Return Values................................................................... 160
Creating Macros .......................................................................................................... 170
Manipulating Substitution Symbols ..................................................................................... 170
Conditional Assembly .................................................................................................... 170
Producing Assembly-Time Messages .................................................................................. 170
Formatting the Listing .................................................................................................... 170
Basic Options Summary ................................................................................................. 182
File Search Path Options Summary .................................................................................... 182
Command File Preprocessing Options Summary .................................................................... 182
Diagnostic Options Summary ........................................................................................... 182
Linker Output Options Summary........................................................................................ 183
Symbol Management Options Summary .............................................................................. 183
Run-Time Environment Options Summary ............................................................................ 183
Link-Time Optimization Options Summary ............................................................................ 184
Dynamic Linking Options Summary .................................................................................... 184
Miscellaneous Options Summary ....................................................................................... 184
Predefined C6000 Macro Names ....................................................................................... 189
Groups of Operators Used in Expressions (Precedence) ........................................................... 233
Compiler Options For Dynamic Linking ................................................................................ 270
Linker Options For Dynamic Linking ................................................................................... 271
Basic Hex Conversion Utility Options .................................................................................. 281
Options for Specifying Hex Conversion Formats ..................................................................... 298
Symbolic Debugging Directives ......................................................................................... 313
Revision History ........................................................................................................... 328
4-4.
4-5.
4-6.
5-1.
5-2.
5-3.
5-4.
5-5.
5-6.
5-7.
5-8.
5-9.
5-10.
5-11.
5-12.
5-13.
5-14.
5-15.
5-16.
6-1.
6-2.
6-3.
6-4.
6-5.
6-6.
8-1.
8-2.
8-3.
8-4.
8-5.
8-6.
8-7.
8-8.
8-9.
8-10.
8-11.
8-12.
8-13.
8-14.
10-1.
10-2.
A-1.
D-1.
CPU Control Registers
Operators Used in Expressions (Precedence)
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9
Preface
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About This Manual
This document describes support for the C64+, C6740, and C6600 variants of the TMS320C6000™
processor series. The C6200, C6400, C6700, and C6700+ variants are not supported in v8.0 and later
versions of the TI Code Generation Tools. If you are using one of these legacy devices, please use v7.4 of
the Code Generation Tools and refer to SPRU186 and SPRU187 for documentation.
The TMS320C6000 Assembly Language Tools User's Guide explains how to use the following Texas
Instruments Code Generation object file tools:
• Assembler
• Archiver
• Linker
• Library information archiver
• Disassembler
• Object file display utility
• Name utility
• Strip utility
• Hex conversion utility
How to Use This Manual
This book helps you learn how to use the Texas Instruments object file and assembly language tools
designed specifically for the TMS320C6000 ™ 32-bit devices. This book consists of four parts:
• Introductory information, consisting of Chapter 1 through Chapter 3, gives you an overview of the
object file and assembly language development tools. Chapter 2, in particular, explains object modules
and how they can be managed to help your TMS320C6000 application load and run. It is highly
recommended that developers become familiar with what object modules are and how they are used
before using the assembler and linker.
• Assembler description, consisting of Chapter 4 through Chapter 6, contains detailed information
about using the assembler. Chapter 4 and Chapter 5 explain how to invoke the assembler and discuss
source statement format, valid constants and expressions, assembler output, and assembler directives.
Chapter 6 focuses on the macro language.
• Linker and other object file tools description, consisting of Chapter 7 through Chapter 10,
describes in detail each of the tools provided with the assembler to help you create executable object
files. Chapter 7 provides details about using the archiver to create object libraries. Chapter 8 explains
how to invoke the linker, how the linker operates, and how to use linker directives. Chapter 9 provides
a brief overview of some of the object file utilities that can be useful in examining the content of object
files as well as removing symbol and debug information to reduce the size of a given object file.
Chapter 10 explains how to use the hex conversion utility.
• Additional Reference material, consisting of Appendix A through Appendix C, provides
supplementary information including symbolic debugging directives used by the TMS320C6000 C/C++
compiler. A description of the XML link information file and a glossary are also provided.
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Notational Conventions
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Notational Conventions
This document uses the following conventions:
• Program listings, program examples, and interactive displays are shown in a special typeface.
Interactive displays use a bold version of the special typeface to distinguish commands that you enter
from items that the system displays (such as prompts, command output, error messages, etc.).
Here is a sample of C code:
#include <stdio.h>
main()
{
printf("hello world\n");
}
•
•
In syntax descriptions, the instruction, command, or directive is in a bold typeface and parameters are
in an italic typeface. Portions of a syntax that are in bold should be entered as shown; portions of a
syntax that are in italics describe the type of information that should be entered.
Square brackets ( [ and ] ) identify an optional parameter. If you use an optional parameter, you specify
the information within the brackets. Unless the square brackets are in the bold typeface, do not enter
the brackets themselves. The following is an example of a command that has an optional parameter:
cl6x [options] [filenames] [--run_linker [link_options] [object files]]
•
Braces ( { and } ) indicate that you must choose one of the parameters within the braces; you do not
enter the braces themselves. This is an example of a command with braces that are not included in the
actual syntax but indicate that you must specify either the --rom_model or --ram_model option:
cl6x --run_linker
{--rom_model | --ram_model} filenames [--output_file= name.out]
--library= libraryname
•
In assembler syntax statements, The leftmost character position, column 1, is reserved for the first
character of a label or symbol. If the label or symbol is optional, it is usually not shown. If it is a
required parameter, it is shown starting against the left margin of the box, as in the example below. No
instruction, command, directive, or parameter, other than a symbol or label, can begin in column 1.
symbol .usect "section name", size in bytes[, alignment]
•
Some directives can have a varying number of parameters. For example, the .byte directive can have
multiple parameters. This syntax is shown as [, ..., parameter].
.byte parameter1[, ... , parametern]
•
•
The TMS320C64x+ devices are referred to as C64x+. The TMS320C6600 devices are referred to as
C6600. The TMS320C6740 devices are referred to as C6740.
Other symbols and abbreviations used throughout this document include the following:
Symbol
Definition
B,b
Suffix — binary integer
H, h
Suffix — hexadecimal integer
LSB
Least significant bit
MSB
Most significant bit
0x
Q, q
Prefix — hexadecimal integer
Suffix — octal integer
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Related Documentation From Texas Instruments
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Related Documentation From Texas Instruments
See the following resources for further information about the TI Code Generation Tools:
• Texas Instruments Wiki: Compiler topics
• Texas Instruments E2E Community: Compiler forum
You can use the following books to supplement this user's guide:
SPRUI04 — TMS320C6000 Optimizing C/C++ Compiler User's Guide. Describes the TMS320C6000
C/C++ compiler and the assembly optimizer. This C/C++ compiler accepts ANSI standard C/C++
source code and produces assembly language source code for the for the C64+, C6740, and
C6600 variants of the TMS320C6000 platform of devices. Refer to SPRU187 when using legacy
C6200, C6400, C6700, and C6700+ devices. The assembly optimizer helps you optimize your
assembly code.
SPRAB89— C6000 Embedded Application Binary Interface. Provides a specification for the ELFbased Embedded Application Binary Interface (EABI) for the C6000 family of processors from
Texas Instruments. The EABI defines the low-level interface between programs, program
components, and the execution environment, including the operating system if one is present.
SPRU190 — TMS320C6000 DSP Peripherals Overview Reference Guide. Provides an overview and
briefly describes the peripherals available on the TMS320C6000 family of digital signal processors
(DSPs).
SPRU732 — TMS320C64x/C64x+ DSP CPU and Instruction Set Reference Guide. Describes the CPU
architecture, pipeline, instruction set, and interrupts for the TMS320C64x and TMS320C64x+ digital
signal processors (DSPs) of the TMS320C6000 DSP family. The C64x/C64x+ DSP generation
comprises fixed-point devices in the C6000 DSP platform. The C64x+ DSP is an enhancement of
the C64x DSP with added functionality and an expanded instruction set.
SPRUGH7 — TMS320C66x CPU and Instruction Set Reference Guide. Describes the CPU
architecture, pipeline, instruction set, and interrupts for the TMS320C66x digital signal processors
(DSPs) of the TMS320C6000 DSP platform. The C66x DSP generation comprises floating-point
devices in the C6000 DSP platform.
SPRUFE8— TMS320C674x CPU and Instruction Set Reference Guide. Describes the CPU
architecture, pipeline, instruction set, and interrupts for the TMS320C674x digital signal processors
(DSPs) of the TMS320C6000 DSP platform. The C674x is a floating-point DSP that combines the
TMS320C67x+™ DSP and the TMS320C64x+™ DSP instruction set architectures into one core.
Trademarks
TMS320C6000 is a trademark of Texas Instruments.
All other trademarks are the property of their respective owners.
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Chapter 1
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Introduction to the Software Development Tools
The TMS320C6000™ is supported by a set of software development tools, which includes an optimizing
C/C++ compiler, an assembly optimizer, an assembler, a linker, and assorted utilities. This chapter
provides an overview of these tools.
The TMS320C6000 is supported by the following assembly language development tools:
• Assembler
• Archiver
• Linker
• Library information archiver
• Object file display utility
• Disassembler
• Name utility
• Strip utility
• Hex conversion utility
This chapter shows how these tools fit into the general software tools development flow and gives a brief
description of each tool. For convenience, it also summarizes the C/C++ compiler and debugging tools.
For detailed information on the compiler and debugger, and for complete descriptions of the
TMS320C6000, refer to the books listed in Related Documentation From Texas Instruments.
Topic
1.1
1.2
...........................................................................................................................
Page
Software Development Tools Overview ................................................................. 14
Tools Descriptions ............................................................................................. 15
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Software Development Tools Overview
1.1
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Software Development Tools Overview
Figure 1-1 shows the TMS320C6000 software development flow. The shaded portion highlights the most
common development path; the other portions are optional. The other portions are peripheral functions
that enhance the development process.
Figure 1-1. TMS320C6000 Software Development Flow
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1.2
Tools Descriptions
The following list describes the tools that are shown in Figure 1-1:
• The C/C++ compiler accepts C/C++ source code and produces TMS320C6000 machine code object
modules. See the TMS320C6000 Optimizing Compiler User's Guide for more information.
• The assembly optimizer allows you to write linear assembly code without being concerned with the
pipeline structure or with assigning registers. It accepts assembly code that has not been registerallocated and is unscheduled. The assembly optimizer assigns registers and uses loop optimization to
turn linear assembly into highly parallel assembly that takes advantage of software pipelining. See the
TMS320C6000 Optimizing Compiler User's Guide for more information.
• The assembler translates assembly language source files into machine language object modules.
Source files can contain instructions, assembler directives, and macro directives. You can use
assembler directives to control the assembly process, including the source listing format, data
alignment, and section content. See Chapter 4 through Chapter 6. See the TMS320C64x/C64x+ DSP
CPU and Instruction Set Reference Guide (SPRU732), TMS320C66x CPU and Instruction Set
Reference Guide (SPRUGH7), and TMS320C674x CPU and Instruction Set Reference Guide
(SPRUFE8) for detailed information on the assembly language instruction set.
• The linker combines object files into a single static executable or dynamic object module. It performs
symbolic relocation and resolves external references. The linker accepts relocatable object modules
(created by the assembler) as input. It also accepts archiver library members and output modules
created by a previous linker run. Link directives allow you to combine object file sections, bind sections
or symbols to addresses or within memory ranges, and define global symbols. See Chapter 8. For
more information about creating a dynamic object module, see Chapter 14 of The C6000 Embedded
Application Binary Interface Application Report (SPRAB89).
• The archiver allows you to collect a group of files into a single archive file, called a library. The most
common use of the archiver is to collect a group of object files into an object library. The linker extracts
object library members to resolve external references during the link. You can also use the archiver to
collect several macros into a macro library. The assembler searches the library and uses the members
that are called as macros by the source file. The archiver allows you to modify a library by deleting,
replacing, extracting, or adding members. See Section 7.1.
• The library information archiver allows you to create an index library of several object file library
variants, which is useful when several variants of a library with different options are available. Rather
than refer to a specific library, you can link against the index library, and the linker will choose the best
match from the indexed libraries. See Section 7.5 for more information about using the archiver to
manage the content of a library.
• You can use the library-build utility to build your own customized run-time-support library. See the
TMS320C6000 Optimizing Compiler User's Guide for more information.
• The hex conversion utility converts object files to TI-Tagged, ASCII-Hex, Intel, Motorola-S, or
Tektronix object format. Converted files can be downloaded to an EPROM programmer. See
Chapter 10.
• The main product of this development process is a executable object file that can be executed on a
TMS320C6000 device. You can use an XDS emulator when refining and correcting your code.
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Tools Descriptions
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In addition, the following utilities are provided to help examine or manage the content of a given object file:
• The object file display utility prints the contents of object files and object libraries in either human
readable or XML formats. See Section 9.1.
• The disassembler decodes the machine code from object modules to show the assembly instructions
that it represents. See Section 9.2.
• The name utility prints a list of symbol names for objects and functions defined or referenced in an
object file or object archive. See Section 9.3.
• The strip utility removes symbol table and debugging information from object files and object libraries.
See Section 9.4.
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Chapter 2
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Introduction to Object Modules
The assembler creates object modules from assembly code, and the linker creates executable object files
from object modules. These executable object files can be executed by a TMS320C6000 device.
Object modules make modular programming easier because they encourage you to think in terms of
blocks of code and data when you write an assembly language program. These blocks are known as
sections. Both the assembler and the linker provide directives that allow you to create and manipulate
sections.
This chapter focuses on the concept and use of sections in assembly language programs.
Topic
2.1
2.2
2.3
2.4
2.5
2.6
2.7
2.8
...........................................................................................................................
Object File Format Specifications.........................................................................
Executable Object Files ......................................................................................
Introduction to Sections ......................................................................................
How the Assembler Handles Sections ..................................................................
How the Linker Handles Sections .........................................................................
Symbols ............................................................................................................
Symbolic Relocations .........................................................................................
Loading a Program .............................................................................................
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18
18
18
19
26
28
30
31
17
Object File Format Specifications
2.1
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Object File Format Specifications
The object files created by the assembler and linker conform to the ELF (Executable and Linking Format)
binary format, which is used by the Embedded Application Binary Interface (EABI). See the
TMS320C6000 Optimizing Compiler User's Guide (SPRUI04) and The C6000 Embedded Application
Binary Interface Application Report (SPRAB89) for information on the EABI ABI.
COFF object files are not supported in v8.0 and later versions of the TI Code Generation Tools. If you
would like to produce COFF output files, please use v7.4 of the Code Generation Tools and refer to
SPRU186 for documentation.
The ELF object files generated by the assembler and linker conform to the December 17, 2003 snapshot
of the System V generic ABI (or gABI).
2.2
Executable Object Files
The linker can be used to produce static executable object modules. An executable object module has the
same format as object files that are used as linker input. The sections in an executable object module,
however, have been combined and placed in target memory, and the relocations are all resolved.
To run a program, the data in the executable object module must be transferred, or loaded, into target
system memory. See Chapter 3 for details about loading and running programs.
2.3
Introduction to Sections
The smallest unit of an object file is a section. A section is a block of code or data that occupies
contiguous space in the memory map. Each section of an object file is separate and distinct.
ELF format executable object files contain segments. An ELF segment is a meta-section. It represents a
contiguous region of target memory. It is a collection of sections that have the same property, such as
writeable or readable. An ELF loader needs the segment information, but does not need the section
information. The ELF standard allows the linker to omit ELF section information entirely from the
executable object file.
Object files usually contain three default sections:
.text section
.data section
.bss section
(1)
contains executable code (1)
usually contains initialized data
usually reserves space for uninitialized variables
Some targets allow content other than text, such as constants, in .text sections.
The assembler and linker allow you to create, name, and link other kinds of sections. The .text, .data, and
.bss sections are archetypes for how sections are handled.
There are two basic types of sections:
Initialized sections
Uninitialized sections
18
contain data or code. The .text and .data sections are initialized; usernamed sections created with the .sect assembler directive are also
initialized.
reserve space in the memory map for uninitialized data. The .bss section is
uninitialized; user-named sections created with the .usect assembler
directive are also uninitialized.
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Introduction to Sections
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Several assembler directives allow you to associate various portions of code and data with the appropriate
sections. The assembler builds these sections during the assembly process, creating an object file
organized as shown in Figure 2-1.
One of the linker's functions is to relocate sections into the target system's memory map; this function is
called placement. Because most systems contain several types of memory, using sections can help you
use target memory more efficiently. All sections are independently relocatable; you can place any section
into any allocated block of target memory. For example, you can define a section that contains an
initialization routine and then allocate the routine in a portion of the memory map that contains ROM. For
information on section placement, see the "Specifying Where to Allocate Sections in Memory" section of
the TMS320C6000 Optimizing Compiler User's Guide .
Figure 2-1 shows the relationship between sections in an object file and a hypothetical target memory.
Figure 2-1. Partitioning Memory Into Logical Blocks
Object file
Target memory
.bss
RAM
.data
EEPROM
.text
ROM
2.3.1 Special Section Names
You can use the .sect and .usect directives to create any section name you like, but certain sections are
treated in a special manner by the linker and the compiler's run-time support library. If you create a section
with the same name as a special section, you should take care to follow the rules for that special section.
A
•
•
•
•
•
•
•
few common special sections are:
.text -- Used for program code.
.bss -- Used for uninitialized objects (global variables).
.data -- Used for initialized non-const objects (global variables).
.const -- Used for initialized const objects (string constants, variables declared const).
.cinit -- Used to initialize C global variables at startup.
.stack -- Used for the function call stack.
.sysmem - Used for the dynamic memory allocation pool.
For more information on sections, see the "Specifying Where to Allocate Sections in Memory" section of
the TMS320C6000 Optimizing Compiler User's Guide .
2.4
How the Assembler Handles Sections
The assembler identifies the portions of an assembly language program that belong in a given section.
The assembler has the following directives that support this function:
• .bss
• .data
• .sect
• .text
• .usect
The .bss and .usect directives create uninitialized sections; the .text, .data, and .sect directives create
initialized sections.
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How the Assembler Handles Sections
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You can create subsections of any section to give you tighter control of the memory map. Subsections are
created using the .sect and .usect directives. Subsections are identified with the base section name and a
subsection name separated by a colon; see Section 2.4.6.
Default Sections Directive
NOTE: If you do not use any of the sections directives, the assembler assembles everything into the
.text section.
2.4.1 Uninitialized Sections
Uninitialized sections reserve space in TMS320C6000 memory; they are usually placed in RAM. These
sections have no actual contents in the object file; they simply reserve memory. A program can use this
space at run time for creating and storing variables.
Uninitialized data areas are built by using the following assembler directives.
• The .bss directive reserves space in the .bss section.
• The .usect directive reserves space in a specific uninitialized user-named section.
Each time you invoke the .bss or .usect directive, the assembler reserves additional space in the .bss or
the user-named section. The syntax is:
.bss symbol, size in bytes[, alignment[, bank offset] ]
symbol
.usect "section name", size in bytes[, alignment[, bank offset] ]
symbol
size in bytes
alignment
bank offset
section name
points to the first byte reserved by this invocation of the .bss or .usect directive. The
symbol corresponds to the name of the variable that you are reserving space for. It can
be referenced by any other section and can also be declared as a global symbol (with
the .global directive).
is an absolute expression (see Section 4.9). The .bss directive reserves size in bytes
bytes in the .bss section. The .usect directive reserves size in bytes bytes in section
name. For both directives, you must specify a size; there is no default value.
is an optional parameter. It specifies the minimum alignment in bytes required by the
space allocated. The default value is byte aligned; this option is represented by the
value 1. The value must be a power of 2.
is an optional parameter. It ensures that the space allocated to the symbol occurs on a
specific memory bank boundary. The bank offset measures the number of bytes to
offset from the alignment specified before assigning the symbol to that location.
specifies the user-named section in which to reserve space. See Section 2.4.3.
Initialized section directives (.text, .data, and .sect) change which section is considered the current section
(see Section 2.4.2). However, the .bss and .usect directives do not change the current section; they simply
escape from the current section temporarily. Immediately after a .bss or .usect directive, the assembler
resumes assembling into whatever the current section was before the directive. The .bss and .usect
directives can appear anywhere in an initialized section without affecting its contents. For an example, see
Section 2.4.7.
The .usect directive can also be used to create uninitialized subsections. See Section 2.4.6 for more
information on creating subsections.
The .nearcommon and .farcommon directives are similar to directives that create uninitialized data
sections, except that common symbols are created, instead.
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2.4.2 Initialized Sections
Initialized sections contain executable code or initialized data. The contents of these sections are stored in
the object file and placed in TMS320C6000 memory when the program is loaded. Each initialized section
is independently relocatable and may reference symbols that are defined in other sections. The linker
automatically resolves these references. The following directives tell the assembler to place code or data
into a section. The syntaxes for these directives are:
.text
.data
.sect "section name"
The .sect directive can also be used to create initialized subsections. See Section 2.4.6, for more
information on creating subsections.
2.4.3 User-Named Sections
User-named sections are sections that you create. You can use them like the default .text, .data, and .bss
sections, but each section with a distinct name is kept distinct during assembly.
For example, repeated use of the .text directive builds up a single .text section in the object file. This .text
section is allocated in memory as a single unit. Suppose there is a portion of executable code (perhaps an
initialization routine) that you want the linker to place in a different location than the rest of .text. If you
assemble this segment of code into a user-named section, it is assembled separately from .text, and you
can use the linker to allocate it into memory separately. You can also assemble initialized data that is
separate from the .data section, and you can reserve space for uninitialized variables that is separate from
the .bss section.
These directives let you create user-named sections:
• The .usect directive creates uninitialized sections that are used like the .bss section. These sections
reserve space in RAM for variables.
• The .sect directive creates initialized sections, like the default .text and .data sections, that can contain
code or data. The .sect directive creates user-named sections with relocatable addresses.
The syntaxes for these directives are:
symbol
.usect "section name", size in bytes[, alignment[, bank offset] ]
.sect "section name"
The maximum number of sections is 232-1 (4294967295).
The section name parameter is the name of the section. For the .usect and .sect directives, a section
name can refer to a subsection; see Section 2.4.6 for details.
Each time you invoke one of these directives with a new name, you create a new user-named section.
Each time you invoke one of these directives with a name that was already used, the assembler resumes
assembling code or data (or reserves space) into the section with that name. You cannot use the same
names with different directives. That is, you cannot create a section with the .usect directive and then try
to use the same section with .sect.
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2.4.4 Current Section
The assembler adds code or data to one section at a time. The section the assembler is currently filling is
the current section. The .text, .data, and .sect directives change which section is considered the current
section. When the assembler encounters one of these directives, it stops assembling into the current
section (acting as an implied end of current section command). The assembler sets the designated
section as the current section and assembles subsequent code into the designated section until it
encounters another .text, .data, or .sect directive.
If one of these directives sets the current section to a section that already has code or data in it from
earlier in the file, the assembler resumes adding to the end of that section. The assembler generates only
one contiguous section for each given section name. This section is formed by concatenating all of the
code or data which was placed in that section.
2.4.5 Section Program Counters
The assembler maintains a separate program counter for each section. These program counters are
known as section program counters, or SPCs.
An SPC represents the current address within a section of code or data. Initially, the assembler sets each
SPC to 0. As the assembler fills a section with code or data, it increments the appropriate SPC. If you
resume assembling into a section, the assembler remembers the appropriate SPC's previous value and
continues incrementing the SPC from that value.
The assembler treats each section as if it began at address 0; the linker relocates the symbols in each
section according to the final address of the section in which that symbol is defined. See Section 2.7 for
information on relocation.
2.4.6 Subsections
A subsection is created by creating a section with a colon in its name. Subsections are logical subdivisions
of larger sections. Subsections are themselves sections and can be manipulated by the assembler and
linker.
The assembler has no concept of subsections; to the assembler, the colon in the name is not special. The
subsection .text:rts would be considered completely unrelated to its parent section .text, and the
assembler will not combine subsections with their parent sections.
Subsections are used to keep parts of a section as distinct sections so that they can be separately
manipulated. For instance, by placing each function and object in a uniquely-named subsection, the linker
gets a finer-grained view of the section for memory placement and unused-function elimination.
By default, when the linker sees a SECTION directive in the linker command file like ".text", it will gather
.text and all subsections of .text into one large output section named ".text". You can instead use the
SECTION directive to control the subsection independently. See Section 8.5.5.1 for an example.
You can create subsections in the same way you create other user-named sections: by using the .sect or
.usect directive.
The syntaxes for a subsection name are:
symbol
.usect "section_name:subsection_name",size in bytes[,alignment[,bank offset]]
.sect "section_name:subsection_name"
A subsection is identified by the base section name followed by a colon and the name of the subsection.
The subsection name may not contain any spaces.
A subsection can be allocated separately or grouped with other sections using the same base name. For
example, you create a subsection called _func within the .text section:
.sect ".text:_func"
Using the linker's SECTIONS directive, you can allocate .text:_func separately, or with all the .text
sections.
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You can create two types of subsections:
• Initialized subsections are created using the .sect directive. See Section 2.4.2.
• Uninitialized subsections are created using the .usect directive. See Section 2.4.1.
Subsections are placed in the same manner as sections. See Section 8.5.5 for information on the
SECTIONS directive.
2.4.7 Using Sections Directives
Figure 2-2 shows how you can build sections incrementally, using the sections directives to swap back
and forth between the different sections. You can use sections directives to begin assembling into a
section for the first time, or to continue assembling into a section that already contains code. In the latter
case, the assembler simply appends the new code to the code that is already in the section.
The format in Figure 2-2 is a listing file. Figure 2-2 shows how the SPCs are modified during assembly. A
line in a listing file has four fields:
Field
Field
Field
Field
1
2
3
4
contains
contains
contains
contains
the source code line counter.
the section program counter.
the object code.
the original source statement.
See Section 4.11 for more information on interpreting the fields in a source listing.
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How the Assembler Handles Sections
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Figure 2-2. Using Sections Directives Example
4 00000000
5 00000000 00000011
00000004 00000022
.data
.word
011h,022h
.bss
.bss
var1,4
buffer,40
ptr
.word
01234h
sum:
.text
MVK
ZERO
10,A1
A4
LDW
NOP
SUB
ADD
B
NOP
*A0++,A2
3
A1,1,A1
A2,A4,A4
aloop
5
STW
A4, *+B14(var1)
ivals
.data
.word
0aah, 0bbh, 0cch
var2
inbuf
.usect
.usect
”newvars”,4
”newvars”,4
.text
LDW
NOP
MPYHL
MVKL
MVKH
STW
*A0++,A2
4
A2,A3,A4
var2,A5
var2,A5
A4,*A5
.sect
B
NOP
”vectors”
sum
5
coeff
9 00000000
10 00000004
14 00000008 00001234
18
19
20
21
22
23
24
25
26
27
28
29
00000000
00000000 00800528
00000004 021085E0
00000008
0000000c
00000010
00000014
00000018
0000001c
01003664
00004000
0087E1A0
021041E0
80000112
00008000
[A1]
00000020 0200007C-
33 0000000c
34 0000000c 000000AA
00000010 000000BB
00000014 000000CC
38 00000000
39 00000004
43
44
45
46
47
48
49
aloop:
00000024
00000024
00000028
0000002c
00000030
00000034
00000038
01003664 xmult:
00006000
020C4480
028000280280006802140274
53 00000000
54 00000000 00000012’
55 00000004 00008000
Field 1 Field 2
Field 3
Field 4
As Figure 2-3 shows, the file in Figure 2-2 creates five sections:
.text
.data
vectors
.bss
24
contains 15 32-bit words of object code.
contains six words of initialized data.
is a user-named section created with the .sect directive; it contains two words of object
code.
reserves 44 bytes in memory.
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newvars
is a user-named section created with the .usect directive; it contains eight bytes in
memory.
The second column shows the object code that is assembled into these sections; the first column shows
the source statements that generated the object code.
Figure 2-3. Object Code Generated by the File in Figure 2-2
Line numbers
Object code
Section
19
20
22
23
24
25
26
27
29
44
45
46
47
48
49
00800528
021085E0
01003664
00004000
0087E1A0
021041E0
80000112
00008000
0200007C01003664
00006000
020C4480
028000280280006802140274
.text
5
5
14
34
34
34
00000011
00000022
00001234
000000AA
000000BB
000000CC
.data
54
54
00000000’
00000024’
vectors
9
10
No data—
44 bytes
reserved
.bss
38
39
No data—
8 bytes
reserved
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How the Linker Handles Sections
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How the Linker Handles Sections
The linker has two main functions related to sections. First, the linker uses the sections in object files as
building blocks; it combines input sections to create output sections in an executable output module.
Second, the linker chooses memory addresses for the output sections; this is called placement. Two linker
directives support these functions:
• The MEMORY directive allows you to define the memory map of a target system. You can name
portions of memory and specify their starting addresses and their lengths.
• The SECTIONS directive tells the linker how to combine input sections into output sections and where
to place these output sections in memory.
Subsections let you manipulate the placement of sections with greater precision. You can specify the
location of each subsection with the linker's SECTIONS directive. If you do not specify a subsection, the
subsection is combined with the other sections with the same base section name. See Section 8.5.5.1.
It is not always necessary to use linker directives. If you do not use them, the linker uses the target
processor's default placement algorithm described in Section 8.7. When you do use linker directives, you
must specify them in a linker command file.
Refer to the following sections for more information about linker command files and linker directives:
• Section 8.5, Linker Command Files
• Section 8.5.4, The MEMORY Directive
• Section 8.5.5, The SECTIONS Directive
• Section 8.7, Default Placement Algorithm
2.5.1 Combining Input Sections
Figure 2-4 provides a simplified example of the process of linking two files together.
Note that this is a simplified example, so it does not show all the sections that will be created or the actual
sequence of the sections. See Section 8.7 for the actual default memory placement map for
TMS320C6000.
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Figure 2-4. Combining Input Sections to Form an Executable Object Module
In Figure 2-4, file1.obj and file2.obj have been assembled to be used as linker input. Each contains the
.text, .data, and .bss default sections; in addition, each contains a user-named section. The executable
object module shows the combined sections. The linker combines the .text section from file1.obj and the
.text section from file2.obj to form one .text section, then combines the two .data sections and the two .bss
sections, and finally places the user-named sections at the end. The memory map shows the combined
sections to be placed into memory.
2.5.2 Placing Sections
Figure 2-4 illustrates the linker's default method for combining sections. Sometimes you may not want to
use the default setup. For example, you may not want all of the .text sections to be combined into a single
.text section. Or you may want a user-named section placed where the .data section would normally be
allocated. Most memory maps contain various types of memory (RAM, ROM, EPROM, FLASH, etc.) in
varying amounts; you may want to place a section in a specific type of memory.
For further explanation of section placement within the memory map, see the discussions in Section 8.5.4
and Section 8.5.5. See Section 8.7 for the actual default memory allocation map for TMS320C6000.
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Symbols
An object file contains a symbol table that stores information about external symbols in the object file. The
linker uses this table when it performs relocation. See Section 2.7.
An object file symbol is a named 32-bit integer value, usually representing an address. A symbol can
represent such things as the starting address of a function, variable, or section.
An object file symbol can also represent an absolute integer, such as the size of the stack. To the linker,
this integer is an unsigned value, but the integer may be treated as signed or unsigned depending on how
it is used. The range of legal values for an absolute integer is 0 to 2^32-1 for unsigned treatment and
-2^31 to 2^31-1 for signed treatment.
Symbols can be bound as global symbols, local symbols, or weak symbols. The linker handles symbols
differently based on their binding. For example, the linker does not allow multiple global definitions of a
symbol, but local symbols can be defined in multiple object files (but only once per object file). The linker
does not resolve references to local symbols in different object files, but it does resolve references to
global symbols in any other object file.
A global symbol is defined in the same manner as any other symbol; that is, it appears as a label or is
defined by a directive, such as .set, .equ, .bss, or .usect. If a global symbol is defined more than once, the
linker issues a multiple-definition error. (The assembler can provide a similar multiple-definition error for
local symbols.)
A weak symbol is a symbol that is used in the current module but is defined in another module. The linker
resolves this symbol's definition at link time. Weak symbols are similar to global symbols, except that if
one object file contains a weak symbol, and another object file contains a global symbol with the same
name, the global symbol is used to resolve references. A weak reference may be unresolved at link time,
in which case the address is treated as 0. Therefore, for weak references, application code must test to
make sure &var is not zero before attempting to read the contents. See Section 2.6.2 for more about weak
symbols.
See Section 4.8 for information about assembler symbols.
2.6.1 External Symbols
External symbols are symbols that are visible to other object modules. Because they are visible across
object modules, they may be defined in one file and referenced in another file. You can use the .def, .ref,
or .global directive to identify a symbol as external:
.def
.ref
.global
The symbol is defined in the current file and may be used in another file.
The symbol is referenced in the current file, but defined in another file.
The symbol can be either of the above. The assembler chooses either .def or .ref as
appropriate for each symbol.
The following code fragment illustrates these definitions.
q:
x:
.def
.ref
.global
.global
x
y
z
q
B
NOP
MVK
MV
MVKL
MVKH
B
NOP
B3
4
1, B1
A0,A1
y,B3
y,B3
z
5
In this example, the .def definition of x says that it is an external symbol defined in this file and that other
files can reference x. The .ref definition of y says that it is an undefined symbol that is defined in another
file. The .global definition of z says that it is defined in some file and available in this file. The .global
definition of q says that it is defined in this file and that other files can reference q.
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The assembler places x, y, z, and q in the object file's symbol table. When the file is linked with other
object files, the entries for x and q resolve references to x and q in other files. The entries for y and z
cause the linker to look through the symbol tables of other files for y's and z's definitions.
The linker attempts to match all references with corresponding definitions. If the linker cannot find a
symbol's definition, it prints an error message about the unresolved reference. This type of error prevents
the linker from creating an executable object module.
An error also occurs if the same symbol is defined more than once.
2.6.2 Weak Symbols
The linker processes absolute symbols that are defined with "weak" binding differently from absolute
symbols that are defined with global binding (the default). Instead of including a weak absolute symbol in
the output file's symbol table by default (as it would for a global absolute symbol), the linker only includes
a weak absolute symbol in the output of a "final" link if the symbol is required to resolve an otherwise
unresolved reference.
This weak symbol handling allows you to associate addresses with symbols known to have been preloaded (such as function addresses in system memory) and then link the current application against a preloaded memory image. If such symbols are defined as weak absolute symbols, the linker can minimize the
number of symbols it includes in the output file's symbol table by omitting those that are not needed to
resolve references. Reducing the size of the output file's symbol table reduces the time required to link,
especially if there are a large number of pre-loaded symbols to link against. This feature is particularly
helpful for OpenCL applications.
You can define a weak absolute symbol using either assembly or the linker command file.
Using Assembly: To define a weak absolute symbol in an input object file, the source file can be written
in assembly. Use the .weak and .set directives in combination as shown in the following example, which
defines a weak absolute symbol "ext_addr_sym":
ext_addr_sym
.weak
.set
ext_addr_sym
0x12345678
Assemble the source file that defines weak symbols, and include the resulting object file in the link. The
"ext_addr_sym" in this example is available as a weak absolute symbol in a final link. It is a candidate for
removal if the symbol is not referenced elsewhere in the application. See .weak directive.
Using the Linker Command File: To define a weak symbol in a linker command file, use the "weak"
operator in an assignment expression to designate that the symbol as eligible for removal from the output
file's symbol table if it is not referenced. In a linker command file, an assignment expression outside a
MEMORY or SECTIONS directive can be used to define a weak linker-defined absolute symbol. For
example, you can define "ext_addr_sym" as follows:
weak(ext_addr_sym) = 0x12345678;
If the linker command file is used to perform the final link, then "ext_addr_sym" is presented to the linker
as a weak absolute symbol; it will not be included in the resulting output file if the symbol is not
referenced. See Section 8.6.2.
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If there are multiple definitions of the same absolute symbol, the linker uses certain rules to determine
which definition takes precedence. Some definitions may have weak binding and others may have strong
binding. "Strong" in this context means that the symbol has not been given a weak binding by either of the
two methods described above. Some definitions may come from an input object file (that is, using
assembly directives) and others may come from an assignment statement in a linker command file. The
linker uses the following guidelines to determine which definition is used when resolving references to a
symbol:
• A strongly bound symbol always takes precedence over a weakly bound symbol.
• If two symbols are both strongly bound or both weakly bound, a symbol defined in a linker command
file takes precedence over a symbol defined in an input object file.
• If two symbols are both strongly bound and both are defined in an input object file, the linker provides a
symbol redefinition error and halts the link process.
2.6.3 The Symbol Table
The assembler generates an entry in the symbol table for each .ref, .def, or .global directive in
Section 2.6.1). These are external symbols, which are visible to other object modules.
The assembler also creates special symbols that point to the beginning of each section.
The assembler does not usually create symbol table entries for any symbols other than those described
above, because the linker does not use them. For example, labels (Section 4.8.2) are not included in the
symbol table unless they are declared with the .global directive. For informational purposes, there are
entries in the symbol table for each symbol in a program.
2.7
Symbolic Relocations
The assembler treats each section as if it began at address 0. Of course, all sections cannot actually
begin at address 0 in memory, so the linker must relocate sections. Relocations are symbol-relative rather
than section-relative.
The linker can relocate sections by:
• Allocating them into the memory map so that they begin at the appropriate address as defined with the
linker's MEMORY directive
• Adjusting symbol values to correspond to the new section addresses
• Adjusting references to relocated symbols to reflect the adjusted symbol values
The linker uses relocation entries to adjust references to symbol values. The assembler creates a
relocation entry each time a relocatable symbol is referenced. The linker then uses these entries to patch
the references after the symbols are relocated. Example 2-1 contains a code fragment for a
TMS320C6000 device for which the assembler generates relocation entries.
Example 2‑1. Code That Generates Relocation Entries
1
2
3
4
5
6
7
8
9
00000000
00000004
00000008
0000000C
00000012! Z:
0180082A'
0180006A'
00004000
00000010 0001E000
00000014 00000212
00000018 00008000
Y:
.global
B
MVKL
MVKH
NOP
X
X
Y,B3
Y,B3
3
IDLE
B
NOP
Y
5
; Uses an external relocation
; Uses an internal relocation
; Uses an internal relocation
In Example 2-1, both symbols X and Y are relocatable. Y is defined in the .text section of this module; X is
defined in another module. When the code is assembled, X has a value of 0 (the assembler assumes all
undefined external symbols have values of 0), and Y has a value of 16. The assembler generates two
relocation entries: one for X and one for Y. The reference to X is an external reference (indicated by the !
character in the listing). The reference to Y is to an internally defined relocatable symbol (indicated by the '
character in the listing).
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After the code is linked, suppose that X is relocated to address 0x7100. Suppose also that the .text
section is relocated to begin at address 0x7200; Y now has a relocated value of 0x7210. The linker uses
the two relocation entries to patch the two references in the object code:
00000012
B
X
0180082A
MVKL
Y
0180006A
MVKH
Y
becomes
becomes
becomes
0fffe012
01B9082A
1860006A
Relocations are symbol-relative rather than section-relative. This means that the relocation in Example 2-1
generated for 'Y' would refer to the symbol 'Y' and resolve the value for 'Y' in the opcode based on where
the definition of 'Y' ends up.
2.7.1 Dynamic Relocation Entries
Under dynamic linking models, the processing of relocation entries is handled slightly differently. If a
relocation refers to a symbol that is imported from another dynamic module, then the static linker
generates a dynamic relocation, which must be processed by the dynamic linker at dynamic load time
(when the definition of the imported symbol is available). Only dynamic shared objects have dynamic
relocations.
See Section 8.12 for information about dynamic linking. For information about creating a dynamic object
module, see Chapter 14 of The C6000 Embedded Application Binary Interface Application Report
(SPRAB89).
2.8
Loading a Program
The linker creates an executable object file which can be loaded in several ways, depending on your
execution environment. These methods include using Code Composer Studio or the hex conversion utility.
For details, see Section 3.1.
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Chapter 3
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Program Loading and Running
Even after a program is written, compiled, and linked into an executable object file, there are still many
tasks that need to be performed before the program does its job. The program must be loaded onto the
target, memory and registers must be initialized, and the program must be set to running.
Some of these tasks need to be built into the program itself. Bootstrapping is the process of a program
performing some of its own initialization. Many of the necessary tasks are handled for you by the compiler
and linker, but if you need more control over these tasks, it helps to understand how the pieces are
expected to fit together.
This chapter will introduce you to the concepts involved in program loading, initialization, and startup.
This chapter does not cover dynamic loading. See Chapter 14 of The C6000 Embedded Application
Binary Interface Application Report (SPRAB89) for information about dynamic loaders.
This chapter currently provides examples for the C6000 device family. Refer to your device documentation
for various device-specific aspects of bootstrapping.
Topic
3.1
3.2
3.3
3.4
3.5
3.6
32
...........................................................................................................................
Loading.............................................................................................................
Entry Point ........................................................................................................
Run-Time Initialization ........................................................................................
Arguments to main .............................................................................................
Run-Time Relocation ..........................................................................................
Additional Information ........................................................................................
Program Loading and Running
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35
35
38
38
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3.1
Loading
A program needs to be placed into the target device's memory before it may be executed. Loading is the
process of preparing a program for execution by initializing device memory with the program's code and
data. A loader might be another program on the device, an external agent (for example, a debugger), or
the device might initialize itself after power-on, which is known as bootstrap loading, or bootloading.
The loader is responsible for constructing the load image in memory before the program starts. The load
image is the program's code and data in memory before execution. What exactly constitutes loading
depends on the environment, such as whether an operating system is present. This section describes
several loading schemes for bare-metal devices. This section is not exhaustive.
A program may be loaded in the following ways:
• A debugger running on a connected host workstation. In a typical embedded development setup,
the device is subordinate to a host running a debugger such as Code Composer Studio (CCS). The
device is connected with a communication channel such as a JTAG interface. CCS reads the program
and writes the load image directly to target memory through the communications interface.
• Another program running on the device. The running program can create the load image and
transfer control to the loaded program. If an operating system is present, it may have the ability to load
and run programs.
• "Burning" the load image onto an EPROM module. The hex converter (hex6x) can assist with this
by converting the executable object file into a format suitable for input to an EPROM programmer. The
EPROM is placed onto the device itself and becomes a part of the device's memory. See Chapter 10
for details.
• Bootstrap loading from a dedicated peripheral, such as an I2C peripheral. The device may require
a small program called a bootloader to perform the loading from the peripheral. The hex converter can
assist in creating a bootloader.
3.1.1 Load and Run Addresses
Consider an embedded device for which the program's load image is burned onto EPROM/ROM. Variable
data in the program must be writable, and so must be located in writable memory, typically RAM.
However, RAM is volatile, meaning it will lose its contents when the power goes out. If this data must have
an initial value, that initial value must be stored somewhere else in the load image, or it would be lost
when power is cycled. The initial value must be copied from the non-volatile ROM to its run-time location
in RAM before it is used. See Section 8.8 for ways this is done.
The load address is the location of an object in the load image.
The run address is the location of the object as it exists during program execution.
An object is a chunk of memory. It represents a section, segment, function, or data.
The load and run addresses for an object may be the same. This is commonly the case for program code
and read-only data, such as the .const section. In this case, the program can read the data directly from
the load address. Sections that have no initial value, such as the .bss section, do not have load data and
are considered to have load and run addresses that are the same. If you specify different load and run
addresses for an uninitialized section, the linker provides a warning and ignores the load address.
The load and run addresses for an object may be different. This is commonly the case for writable data,
such as the .data section. The .data section's starting contents are placed in ROM and copied to RAM.
This often occurs during program startup, but depending on the needs of the object, it may be deferred to
sometime later in the program as described in Section 3.5.
Symbols in assembly code and object files almost always refer to the run address. When you look at an
address in the program, you are almost always looking at the run address. The load address is rarely
used for anything but initialization.
The load and run addresses for a section are controlled by the linker command file and are recorded in
the object file metadata.
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The load address determines where a loader places the raw data for the section. Any references to the
section (such as references to labels in it) refer to its run address. The application must copy the section
from its load address to its run address before the first reference of the symbol is encountered at run time;
this does not happen automatically simply because you specify a separate run address. For examples that
specify load and run addresses, see Section 8.5.6.1.
For an example that illustrates how to move a block of code at run time, see Example 8-10. To create a
symbol that lets you refer to the load-time address, rather than the run-time address, see the .label
directive. To use copy tables to copy objects from load-space to run-space at boot time, see Section 8.8.
ELF format executable object files contain segments. See Section 2.3 for information about sections and
segments.
3.1.2 Bootstrap Loading
The details of bootstrap loading (bootloading) vary a great deal between devices. Not every device
supports every bootloading mode, and using the bootloader is optional. This section discusses various
bootloading schemes to help you understand how they work. Refer to your device's data sheet to see
which bootloading schemes are available and how to use them.
A typical embedded system uses bootloading to initialize the device. The program code and data may be
stored in ROM or FLASH memory. At power-on, an on-chip bootloader (the primary bootloader) built into
the device hardware starts automatically.
Figure 3-1. Bootloading Sequence (Simplified)
The primary bootloader is typically very small and copies a limited amount of memory from a dedicated
location in ROM to a dedicated location in RAM. (Some bootloaders support copying the program from an
I/O peripheral.) After the copy is completed, it transfers control to the program.
3.1.2.1
Boot, Load, and Run Addresses
The boot address of a bootloaded object is where its raw data exists in ROM before power-on.
The boot, load, and run addresses for an object may all be the same; this is commonly the case for .const
data. If they are different, the object's contents must be copied to the correct location before the object
may be used.
The boot address may be different than the load address. The bootloader is responsible for copying the
raw data to the load address.
The boot address is not controlled by the linker command file or recorded in the object file; it is strictly a
convention shared by the bootloader and the program.
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3.1.2.2
Primary Bootloader
The detailed operation of the primary bootloader is device-specific. Some devices have complex
capabilities such as booting from an I/O peripheral or configuring memory controller parameters.
3.2
Entry Point
The entry point is the address at which the execution of the program begins. This is the address of the
startup routine. The startup routine is responsible for initializing and calling the rest of the program. For a
C/C++ program, the startup routine is usually named _c_int00 (see Section 3.3.1). After the program is
loaded, the value of the entry point is placed in the PC register and the CPU is allowed to run.
The object file has an entry point field. For a C/C++ program, the linker will fill in _c_int00 by default. You
can select a custom entry point; see Section 8.4.12. The device itself cannot read the entry point field from
the object file, so it has to be encoded in the program somewhere.
• If you are using a bootloader, the boot table includes an entry point field. When it finishes running, the
bootloader branches to the entry point.
• If you are using an interrupt vector, the entry point is installed as the RESET interrupt handler. When
RESET is applied, the startup routine will be invoked.
• If you are using a hosted debugger, such as CCS, the debugger may explicitly set the program counter
(PC) to the value of the entry point.
3.3
Run-Time Initialization
After the load image is in place, the program can run. The subsections that follow describe bootstrap
initialization of a C/C++ program. An assembly-only program may not need to perform all of these steps.
3.3.1
_c_int00
The function _c_int00 is the startup routine (also called the boot routine) for C/C++ programs. It performs
all the steps necessary for a C/C++ program to initialize itself.
The name _c_int00 means that it is the interrupt handler for interrupt number 0, RESET, and that it sets
up the C environment. Its name need not be exactly _c_int00, but the linker sets _c_int00 as the entry
point for C programs by default. The compiler's run-time-support library provides a default implementation
of _c_int00.
The startup routine is responsible for performing the following actions:
1. Set up the stack by initializing SP
2. Set up the data page pointer DP (for architectures that have one)
3. Set configuration registers
4. Process the .cinit table to autoinitialize global variables (when using the --rom_model option)
5. Process the .pinit table to construct global C++ objects.
6. Call the function main with appropriate arguments
7. Call exit when main returns
3.3.2 RAM Model vs. ROM Model
The .cinit section is loaded into memory along with other initialized sections. The linker defines a "cinit"
symbol that points to the beginning of the initialization tables in memory. When the program begins
running, the C boot routine copies data from these tables into the .bss section.
3.3.2.1
Autoinitializing Variables at Run Time (--rom_model)
Autoinitializing variables at run time is the default method of autoinitialization. To use this method, invoke
the linker with the --rom_model option.
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Run-Time Initialization
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Using this method, the .cinit section is loaded into memory along with all the other initialized sections. The
linker defines a special symbol called cinit that points to the beginning of the initialization tables in
memory. When the program begins running, the C boot routine copies data from the tables (pointed to by
.cinit) into the specified variables in the .bss section. This allows initialization data to be stored in slow
non-volatile memory and copied to fast memory each time the program is reset.
Figure 3-2 illustrates autoinitialization at run time. Use this method in any system where your application
runs from code burned into slow memory or needs to survive a reset.
Figure 3-2. Autoinitialization at Run Time
Object file
.cinit
section
Memory
cint
Loader
Initialization
tables
(EXT_MEM)
Boot
routine
.bss
section
(D_MEM)
3.3.2.2
Initializing Variables at Load Time (--ram_model)
Initialization of variables at load time enhances performance by reducing boot time and by saving the
memory used by the initialization tables. To use this method, invoke the linker with the --ram_model
option.
When you use the --ram_model linker option, the linker sets the STYP_COPY bit in the .cinit section's
header. This tells the loader not to load the .cinit section into memory. (The .cinit section occupies no
space in the memory map.) The linker also sets the cinit symbol to -1 (normally, cinit points to the
beginning of the initialization tables). This indicates to the boot routine that the initialization tables are not
present in memory; accordingly, no run-time initialization is performed at boot time.
A loader must be able to perform the following tasks to use initialization at load time:
• Detect the presence of the .cinit section in the object file.
• Determine that STYP_COPY is set in the .cinit section header, so that it knows not to copy the .cinit
section into memory.
• Understand the format of the initialization tables.
Figure 3-3 illustrates the initialization of variables at load time.
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Run-Time Initialization
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Figure 3-3. Initialization at Load Time
Object file
.cinit
Memory
Loader
.bss
3.3.2.3
The --rom_model and --ram_model Linker Options
The following list outlines what happens when you invoke the linker with the --ram_model or --rom_model
option.
• The symbol _c_int00 is defined as the program entry point. The _c_int00 symbol is the start of the C
boot routine in boot.obj; referencing _c_int00 ensures that boot.obj is automatically linked in from the
appropriate run-time-support library.
• The .cinit output section is padded with a termination record to tell the boot routine (autoinitialize at run
time) or the loader (initialize at load time) when to stop reading initialization tables.
• When you initialize at load time (--ram_model option):
– The linker sets cinit to -1. This indicates that the initialization tables are not in memory, so no
initialization is performed at run time.
– The STYP_COPY flag (0010h) is set in the .cinit section header. STYP_COPY is the special
attribute that tells the loader to perform initialization directly and not to load the .cinit section into
memory. The linker does not allocate space in memory for the .cinit section.
• When you autoinitialize at run time (--rom_model option), the linker defines cinit as the starting address
of the .cinit section. The C boot routine uses this symbol as the starting point for autoinitialization.
3.3.3 Copy Tables
The RTS function copy_in can be used at run-time to move code and data around, usually from its load
address to its run address. This function reads size and location information from copy tables. The linker
automatically generates several kinds of copy tables. Refer to Section 8.8.
You can create and control code overlays with copy tables. See Section 8.8.4 for details and examples.
Using copy tables is similar to performing run-time relocations as described in Section 3.5, however copy
tables require a specific table format.
3.3.3.1
BINIT
The BINIT (boot-time initialization) copy table is special in that the target will automatically perform the
copying at auto-initialization time. Refer to Section 8.8.4.2 for more about the BINIT copy table name. The
BINIT copy table is copied immediately before .cinit processing.
3.3.3.2
CINIT
EABI .cinit tables are special kinds of copy tables. Refer to Section 3.3.2.1 for more about using the .cinit
section with the ROM model and Section 3.3.2.2 for more using it with the RAM model.
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Arguments to main
3.4
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Arguments to main
Some programs expect arguments to main (argc, argv) to be valid. Normally this isn't possible for an
embedded program, but the TI runtime does provide a way to do it. The user must allocate an .args
section of an appropriate size using the --args linker option. It is the responsibility of the loader to populate
the .args section. It is not specified how the loader determines which arguments to pass to the target. The
format of the arguments is the same as an array of pointers to char on the target.
See Section 8.4.4 for information about allocating memory for argument passing.
3.5
Run-Time Relocation
At times you may want to load code into one area of memory and move it to another area before running
it. For example, you may have performance-critical code in an external-memory-based system. The code
must be loaded into external memory, but it would run faster in internal memory. Because internal memory
is limited, you might swap in different speed-critical functions at different times.
The linker provides a way to handle this. Using the SECTIONS directive, you can optionally direct the
linker to allocate a section twice: first to set its load address and again to set its run address. Use the load
keyword for the load address and the run keyword for the run address. See Section 3.1.1 for more about
load and run addresses. If a section is assigned two addresses at link time, all labels defined in the
section are relocated to refer to the run-time address so that references to the section (such as branches)
are correct when the code runs.
If you provide only one allocation (either load or run) for a section, the section is allocated only once and
loads and runs at the same address. If you provide both allocations, the section is actually allocated as if it
were two separate sections of the same size.
Uninitialized sections (such as .bss) are not loaded, so the only significant address is the run address. The
linker allocates uninitialized sections only once; if you specify both run and load addresses, the linker
warns you and ignores the load address.
For a complete description of run-time relocation, see Section 8.5.6.
3.6
Additional Information
See the following sections and documents for additional information:
Section 8.4.4, "Allocate Memory for Use by the Loader to Pass Arguments (--arg_size Option)"
Section 8.4.12, "Define an Entry Point (--entry_point Option)"
Section 8.5.6.1 ,"Specifying Load and Run Addresses"
Section 8.8, "Linker-Generated Copy Tables"
Section 8.10.1, "Run-Time Initialization"
.label directive
Chapter 10, "Hex Conversion Utility Description"
"Run-Time Initialization," "Initialization by the Interrupt Vector," and "System Initialization" sections in the
TMS320C6000 Optimizing C/C++ Compiler User's Guide
Creating a Second-Level Bootloader for FLASH Bootloading on TMS320C6000 Platform With Code
Composer Studio (SPRA999).
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Chapter 4
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Assembler Description
The TMS320C6000 assembler translates assembly language source files into machine language object
files. These files are object modules, which are discussed in Chapter 2. Source files can contain the
following assembly language elements:
Assembler directives
Macro directives
Assembly language instructions
Topic
4.1
4.2
4.3
4.4
4.5
4.6
4.7
4.8
4.9
4.10
4.11
4.12
4.13
described in Chapter 5
described in Chapter 6
described in the TMS320C64x/C64x+ DSP CPU and
Instruction Set Reference Guide, TMS320C6740 DSP CPU
and Instruction Set Reference Guide, and TMS320C66x CPU
and Instruction Set Reference Guide.
...........................................................................................................................
Assembler Overview ...........................................................................................
The Assembler's Role in the Software Development Flow .......................................
Invoking the Assembler ......................................................................................
The Application Binary Interface ..........................................................................
Naming Alternate Directories for Assembler Input .................................................
Source Statement Format ....................................................................................
Literal Constants ................................................................................................
Assembler Symbols............................................................................................
Expressions ......................................................................................................
Built-in Functions and Operators .........................................................................
Source Listings ..................................................................................................
Debugging Assembly Source ..............................................................................
Cross-Reference Listings ....................................................................................
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41
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Assembler Overview
4.1
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Assembler Overview
The assembler does the following:
• Processes the source statements in a text file to produce a relocatable object file
• Produces a source listing (if requested) and provides you with control over this listing
• Allows you to divide your code into sections and maintain a section program counter (SPC) for each
section of object code
• Defines and references global symbols and appends a cross-reference listing to the source listing (if
requested)
• Allows conditional assembly
• Supports macros, allowing you to define macros inline or in a library
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4.2
The Assembler's Role in the Software Development Flow
Figure 4-1 illustrates the assembler's role in the software development flow. The shaded portion highlights
the most common assembler development path. The assembler accepts assembly language source files
as input, both those you create and those created by the TMS320C6000 C/C++ compiler.
Figure 4-1. The Assembler in the TMS320C6000 Software Development Flow
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Invoking the Assembler
4.3
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Invoking the Assembler
To invoke the assembler, enter the following:
cl6x input file [options]
cl6x
input file
options
is the command that invokes the assembler through the compiler. The compiler considers
any file with an .asm extension to be an assembly file and invokes the assembler.
names the assembly language source file.
identify the assembler options that you want to use. Options are case sensitive and can
appear anywhere on the command line following the command. Precede each option with
one or two hyphens as shown.
The valid assembler options are listed in Table 4-1.
Some runtime model options, such as --big_endian and --silicon version, influence the behavior of the
assembler. These options are passed to the compiler, assembler, and linker from the shell utility, which is
detailed in the TMS320C6000 Optimizing Compiler User's Guide.
Table 4-1. TMS320C6000 Assembler Options
Option
Alias
-ar=num
Description
Suppresses the assembler remark identified by num. A remark is an informational assembler
message that is less severe than a warning. If you do not specify a value for #, all remarks are
suppressed.
--asm_define=name[=def]
-ad
Sets the name symbol. This is equivalent to defining name with a .set directive in the case of a
numeric value or with an .asg directive otherwise. If value is omitted, the symbol is set to 1.
See Section 4.8.5.
--asm_dependency
-apd
Performs preprocessing for assembly files, but instead of writing preprocessed output, writes a
list of dependency lines suitable for input to a standard make utility. The list is written to a file
with the same name as the source file but with a .ppa extension.
--asm_includes
-api
Performs preprocessing for assembly files, but instead of writing preprocessed output, writes a
list of files included with the .include directive. The list is written to a file with the same name
as the source file but with a .ppa extension.
--asm_listing
-al
Produces a listing file with the same name as the input file with a .lst extension.
--asm_listing_cross_reference
-ax
Produces a cross-reference table and appends it to the end of the listing file. If you do not
request a listing file but use the --asm_listing_cross_reference option, the assembler creates a
listing file automatically, naming it with the same name as the input file with a .lst extension.
--asm_undefine=name
-au
Undefines the predefined constant name, which overrides any --asm_define options for the
specified constant.
--cmd_file=filename
-@
Appends the contents of a file to the command line. You can use this option to avoid limitations
on command line length imposed by the host operating system. Use an asterisk or a
semicolon (* or ;) at the beginning of a line in the command file to include comments.
Comments that begin in any other column must begin with a semicolon. Within the command
file, filenames or option parameters containing embedded spaces or hyphens must be
surrounded with quotation marks. For example: "this-file.asm"
--include_file=filename
-ahi
Includes the specified file for the assembly module. The file is included before source file
statements. The included file does not appear in the assembly listing files.
--include_path=pathname
-I
Specifies a directory where the assembler can find files named by the .copy, .include, or .mlib
directives. There is no limit to the number of directories you can specify in this manner; each
pathname must be preceded by the --include_path option. See Section 4.5.1.
--quiet
-q
Suppresses the banner and progress information (assembler runs in quiet mode).
--symdebug:dwarf or
--symdebug:none
-g
(DWARF is on by default) Enables assembler source debugging in the C source debugger.
Line information is output to the object module for every line of source in the assembly
language source file. You cannot use this option on assembly code that contains .line
directives. See Section 4.12.
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The Application Binary Interface
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4.4
The Application Binary Interface
An Application Binary Interface (ABI) defines the low level interface between object files, and between an
executable and its execution environment. The ABI exists to allow ABI-compliant object code to link
together, regardless of its source, and allows the resulting executable to run on any system that supports
that ABI.
The C6000 compiler supports only the C6000 EABI ABI. For details, see The C6000 Embedded
Application Binary Interface Application Report (SPRAB89).
COFF object files are no longer supported in v8.0 and later versions of the TI Code Generation Tools. If
you would like to produce COFF output files, please use v7.4 of the Code Generation Tools and refer to
SPRU186 for documentation.
Object modules conforming to different ABIs cannot be linked together. The linker detects this situation
and generates an error; you will need to recompile C code or reassemble assembly code in order to move
from COFF to ELF. Note that converting an assembly file from the COFF API to EABI requires some
changes to the assembly code. See Chapter 14 of The C6000 Embedded Application Binary Interface
Application Report (SPRAB89 for details.
4.5
Naming Alternate Directories for Assembler Input
The .copy, .include, and .mlib directives tell the assembler to use code from external files. The .copy and
.include directives tell the assembler to read source statements from another file, and the .mlib directive
names a library that contains macro functions. Chapter 5 contains examples of the .copy, .include, and
.mlib directives. The syntax for these directives is:
.copy ["]filename["]
.include ["]filename["]
.mlib ["]filename["]
The filename names a copy/include file that the assembler reads statements from or a macro library that
contains macro definitions. If filename begins with a number the double quotes are required. Quotes are
recommended so that there is no issue in dealing with path information that is included in the filename
specification or path names that include white space. The filename may be a complete pathname, a partial
pathname, or a filename with no path information.
The assembler searches for the file in the following locations in the order given:
1. The directory that contains the current source file. The current source file is the file being assembled
when the .copy, .include, or .mlib directive is encountered.
2. Any directories named with the --include_path option
3. Any directories named with the C6X_A_DIR environment variable
4. Any directories named with the C6X_C_DIR environment variable
Because of this search hierarchy, you can augment the assembler's directory search algorithm by using
the --include_path option (described in Section 4.5.1) or the C6X_A_DIR environment variable (described
in Section 4.5.2). The C6X_C_DIR environment variable is discussed in the TMS320C6000 Optimizing
Compiler User's Guide.
4.5.1 Using the --include_path Assembler Option
The --include_path assembler option names an alternate directory that contains copy/include files or
macro libraries. The format of the --include_path option is as follows:
cl6x --include_path= pathname source filename [other options]
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Naming Alternate Directories for Assembler Input
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There is no limit to the number of --include_path options per invocation; each --include_path option names
one pathname. In assembly source, you can use the .copy, .include, or .mlib directive without specifying
path information. If the assembler does not find the file in the directory that contains the current source
file, it searches the paths designated by the --include_path options.
For example, assume that a file called source.asm is in the current directory; source.asm contains the
following directive statement:
.copy "copy.asm"
Assume the following paths for the copy.asm file:
UNIX:
Windows:
/tools/files/copy.asm
c:\tools\files\copy.asm
You could set up the search path with the commands shown below:
Operating System
Enter
UNIX (Bourne shell)
cl6x --include_path=/tools/files source.asm
Windows
cl6x --include_path=c:\tools\files source.asm
The assembler first searches for copy.asm in the current directory because source.asm is in the current
directory. Then the assembler searches in the directory named with the --include_path option.
4.5.2 Using the C6X_A_DIR Environment Variable
An environment variable is a system symbol that you define and assign a string to. The assembler uses
the C6X_A_DIR environment variable to name alternate directories that contain copy/include files or
macro libraries.
The assembler looks for the C6X_A_DIR environment variable and then reads and processes it. If the
assembler does not find the C6X_A_DIR variable, it then searches for C6X_C_DIR. The processorspecific variables are useful when you are using Texas Instruments tools for different processors at the
same time.
See the TMS320C6000 Optimizing Compiler User's Guide for details on C6X_C_DIR.
The command syntax for assigning the environment variable is as follows:
44
Operating System
Enter
UNIX (Bourne Shell)
C6X_A_DIR=" pathname1 ; pathname2 ; . . . "; export C6X_A_DIR
Windows
set C6X_A_DIR= pathname1 ; pathname2 ; . . .
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The pathnames are directories that contain copy/include files or macro libraries. The pathnames must
follow these constraints:
• Pathnames must be separated with a semicolon.
• Spaces or tabs at the beginning or end of a path are ignored. For example the space before and after
the semicolon in the following is ignored:
set C6X_A_DIR= c:\path\one\to\tools ; c:\path\two\to\tools
•
Spaces and tabs are allowed within paths to accommodate Windows directories that contain spaces.
For example, the pathnames in the following are valid:
set C6X_A_DIR=c:\first path\to\tools;d:\second path\to\tools
In assembly source, you can use the .copy, .include, or .mlib directive without specifying path information.
If the assembler does not find the file in the directory that contains the current source file or in directories
named by the --include_path option, it searches the paths named by the environment variable.
For example, assume that a file called source.asm contains these statements:
.copy "copy1.asm"
.copy "copy2.asm"
Assume the following paths for the files:
UNIX:
Windows:
/tools/files/copy1.asm and /dsys/copy2.asm
c:\tools\files\copy1.asm and c:\dsys\copy2.asm
You could set up the search path with the commands shown below:
Operating System
Enter
UNIX (Bourne shell)
C6X_A_DIR="/dsys"; export C6X_A_DIR
cl6x --include_path=/tools/files source.asm
Windows
set C6X_A_DIR=c:\dsys
cl6x --include_path=c:\tools\files source.asm
The assembler first searches for copy1.asm and copy2.asm in the current directory because source.asm
is in the current directory. Then the assembler searches in the directory named with the --include_path
option and finds copy1.asm. Finally, the assembler searches the directory named with C6X_A_DIR and
finds copy2.asm.
The environment variable remains set until you reboot the system or reset the variable by entering one of
these commands:
Operating System
Enter
UNIX (Bourne shell)
unset C6X_A_DIR
Windows
set C6X_A_DIR=
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Source Statement Format
4.6
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Source Statement Format
Each line in a TMS320C6000 assembly input file can be empty, a comment, an assembler directive, a
macro invocation, or an assembly instruction.
Assembly language source statements can contain five ordered fields (label, mnemonic, unit specifier,
operand list, and comment). The general syntax for source statements is as follows:
[label[:]] [||] [[ register ]] mnemonic [unit specifier] [operand list][;comment]
A label can only be associated with the first instruction in an execute packet (a group of instructions that is
to be executed in parallel).
Following are examples of source statements:
two
Label:
.set 2
; Symbol Two = 2
MVK
two,A2 ; Move 2 into register A2
.word 016h
; Initialize a word with 016h
There is no limit on characters per source statement. Each statement is one logical line of the input file.
Use a backslash (\) to indicate continuation of the same instruction/directive across multiple lines.
Follow these guidelines:
• All statements must begin with a label, a blank, an asterisk, or a semicolon.
• Labels are optional for most statements; if used, they must begin in column 1.
• One or more space or tab characters must separate each field.
• Comments are optional. Comments that begin in column 1 can begin with an asterisk or a semicolon (*
or ;), but comments that begin in any other column must begin with a semicolon.
• In a conditional instruction, the condition register must be surrounded by square brackets.
• The functional unit specifier is optional. If you do not specify the functional unit, the assembler assigns
a legal functional unit based on the mnemonic field and the other instructions in the execute packet.
NOTE: A mnemonic cannot begin in column 1 or it will be interpreted as a label. Mnemonic opcodes
and assembler directive names without the . prefix are valid label names. Remember to
always use whitespace before the mnemonic, or the assembler will think the identifier is a
new label definition.
The following sections describe each of the fields.
4.6.1 Label Field
A label must be a legal identifier (see Section 4.8.1) placed in column 1. Every instruction may optionally
have a label. Many directives allow a label, and some require a label.
A label can be followed by a colon (:). The colon is not treated as part of the label name. If you do not use
a label, the first character position must contain a blank, a semicolon, or an asterisk. You cannot use a
label on an instruction that is in parallel with a previous instruction.
When you use a label on an assembly instruction or data directive, an assembler symbol (Section 4.8)
with the same name is created. Its value is the current value of the section program counter (SPC, see
Section 2.4.5). This symbol represents the address of that instruction. In the following example, the .word
directive is used to create an array of 3 words. Because a label was used, the assembly symbol Start
refers to the first word, and the symbol will have the value 40h.
.
.
.
.
.
.
.
.
9
10 00000040 0000000A
00000044 00000003
00000048 00000007
46
* Assume some code was assembled
Start: .word 0Ah,3,7
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Source Statement Format
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When a label appears on a line by itself, it points to the instruction on the next line (the SPC is not
incremented):
1 00000000
2 00000000 00000003
Here:
.word 3
A label on a line by itself is equivalent to writing:
Here: .equ $
; $ provides the current value of the SPC
If you do not use a label, the character in column 1 must be a blank, an asterisk, or a semicolon.
4.6.2 Mnemonic Field
The mnemonic field follows the label field. The mnemonic field cannot start in column 1; if it does, it is
interpreted as a label. There is one exception: the parallel bars (||) of the mnemonic field can start in
column 1. The mnemonic field contains one of the following items:
• Parallel bars (||) indicate instructions that are in parallel with a previous instruction. You can have up to
eight instructions that will be executed in parallel. The following example demonstrates six instructions
to be executed in parallel:
||
||
||
||
||
•
Inst1
Inst2
Inst3
Inst4
Inst5
Inst6
Inst7
These five instructions run
in parallel with the first
instruction.
Square brackets ([ ]) indicate conditional instructions. The machine-instruction mnemonic is executed
based on the value of the register within the brackets; valid register names are A0, A1, A2, B0, B1, and
B2. These registers are often called predicate registers.
The instruction is executed if the value of the register is nonzero. If the register name is preceded by
an exclamation point (!), then the instruction is executed if the value of the register is 0. For example:
[A1] ZERO A2
; If A1 is not equal to zero, A2 = 0
The preceding exclamation point, if specified, is called a "logical NOT operator" or a "unary NOT
operator".
Next, the mnemonic field contains one of the following items:
• Machine-instruction mnemonic (such as ADDK, MVKH, B)
• Assembler directive (such as .data, .list, .equ, .macro, .var, .mexit)
The || and "[predicate register]" constructs are not legal in combination with an assembler directive.
• Macro invocation
4.6.3 Unit Specifier Field
The unit specifier field is an optional field that follows the mnemonic field for machine-instruction
mnemonics. The unit specifier field begins with a period (.) followed by a functional unit specifier. In
general, one instruction can be assigned to each functional unit in a single instruction cycle. There are
eight functional units, two of each functional type:
.D1 and .D2
Data/addition/subtraction
.L1 and .L2
ALU/compares/long data arithmetic
.M1 and .M2
Multiply
.S1 and .S2
Shift/ALU/branch/bit field
ALU refers to an arithmetic logic unit.
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There are several ways to use the unit specifier field:
• You can specify the particular functional unit (for example, .D1).
• You can specify only the functional type (for example, .M), and the assembler assigns the specific unit
(for example, .M2).
• If you do not specify the functional unit, the assembler assigns the functional unit based on the
mnemonic field, operand fields, and other instructions in the same execute packet.
For more information on functional units, including which assembly instructions require which functional
type, see the TMS320C64x/C64x+ DSP CPU and Instruction Set Reference Guide, or TMS320C66x DSP
CPU and Instruction Set Reference Guide, or TMS320C674x CPU and Instruction Set Reference Guide.
4.6.4 Operand Field
The operand field follows the mnemonic field and contains zero or more comma-separated operands. An
operand can be one of the following:
• an immediate operand (usually a constant or symbol) (see Section 4.7 and Section 4.8)
• a register operand
• a memory reference operand
• an expression that evaluates to one of the above (see Section 4.9)
An immediate operand is encoded directly in the instruction. The value of an immediate operand must be
a constant expression. Most instructions with an immediate operand require an absolute constant
expression, such as 1234. Some instructions (such as a call instruction) allow a relocatable constant
expression, such as a symbol defined in another file. (See Section 4.9 for details about types of
expressions.)
A register operand is a special pre-defined symbol that represents a CPU register.
A memory reference operand uses one of several memory addressing modes to refer to a location in
memory. Memory reference operands use a special target-specific syntax defined in the appropriate CPU
and Instruction Set Reference Guide.
You must separate operands with commas. Not all operand types are supported for all operands. See the
description of the specific instruction in the CPU and Instruction Set Reference Guide for your device
family.
4.6.5 Comment Field
A comment can begin in any column and extends to the end of the source line. A comment can contain
any ASCII character, including blanks. Comments are printed in the assembly source listing, but they do
not affect the assembly.
A source statement that contains only a comment is valid. If it begins in column 1, it can start with a
semicolon ( ; ) or an asterisk ( *). Comments that begin anywhere else on the line must begin with a
semicolon. The asterisk identifies a comment only if it appears in column 1.
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4.7
Literal Constants
A literal constant (also known as a literal or in some other documents as an immediate value) is a value
that represents itself, such as 12, 3.14, or "hello".
The assembler supports several types of literals:
• Binary integer literals
• Octal integer literals
• Decimal integer literals
• Hexadecimal integer literals
• Character literals
• Character string literals
• Floating-point literals
Error checking for invalid or incomplete literals is performed.
4.7.1 Integer Literals
The assembler maintains each integer literal internally as a 32-bit signless quantity. Literals are
considered unsigned values, and are not sign extended. For example, the literal 00FFh is equal to 00FF
(base 16) or 255 (base 10); it does not equal -1. which is 0FFFFFFFFh (base 16). Note that if you store
0FFh in a .byte location, the bits will be exactly the same as if you had stored -1. It is up to the reader of
that location to interpret the signedness of the bits.
4.7.1.1
Binary Integer Literals
A binary integer literal is a string of up to 32 binary digits (0s and 1s) followed by the suffix B (or b). Binary
literals of the form "0[bB][10]+" are also supported. If fewer than 32 digits are specified, the assembler
right justifies the value and fills the unspecified bits with zeros. These are examples of valid binary literals:
00000000B
0100000b
01b
11111000B
0b00101010
0B101010
4.7.1.2
Literal equal to 010 or 016
Literal equal to 3210 or 2016
Literal equal to 110 or 116
Literal equal to 24810 or 0F816
Literal equal to 4210 or 2A16
Literal equal to 4210 or 2A16
Octal Integer Literals
An octal integer literal is a string of up to 11 octal digits (0 through 7) followed by the suffix Q (or q). Octal
literals may also begin with a 0, contain no 8 or 9 digits, and end with no suffix. These are examples of
valid octal literals:
10Q
054321
100000Q
226q
Literal equal to 810 or 816
Literal equal to 2273710 or 58D116
Literal equal to 3276810 or 800016
Literal equal to 15010 or 9616
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Literal Constants
4.7.1.3
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Decimal Integer Literals
A decimal integer literal is a string of decimal digits ranging from -2147 483 648 to 4 294 967 295. These
are examples of valid decimal integer literals:
1000
-32768
25
4815162342
4.7.1.4
Literal equal
Literal equal
Literal equal
Literal equal
to
to
to
to
100010 or 3E816
-32 76810 or -800016
2510 or 1916
481516234210 or 11F018BE616
Hexadecimal Integer Literals
A hexadecimal integer literal is a string of up to eight hexadecimal digits followed by the suffix H (or h) or
preceded by 0x. A hexadecimal literal must begin with a decimal value (0-9) if it is indicated by the H or h
suffix.
Hexadecimal digits include the decimal values 0-9 and the letters A-F or a-f. If fewer than eight
hexadecimal digits are specified, the assembler right-justifies the bits.
These are examples of valid hexadecimal literals:
78h
0x78
0Fh
37ACh
4.7.1.5
Literal equal to 12010 or 007816
Literal equal to 12010 or 007816
Literal equal to 1510 or 000F16
Literal equal to 1425210 or 37AC16
Character Literals
A character literal is a single character enclosed in single quotes. The characters are represented
internally as 8-bit ASCII characters. Two consecutive single quotes are required to represent each single
quote that is part of a character literal. A character literal consisting only of two single quotes is valid and
is assigned the value 0. These are examples of valid character literals:
'a'
Defines the character literal a and is represented internally as 6116
'C'
Defines the character literal C and is represented internally as 4316
''''
Defines the character literal ' and is represented internally as 2716
''
Defines a null character and is represented internally as 0016
Notice the difference between character literals and character string literals (Section 4.7.2 discusses
character strings). A character literal represents a single integer value; a string is a sequence of
characters.
4.7.2 Character String Literals
A character string is a sequence of characters enclosed in double quotes. Double quotes that are part of
character strings are represented by two consecutive double quotes. The maximum length of a string
varies and is defined for each directive that requires a character string. Characters are represented
internally as 8-bit ASCII characters.
These are examples of valid character strings:
"sample program"
"PLAN ""C"""
50
defines the 14-character string sample program.
defines the 8-character string PLAN "C".
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Character strings are used for the following:
• Filenames, as in .copy "filename"
• Section names, as in .sect "section name"
• Data initialization directives, as in .byte "charstring"
• Operands of .string directives
4.7.3 Floating-Point Literals
A floating-point literal is a string of decimal digits followed by a required decimal point, an optional
fractional portion, and an optional exponent portion. The syntax for a floating-point number is:
[ +|- ] nnn . [ nnn] [ E|e [ +|- ] nnn ]
Replace nnn with a string of decimal digits. You can precede nnn with a + or a -. You must specify a
decimal point. For example, 3.e5 is valid, but 3e5 is not valid. The exponent indicates a power of 10.
These are examples of valid floating-point literals:
3.0
3.14
3.
-0.314e13
+314.59e-2
The assembler syntax does not support all C89-style float literals nor C99-style hexadecimal constants,
but the $strtod built-in mathematical function supports both. If you want to specify a floating-point literal
using one of those formats, use $strtod. For example:
$strtod(".3")
$strtod("0x1.234p-5")
You cannot directly use NaN, Inf, or -Inf as floating-point literals. Instead, use $strtod to express these
values. The "NaN" and "Inf" strings are handled case-insensitively. See Section 4.10.1 for built-in
functions.
$strtod("NaN")
$strtod("Inf")
4.8
Assembler Symbols
An assembler symbol is a named 32-bit signless integer value, usually representing an address or
absolute integer. A symbol can represent such things as the starting address of a function, variable, or
section. The name of a symbol must be a legal identifier. The identifier becomes a symbolic
representation of the symbol's value, and may be used in subsequent instructions to refer to the symbol's
location or value.
Some assembler symbols become external symbols, and are placed in the object file's symbol table. A
symbol is valid only within the module in which it is defined, unless you use the .global directive or the .def
directive to declare it as an external symbol (see .global directive).
See Section 2.6 for more about symbols and the symbol tables in object files.
4.8.1 Identifiers
Identifiers are names used as labels, registers, symbols, and substitution symbols. An identifier is a string
of alphanumeric characters, the dollar sign, and underscores (A-Z, a-z, 0-9, $, and _). The first character
in an identifier cannot be a number, and identifiers cannot contain embedded blanks. The identifiers you
define are case sensitive; for example, the assembler recognizes ABC, Abc, and abc as three distinct
identifiers.
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4.8.2 Labels
An identifier used as a label becomes an assembler symbol, which represent an address in the program.
Labels within a file must be unique.
NOTE: A mnemonic cannot begin in column 1 or it will be interpreted as a label. Mnemonic opcodes
and assembler directive names without the . prefix are valid label names. Remember to
always use whitespace before the mnemonic, or the assembler will think the identifier is a
new label definition.
Symbols derived from labels can also be used as the operands of .bss, .global, .ref, or .def directives.
.global label1
label2: MVKL
MVKH
B
NOP
label2, B3
label2, B3
label1
5
4.8.3 Local Labels
Local labels are special labels whose scope and effect are temporary. A local label can be defined in two
ways:
• $n, where n is a decimal digit in the range 0-9. For example, $4 and $1 are valid local labels. See
Example 4-1.
• name?, where name is any legal identifier as described above. The assembler replaces the question
mark with a period followed by a unique number. When the source code is expanded, you will not see
the unique number in the listing file. Your label appears with the question mark as it did in the source
definition. See Example 4-2.
You cannot declare these types of labels as global.
Normal labels must be unique (they can be declared only once), and they can be used as constants in the
operand field. Local labels, however, can be undefined and defined again. Local labels cannot be defined
by directives.
A
•
•
•
•
52
local label can be undefined or reset in one of these ways:
By using the .newblock directive
By changing sections (using a .sect, .text, or .data directive)
By entering an include file (specified by the .include or .copy directive)
By leaving an include file (specified by the .include or .copy directive)
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Example 4-1. Local Labels of the Form $n
This is an example of code that declares and uses a local label legally:
$1:
SUB
[A1] B
SUBC
NOP
A1,1,A1
$1
A3,A0,A3
4
.newblock
$1
SUB
[A2] B
MPY
NOP
; undefine $1 to use it again
A2,1,A2
$1
A3,A3,A3
4
The following code uses a local label illegally:
$1:
SUB
[A1] B
SUBC
NOP
$1
SUB
[A2] B
MPY
NOP
A1,1,A1
$1
A3,A0,A3
4
A2,1,A2
$1
A3,A3,A3
4
; WRONG - $1 is multiply defined
The $1 label is not undefined before being reused by the second branch instruction. Therefore, $1 is
redefined, which is illegal.
Local labels are especially useful in macros. If a macro contains a normal label and is called more than
once, the assembler issues a multiple-definition error. If you use a local label and .newblock within a
macro, however, the local label is used and reset each time the macro is expanded.
Up to ten local labels of the $n form can be in effect at one time. Local labels of the form name? are not
limited. After you undefine a local label, you can define it and use it again. Local labels do not appear in
the object code symbol table.
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Example 4-2. Local Labels of the Form name?
****************************************************************
** First definition of local label mylab
**
****************************************************************
nop
mylab? nop
B mylab?
nop 5
****************************************************************
** Include file has second definition of mylab
**
****************************************************************
.copy "a.inc"
****************************************************************
** Third definition of mylab, reset upon exit from .include
**
****************************************************************
mylab? nop
B mylab?
nop 5
****************************************************************
** Fourth definition of mylab in macro, macros use different **
** namespace to avoid conflicts
**
****************************************************************
mymac .macro
mylab? nop
B mylab?
nop 5
.endm
****************************************************************
** Macro invocation
**
****************************************************************
mymac
****************************************************************
** Reference to third definition of mylab. Definition is not **
** reset by macro invocation.
**
****************************************************************
B mylab?
nop 5
****************************************************************
** Changing section, allowing fifth definition of mylab
**
****************************************************************
.sect "Sect_One"
nop
mylab? .word 0
nop
nop
B mylab?
nop 5
****************************************************************
** The .newblock directive allows sixth definition of mylab
**
****************************************************************
.newblock
mylab? .word 0
nop
nop
B mylab?
nop 5
For more information about using labels in macros see Section 6.6.
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4.8.4 Symbolic Constants
A symbolic constant is a symbol with a value that is an absolute constant expression (see Section 4.9). By
using symbolic constants, you can assign meaningful names to constant expressions. The .set and
.struct/.tag/.endstruct directives enable you to set symbolic constants (see Define Assembly-Time
Constant). Once defined, symbolic constants cannot be redefined.
If you use the .set directive to assign a value to a symbol , the symbol becomes a symbolic constant and
may be used where a constant expression is expected. For example:
sym
.set 3
MVK sym,B1
You can also use the .set directive to assign symbolic constants for other symbols, such as register
names. In this case, the symbolic constant becomes a synonym for the register:
sym
.set B1
MVK 10,sym
The following example shows how the .set directive can be used with the .struct, .tag. and .endstruct
directives. It creates the symbolic constants K, maxbuf, item, value, delta, and i_len.
K
.set
maxbuf .set
1024
2*K
; constant definitions
item
value
delta
i_len
.struct
.int
.int
.endstruct
;
;
;
;
item structure
value offset =
delta offset =
item size
=
definition
0
4
8
array
.tag item
.bss array, i_len*K ; declare an array of K "items"
.text
LDW
*+B14(array.delta + 2*i_len),A1
; access array [2].delta
The assembler also has many predefined symbolic constants; these are discussed in Section 4.8.6.
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4.8.5 Defining Symbolic Constants (--asm_define Option)
The --asm_define option equates a constant value or a string with a symbol. The symbol can then be used
in place of a value in assembly source. The format of the --asm_define option is as follows:
cl6x --asm_define=name[=value]
The name is the name of the symbol you want to define. The value is the constant or string value you
want to assign to the symbol. If the value is omitted, the symbol is set to 1. If you want to define a quoted
string and keep the quotation marks, do one of the following:
•
•
•
For Windows, use --asm_define= name ="\" value \"". For example, --asm_define=car="\"sedan\""
For UNIX, use --asm_define= name ='" value "'. For example, --asm_define=car='"sedan"'
For Code Composer, enter the definition in a file and include that file with the --cmd_file (or -@) option.
Once you have defined the name with the --asm_define option, the symbol can be used with assembly
directives and instructions as if it had been defined with the .set directive. For example, on the command
line you enter:
cl6x --asm_define=SYM1=1 --asm_define=SYM2=2 --asm_define=SYM3=3 --asm_define=SYM4=4 value.asm
Since you have assigned values to SYM1, SYM2, SYM3, and SYM4, you can use them in source code.
Example 4-3 shows how the value.asm file uses these symbols without defining them explicitly.
Within assembler source, you can test the symbol defined with the --asm_define option with these
directives:
Type of Test
Directive Usage
Existence
.if $isdefed(" name ")
Nonexistence
.if $isdefed(" name ") = 0
Equal to value
.if name = value
Not equal to value
.if name != value
The argument to the $isdefed built-in function must be enclosed in quotes. The quotes cause the
argument to be interpreted literally rather than as a substitution symbol.
Example 4‑3. Using Symbolic Constants Defined on Command Line
IF_4:
IF_5:
IF_6:
IF_7:
56
.if
.byte
.else
.byte
.endif
SYM4 = SYM2 * SYM2
SYM4
; Equal values
SYM2 * SYM2
; Unequal values
.if
.byte
.else
.byte
.endif
SYM1 <= 10
10
; Less than / equal
SYM1
; Greater than
.if
.byte
.else
.byte
.endif
SYM3 * SYM2 != SYM4 + SYM2
SYM3 * SYM2
; Unequal value
.if
.byte
.elseif
.byte
.endif
SYM1 = SYM2
SYM1
SYM2 + SYM3 = 5
SYM2 + SYM3
SYM4 + SYM4
; Equal values
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4.8.6 Predefined Symbolic Constants
The assembler has several types of predefined symbols.
$, the dollar-sign character, represents the current value of the section program counter (SPC).
In addition, the following predefined processor symbolic constants are available:
Table 4-2. C6000 Processor Symbolic Constants
Symbol name
Description
_ _TI_EABI_ _
Set to 1 if EABI is enabled. EABI is now the only supported ABI; see
Section 4.4.
.TMS320C6X
Always set to 1
.TMS320C6400_PLUS
Set to 1 if target is C6400+, C6740, or C6600; otherwise 0
.TMS320C6600
Set to 1 if target is C6600, otherwise 0
.TMS320C6740
Set to 1 if target is C6740 or C6600, otherwise 0
.LITTLE_ENDIAN
Set to 1 if little-endian mode is selected (the -me assembler option is not
used); otherwise 0
.ASSEMBLER_VERSION
Set to major * 1000000 + minor * 1000 + patch version.
.BIG_ENDIAN
Set to 1 if big-endian mode is selected (the -me assembler option is used);
otherwise 0
.SMALL_MODEL
Set to 1 if --memory_model:code=near and --memory_model:data=near,
otherwise 0.
.LARGE_MODEL
Set to 1 if .SMALL_MODEL is 0, otherwise 0.
4.8.7 Registers
The names of C6000 registers are predefined symbols, including A0-A15 and B0-B15; and A16-31 and
B16-31.
In addition, control register names are predefined symbols.
Register symbols and aliases can be entered as all uppercase or all lowercase characters.
Control register symbols can be entered in all upper-case or all lower-case characters. For example, CSR
can also be entered as csr.
See the "Register Conventions" section of the TMS320C6000 Optimizing Compiler User's Guide for
details about the registers and their uses.
Table 4-3. CPU Control Registers
Register
Description
AMR
Addressing mode register
CSR
Control status register
DNUM
DSP core number register
ECR
Exception clear register
EFR
Exception flag register
FADCR
(C6740 and C6600 only) Floating-point adder configuration register
FAUCR
(C6740 and C6600 only) Floating-point auxiliary configuration register
FMCR
(C6740 and C6600 only) Floating-point multiplier configuration register
GFPGFR
Galois field polynomial generator function register
GPLYA
GMPY A-side polynomial register
GPLYB
GMPY B-side polynomial register
ICR
Interrupt clear register
IER
Interrupt enable register
IERR
Interrupt exception report register
IFR
Interrupt flag register (read only)
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Table 4-3. CPU Control Registers (continued)
58
Register
Description
ILC
Inner loop count register
IRP
Interrupt return pointer
ISR
Interrupt set register
ISTP
Interrupt service table pointer
ITSR
Interrupt task state register
NRP
Nonmaskable interrupt return pointer
NTSR
NMI/Exception task state register
PCE1
Program counter, E1 phase
REP
Restricted entry point address register
RILC
Reload inner loop count register
SSR
Saturation status register
TSCH
Time-stamp counter (high 32) register
TSCL
Time-stamp counter (low 32) register
TSR
Task status register
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4.8.8 Register Pairs
Many instructions in the C6000 instruction set across the various available target processors support a 64bit register operand that can be specified as a register pair.
A register pair should be specified on the A side or the B side, depending on which functional unit an
instruction is to be executed on, and whether a cross functional unit data path is utilized by the instruction.
You cannot mix A-side and B-side registers in the same register pair operand.
The syntax for a register pair is as follows where (n%2 == 0):
Rn+1:Rn
The legal register pairs are:
A1:A0
A3:A2
A5:A4
A7:A6
A9:A8
A11:A10
A13:A12
A15:A14
A17:A16
A19:A18
A21:A20
A23:A22
A25:A24
A27:A26
A29:A30
A31:A32
B1:B0
B3:B2
B5:B4
B7:B6
B9:B8
B11:B10
B13:B12
B15:B14
B17:B16
B19:B18
B21:B20
B23:B22
B25:B24
B27:B26
B29:B30
B31:B32
Here is an example of an ADD instruction that uses a register pair operand:
ADD.L1 A5:A4,A1,A3:A2
For details on using register pairs in linear assembly, see the TMS320C6000 Optimizing Compiler User's
Guide.
For more information on functional units, including which assembly instructions require which functional
type, see the TMS320C64x/C64x+ DSP CPU and Instruction Set Reference Guide, TMS320C66x CPU
and Instruction Set Reference Guide, or TMS320C6740 DSP CPU and Instruction Set Reference Guide.
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4.8.9 Register Quads (C6600 Only)
Several instructions in the C6600 instruction set support a 128-bit register operand which can be specified
as a register quad.
A register quad should be specified on the A side or the B side, depending on which functional unit an
instruction is to be executed on, and whether a cross functional unit data path is utilized by the instruction.
You cannot mix A-side and B-side registers in the same register quad operand.
The general syntax for a register quad is as follows, where (n%4 == 0):
Rn+3:Rn+2:Rn+1:Rn
or
Rn+3::Rn
The legal register quads are:
A Register Quads
Short Form
B Register Quads
Short Form
A3:A2:A1:A0
A3::A0
B3:B2:B1:B0
B3::B0
A7:A6:A5:A4
A7::A4
B7:B6:B5:B4
B7::B4
A11:A10:A9:A8
A11::A8
B11:B10:B9:B8
B11::B8
A15:A14:A13:A12
A15::A12
B15:B14:B13:B12
B15::B12
A19:A18:A17:A16
A19::A16
B19:B18:B17:B16
B19::B16
A23:A22:A21:A20
A23::A20
B23:B22:B21:B20
B23::B20
A27:A26:A25:A24
A27::A24
B27:B26:B25:B24
B27::B24
A31:A30:A29:A28
A31::A28
B31:B30:B29:B28
B31::B28
Here is an example of an ADD instruction that uses register quad operands:
QMPYSP
.M1
A27:A26:A25:A24, A11:A10:A9:A8, A19:A18:A17:A16
For details on using register quads in C6600 linear assembly, see the TMS320C6000 Optimizing Compiler
User's Guide.
For more information on functional units, including which assembly instructions require which functional
type, see the TMS320C66x CPU and Instruction Set Reference Guide.
4.8.10 Substitution Symbols
Symbols can be assigned a string value. This enables you to create aliases for character strings by
equating them to symbolic names. Symbols that represent character strings are called substitution
symbols. When the assembler encounters a substitution symbol, its string value is substituted for the
symbol name. Unlike symbolic constants, substitution symbols can be redefined.
A string can be assigned to a substitution symbol anywhere within a program; for example:
.global
.asg
.asg
.asg
LDW
NOP
STW
_table
"B14", PAGEPTR
"*+B15(4)", LOCAL1
"*+B15(8)", LOCAL2
*+PAGEPTR(_table),A0
4
A0,LOCAL1
When you are using macros, substitution symbols are important because macro parameters are actually
substitution symbols that are assigned a macro argument. The following code shows how substitution
symbols are used in macros:
MAC .macro src1, src2, dst ; Multiply/Accumulate macro
MPY
src1, src2, src2
NOP
ADD
src2, dst, dst
.endm
* MAC macro invocation
MAC
A0,A1,A2
See Chapter 6 for more information about macros.
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4.9
Expressions
Nearly all values and operands in assembly language are expressions, which may be any of the following:
• a literal constant
• a register
• a register pair
• a memory reference
• a symbol
• a built-in function invocation
• a mathematical or logical operation on one or more expressions
This section defines several types of expressions that are referred to throughout this document. Some
instruction operands accept limited types of expressions. For example, the .if directive requires its operand
be an absolute constant expression with an integer value. Absolute in the context of assembly code
means that the value of the expression must be known at assembly time.
A constant expression is any expression that does not in any way refer to a register or memory reference.
An immediate operand will usually not accept a register or memory reference. It must be given a constant
expression. Constant expressions may be any of the following:
• a literal constant
• an address constant expression
• a symbol whose value is a constant expression
• a built-in function invocation on a constant expression
• a mathematical or logical operation on one or more constant expressions
An address constant expression is a special case of a constant expression. Some immediate operands
that require an address value can accept a symbol plus an addend; for example, some branch
instructions. The symbol must have a value that is an address, and it may be an external symbol. The
addend must be an absolute constant expression with an integer value. For example, a valid address
constant expression is "array+4".
A constant expression may be absolute or relocatable. Absolute means known at assembly time.
Relocatable means constant, but not known until link time. External symbols are relocatable, even if they
refer to a symbol defined in the same module.
An absolute constant expression may not refer to any external symbols anywhere in the expression. In
other words, an absolute constant expression may be any of the following:
• a literal constant
• an absolute address constant expression
• a symbol whose value is an absolute constant expression
• a built-in function invocation whose arguments are all absolute constant expressions
• a mathematical or logical operation on one or more absolute constant expressions
A relocatable constant expression refers to at least one external symbol. Such expressions may contain at
most one external symbol. A relocatable constant expression may be any of the following:
• an external symbol
• a relocatable address constant expression
• a symbol whose value is a relocatable constant expression
• a built-in function invocation with any arguments that are relocatable constant expressions
• a mathematical or logical operation on one or more expressions, at least one of which is a relocatable
constant expression
In some cases, the value of a relocatable address expression may be known at assembly time. For
example, a relative displacement branch may branch to a label defined in the same section.
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4.9.1 Mathematical and Logical Operators
The operands of a mathematical or logical operator must be well-defined expressions. That is, you must
use the correct number of operands and the operation must make sense. For example, you cannot take
the XOR of a floating-point value. In addition, well-defined expressions contain only symbols or assemblytime constants that have been defined before they occur in the directive's expression.
Three main factors influence the order of expression evaluation:
Parentheses
Precedence groups
Left-to-right evaluation
Expressions enclosed in parentheses are always evaluated first.
8 / (4 / 2) = 4, but 8 / 4 / 2 = 1
You cannot substitute braces ( { } ) or brackets ( [ ] ) for parentheses.
Operators, listed in Table 4-4, are divided into nine precedence groups.
When parentheses do not determine the order of expression evaluation,
the highest precedence operation is evaluated first.
8 + 4 / 2 = 10 (4 / 2 is evaluated first)
When parentheses and precedence groups do not determine the order of
expression evaluation, the expressions are evaluated from left to right,
except for Group 1, which is evaluated from right to left.
8 / 4*2 = 4, but 8 / (4*2) = 1
Table 4-4 lists the operators that can be used in expressions, according to precedence group.
Table 4-4. Operators Used in Expressions (Precedence)
(1)
(2)
Group (1)
Operator
Description (2)
1
+
~
!
Unary plus
Unary minus
1s complement
Logical NOT
2
*
/
%
Multiplication
Division
Modulo
3
+
-
Addition
Subtraction
4
<<
>>
Shift left
Shift right
5
<
<=
>
>=
Less than
Less than or equal to
Greater than
Greater than or equal to
6
=[=]
!=
Equal to
Not equal to
7
&
Bitwise AND
8
^^
Bitwise exclusive OR (XOR)
9
|
Bitwise OR
Group 1 operators are evaluated right to left. All other operators are evaluated left to right.
Unary + and - have higher precedence than the binary forms.
The assembler checks for overflow and underflow conditions when arithmetic operations are performed
during assembly. It issues a warning (the "value truncated" message) whenever an overflow or underflow
occurs. The assembler does not check for overflow or underflow in multiplication.
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4.9.2 Relational Operators and Conditional Expressions
The assembler supports relational operators that can be used in any expression; they are especially
useful for conditional assembly. Relational operators include the following:
=
Equal to
<
>
Less than
Greater than
!=
<=
>=
Not equal to
Less than or equal to
Greater than or equal to
Conditional expressions evaluate to 1 if true and 0 if false and can be used only on operands of equivalent
types; for example, absolute value compared to absolute value, but not absolute value compared to
relocatable value.
4.9.3 Well-Defined Expressions
Some assembler directives, such as .if, require well-defined absolute constant expressions as operands.
Well-defined expressions contain only symbols or assembly-time constants that have been defined before
they occur in the directive's expression. In addition, they must use the correct number of operands and the
operation must make sense. The evaluation of a well-defined expression must be unambiguous.
This is an example of a well-defined expression:
1000h+X
where X was previously defined as an absolute symbol.
4.9.4 Legal Expressions
With the exception of the following expression contexts, there is no restriction on combinations of
operations, constants, internally defined symbols, and externally defined symbols.
• When using the register relative addressing mode, the expression in brackets or parenthesis must be a
well-defined expression, as described in Section 4.9.3. For example:
*+A4[15]
•
Expressions used to describe the offset in register relative addressing mode for the registers B14 and
B15, or expressions used as the operand to the branch instruction, are subject to the same limitations.
For these two cases, all legal expressions can be reduced to one of two forms:
*+XA4[7]
relocatable symbol ± absolute symbol
or
a well-defined expression
B (extern_1-10)
*+B14/B15[14]
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4.9.5 Expression Examples
Following are examples of expressions that use relocatable and absolute symbols. These examples use
four symbols that are defined in the same section:
.global extern_1 ; Defined in an external module
intern_1: .word '"D'
; Relocatable, defined in
;
current module
intern_2
; Relocatable, defined in
;
current module
intern_3
; Relocatable, defined in
;
current module
•
•
Example 1
The internal values must be forrmed by absolute constant expressions. The following examples are
illegal because variables are used where constants are required.
.word
extern_1 * intern_2 - 13
; Illegal
MVKL
(intern_1 - extern_1),A1
; Illegal
Example 2
The first statement in the following example is valid; the statements that follow it are illegal
B (extern_1 - 10)
B (10-extern_1)
LDW *+B14 (-(intern_1)), A1
LDW *+B14 (extern_1/10), A1
B (intern_1 + extern_1)
•
•
;
;
;
;
;
Legal
Can't negate reloc. symbol
Can't negate reloc. symbol
/ not an additive operator
Multiple relocatables
Example 3
The first statement below is legal; although intern_1 and intern_2 are relocatable, their difference is
absolute because they are in the same section. Subtracting one relocatable symbol from another
reduces the expression to relocatable symbol + absolute value. The second statement is illegal
because the sum of two relocatable symbols is not an absolute value.
B (intern_1 - intern_2 + extern_3)
; Legal
B (intern_1 + intern_2 + extern_3)
; Illegal
Example 4
A relocatable symbol's placement in the expression is important to expression evaluation. Although the
statement below is similar to the first statement in the previous example, it is illegal because of left-toright operator precedence; the assembler attempts to add intern_1 to extern_3.
B (intern_1 + extern_3 - intern_2)
64
; Illegal
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4.10 Built-in Functions and Operators
The assembler supports built-in mathematical functions and built-in addressing operators.
The built-in substitution symbol functions are discussed in Section 6.3.2.
4.10.1 Built-In Math and Trigonometric Functions
The assembler supports built-in functions for conversions and various math computations. Table 4-5
describes the built-in functions. The expr must be an absolute constant expression.
Table 4-5. Built-In Mathematical Functions
Function
Description
$acos(expr)
Returns the arccosine of expr as a floating-point value
$asin(expr)
Returns the arcsine of expr as a floating-point value
$atan(expr)
Returns the arctangent of expr as a floating-point value
$atan2(expr, y)
Returns the arctangent of expr as a floating-point value in range [-π, π]
$ceil(expr)
Returns the smallest integer not less than expr
$cos(expr)
Returns the cosine of expr as a floating-point value
$cosh(expr)
Returns the hyperbolic cosine of expr as a floating-point value
$cvf(expr)
Converts expr to a floating-point value
$cvi(expr)
converts expr to integer value
$exp(expr)
Returns the exponential function e
$fabs(expr)
Returns the absolute value of expr as a floating-point value
$floor(expr)
Returns the largest integer not greater than expr
$fmod(expr, y)
Returns the remainder of expr1 ÷ expr2
$int(expr)
Returns 1 if expr has an integer value; else returns 0. Returns an integer.
$ldexp(expr, expr2)
Multiplies expr by an integer power of 2. That is, expr1 × 2 expr2
$log(expr)
Returns the natural logarithm of expr, where expr>0
$log10(expr)
Returns the base 10 logarithm of expr, where expr>0
$max(expr1, expr2)
Returns the maximum of two values
$min(expr1, expr2)
Returns the minimum of two values
$pow(expr1, expr2)
Returns expr1raised to the power of expr2
$round(expr)
Returns expr rounded to the nearest integer
$sgn(expr)
Returns the sign of expr.
$sin(expr)
Returns the sine of expr
$sinh(expr)
Returns the hyperbolic sine of expr as a floating-point value
$sqrt(expr)
Returns the square root of expr, expr≥0, as a floating-point value
$strtod(str)
Converts a character string to a double precision floating-point value. The string contains a properlyformatted C99-style floating-point literal.
$tan(expr)
Returns the tangent of expr as a floating-point value
$tanh(expr)
Returns the hyperbolic tangent of expr as a floating-point value
$trunc(expr)
Returns expr rounded toward 0
expr
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4.10.2 C6x Built-In ELF Relocation Generating Operators
The assembler supports several C6000-specific ELF relocation generating built-in operators. The
operators are used in compiler-generated code to support symbolic addressing of objects.
The operators are used to support various forms of DP-relative and PC-relative addressing instruction
sequences. For more detailed information about DP-relative and PC-relative addressing instruction
sequences, please see The C6000 Embedded Application Binary Interface Application Report
(SPRAB89).
4.10.2.1 $DPR_BYTE(sym) / $DPR_HWORD(sym) / $DPR_WORD(sym)
The $DPR_BYTE(sym), $DPR_HWORD(sym), or $DPR_WORD(sym) operator can be applied in the
source operand of a MVKL or MVKH instruction to load the DP-relative offset of a symbol's address into a
register. These operators are used by the compiler when accessing data objects that are not within the
signed 15-bit offset range that is needed for using the DP-relative addressing mode.
EABI requires that all sections that are accessed via DP-relative addressing be grouped together. The
linker then uses the address of the first section in that group as the "static base" whose value is attached
to the symbol __c6xabi_DSBT_BASE. DP-relative addressing then implicitly incorporates the value of
__c6xabi_DSBT_BASE into the resolution of the referenced symbol. In the examples that follow,
"static_base" in the comments indicates the location of this static base. See Chapter 4 of the The C6000
Embedded Application Binary Interface Application Report (SPRAB89) for more details about data
allocation and addressing.
For example, suppose the compiler needs to access a 32-bit aligned data object called 'xyz' that is defined
in the .far section. The compiler must assume that the .far section is too far away from the base of the
.bss section (whose address the runtime library's boot routine has loaded into the DP register), so using
DP-relative addressing mode to access 'xyz' directly is not possible. Instead, the compiler will use a
MVKL/MVKH/LDW sequence of instructions:
MVKL
MVKH
LDW
$DPR_WORD(xyz),A0
$DPR_WORD(xyz),A0
*+DP[A0],A1
; load (xyz - static_base)/4 into A0
; load *xyz into A1
This sequence of instructions is also referred to as far DP-relative addressing. The LDW instruction uses a
scaled version of DP-relative indexed addressing. Similar to the $DPR_WORD(sym) operator, the
$DPR_BYTE(sym) operator is provided to facilitate far DP-relative addressing of 8-bit data objects:
MVKL
MVKH
LDB
$DPR_BYTE(xyz),A0
$DPR_BYTE(xyz),A0
*+DP[A0],A1
; load (xyz - static_base) into A0
; load *xyz into A1
The $DPR_HWORD(sym) operator is provided to facilitate far DP-relative addressing of 16-bit data
objects:
MVKL
MVKH
LDH
$DPR_HWORD(xyz),A0
$DPR_HWORD(xyz),A0
*+DP[A0],A1
; load (xyz - static_base)/2 into A0
; load *xyz into A1
If the data being accessed is within range of the anticipated value of the DP (assuming the static base is
loaded into the DP before the MVK instructions are used), then a more efficient way to access the data
can be to use MVK instructions. For example, the compiler can compute the address of an 8-bit data
object in the .bss section:
MVK
ADD
$DPR_BYTE(_char_X),A4
DP,A4,A4
; load (_char_X - static_base) into A4
; compute address of _char_X
Similarly, the compiler can compute the address of a 16-bit data object that is defined in the .bss section:
MVK
ADD
$DPR_HWORD(_short_X),A4 ; load (_short_X - static_base)/2 into A4
DP,A4,A4
; compute address of _short_X
It can also compute a 32-bit data object that is defined in the .bss section:
MVK
ADD
66
$DPR_WORD(_int_X),A4
DP,A4,A4
; load (_int_X - static_base)/4 into A4
; compute address of _int_X
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4.10.2.2 $GOT(sym) / $DPR_GOT(sym)
The $GOT(sym) operator can be applied in the source operand of an LDW instruction. The
$DPR_GOT(sym) operator can be applied in the source operand of a MVKL or MVKH instruction. These
operators are used in the context of compiler-generated code under a dynamic linking ABI (either the
Bare-Metal or Linux Dynamic Linking Model. See Chapter 14 of The C6000 Embedded Application Binary
Interface Application Report (SPRAB89) for more details on the dynamic linking models supported in the
C6000 Code Generation Tools (CGT).
Symbols that are preemptable or are imported by a dynamic module will be accessed via the Global Offset
Table (GOT). A GOT entry for a symbol will contain the address of the symbol as it is determined at
dynamic load time. To facilitate this resolution, the static linker will emit a dynamic relocation entry that is
to be processed by the dynamic linker/loader. For more information on the GOT, see The C6000
Embedded Application Binary Interface Application Report (SPRAB89).
If the GOT entry for a symbol, xyz, is accessible using DP-relative addressing mode, then the compiler will
generate a sequence to load the symbol that uses the $GOT(sym) op0erator as the offset part of the DPrelative addressing mode operand:
LDW
*+DP[$GOT(xyz)],A0
LDW
*A0,A1
; load address of xyz into A0
; via access to GOT entry
; load xyz into A2
The actual semantics of the $GOT(sym) operator is to return the DP- relative offset of the GOT entry for
the referenced symbol (xyz above).
While $DPR_GOT(sym) is semantically similar to the $GOT(sym) operator, it is used when the GOT is not
accessible using DP-relative addressing mode (offset is not within signed 15-bit range of the static base
address that is loaded into the data pointer register (DP)). The DP-relative offset to the GOT entry is then
loaded into an index register using a MVKL/MVKH instruction sequence, and the GOT entry is then
accessed via DP-relative indexed addressing to load the address of the referenced symbol:
MVKL
MVKH
LDW
LDW
$DPR_GOT(xyz),A0
$DPR_GOT(xyz),A0
*+DP[A0],A1
*A1,A2
;
;
;
;
load DP-relative offset of
GOT entry for xyz into A0
get address of xyz via GOT entry
load xyz into A2
4.10.2.3 $PCR_OFFSET(x,y)
The $PCR_OFFSET(x,y) operator can be applied in the source operand of a MVKL, MVKH, or ADDK
instruction to compute a PC-relative offset to be loaded into (in the case of MVKL/MVKH) or added to (in
the case of ADDK) a register.
This operator is used in the context of compiler-generated code under the Linux ABI (using --linux
compiler option). It helps the compiler to generate position-independent code by accessing a symbol that
is defined in the same RO segment using PC-relative addressing.
For example, if there is to be a call to a function defined in the same file, but you would like to avoid
generating a dynamic relocation that accesses the symbol that represents the destination of the call, then
you can use the $PCR_OFFSET operator as follows:
dest:
<code>
...
make_pcr_call:
MVC PCE1, B0
; set up PC reference point in B0
MVKL $PCR_OFFSET(dest, make_pcr_call), B1 ; compute dest - make_pcr_call
MVKH $PCR_OFFSET(dest, make_pcr_call), B1 ; and load it into B1
ADD B0,B1,B0
; compute dest address into B0 register
B B0
; call dest indirectly through B0
...
The above code sequence is position independent. No matter what address 'dest' is placed at load time,
the call to 'dest' will still work since it is independent of the actual address of 'dest'. However, the call does
have to maintain its position relative to the definition of 'dest'.
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Also in the above sequence, the compiler creates a coupling between the MVC instruction and the
'make_pcr_call' label. The 'make_pcr_call' label must be associated with the address of the MVC
instruction so that when the $PCR_OFFSET(dest, make_pcr_call) operator is applied, the 'make_pcr_call'
symbol becomes a representative for the PC reference point. This means that the result of 'dest make_pcr_call' becomes the PC-relative offset which when added to the PC reference point in B0 gives
the address of 'dest'.
The relocation that is generated for the $PCR_OFFSET() operator is handled during the static link step in
which a dynamic module is built. This static relocation can then be discarded and no dynamic relocation
will be needed to resolve the call to 'dest' in the above example.
4.10.2.4 $LABEL_DIFF(x,y) Operator
The $LABEL_DIFF(x,y) operator can be applied to an argument for a 32-bit data-defining directive (like
.word, for example). The operator simply computes the difference between two labels that are defined in
the same section. This operator is sometimes used by the compiler under the Linux ABI (--linux compiler
option) when generating position independent code for a switch statement.
For example, in Example 4-4 a switch table is generated which contains the PC-relative offsets of the
switch case labels:
Example 4-4. Generating a Switch Table With Offset Switch Case Labels
.asg A15, FP
.asg B14, DP
.asg B15, SP
.sect ".text"
.clink
.global myfunc
;******************************************************************************
;* FUNCTION NAME: myfunc *
;******************************************************************************
myfunc:
;** --------------------------------------------------------------------------*
B .S1
$C$L10
||
SUB .L2X
A4,10,B5
||
STW .D2T2
B3,*SP--(16)
CMPGTU .L2 B5,7,B0
||
STW .D2T1
A4,*+SP(12)
||
MV .S2X
A4,B4
[ B0] BNOP .S1 $C$L9,3
; BRANCH OCCURS {$C$L10} ; |6|
;** --------------------------------------------------------------------------*
$C$L1:
<case 0 code>
...
;** --------------------------------------------------------------------------*
$C$L2:
<case 1 code>
...
;** --------------------------------------------------------------------------*
$C$L3:
<case 2 code>
...
;** --------------------------------------------------------------------------*
$C$L4:
<case 3 code>
...
;** --------------------------------------------------------------------------*
$C$L5:
<case 4 code>
...
;** --------------------------------------------------------------------------*
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Example 4-4. Generating a Switch Table With Offset Switch Case Labels (continued)
$C$L6:
<case 5 code>
...
;** --------------------------------------------------------------------------*
$C$L7:
<case 6 code>
...
;** --------------------------------------------------------------------------*
$C$L8:
<case 7 code>
...
;** --------------------------------------------------------------------------*
$C$L9:
<default case code>
...
;** --------------------------------------------------------------------------*
$C$L10:
NOP 2
; BRANCHCC OCCURS {$C$L9} {-9} ;
;** --------------------------------------------------------------------------*
SUB .L2
B4,10,B5
; Norm switch value -> switch table index
||
ADDKPC .S2 $C$SW1,B4,0 ; Load address of switch table to B4
LDW .D2T2
*+B4[B5],B5 ; Load PC-relative offset from switch table
NOP
4
ADD .L2
B5,B4,B4
; Combine to get case label into B5
BNOP .S2
B4,5
; Branch to case label
; BRANCH OCCURS {B4} ;
; Switch table definition
.align 32
.clink
$C$SW1: .nocmp
.word $LABEL_DIFF($C$L1,$C$SW1)
.word $LABEL_DIFF($C$L2,$C$SW1)
.word $LABEL_DIFF($C$L3,$C$SW1)
.word $LABEL_DIFF($C$L4,$C$SW1)
.word $LABEL_DIFF($C$L5,$C$SW1)
.word $LABEL_DIFF($C$L6,$C$SW1)
.word $LABEL_DIFF($C$L7,$C$SW1)
.word $LABEL_DIFF($C$L8,$C$SW1)
.align 32
.sect ".text"
...
;
;
;
;
;
;
;
;
10
11
12
13
14
15
16
17
Example 4-4 mixes data into the code section. Compression is disabled for the code section that contains
the $LABEL_DIFF() operator, since the label difference must resolve to a constant value during assembly.
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4.11 Source Listings
A source listing shows source statements and the object code they produce. To obtain a listing file, invoke
the assembler with the --asm_listing option (see Section 4.3).
Two banner lines, a blank line, and a title line are at the top of each source listing page. Any title supplied
by the .title directive is printed on the title line. A page number is printed to the right of the title. If you do
not use the .title directive, the name of the source file is printed. The assembler inserts a blank line below
the title line.
Each line in the source file produces at least one line in the listing file. This line shows a source statement
number, an SPC value, the object code assembled, and the source statement. Figure 4-2 shows these in
an actual listing file.
Field 1: Source Statement Number
Line number
The source statement number is a decimal number. The assembler numbers source lines as it
encounters them in the source file; some statements increment the line counter but are not listed. (For
example, .title statements and statements following a .nolist are not listed.) The difference between two
consecutive source line numbers indicates the number of intervening statements in the source file that
are not listed.
Include file letter
A letter preceding the line number indicates the line is assembled from the include file designated by
the letter.
Nesting level number
A number preceding the line number indicates the nesting level of macro expansions or loop blocks.
Field 2: Section Program Counter
This field contains the SPC value, which is hexadecimal. All sections (.text, .data, .bss, and named
sections) maintain separate SPCs. Some directives do not affect the SPC and leave this field blank.
Field 3: Object Code
This field contains the hexadecimal representation of the object code. All machine instructions and
directives use this field to list object code. This field also indicates the relocation type associated with
an operand for this line of source code. If more than one operand is relocatable, this column indicates
the relocation type for the first operand. The characters that can appear in this column and their
associated relocation types are listed below:
!
'
+
"
%
undefined external reference
.text relocatable
.sect relocatable
.data relocatable
.bss, .usect relocatable
relocation expression
Field 4: Source Statement Field
This field contains the characters of the source statement as they were scanned by the assembler. The
assembler accepts a maximum line length of 200 characters. Spacing in this field is determined by the
spacing in the source statement.
Figure 4-2 shows an assembler listing with each of the four fields identified.
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Figure 4-2. Example Assembler Listing
Include file
letter
Nesting level
number
Line number
2
** Global variables
4 00000000
5 00000004
6
.bss
.bss
8
A
A
10
1
2
A
5
A
7
A
9
A
11
A
13
11
15
16
17
18
19
20
var1, 4
var2, 4
** Include multiply macro
mpy32
.copy
.macro
mpy32.inc
A,B
.endm
00000000
00000000
_func
00000000 0200006C00000004 0000016E00000008 00006000
0000000c
.text
LDW
LDW
NOP
mpy32
*+B14(var1),A4
*+B14(var2),B0
4
A4,B0
1
1
1
1
1
21 00000024 000C6362
22 00000028 00008000
23
Field 1
Field 2
Field 3
B
NOP
* end _func
B3
5
Field 4
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Debugging Assembly Source
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4.12 Debugging Assembly Source
By default, when you compile an assembly file, the assembler provides symbolic debugging information
that allows you to step through your assembly code in a debugger rather than using the Disassembly
window in Code Composer Studio. This enables you to view source comments and other source-code
annotations while debugging. The default has the same behavior as using the --symdebug:dwarf option.
You can disable the generation of debugging information by using the --symdebug:none option.
The .asmfunc and .endasmfunc (see .asmfunc directive) directives enable you to use C characteristics in
assembly code that makes the process of debugging an assembly file more closely resemble debugging a
C/C++ source file.
The .asmfunc and .endasmfunc directives allow you to name certain areas of your code, and make these
areas appear in the debugger as C functions. Contiguous sections of assembly code that are not enclosed
by the .asmfunc and .endasmfunc directives are automatically placed in assembler-defined functions
named with this syntax:
$ filename : starting source line : ending source line $
If you want to view your variables as a user-defined type in C code, the types must be declared and the
variables must be defined in a C file. This C file can then be referenced in assembly code using the .ref
directive (see .ref directive). Example 4-5 shows the cvar.c C program that defines a variable, svar, as the
structure type X. The svar variable is then referenced in the addfive.asm assembly program in Example 46 and 5 is added to svar's second data member.
Compile both source files with the --symdebug:dwarf option (-g) and link them as follows:
cl6x --symdebug:dwarf cvars.c addfive.asm --run_linker --library=lnk.cmd --library=rts6600.lib
--output_file=addfive.out
When you load this program into a symbolic debugger, addfive appears as a C function. You can monitor
the values in svar while stepping through main just as you would any regular C variable.
Example 4‑5. Viewing Assembly Variables as C Types C Program
typedef struct
{
int m1;
int m2;
} X;
X svar = { 1, 2 };
Example 4‑6. Assembly Program for Example 4-5
;-------------------------------------------------------------------------------------; Tell the assembler we're referencing variable "_svar", which is defined in
; another file (cvars.c).
;-------------------------------------------------------------------------------------.ref _svar
;-------------------------------------------------------------------------------------; addfive() - Add five to the second data member of _svar
;-------------------------------------------------------------------------------------.text
.global addfive
addfive: .asmfunc
LDW
.D2T2
*+B14(_svar+4),B4 ; load svar.m2 into B4
RET
.S2
B3
; return from function
NOP
3
; delay slots 1-3
ADD
.D2
5,B4,B4
; add 5 to B4 (delay slot 4)
STW
.D2T2
B4,*+B14(_svar+4) ; store B4 back into svar.m2 (delay slot 5)
.endasmfunc
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Cross-Reference Listings
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4.13 Cross-Reference Listings
A cross-reference listing shows symbols and their definitions. To obtain a cross-reference listing, invoke
the assembler with the --asm_listing_cross_reference option (see Section 4.3) or use the .option directive
with the X operand (see Select Listing Options). The assembler appends the cross-reference to the end of
the source listing. Example 4-7 shows the four fields contained in the cross-reference listing.
Example 4‑7. An Assembler Cross-Reference Listing
LABEL
VALUE
.BIG_ENDIAN
.LITTLE_ENDIAN
.TMS320C6400_PLUS
.TMS320C6600
.TMS320C6740
_func
var1
var2
00000000
00000001
00000001
00000000
00000001
00000000'
0000000000000004-
Label
Value
Definition
Reference
DEFN
0
0
0
0
0
18
4
5
REF
17
18
column contains each symbol that was defined or referenced during the assembly.
column contains an 8-digit hexadecimal number (which is the value assigned to the
symbol) or a name that describes the symbol's attributes. A value may also be
preceded by a character that describes the symbol's attributes. Table 4-6 lists these
characters and names.
(DEFN) column contains the statement number that defines the symbol. This
column is blank for undefined symbols.
(REF) column lists the line numbers of statements that reference the symbol. A
blank in this column indicates that the symbol was never used.
Table 4-6. Symbol Attributes
Character or Name
Meaning
REF
External reference (global symbol)
UNDF
Undefined
'
Symbol defined in a .text section
"
Symbol defined in a .data section
+
Symbol defined in a .sect section
-
Symbol defined in a .bss or .usect section
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Chapter 5
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Assembler Directives
Assembler directives supply data to the program and control the assembly process. Assembler directives
enable you to do the following:
• Assemble code and data into specified sections
• Reserve space in memory for uninitialized variables
• Control the appearance of listings
• Initialize memory
• Assemble conditional blocks
• Define global variables
• Specify libraries from which the assembler can obtain macros
• Examine symbolic debugging information
This chapter is divided into two parts: the first part (Section 5.1 through Section 5.11) describes the
directives according to function, and the second part (Section 5.12) is an alphabetical reference.
Topic
5.1
5.2
5.3
5.4
5.5
5.6
5.7
5.8
5.9
5.10
5.11
5.12
74
...........................................................................................................................
Directives Summary ...........................................................................................
Directives that Define Sections ............................................................................
Directives that Initialize Values ............................................................................
Directives that Perform Alignment and Reserve Space ...........................................
Directives that Format the Output Listings ............................................................
Directives that Reference Other Files ...................................................................
Directives that Enable Conditional Assembly ........................................................
Directives that Define Union or Structure Types ....................................................
Directives that Define Enumerated Types ..............................................................
Directives that Define Symbols at Assembly Time..................................................
Miscellaneous Directives.....................................................................................
Directives Reference...........................................................................................
Assembler Directives
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75
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81
83
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85
86
86
87
87
88
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5.1
Directives Summary
Table 5-1 through Table 5-16 summarize the assembler directives.
Besides the assembler directives documented here, the TMS320C6000 software tools support the
following directives:
• Macro directives are discussed in Chapter 6; they are not discussed in this chapter.
• The assembly optimizer uses several directives that supply data and control the optimization process.
Assembly optimizer directives are discussed in the TMS320C6000 Optimizing Compiler User's Guide.
• The C compiler uses directives for symbolic debugging. Unlike other directives, symbolic debugging
directives are not used in most assembly language programs. Appendix A discusses these directives;
they are not discussed in this chapter.
Labels and Comments Are Not Shown in Syntaxes
NOTE: Most source statements that contain a directive can also contain a label and a comment.
Labels begin in the first column (only labels and comments can appear in the first column),
and comments must be preceded by a semicolon, or an asterisk if the comment is the only
element in the line. To improve readability, labels and comments are not shown as part of
the directive syntax here. See the detailed description of each directive for using labels with
directives.
Table 5-1. Directives that Control Section Use
Mnemonic and Syntax
Description
See
.bss symbol, size in bytes[, alignment
[, bank offset]]
Reserves size bytes in the .bss (uninitialized data) section
.bss topic
.data
Assembles into the .data (initialized data) section
.data topic
.sect "section name"
Assembles into a named (initialized) section
.sect topic
.text
Assembles into the .text (executable code) section
.text topic
symbol .usect "section name", size in bytes
[, alignment[, bank offset]]
Reserves size bytes in a named (uninitialized) section
.usect topic
Table 5-2. Directives that Gather Sections into Common Groups
Mnemonic and Syntax
Description
See
.endgroup
Ends the group declaration
.endgroup topic
.gmember section name
Designates section name as a member of the group
.gmember topic
.group group section name group type :
Begins a group declaration
.group topic
Table 5-3. Directives that Affect Unused Section Elimination
Mnemonic and Syntax
Description
.retain "section name"
Instructs the linker to include the current or specified section in the .retain topic
linked output file, regardless of whether the section is referenced or
not
See
.retainrefs "section name"
Instructs the linker to include any data object that references the
current or specified section.
.retain topic
Table 5-4. Directives that Initialize Values (Data and Memory)
Mnemonic and Syntax
Description
See
.bits value1[, ... , valuen]
Initializes one or more successive bits in the current section
.bits topic
.byte value1[, ... , valuen]
Initializes one or more successive bytes in the current section
.byte topic
.char value1[, ... , valuen]
Initializes one or more successive bytes in the current section
.char topic
.cstring {expr1|"string1"}[,... , {exprn|"stringn"}]
Initializes one or more text strings
.string topic
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Table 5-4. Directives that Initialize Values (Data and Memory) (continued)
Mnemonic and Syntax
Description
See
.double value1[, ... , valuen]
Initializes one or more 64-bit, IEEE double-precision, floating-point
constants
.double topic
.field value[, size]
Initializes a field of size bits (1-32) with value
.field topic
.float value1[, ... , valuen]
Initializes one or more 32-bit, IEEE single-precision, floating-point
constants
.float topic
.half value1[, ... , valuen]
Initializes one or more 16-bit integers (halfword)
.half topic
.int value1[, ... , valuen]
Initializes one or more 32-bit integers
.int topic
.long value1[, ... , valuen]
Initializes one or more 32-bit integers
.long topic
.short value1[, ... , valuen]
Initializes one or more 16-bit integers (halfword)
.short topic
.string {expr1|"string1"}[,... , {exprn|"stringn"}]
Initializes one or more text strings
.string topic
.ubyte value1[, ... , valuen]
Initializes one or more successive unsigned bytes in the current
section
.ubyte topic
.uchar value1[, ... , valuen]
Initializes one or more successive unsigned bytes in the current
section
.uchar topic
.uhalf value1[, ... , valuen]
Initializes one or more unsigned 16-bit integers (halfword)
.uhalf topic
.uint value1[, ... , valuen]
Initializes one or more unsigned 32-bit integers
.uint topic
.ulong value1[, ... , valuen]
Initializes one or more unsigned 32-bit integers
.long topic
.ushort value1[, ... , valuen]
Initializes one or more unsigned 16-bit integers (halfword)
.short topic
.uword value1[, ... , valuen]
Initializes one or more unsigned 32-bit integers
.uword topic
.word value1[, ... , valuen]
Initializes one or more 32-bit integers
.word topic
Table 5-5. Directives that Perform Alignment and Reserve Space
Mnemonic and Syntax
Description
See
.align [size in bytes]
Aligns the SPC on a boundary specified by size in bytes, which
must be a power of 2; defaults to byte boundary
.align topic
.bes size
Reserves size bytes in the current section; a label points to the end .bes topic
of the reserved space
.space size
Reserves size bytes in the current section; a label points to the
beginning of the reserved space
.space topic
Table 5-6. Directives that Format the Output Listing
Mnemonic and Syntax
Description
See
.drlist
Enables listing of all directive lines (default)
.drlist topic
.drnolist
Suppresses listing of certain directive lines
.drnolist topic
.fclist
Allows false conditional code block listing (default)
.fclist topic
.fcnolist
Suppresses false conditional code block listing
.fcnolist topic
.length [page length]
Sets the page length of the source listing
.length topic
.list
Restarts the source listing
.list topic
.mlist
Allows macro listings and loop blocks (default)
.mlist topic
.mnolist
Suppresses macro listings and loop blocks
.mnolist topic
.nolist
Stops the source listing
.nolist topic
.option option1 [, option2 , . . .]
Selects output listing options; available options are A, B, D, H, L,
M, N, O, R, T, W, and X
.option topic
.page
Ejects a page in the source listing
.page topic
.sslist
Allows expanded substitution symbol listing
.sslist topic
.ssnolist
Suppresses expanded substitution symbol listing (default)
.ssnolist topic
.tab size
Sets tab to size characters
.tab topic
.title "string"
Prints a title in the listing page heading
.title topic
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Table 5-6. Directives that Format the Output Listing (continued)
Mnemonic and Syntax
Description
See
.width [page width]
Sets the page width of the source listing
.width topic
Table 5-7. Directives that Reference Other Files
Mnemonic and Syntax
Description
See
.copy ["]filename["]
Includes source statements from another file
.copy topic
.include ["]filename["]
Includes source statements from another file
.include topic
.mlib ["]filename["]
Specifies a macro library from which to retrieve macro definitions
.mlib topic
Table 5-8. Directives that Affect Symbol Linkage and Visibility
Mnemonic and Syntax
Description
See
.common symbol, size in bytes [, alignment]r
.common symbol, structure tag [, alignment]
Defines a common symbol for a variable.
.common topic
.def symbol1[, ... , symboln]
Identifies one or more symbols that are defined in the current
module and that can be used in other modules
.def topic
.farcommon symbol, size in bytes [, alignment]r
.farcommon symbol, structure tag [, alignment]
Defines a common symbol in far memory
.farcommon topic
.global symbol1[, ... , symboln]
Identifies one or more global (external) symbols
.global topic
.nearcommon symbol, size in bytes [, alignment]r
.nearcommon symbol, structure tag [, alignment]
Defines a common symbol in near memory
.farcommon topic
.ref symbol1[, ... , symboln]
Identifies one or more symbols used in the current module that are
defined in another module
.ref topic
.symdepend dst symbol name[, src symbol name] Creates an artificial reference from a section to a symbol
.symdepend topic
.weak symbol name
.weak topic
Identifies a symbol used in the current module that is defined in
another module
Table 5-9. Directives that Control Dynamic Symbol Visibility
Mnemonic and Syntax
Description
See
.export "symbolname"
Sets visibility of symbolname to STV_EXPORT
.export topic
.hidden"symbolname"
Sets visibility of symbolname to STV_HIDDEN
.hidden topic
.import "symbolname"
Sets visibility of symbolname to STV_IMPORT
.import topic
.protected "symbolname"
Sets visibility of symbolname to STV_PROTECTED
.protected topic
Table 5-10. Directives that Enable Conditional Assembly
Mnemonic and Syntax
Description
See
.if condition
Assembles code block if the condition is true
.if topic
.else
Assembles code block if the .if condition is false. When using the .if .else topic
construct, the .else construct is optional.
.elseif condition
Assembles code block if the .if condition is false and the .elseif
condition is true. When using the .if construct, the .elseif construct
is optional.
.elseif topic
.endif
Ends .if code block
.endif topic
.loop [count]
Begins repeatable assembly of a code block; the loop count is
determined by the count.
.loop topic
.break [end condition]
Ends .loop assembly if end condition is true. When using the .loop
construct, the .break construct is optional.
.break topic
.endloop
Ends .loop code block
.endloop topic
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Table 5-11. Directives that Define Union or Structure Types
Mnemonic and Syntax
Description
See
.cstruct
Acts like .struct, but adds padding and alignment like that which is
done to C structures
.cstruct topic
.cunion
Acts like .union, but adds padding and alignment like that which is
done to C unions
.cunion topic
.emember
Sets up C-like enumerated types in assembly code
.endenum
Sets up C-like enumerated types in assembly code
.endstruct
Ends a structure definition
.cstruct topic,
.struct topic
.endunion
Ends a union definition
.cunion topic,
.union topic
.enum
Sets up C-like enumerated types in assembly code
Section 5.9
.union
Begins a union definition
.union topic
.struct
Begins structure definition
.struct topic
.tag
Assigns structure attributes to a label
.cstruct topic,
.struct topic.union
topic
Section 5.9
Section 5.9
Table 5-12. Directives that Define Symbols
Mnemonic and Syntax
Description
See
.asg ["]character string["], substitution symbol
Assigns a character string to substitution symbol. Substitution
symbols created with .asg can be redefined.
.asg topic
.clearmap
Cancels all .map assignments. Used by compiler for linear
assembly source.
.clearmap topic
.define ["]character string["], substitution symbol
Assigns a character string to substitution symbol. Substitution
symbols created with .define cannot be redefined.
.asg topic
symbol .equ value
Equates value with symbol
.equ topic
.elfsym name, SYM_SIZE(size)
Provides ELF symbol information
.elfsym topic
.eval expression ,
substitution symbol
Performs arithmetic on a numeric substitution symbol
.eval topic
.label symbol
Defines a load-time relocatable label in a section
.label topic
.map symbol/register
Assigns symbol to register. Used by compiler for linear assembly
source.
.map topic
.newblock
Undefines local labels
.newblock topic
symbol .set value
Equates value with symbol
.set topic
.unasg symbol
Turns off assignment of symbol as a substitution symbol
.unasg topic
.undefine symbol
Turns off assignment of symbol as a substitution symbol
.unasg topic
Table 5-13. Directives that Create or Affect Macros
Mnemonic and Syntax
macname .macro
Description
See
[parameter1 ][,... , parametern ] Begin definition of macro named macname
.macro topic
.endm
End macro definition
.endm topic
.mexit
Go to .endm
Section 6.2
.mlib filename
Identify library containing macro definitions
.mlib topic
.var
Adds a local substitution symbol to a macro's parameter list
.var topic
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Table 5-14. Directives that Control Diagnostics
Mnemonic and Syntax
Description
See
.emsg string
Sends user-defined error messages to the output device;
produces no .obj file
.emsg topic
.mmsg string
Sends user-defined messages to the output device
.mmsg topic
.noremark[num]
Identifies the beginning of a block of code in which the assembler
suppresses the num remark
.noremark topic
.remark [num]
Resumes the default behavior of generating the remark(s)
previously suppressed by .noremark
.remark topic
.wmsg string
Sends user-defined warning messages to the output device
.wmsg topic
Table 5-15. Directives that Perform Assembly Source Debug
Mnemonic and Syntax
Description
See
.asmfunc
Identifies the beginning of a block of code that contains a function
.asmfunc topic
.endasmfunc
Identifies the end of a block of code that contains a function
.endasmfunc
topic
Table 5-16. Directives that Perform Miscellaneous Functions
Mnemonic and Syntax
Description
See
.cdecls [options ,]"filename"[, "filename2"[, ...]
Share C headers between C and assembly code
.cdecls topic
.end
Ends program
.end topic
.nocmp
Instructs tools to not utilize 16-bit instructions for section
.nocmp topic
In addition to the assembly directives that you can use in your code, the C/C++ compiler produces several
directives when it creates assembly code. These directives are to be used only by the compiler; do not
attempt to use these directives.
• DWARF directives listed in Section A.1
• The .battr directive is used to encode build attributes for the object file. For more information about
build attributes generated and used by the C6000 Code Generation Tools, please see The C6000
Embedded Application Binary Interface application report (SPRAB89).
• The .bound directive is used internally.
• The .comdat directive is used internally.
• The .compiler_opts directive indicates that the assembly code was produced by the compiler, and
which build model options were used for this file.
• The .tls directive is used internally.
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Directives that Define Sections
5.2
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Directives that Define Sections
These directives associate portions of an assembly language program with the appropriate sections:
• The .bss directive reserves space in the .bss section for uninitialized variables.
• The .data directive identifies portions of code in the .data section. The .data section usually contains
initialized data.
• The .retain directive can be used to indicate that the current or specified section must be included in
the linked output. Thus even if no other sections included in the link reference the current or specified
section, it is still included in the link.
• The .retainrefs directive can be used to force sections that refer to the specified section. This is useful
in the case of interrupt vectors.
• The .sect directive defines an initialized named section and associates subsequent code or data with
that section. A section defined with .sect can contain code or data.
• The .text directive identifies portions of code in the .text section. The .text section usually contains
executable code.
• The .usect directive reserves space in an uninitialized named section. The .usect directive is similar to
the .bss directive, but it allows you to reserve space separately from the .bss section.
Chapter 2 discusses these sections in detail.
Example 5-1 shows how you can use sections directives to associate code and data with the proper
sections. This is an output listing; column 1 shows line numbers, and column 2 shows the SPC values.
(Each section has its own program counter, or SPC.) When code is first placed in a section, its SPC
equals 0. When you resume assembling into a section after other code is assembled, the section's SPC
resumes counting as if there had been no intervening code.
The directives in Example 5-1 perform the following tasks:
.text
.data
var_defs
.bss
xy
80
initializes words with the values 1, 2, 3, 4, 5, 6, 7, and 8.
initializes words with the values 9, 10, 11, 12, 13, 14, 15, and 16.
initializes words with the values 17 and 18.
reserves 19 bytes.
reserves 20 bytes.
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The .bss and .usect directives do not end the current section or begin new sections; they reserve the
specified amount of space, and then the assembler resumes assembling code or data into the current
section.
Example 5‑1. Sections Directives
00000004
6 00000008
0000000c
7
8
9
10
11 00000000
12 00000000
00000004
13 00000008
0000000c
14
15
16
17
18
19 00000000
20 00000000
00000004
21
22
23
24
25 00000010
26 00000010
00000014
27 00000000
28 00000018
0000001c
29
30
31
32
33 00000010
34 00000010
00000014
35 00000000
36 00000018
0000001c
5.3
00000002
00000003
00000004
00000009
0000000A
0000000B
0000000C
00000011
00000012
0000000D
0000000E
.word
**************************************************
*
Start assembling into the .data section
*
**************************************************
.data
.word
9, 10
.word
**************************************************
*
Resume assembling into the .data section
*
**************************************************
.data
.word
13, 14
.bss
.word
sym, 19
15, 16
; Reserve space in .bss
; Still in .data
**************************************************
*
Resume assembling into the .text section
*
**************************************************
.text
.word
5, 6
usym
00000007
00000008
11, 12
**************************************************
*
Start assembling into a named,
*
*
initialized section, var_defs
*
**************************************************
.sect
"var_defs"
.word
17, 18
0000000F
00000010
00000005
00000006
3,4
.usect
.word
"xy", 20
7, 8
; Reserve space in xy
; Still in .text
Directives that Initialize Values
Several directives assemble values for the current section. For example:
• The .byte and .char directives place one or more 8-bit values into consecutive bytes of the current
section. These directives are similar to .word, .int, and .long, except that the width of each value is
restricted to 8 bits.
• The .double directive calculates the double-precision (64-bit) IEEE floating-point representation of one
or more floating-point values and stores them in two consecutive words in the current section. The
.double directive automatically aligns to the double-word boundary.
• The .field directive places a single value into a specified number of bits in the current word. With .field,
you can pack multiple fields into a single word; the assembler does not increment the SPC until a word
is filled. If a field will not fit in the space remaining in the current word, .field will insert zeros to fill the
current word and then place the field in the next word. See the .field topic.
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Directives that Initialize Values
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Figure 5-1 shows how fields are packed into a word. Using the following assembled code, notice that
the SPC does not change (the fields are packed into the same word):
1 00000000 00000003
2 00000000 00000083
3 00000000 00002083
.field
.field
.field
3,4
8,5
16,7
Figure 5-1. The .field Directive
•
•
•
•
•
The .float directive calculates the single-precision (32-bit) IEEE floating-point representation of a single
floating-point value and stores it in a word in the current section that is aligned to a word boundary.
The .half and .short directives place one or more 16-bit values into consecutive 16-bit fields
(halfwords) in the current section. These directives automatically align to a short (2-byte) boundary.
The .int, .long, and .word directives place one or more 32-bit values into consecutive 32-bit fields
(words) in the current section. These directives automatically align to a word boundary.
The .string and .cstring directives place 8-bit characters from one or more character strings into the
current section. The .string and .cstring directives are similar to .byte, placing an 8-bit character in each
consecutive byte of the current section. The .cstring directive adds a NUL character needed by C; the
.string directive does not add a NUL character.
The .ubyte, .uchar, .uhalf, .uint, .ulong, .ushort, and .uword directives are provided as unsigned
versions of their respective signed directives. These directives are used primarily by the C/C++
compiler to support unsigned types in C/C++.
Directives that Initialize Constants When Used in a .struct/.endstruct Sequence
NOTE:
The .bits, .byte, .char, .int, .long, .word, .double, .half, .short, .string, .ubyte, .uchar, .uhalf,
.uint, .ulong, .ushort, .uword, .float, and .field directives do not initialize memory when they
are part of a .struct/ .endstruct sequence; rather, they define a member’s size. For more
information, see the .struct/.endstruct directives.
Figure 5-2 compares the .byte, .half, .word, and .string directives using the following assembled code:
1
2
3
4
5
82
00000000 000000AB
00000004
00000008
0000000c
0000000d
0000000e
0000000f
0000CDEF
89ABCDEF
00000068
00000065
0000006C
00000070
.byte
0ABh
.align 4
.half
0CDEFh
.word
089ABCDEFh
.string "help"
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Directives that Perform Alignment and Reserve Space
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Figure 5-2. Initialization Directives
5.4
Directives that Perform Alignment and Reserve Space
These directives align the section program counter (SPC) or reserve space in a section:
• The .align directive aligns the SPC at the next byte boundary. This directive is useful with the .field
directive when you do not want to pack two adjacent fields in the same byte. The size specified by the
.align directive must equal a power of 2; the value must be between 1 and 32,768, inclusive.
Figure 5-3 demonstrates the .align directive. Using the following assembled code:
1
2 00000000 00AABBCC
3
4 00000000 0BAABBCC
5 00000004 000000DE
.field
.align
.field
.field
0AABBCCh,24
2
0Bh,5
0DEh,10
Figure 5-3. The .align Directive
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Directives that Format the Output Listings
•
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The .bes and .space directives reserve a specified number of bytes in the current section. The
assembler fills these reserved bytes with 0s.
– When you use a label with .space, it points to the first byte that contains reserved bits.
– When you use a label with .bes, it points to the last byte that contains reserved bits.
Figure 5-4 shows how the .space and .bes directives work for the following assembled code:
1
2 00000000
00000004
3 00000008
4 0000001c
5 00000033
6 00000034
00000100
00000200
Res_1:
0000000F
Res_2:
000000BA
.word
100h, 200h
.space
.word
.bes
.byte
17
15
20
0BAh
Res_1 points to the first byte in the space reserved by .space. Res_2 points to the last byte in the
space reserved by .bes.
Figure 5-4. The .space and .bes Directives
Res_1 = 08h
17 bytes
reserved
20 bytes
reserved
5.5
Res_2 = 33h
Directives that Format the Output Listings
These directives format the listing file:
• The .drlist directive causes printing of the directive lines to the listing; the .drnolist directive turns it off
for certain directives. You can use the .drnolist directive to suppress the printing of the following
directives. You can use the .drlist directive to turn the listing on again.
.asg
.break
.emsg
•
•
•
•
84
.eval
.fclist
.fcnolist
.length
.mlist
.mmsg
.mnolist
.sslist
.ssnolist
.var
.width
.wmsg
The source code listing includes false conditional blocks that do not generate code. The .fclist and
.fcnolist directives turn this listing on and off. You can use the .fclist directive to list false conditional
blocks exactly as they appear in the source code. You can use the .fcnolist directive to list only the
conditional blocks that are actually assembled.
The .length directive controls the page length of the listing file. You can use this directive to adjust
listings for various output devices.
The .list and .nolist directives turn the output listing on and off. You can use the .nolist directive to
prevent the assembler from printing selected source statements in the listing file. Use the .list directive
to turn the listing on again.
The source code listing includes macro expansions and loop blocks. The .mlist and .mnolist directives
turn this listing on and off. You can use the .mlist directive to print all macro expansions and loop
blocks to the listing, and the .mnolist directive to suppress this listing.
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•
The .option directive controls certain features in the listing file. This directive has the following
operands:
A
B
D
H
L
M
N
O
R
T
W
X
•
•
•
•
•
5.6
turns on listing of all directives and data, and subsequent expansions, macros, and blocks.
limits the listing of .byte and .char directives to one line.
turns off the listing of certain directives (same effect as .drnolist).
limits the listing of .half and .short directives to one line.
limits the listing of .long directives to one line.
turns off macro expansions in the listing.
turns off listing (performs .nolist).
turns on listing (performs .list).
resets the B, H, L, M, T, and W directives (turns off the limits of B, H, L, M, T, and W).
limits the listing of .string directives to one line.
limits the listing of .word and .int directives to one line.
produces a cross-reference listing of symbols. You can also obtain a cross-reference listing
by invoking the assembler with the --asm_listing_cross_reference option (see Section 4.3).
The .page directive causes a page eject in the output listing.
The source code listing includes substitution symbol expansions. The .sslist and .ssnolist directives
turn this listing on and off. You can use the .sslist directive to print all substitution symbol expansions
to the listing, and the .ssnolist directive to suppress this listing. These directives are useful for
debugging the expansion of substitution symbols.
The .tab directive defines tab size.
The .title directive supplies a title that the assembler prints at the top of each page.
The .width directive controls the page width of the listing file. You can use this directive to adjust
listings for various output devices.
Directives that Reference Other Files
These directives supply information for or about other files that can be used in the assembly of the current
file:
• The .copy and .include directives tell the assembler to begin reading source statements from another
file. When the assembler finishes reading the source statements in the copy/include file, it resumes
reading source statements from the current file. The statements read from a copied file are printed in
the listing file; the statements read from an included file are not printed in the listing file.
• The .def directive identifies a symbol that is defined in the current module and that can be used in
another module. The assembler includes the symbol in the symbol table.
• The .global directive declares a symbol external so that it is available to other modules at link time.
(For more information about global symbols, see Section 2.6.1). The .global directive does double duty,
acting as a .def for defined symbols and as a .ref for undefined symbols. The linker resolves an
undefined global symbol reference only if the symbol is used in the program. The .global directive
declares a 16-bit symbol.
• The .mlib directive supplies the assembler with the name of an archive library that contains macro
definitions. When the assembler encounters a macro that is not defined in the current module, it
searches for it in the macro library specified with .mlib.
• The .ref directive identifies a symbol that is used in the current module but is defined in another
module. The assembler marks the symbol as an undefined external symbol and enters it in the object
symbol table so the linker can resolve its definition. The .ref directive forces the linker to resolve a
symbol reference.
• The .symdepend directive creates an artificial reference from the section defining the source symbol
name to the destination symbol. The .symdepend directive prevents the linker from removing the
section containing the destination symbol if the source symbol section is included in the output module.
• The .weak directive identifies a symbol that is used in the current module but is defined in another
module. It is equivalent to the .ref directive, except that the reference has weak linkage.
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Directives that Enable Conditional Assembly
Conditional assembly directives enable you to instruct the assembler to assemble certain sections of code
according to a true or false evaluation of an expression. Two sets of directives allow you to assemble
conditional blocks of code:
•
The .if/.elseif/.else/.endif directives tell the assembler to conditionally assemble a block of code
according to the evaluation of an expression.
.if condition
marks the beginning of a conditional block and assembles code
if the .if condition is true.
[.elseif condition]
marks a block of code to be assembled if the .if condition is
false and the .elseif condition is true.
.else
marks a block of code to be assembled if the .if condition is
false and any .elseif conditions are false.
.endif
marks the end of a conditional block and terminates the block.
•
The .loop/.break/.endloop directives tell the assembler to repeatedly assemble a block of code
according to the evaluation of an expression.
.loop [count]
marks the beginning of a repeatable block of code. The optional
expression evaluates to the loop count.
.break [end condition]
tells the assembler to assemble repeatedly when the .break end
condition is false and to go to the code immediately after
.endloop when the expression is true or omitted.
.endloop
marks the end of a repeatable block.
The assembler supports several relational operators that are useful for conditional expressions. For more
information about relational operators, see Section 4.9.2.
5.8
Directives that Define Union or Structure Types
These directives set up specialized types for later use with the .tag directive, allowing you to use symbolic
names to refer to portions of a complex object. The types created are analogous to the struct and union
types of the C language.
The .struct, .union, .cstruct, and .cunion directives group related data into an aggregate structure which is
more easily accessed. These directives do not allocate space for any object. Objects must be separately
allocated, and the .tag directive must be used to assign the type to the object.
COORDT
X
Y
T_LEN
.struct
.byte
.byte
.endstruct
; structure tag definition
;
COORD
.tag COORDT
.bss COORD, T_LEN
; declare COORD (coordinate)
; actual memory allocation
LDB
*+B14(COORD.Y), A2 ; move member Y of structure
; COORD into register A2
The .cstruct and .cunion directives guarantee that the data structure will have the same alignment and
padding as if the structure were defined in analogous C code. This allows structures to be shared between
C and assembly code. See Chapter 11. For .struct and .union, element offset calculation is left up to the
assembler, so the layout may be different than .cstruct and .cunion.
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5.9
Directives that Define Enumerated Types
These directives set up specialized types for later use in expressions allowing you to use symbolic names
to refer to compile-time constants. The types created are analogous to the enum type of the C language.
This allows enumerated types to be shared between C and assembly code. See Chapter 11.
See Section 11.2.10 for an example of using .enum.
5.10 Directives that Define Symbols at Assembly Time
Assembly-time symbol directives equate meaningful symbol names to constant values or strings.
• The .asg directive assigns a character string to a substitution symbol. The value is stored in the
substitution symbol table. When the assembler encounters a substitution symbol, it replaces the
symbol with its character string value. Substitution symbols created with .asg can be redefined.
.asg "10, 20, 30, 40", coefficients
; Assign string to substitution symbol.
.byte coefficients
; Place the symbol values 10, 20, 30, and 40
; into consecutive bytes in current section.
•
•
The .define directive assigns a character string to a substitution symbol. The value is stored in the
substitution symbol table. When the assembler encounters a substitution symbol, it replaces the
symbol with its character string value. Substitution symbols created with .define cannot be redefined.
The .eval directive evaluates a well-defined expression, translates the results into a character string,
and assigns the character string to a substitution symbol. This directive is most useful for manipulating
counters:
.asg
.loop
.byte
.break
.eval
.endloop
•
•
1 , x
x*10h
x = 4
x+1, x
;
;
;
;
;
;
x = 1
Begin conditional loop.
Store value into current section.
Break loop if x = 4.
Increment x by 1.
End conditional loop.
The .label directive defines a special symbol that refers to the load-time address within the current
section. This is useful when a section loads at one address but runs at a different address. For
example, you may want to load a block of performance-critical code into slower off-chip memory to
save space and move the code to high-speed on-chip memory to run. See the .label topic for an
example using a load-time address label.
The .set and .equ directives set a constant value to a symbol. The symbol is stored in the symbol table
and cannot be redefined; for example:
bval .set 0100h
; Set bval = 0100h
.long bval, bval*2, bval+12
; Store the values 0100h, 0200h, and 010Ch
; into consecutive words in current section.
•
•
•
The .set and .equ directives produce no object code. The two directives are identical and can be used
interchangeably.
The .unasg directive turns off substitution symbol assignment made with .asg.
The .undefine directive turns off substitution symbol assignment made with .define.
The .var directive allows you to use substitution symbols as local variables within a macro.
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Miscellaneous Directives
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5.11 Miscellaneous Directives
These directives enable miscellaneous functions or features:
• The .asmfunc and .endasmfunc directives mark function boundaries. These directives are used with
the compiler --symdebug:dwarf (-g) option to generate debug information for assembly functions.
• The .cdecls directive enables programmers in mixed assembly and C/C++ environments to share C
headers containing declarations and prototypes between C and assembly code.
• The .end directive terminates assembly. If you use the .end directive, it should be the last source
statement of a program. This directive has the same effect as an end-of-file character.
• The .group, .gmember, and .endgroup directives define an ELF group section to be shared by
several sections.
• The .import, .export, .hidden, and .protected directives set the dynamic visibility of a global symbol.
See Section 8.12 for an explanation of symbol visibility.
• The .newblock directive resets local labels. Local labels are symbols of the form $n, where n is a
decimal digit, or of the form NAME?, where you specify NAME. They are defined when they appear in
the label field. Local labels are temporary labels that can be used as operands for jump instructions.
The .newblock directive limits the scope of local labels by resetting them after they are used. See
Section 4.8.3 for information on local labels.
• The .nocmp directive instructs the tools to not utilize 16-bit instructions for the section .nocmp appears
in.
• The .noremark directive begins a block of code in which the assembler suppresses the specified
assembler remark. A remark is an informational assembler message that is less severe than a
warning. The .remark directive re-enables the remark(s) previously suppressed by .noremark.
These three directives enable you to define your own error and warning messages:
• The .emsg directive sends error messages to the standard output device. The .emsg directive
generates errors in the same manner as the assembler, incrementing the error count and preventing
the assembler from producing an object file.
• The .mmsg directive sends assembly-time messages to the standard output device. The .mmsg
directive functions in the same manner as the .emsg and .wmsg directives but does not set the error
count or the warning count. It does not affect the creation of the object file.
• The .wmsg directive sends warning messages to the standard output device. The .wmsg directive
functions in the same manner as the .emsg directive but increments the warning count rather than the
error count. It does not affect the creation of the object file.
For more information about using the error and warning directives in macros, see Section 6.7.
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5.12 Directives Reference
The remainder of this chapter is a reference. Generally, the directives are organized alphabetically, one
directive per topic. Related directives (such as .if/.else/.endif), however, are presented together in one
topic.
.align
Align SPC on the Next Boundary
.align [size in bytes]
Syntax
Description
The .align directive aligns the section program counter (SPC) on the next boundary,
depending on the size in bytes parameter. The size can be any power of 2, although
only certain values are useful for alignment. An operand of 1 aligns the SPC on the next
byte boundary, and this is the default if no size in bytes is given. The size in bytes must
equal a power of 2; the value must be between 1 and 32,768, inclusive. The assembler
assembles words containing null values (0) up to the next size in bytes boundary:
1
aligns SPC to byte boundary
2
aligns SPC to halfword boundary
4
aligns SPC to word boundary
8
aligns SPC to doubleword boundary
Using the .align directive has two effects:
• The assembler aligns the SPC on an x-byte boundary within the current section.
• The assembler sets a flag that forces the linker to align the section so that individual
alignments remain intact when a section is loaded into memory.
Example
This example shows several types of alignment, including .align 2, .align 8, and a default
.align.
1 00000000 00000004
2
3 00000002 00000045
00000003 00000072
00000004 00000072
00000005 0000006F
00000006 00000072
00000007 00000063
00000008 0000006E
00000009 00000074
4
5 00000008 0003746E
6 00000008 002B746E
7
8 0000000c 00000003
9
10 00000010 00000005
11
12 00000011 00000004
.byte
.align
.string
.align
.field
.field
.align
.field
.align
.field
.align
.byte
4
2
"Errorcnt"
3,3
5,4
2
3,3
8
5,4
4
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Directives Reference
.asg/.define/.eval
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Assign a Substitution Symbol
.asg "character string",substitution symbol
Syntax
.define "character string",substitution symbol
.eval expression,substitution symbol
Description
The .asg and .define directives assign character strings to substitution symbols.
Substitution symbols are stored in the substitution symbol table. The .asg directive can
be used in many of the same ways as the .set directive, but while .set assigns a
constant value (which cannot be redefined) to a symbol, .asg assigns a character string
(which can be redefined) to a substitution symbol.
• The assembler assigns the character string to the substitution symbol.
• The substitution symbol must be a valid symbol name. The substitution symbol is up
to 128 characters long and must begin with a letter. Remaining characters of the
symbol can be a combination of alphanumeric characters, the underscore (_), and
the dollar sign ($).
The .define directive functions in the same manner as the .asg directive, except that
.define disallows creation of a substitution symbol that has the same name as a register
symbol or mnemonic. It does not create a new symbol name space in the assembler,
rather it uses the existing substitution symbol name space. The .define directive is used
to prevent corruption of the assembly environment when converting C/C++ headers. See
Chapter 11 for more information about using C/C++ headers in assembly source.
The .eval directive performs arithmetic on substitution symbols, which are stored in the
substitution symbol table. This directive evaluates the expression and assigns the string
value of the result to the substitution symbol. The .eval directive is especially useful as a
counter in .loop/.endloop blocks.
• The expression is a well-defined alphanumeric expression in which all symbols have
been previously defined in the current source module, so that the result is an
absolute expression.
• The substitution symbol must be a valid symbol name. The substitution symbol is up
to 128 characters long and must begin with a letter. Remaining characters of the
symbol can be a combination of alphanumeric characters, the underscore (_), and
the dollar sign ($).
See the .unasg/.undefine topic for information on turning off a substitution symbol.
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Example
This example shows how .asg and .eval can be used.
1
2
3
4
5
6 00000000 003B22E4
#
7 00000004 00BC22E4
#
1
#
1
#
1
#
1
#
1
#
1
#
1
#
1
#
1
#
1
#
8 00000008 00006000
9 0000000c 010401E0
10
11
12
13
14
15
00000010 00000000
00000014 00000064
00000018 000000C8
0000001c 0000012C
00000020 00000190
.sslist ; show expanded substitution symbols
.asg
.asg
*+B14(100), GLOB100
*+B15(4),
ARG0
LDW
LDW
LDW
LDW
NOP
ADD
GLOB100,A0
*+B14(100),A0
ARG0,A1
*+B15(4),A1
4
A0,A1,A2
.asg
0,x
.loop
5
.word
100*x
.eval
x+1,x
.endloop
.word
100*x
.word
100*0
.eval
x+1,x
.eval
0+1,x
.word
100*x
.word
100*1
.eval
x+1,x
.eval
1+1,x
.word
100*x
.word
100*2
.eval
x+1,x
.eval
2+1,x
.word
100*x
.word
100*3
.eval
x+1,x
.eval
3+1,x
.word
100*x
.word
100*4
.eval
x+1,x
.eval
4+1,x
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.asmfunc/.endasmfunc Mark Function Boundaries
symbol
Syntax
.asmfunc [stack_usage(num)]
.endasmfunc
Description
The .asmfunc and .endasmfunc directives mark function boundaries. These directives
are used with the compiler -g option (--symdebug:dwarf) to allow assembly code
sections to be debugged in the same manner as C/C++ functions.
You should not use the same directives generated by the compiler (see Appendix A) to
accomplish assembly debugging; those directives should be used only by the compiler to
generate symbolic debugging information for C/C++ source files.
The symbol is a label that must appear in the label field.
The .asmfunc directive has an optional parameter, stack_usage, which indicates that the
function may use up to num bytes.
Consecutive ranges of assembly code that are not enclosed within a pair of .asmfunc
and .endasmfunc directives are given a default name in the following format:
$ filename : beginning source line : ending source line $
Example
This example generates debug information for the user_func section.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
92
00000000
.sect
".text"
.global userfunc
.global _printf
userfunc:
00000000
00000004
00000008
0000000c
00000010
00000010!
01BC94F6
01800E2A'
01800028+
01800068+
.asmfunc stack_usage(16)
CALL
.S1
_printf
STW
.D2T2
B3,*B15--(16)
MVKL
.S2
RL0,B3
MVKL
.S1
SL1+0,A3
MVKH
.S1
SL1+0,A3
00000014 01BC22F5
00000018 0180006A' ||
STW
MVKH
.D2T1
.S2
0000001c
00000020
00000024
00000028
0000002c
01BC92E6
020008C0
00004000
000C0362
00008000
RL0:
LDW
.D2T2
ZERO
.D1
NOP
RET
.S2
NOP
.endasmfunc
00000000
00000000
00000001
00000002
00000003
00000004
00000005
00000006
00000007
00000008
00000009
0000000a
0000000b
0000000c
0000000d
00000048
00000065
0000006C
0000006C
0000006F
00000020
00000057
0000006F
00000072
0000006C
00000064
00000021
0000000A
00000000
SL1:
A3,*+B15(4)
RL0,B3
*++B15(16),B3
A4
3
B3
5
.sect
".const"
.string "Hello World!",10,0
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.bits
Initialize Bits
.bits value1[, ... , valuen ]
Syntax
Description
The .bits directive places one or more values into consecutive bits of the current section.
The .bits directive is similar to the .field directive (see .field topic ). However, the .bits
directive does not allow you to specify the number of bits to fill or increment the SPC.
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.bss
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Reserve Space in the .bss Section
.bss symbol,size in bytes[, alignment[, bank offset]]
Syntax
Description
The .bss directive reserves space for variables in the .bss section. This directive is
usually used to allocate space in RAM.
• The symbol is a required parameter. It defines a symbol that points to the first
location reserved by the directive. The symbol name must correspond to the variable
that you are reserving space for.
• The size in bytes is a required parameter; it must be an absolute constant
expression. The assembler allocates size bytes in the .bss section. There is no
default size.
• The alignment is an optional parameter that ensures that the space allocated to the
symbol occurs on the specified boundary. This must be set to a power of 2. If the
SPC is already aligned to the specified boundary, it is not incremented.
• The bank offset is an optional parameter that ensures that the space allocated to the
symbol occurs on a specific memory bank boundary. The bank offset value measures
the number of bytes to offset from the alignment specified before assigning the
symbol to that location.
For more information about sections, see Chapter 2.
Example
In this example, the .bss directive allocates space for a variable, array. The symbol array
points to 100 bytes of uninitialized space (at .bss SPC = 0). Symbols declared with the
.bss directive can be referenced in the same manner as other symbols and can also be
declared global.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
94
00000000
00000000 008001A0
*******************************************
** Start assembling into .text section. **
*******************************************
.text
MV
A0,A1
00000000
*******************************************
** Allocate 100 bytes in .bss.
**
*******************************************
.bss
array,100
00000004 010401A0
*******************************************
** Still in .text
**
*******************************************
MV
A1,A2
*******************************************
** Declare external .bss symbol
**
*******************************************
.global array
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.byte/.ubyte/.char/.uchar Initialize Byte
.byte value1[, ... , valuen ]
Syntax
.ubyte value1[, ... , valuen ]
.char value1[, ... , valuen ]
.uchar value1[, ... , valuen ]
Description
The .byte, .ubyte, .char, and .uchar directives place one or more values into
consecutive bytes of the current section. A value can be one of the following:
• An expression that the assembler evaluates and treats as an 8-bit signed number
• A character string enclosed in double quotes. Each character in a string represents a
separate value, and values are stored in consecutive bytes. The entire string must be
enclosed in quotes.
With little-endian ordering, the first byte occupies the eight least significant bits of a full
32-bit word. The second byte occupies bits eight through 15 while the third byte
occupies bits 16 through 23. The assembler truncates values greater than eight bits.
If you use a label, it points to the location of the first byte that is initialized.
When you use these directives in a .struct/.endstruct sequence, they define a member's
size; they do not initialize memory. For more information, see the .struct/.endstruct/.tag
topic.
Example
In this example, 8-bit values (10, -1, abc, and a) are placed into consecutive bytes in
memory with .byte. Also, 8-bit values (8, -3, def, and b) are placed into consecutive
bytes in memory with .char. The label STRX has the value 0h, which is the location of
the first initialized byte. The label STRY has the value 6h, which is the first byte
initialized by the .char directive.
1 00000000
00000001
00000002
00000003
00000004
00000005
2 00000006
0000000A
000000FF
00000061
00000062
00000063
00000061
00000008
STRX
.byte
10,-1,"abc",'a'
STRY
.char
8,-3,"def",'b'
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.cdecls
Share C Headers Between C and Assembly Code
Syntax
Single Line:
.cdecls [options ,] " filename "[, " filename2 "[,...]]
Multiple Lines:
Syntax
.cdecls [options]
%{
/*---------------------------------------------------------------------------------*/
/* C/C++ code - Typically a list of #includes and a few defines */
/*---------------------------------------------------------------------------------*/
%}
Description
The .cdecls directive allows programmers in mixed assembly and C/C++ environments
to share C headers containing declarations and prototypes between the C and assembly
code. Any legal C/C++ can be used in a .cdecls block and the C/C++ declarations cause
suitable assembly to be generated automatically, allowing you to reference the C/C++
constructs in assembly code; such as calling functions, allocating space, and accessing
structure members; using the equivalent assembly mechanisms. While function and
variable definitions are ignored, most common C/C++ elements are converted to
assembly, for instance: enumerations, (non-function-like) macros, function and variable
prototypes, structures, and unions.
The .cdecls options control whether the code is treated as C or C++ code; and how the
.cdecls block and converted code are presented. Options must be separated by
commas; they can appear in any order:
C
CPP
NOLIST
LIST
NOWARN
WARN
Treat the code in the .cdecls block as C source code (default).
Treat the code in the .cdecls block as C++ source code. This is the
opposite of the C option.
Do not include the converted assembly code in any listing file generated
for the containing assembly file (default).
Include the converted assembly code in any listing file generated for the
containing assembly file. This is the opposite of the NOLIST option.
Do not emit warnings on STDERR about C/C++ constructs that cannot
be converted while parsing the .cdecls source block (default).
Generate warnings on STDERR about C/C++ constructs that cannot be
converted while parsing the .cdecls source block. This is the opposite of
the NOWARN option.
In the single-line format, the options are followed by one or more filenames to include.
The filenames and options are separated by commas. Each file listed acts as if #include
"filename" was specified in the multiple-line format.
In the multiple-line format, the line following .cdecls must contain the opening .cdecls
block indicator %{. Everything after the %{, up to the closing block indicator %}, is
treated as C/C++ source and processed. Ordinary assembler processing then resumes
on the line following the closing %}.
The text within %{ and %} is passed to the C/C++ compiler to be converted into
assembly language. Much of C language syntax, including function and variable
definitions as well as function-like macros, is not supported and is ignored during the
conversion. However, all of what traditionally appears in C header files is supported,
including function and variable prototypes; structure and union declarations; nonfunction-like macros; enumerations; and #defines.
96
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The resulting assembly language is included in the assembly file at the point of the
.cdecls directive. If the LIST option is used, the converted assembly statements are
printed in the listing file.
The assembly resulting from the .cdecls directive is treated similarly to a .include file.
Therefore the .cdecls directive can be nested within a file being copied or included. The
assembler limits nesting to ten levels; the host operating system may set additional
restrictions. The assembler precedes the line numbers of copied files with a letter code
to identify the level of copying. An A indicates the first copied file, B indicates a second
copied file, etc.
The .cdecls directive can appear anywhere in an assembly source file, and can occur
multiple times within a file. However, the C/C++ environment created by one .cdecls is
not inherited by a later .cdecls; the C/C++ environment starts new for each .cdecls.
See Chapter 11 for more information on setting up and using the .cdecls directive with C
header files.
Example
In this example, the .cdecls directive is used call the C header.h file.
C header file:
#define WANT_ID 10
#define NAME "John\n"
extern int a_variable;
extern float cvt_integer(int src);
struct myCstruct { int member_a; float member_b; };
enum status_enum { OK = 1, FAILED = 256, RUNNING = 0 };
Source file:
.cdecls C,LIST,"myheader.h"
size:
aoffset:
boffset:
okvalue:
failval:
id
.int $sizeof(myCstruct)
.int myCstruct.member_a
.int myCstruct.member_b
.int status_enum.OK
.int status_enum.FAILED
.if $defined(WANT_ID)
.cstring NAME
.endif
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Listing File:
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
2
3
4
5
6
7
8
.cdecls C,LIST,"myheader.h"
; -----------------------------------------; Assembly Generated from C/C++ Source Code
; -----------------------------------------; =========== MACRO DEFINITIONS ===========
.define "10",WANT_ID
.define """John\n""",NAME
; =========== TYPE DEFINITIONS ===========
status_enum
.enum
00000001 OK
.emember 1
00000100 FAILED
.emember 256
00000000 RUNNING
.emember 0
.endenum
myCstruct
.struct 0,4
; struct size=(8 bytes|64 bits), alignment=4
00000000 member_a
.field 32
; int member_a - offset 0 bytes, size (4 bytes|32 bits)
00000004 member_b
.field 32
; float member_b - offset 4 bytes, size (4 bytes|32 bits)
00000008
.endstruct
; final size=(8 bytes|64 bits)
; =========== EXTERNAL FUNCTIONS ===========
.global _cvt_integer
00000000
00000004
00000008
0000000c
00000010
00000008
00000000
00000004
00000001
00000100
00000014
00000015
00000016
00000017
00000018
00000019
0000004A
0000006F
00000068
0000006E
0000000A
00000000
9
98
; =========== EXTERNAL VARIABLES ===========
.global _a_variable
size:
.int $sizeof(myCstruct)
aoffset: .int myCstruct.member_a
boffset: .int myCstruct.member_b
okvalue: .int status_enum.OK
failval: .int status_enum.FAILED
.if $defined(WANT_ID)
id
.cstring NAME
.endif
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.common
Create a Common Symbol
.common symbol,size in bytes[, alignment]
Syntax
.common symbol,structure tag[, alignment]
Description
The .common directive creates a common symbol in a common block, rather than
placing the variable in a memory section.
This directive is used by the compiler when the --common option is enabled (the default),
which causes uninitialized file scope variables to be emitted as common symbols. The
benefit of common symbols is that generated code can remove unused variables that
would otherwise increase the size of the .bss section. (Uninitialized variables of a size
larger than 32 bytes are separately optimized through placement in separate subsections
that can be omitted from a link.) This optimization happens for C/C++ code by default
unless you use the --common=off compiler option.
• The symbol is a required parameter. It defines a name for the symbol created by this
directive. The symbol name must correspond to the variable that you are reserving
space for.
• The size in bytes is a required parameter; it must be an absolute expression. The
assembler allocates size bytes in the section used for common symbols. There is no
default size.
• A structure tag can be used in place of a size to specify a structure created with the
.struct directive. Either a size or a structure tag is required for this argument.
• The alignment is an optional parameter that ensures that the space allocated to the
symbol occurs on the specified boundary. The boundary must be set to a power of 2
between 20 and 215, inclusive. If the SPC is already aligned at the specified boundary,
it is not incremented.
Common symbols are symbols that are placed in the symbol table of an ELF object file.
They represent an uninitialized variable. Common symbols do not reference a section.
(In contrast, initialized variables need to reference a section that contains the initialized
data.) The value of a common symbol is its required alignment; it has no address and
stores no address. While symbols for an uninitialized common block can appear in
executable object files, common symbols may only appear in relocatable object files.
Common symbols are preferred over weak symbols. See the section on the "Symbol
Table" in the System V ABI specification for more about common symbols.
When object files containing common symbols are linked, space is reserved in an
uninitialized section for each common symbol. A symbol is created in place of the
common symbol to refer to its reserved location.
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.copy/.include
Syntax
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Copy Source File
.copy "filename"
.include "filename"
Description
The .copy and .include directives tell the assembler to read source statements from a
different file. The statements that are assembled from a copy file are printed in the
assembly listing. The statements that are assembled from an included file are not printed
in the assembly listing, regardless of the number of .list/.nolist directives assembled.
When a .copy or .include directive is assembled, the assembler:
1. Stops assembling statements in the current source file
2. Assembles the statements in the copied/included file
3. Resumes assembling statements in the main source file, starting with the statement
that follows the .copy or .include directive
The filename is a required parameter that names a source file. It is enclosed in double
quotes and must follow operating system conventions.
You can specify a full pathname (for example, /320tools/file1.asm). If you do not specify
a full pathname, the assembler searches for the file in:
1. The directory that contains the current source file
2. Any directories named with the --include_path assembler option
3. Any directories specified by the C6X_A_DIR environment variable
4. Any directories specified by the C6X_C_DIR environment variable
For more information about the --include_path option and C6X_A_DIR, see Section 4.5.
For more information about C6X_C_DIR, see the TMS320C6000 Optimizing Compiler
User's Guide.
The .copy and .include directives can be nested within a file being copied or included.
The assembler limits nesting to 32 levels; the host operating system may set additional
restrictions. The assembler precedes the line numbers of copied files with a letter code
to identify the level of copying. A indicates the first copied file, B indicates a second
copied file, etc.
Example 1
In this example, the .copy directive is used to read and assemble source statements
from other files; then, the assembler resumes assembling into the current file.
The original file, copy.asm, contains a .copy statement copying the file byte.asm. When
copy.asm assembles, the assembler copies byte.asm into its place in the listing (note
listing below). The copy file byte.asm contains a .copy statement for a second file,
word.asm.
When it encounters the .copy statement for word.asm, the assembler switches to
word.asm to continue copying and assembling. Then the assembler returns to its place
in byte.asm to continue copying and assembling. After completing assembly of byte.asm,
the assembler returns to copy.asm to assemble its remaining statement.
copy.asm
(source file)
.space 29
.copy "byte.asm"
** Back in original file
.string "done"
100
byte.asm
(first copy file)
** In byte.asm
.byte 32,1+ 'A'
.copy "word.asm"
word.asm
(second copy file)
** In word.asm
.word 0ABCDh, 56q
** Back in byte.asm
.byte 67h + 3q
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Listing file:
A
A
A
B
B
A
A
Example 2
1 00000000
2
1
2 0000001d 00000020
0000001e 00000042
3
1
2 00000020 0000ABCD
00000024 0000002E
4
5 00000028 0000006A
3
4
5 00000029 00000064
0000002a 0000006F
0000002b 0000006E
0000002c 00000065
.space 29
.copy "byte.asm"
** In byte.asm
.byte 32,1+ 'A'
.copy "word.asm"
** In word.asm
.word 0ABCDh, 56q
** Back in byte.asm
.byte 67h + 3q
** Back in original file
.string "done"
In this example, the .include directive is used to read and assemble source statements
from other files; then, the assembler resumes assembling into the current file. The
mechanism is similar to the .copy directive, except that statements are not printed in the
listing file.
include.asm
(source file)
.space 29
.include "byte2.asm"
** Back in original file
byte2.asm
(first copy file)
** In byte2.asm
.byte 32,1+ 'A'
.include
"word2.asm"
** Back in byte2.asm
word2.asm
(second copy file)
** In word2.asm
.word 0ABCDh, 56q
.string "done"
.byte 67h + 3q
Listing file:
1 00000000
2
3
4
5 00000029 00000064
0000002a 0000006F
0000002b 0000006E
0000002c 00000065
.space 29
.include "byte2.asm"
** Back in original file
.string "done"
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.cstruct/.cunion/.endstruct/.endunion/.tag Declare C Structure Type
Syntax
[stag]
.cstruct|.cunion
[expr]
[mem0]
[mem1]
.
.
element
element
.
.
[expr0]
[expr1]
[memn]
.tag stag
[exprn]
[memN]
element
[exprN]
[size]
label
Description
.
.
.endstruct|.endunion
.tag
stag
The .cstruct and .cunion directives have been added to support ease of sharing of
common data structures between assembly and C code. The .cstruct and .cunion
directives can be used exactly like the existing .struct and .union directives except that
they are guaranteed to perform data layout matching the layout used by the C compiler
for C struct and union data types.
In particular, the .cstruct and .cunion directives force the same alignment and padding as
used by the C compiler when such types are nested within compound data structures.
The .endstruct directive terminates the structure definition. The .endunion directive
terminates the union definition.
The .tag directive gives structure characteristics to a label, simplifying the symbolic
representation and providing the ability to define structures that contain other structures.
The .tag directive does not allocate memory. The structure tag (stag) of a .tag directive
must have been previously defined.
Following are descriptions of the parameters used with the .struct, .endstruct, and .tag
directives:
• The stag is the structure's tag. Its value is associated with the beginning of the
structure. If no stag is present, the assembler puts the structure members in the
global symbol table with the value of their absolute offset from the top of the
structure. The stag is optional for .struct, but is required for .tag.
• The element is one of the following descriptors: .byte, .char, .int, .long, .word,
.double, .half, .short, .string, .float, and .field. All of these except .tag are typical
directives that initialize memory. Following a .struct directive, these directives
describe the structure element's size. They do not allocate memory. A .tag directive
is a special case because stag must be used (as in the definition of stag).
• The expr is an optional expression indicating the beginning offset of the structure.
The default starting point for a structure is 0.
• The exprn/N is an optional expression for the number of elements described. This
value defaults to 1. A .string element is considered to be one byte in size, and a .field
element is one bit.
• The memn/N is an optional label for a member of the structure. This label is absolute
and equates to the present offset from the beginning of the structure. A label for a
structure member cannot be declared global.
• The size is an optional label for the total size of the structure.
Example
102
This example illustrates a structure in C that will be accessed in assembly code.
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typedef struct STRUCT1
; {
int i0;
/* offset 0 */
;
short s0;
/* offset 4 */
; } struct1;
/* size 8, alignment 4 */
;
; typedef struct STRUCT2
; {
struct1 st1; /* offset 0 */
;
short s1;
/* offset 8 */
; } struct2;
/* size 12, alignment 4 */
;
; The structure will get the following offsets once the C compiler lays out the structure
; elements according to the C standard rules:
;
; offsetof(struct1, i0) = 0
; offsetof(struct1, s0) = 4
; sizeof(struct1)
= 8
; offsetof(struct2, s1) = 0
; offsetof(struct2, i1) = 8
; sizeof(struct2)
= 12
;
; Attempts to replicate this structure in assembly using the .struct/.union directives will not
; create the correct offsets because the assembler tries to use the most compact arrangement:
struct1
i0
s0
struct1len
.struct
.int
.short
.endstruct
struct2
st1
s1
endstruct2
.struct
.tag struct1
.short
.endstruct
; bytes 0-3
; bytes 4-5
; size 6, alignment 4
; bytes 0-5
; bytes 6-7
; size 8, alignment 4
.sect
.word
.word
.word
"data1"
struct1.i0
struct1.s0
struct1len
; 0
; 4
; 6
.sect
.word
.word
.word
"data2"
struct2.st1
struct2.s1
endstruct2
; 0
; 6
; 8
;
; The .cstruct/.cunion directives calculate offsets in the same manner as the C compiler. The resulting
; assembly structure can be used to access the elements of the C structure. Compare the difference
; in the offsets of those structures defined via .struct above and the offsets for the C code.
cstruct1
i0
s0
cstruct1len
.cstruct
.int
.short
.endstruct
cstruct2
st1
s1
cendstruct2
.cstruct
.tag cstruct1
; bytes 0-7
.short
; bytes 8-9
.endstruct
; size 12, alignment 4
; bytes 0-3
; bytes 4-5
; size 8, alignment 4
.sect
.word
.word
.word
"data3"
cstruct1.i0, struct1.i0
cstruct1.s0, struct1.s0
cstruct1len, struct1len
.sect
.word
.word
.word
"data4"
cstruct2.st1, struct2.st1 ; 0
cstruct2.s1, struct2.s1
; 8
cendstruct2, endstruct2
; 12
; 0
; 4
; 8
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.data
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Assemble Into the .data Section
.data
Syntax
Description
The .data directive sets .data as the current section; the lines that follow will be
assembled into the .data section. The .data section is normally used to contain tables of
data or preinitialized variables.
For more information about sections, see Chapter 2.
Example
In this example, code is assembled into the .data and .text sections.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
104
00000000
00000000
***********************************************
**
Reserve space in .data
**
***********************************************
.data
.space 0CCh
00000000
00000000 00800358
***********************************************
**
Assemble into .text
**
***********************************************
.text
ABS
A0,A1
000000cc
000000cc FFFFFFFF
000000d0 000000FF
***********************************************
**
Assemble into .data
**
***********************************************
table: .data
.word
-1
.byte
0FFh
00000004
00000004 008001A0
***********************************************
**
Assemble into .text
**
***********************************************
.text
MV
A0,A1
000000d1
000000d4 00000000
000000d8 0000000A
000000dc 0000000B
***********************************************
** Resume assembling into the .data section **
***********************************************
.data
coeff
.word
00h,0ah,0bh
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.double
Initialize Double-Precision Floating-Point Value
.double value1 [, ... , valuen]
Syntax
The .double directive places the IEEE double-precision floating-point representation of
one or more floating-point values into the current section. Each value must be an
absolute constant expression with an arithmetic type or a symbol equated to an absolute
constant expression with an arithmetic type. Each constant is converted to a floatingpoint value in IEEE double-precision 64-bit format. Double-precision floating point
constants are aligned to a double word boundary.
Description
The 64-bit value is stored in the format shown in Figure 5-5.
Figure 5-5. Double-Precision Floating-Point Format
S E E E E E E E E E E E MMMMMMMMMM MMMMMMMMMM
31
20
0
MMMMMMMMMM MMMMMMMMMMMM MMMMMMMMMM
31
0
Legend:
S = sign
E = exponent (11-bit biased)
M = mantissa (52-bit fraction)
When you use .double in a .struct/.endstruct sequence, .double defines a member's size;
it does not initialize memory. For more information, see the .struct/.endstruct/.tag topic.
Example
This example shows the .double directive.
1 00000000
00000004
2 00000008
0000000c
3 00000010
00000014
2C280291
C5308B2A
00000000
40180000
00000000
407C8000
.double -2.0e25
.double 6
.double 456
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.drlist/.drnolist
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Control Listing of Directives
.drlist
Syntax
.drnolist
Description
Two directives enable you to control the printing of assembler directives to the listing file:
The .drlist directive enables the printing of all directives to the listing file.
The .drnolist directive suppresses the printing of the following directives to the listing
file. The .drnolist directive has no affect within macros.
•
•
•
•
•
.asg
.break
.emsg
.eval
.fclist
•
•
•
•
•
.fcnolist
.mlist
.mmsg
.mnolist
.sslist
•
•
•
.ssnolist
.var
.wmsg
By default, the assembler acts as if the .drlist directive had been specified.
Example
This example shows how .drnolist inhibits the listing of the specified directives.
Source file:
.length 65
.width 85
.asg
0, x
.loop
2
.eval
x+1, x
.endloop
.drnolist
.length 55
.width 95
.asg
1, x
.loop
3
.eval
x+1, x
.endloop
Listing file:
3
4
5
6
1
1
7
8
12
13
14
106
.asg
0, x
.loop
2
.eval
x+1, x
.endloop
.eval
0+1, x
.eval
1+1, x
.drnolist
.loop
3
.eval
x+1, x
.endloop
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.elfsym
ELF Symbol Information
.elfsym name, SYM_SIZE(size)
Syntax
Description
The .elfsym directive provides additional information for symbols in the ELF format. This
directive is designed to convey different types of information, so the type, data pair is
used to represent each type. Currently, this directive only supports the SYM_SIZE type.
SYM_SIZE indicates the allocation size (in bytes) of the symbol indicated by name.
Example
This example shows the use of the ELF symbol information directive.
.sect
".examp"
.alignment 4
.elfsym
ex_sym, SYM_SIZE(4)
ex_sym:
.word
0
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.emsg/.mmsg/.wmsg Define Messages
.emsg string
Syntax
.mmsg string
.wmsg string
Description
These directives allow you to define your own error and warning messages. When you
use these directives, the assembler tracks the number of errors and warnings it
encounters and prints these numbers on the last line of the listing file.
The .emsg directive sends an error message to the standard output device in the same
manner as the assembler. It increments the error count and prevents the assembler from
producing an object file.
The .mmsg directive sends an assembly-time message to the standard output device in
the same manner as the .emsg and .wmsg directives. It does not, however, set the error
or warning counts, and it does not prevent the assembler from producing an object file.
The .wmsg directive sends a warning message to the standard output device in the
same manner as the .emsg directive. It increments the warning count rather than the
error count, however. It does not prevent the assembler from producing an object file.
Example
This example sends the message ERROR -- MISSING PARAMETER to the standard
output device.
Source file:
MSG_EX
.global
.macro
.if
.emsg
.else
MVK
.endif
.endm
PARAM
parm1
$symlen(parm1) = 0
"ERROR -- MISSING PARAMETER"
parm1, A1
MSG_EX PARAM
MSG_EX
Listing file:
1
2
3
4
5
6
7
8
9
10 00000000
1
1
1
1
1
00000000 00800028!
MSG_EX
.global PARAM
.macro parm1
.if
$symlen(parm1) = 0
.emsg
"ERROR -- MISSING PARAMETER"
.else
MVK parm1, A1
.endif
.endm
MSG_EX PARAM
.if
$symlen(parm1) = 0
.emsg
"ERROR -- MISSING PARAMETER"
.else
MVK PARAM, A1
.endif
11
12 00000004
MSG_EX
.if
$symlen(parm1) = 0
.emsg
"ERROR -- MISSING PARAMETER"
***** USER ERROR ***** - : ERROR -- MISSING PARAMETER
1
.else
1
MVK parm1, A1
1
.endif
1
1
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1 Error, No Warnings
In addition, the following messages are sent to standard output by the assembler:
"t.asm", ERROR!
at line 10: [ ***** USER ERROR ***** - ] ERROR -MISSING PARAMETER
.emsg
"ERROR -- MISSING PARAMETER"
1 Assembly Error, No Assembly Warnings
Errors in Source - Assembler Aborted
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.end
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End Assembly
.end
Syntax
Description
The .end directive is optional and terminates assembly. The assembler ignores any
source statements that follow a .end directive. If you use the .end directive, it must be
the last source statement of a program.
This directive has the same effect as an end-of-file character. You can use .end when
you are debugging and you want to stop assembling at a specific point in your code.
Ending a Macro
NOTE: Do not use the .end directive to terminate a macro; use the .endm macro
directive instead.
Example
This example shows how the .end directive terminates assembly. Any source statements
that follow the .end directive are ignored by the assembler.
Source file:
start:
.text
ZERO
ZERO
ZERO
.end
ZERO
A0
A1
A3
A4
Listing file:
1
2
3
4
5
110
00000000
00000000 000005E0
00000004 008425E0
00000008 018C65E0
start:
.text
ZERO
ZERO
ZERO
.end
A0
A1
A3
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.farcommon/.nearcommon Create a Common Symbol
.farcommon symbol,size in bytes[, alignment]
Syntax
.farcommon symbol,structure tag[, alignment]
.nearcommon symbol,size in bytes[, alignment]
.nearcommon symbol,structure tag[, alignment]
Description
The .farcommon and .nearcommon directives create a common symbol in a common
block, rather than placing variables in a section. The .farcommon directive places the
symbol in far memory, and the .nearcommon directive places the symbol in near
memory.
A common symbol cannot be created for a symbol that has a memory bank
specification, for example because the DATA_MEM_BANK pragma was used to align
the variable.
These directives are used by the compiler when the --common option is enabled (the
default), which causes uninitialized file scope variables to be emitted as common
symbols. The benefit of common symbols is that generated code can remove unused
variables that would otherwise increase the size of the .bss section. (Uninitialized
variables of a size larger than 32 bytes are separately optimized through placement in
separate subsections that can be omitted from a link.) This optimization happens for
C/C++ code by default unless you use the --common=off compiler option.
• The symbol is a required parameter. It defines a name for the symbol created by this
directive. The symbol name must correspond to the variable that you are reserving
space for.
• The size in bytes is a required parameter; it must be an absolute expression. The
assembler allocates size bytes in the section used for common symbols. There is no
default size.
• A structure tag can be used in place of a size to specify a structure created with the
.struct directive. Either a size or a structure tag is required for this argument.
• The alignment is an optional parameter that ensures that the space allocated to the
symbol occurs on the specified boundary. This boundary must be set to a power of 2.
If the SPC is already aligned to the specified boundary, it is not incremented.
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.fclist/.fcnolist
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Control Listing of False Conditional Blocks
.fclist
Syntax
.fcnolist
Description
Two directives enable you to control the listing of false conditional blocks:
The .fclist directive allows the listing of false conditional blocks (conditional blocks that
do not produce code).
The .fcnolist directive suppresses the listing of false conditional blocks until a .fclist
directive is encountered. With .fcnolist, only code in conditional blocks that are actually
assembled appears in the listing. The .if, .elseif, .else, and .endif directives do not
appear.
By default, all conditional blocks are listed; the assembler acts as if the .fclist directive
had been used.
Example
This example shows the assembly language and listing files for code with and without
the conditional blocks listed.
Source file:
a
b
.set
0
.set
1
.fclist
; list false conditional blocks
.if
a
MVK
5,A0
.else
MVK
0,A0
.endif
.fcnolist ; do not list false conditional blocks
.if
a
MVK
5,A0
.else
MVK
0,A0
.endif
Listing file:
1
00000000
2
00000001
3
4
5
6
7 00000000 00000028
8
9
13 00000004 00000028
112
a
b
.set
0
.set
1
.fclist
; list false conditional blocks
.if
a
MVK
5,A0
.else
MVK
0,A0
.endif
.fcnolist ; do not list false conditional blocks
MVK
0,A0
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.field
Initialize Field
.field value[, size in bits]
Syntax
Description
The .field directive initializes a multiple-bit field within a single word (32 bits) of memory.
This directive has two operands:
• The value is a required parameter; it is an expression that is evaluated and placed in
the field. The value must be absolute.
• The size in bits is an optional parameter; it specifies a number from 1 to 32, which is
the number of bits in the field. The default size is 32 bits. If you specify a value that
cannot fit in size in bits, the assembler truncates the value and issues a warning
message. For example, .field 3,1 causes the assembler to truncate the value 3 to 1;
the assembler also prints the message:
"t.asm", WARNING! at line 1: [W0001] Value truncated to 1
.field 3, 1
Successive .field directives pack values into the specified number of bits starting at the
current 32-bit location. Fields are packed starting at the least significant bit (bit 0),
moving toward the most significant bit (bit 31) as more fields are added. If the assembler
encounters a field size that does not fit in the current 32-bit word, it fills the remaining
bits of the current byte with 0s, increments the SPC to the next word boundary, and
begins packing fields into the next word.
The .field directive is similar to the .bits directive (see the .bits topic). However, the .bits
directive does not allow you to specify the number of bits in the field and does not
automatically increment the SPC when a word boundary is reached.
Use the .align directive to force the next .field directive to begin packing a new word.
If you use a label, it points to the byte that contains the specified field.
When you use .field in a .struct/.endstruct sequence, .field defines a member's size; it
does not initialize memory. For more information, see the .struct/.endstruct/.tag topic.
Example
This example shows how fields are packed into a word. The SPC does not change until
a word is filled and the next word is begun.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
00000000 00BBCCDD
************************************
**
Initialize a 24-bit field. **
************************************
.field 0BBCCDDh, 24
00000000 0ABBCCDD
************************************
**
Initialize a 5-bit field
**
************************************
.field 0Ah, 5
00000004 0000000C
***********************************
**
Initialize a 4-bit field
**
**
in a new word.
**
************************************
.field 0Ch, 4
00000004 0000001C
************************************
**
Initialize a 3-bit field
**
************************************
x:
.field 01h, 3
************************************
**
Initialize a 32-bit field
**
**
relocatable field in the
**
**
next word
**
************************************
00000008 00000004'
.field x
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Figure 5-6 shows how the directives in this example affect memory.
Figure 5-6. The .field Directive
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.float
Initialize Single-Precision Floating-Point Value
.float value[, ... , valuen]
Syntax
The .float directive places the IEEE single-precision floating-point representation of a
single floating-point constant into a word in the current section. The value must be an
absolute constant expression with an arithmetic type or a symbol equated to an absolute
constant expression with an arithmetic type. Each constant is converted to a floatingpoint value in IEEE single-precision 32-bit format.
Description
With big-endian ordering, the 32-bit value is stored exponent byte first, most significant
byte of fraction second, and least significant byte of fraction third, in the format shown in
Figure 5-7.
Figure 5-7. Single-Precision Floating-Point Format
S E E E E E E E E MMMMMMMMMMMMM MMMMMMMMMM
31
0
23
value = (-1)S x (1.0 + mantissa) x (2)exponent-127
Legend:
S = sign (1 bit)
E = exponent (8-bit biased)
M = mantissa (23-bit fraction)
When you use .float in a .struct/.endstruct sequence, .float defines a member's size; it
does not initialize memory. For more information, see the .struct/.endstruct/.tag topic.
Example
Following are examples of the .float directive:
1 00000000 E9045951
2 00000004 40400000
3 00000008 42F60000
.float
.float
.float
-1.0e25
3
123
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.global/.def/.ref
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Identify Global Symbols
.global symbol1[, ... , symboln]
Syntax
.def symbol1[, ... , symboln]
.ref symbol1[, ... , symboln]
Description
Three directives identify global symbols that are defined externally or can be referenced
externally:
The .def directive identifies a symbol that is defined in the current module and can be
accessed by other files. The assembler places this symbol in the symbol table.
The .ref directive identifies a symbol that is used in the current module but is defined in
another module. The linker resolves this symbol's definition at link time.
The .global directive acts as a .ref or a .def, as needed.
A global symbol is defined in the same manner as any other symbol; that is, it appears
as a label or is defined by the .set, .equ, .bss, or .usect directive. If a global symbol is
defined more than once, the linker issues a multiple-definition error. (The assembler can
provide a similar multiple-definition error for local symbols.) The .ref directive always
creates a symbol table entry for a symbol, whether the module uses the symbol or not;
.global, however, creates an entry only if the module actually uses the symbol.
A symbol can be declared global for either of two reasons:
• If the symbol is not defined in the current module (which includes macro, copy, and
include files), the .global or .ref directive tells the assembler that the symbol is
defined in an external module. This prevents the assembler from issuing an
unresolved reference error. At link time, the linker looks for the symbol's definition in
other modules.
• If the symbol is defined in the current module, the .global or .def directive declares
that the symbol and its definition can be used externally by other modules. These
types of references are resolved at link time.
Example
This example shows four files. The file1.lst and file2.lst refer to each other for all symbols
used; file3.lst and file4.lst are similarly related.
The file1.lst and file3.lst files are equivalent. Both files define the symbol INIT and
make it available to other modules; both files use the external symbols X, Y, and Z. Also,
file1.lst uses the .global directive to identify these global symbols; file3.lst uses .ref and
.def to identify the symbols.
The file2.lst and file4.lst files are equivalent. Both files define the symbols X, Y, and Z
and make them available to other modules; both files use the external symbol INIT. Also,
file2.lst uses the .global directive to identify these global symbols; file4.lst uses .ref and
.def to identify the symbols.
file1.lst
1
2
3
4
5 00000000
6 00000000 00902058
7 00000004 00000000!
8
9
10
11
116
; Global symbol defined in this file
.global INIT
; Global symbols defined in file2.lst
.global X, Y, Z
INIT:
ADD.L1 0x01,A4,A1
.word
X
;
.
;
.
;
.
.end
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file2.lst
1
2
3
4
5
6
7
8 00000000
9
10
11
12
; Global symbols defined in this file
.global X, Y, Z
; Global symbol defined in file1.lst
.global INIT
00000001 X:
.set
1
00000002 Y:
.set
2
00000003 Z:
.set
3
00000000!
.word
INIT
;
.
;
.
;
.
.end
file3.lst
1
2
3
4
5 00000000
6 00000000 00902058
7 00000004 00000000!
8
9
10
11
; Global symbol defined in this file
.def
INIT
; Global symbols defined in file4.lst
.ref
X, Y, Z
INIT:
ADD.L1 0x01,A4,A1
.word
X
;
.
;
.
;
.
.end
file4.lst
1
2
3
4
5
6
7
8 00000000
9
10
11
12
; Global symbols defined in this file
.def
X, Y, Z
; Global symbol defined in file3.lst
.ref
INIT
00000001 X:
.set
1
00000002 Y:
.set
2
00000003 Z:
.set
3
00000000!
.word
INIT
;
.
;
.
;
.
.end
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.group/.gmember/.endgroup Define Common Data Section
.group group section name group type
Syntax
.gmember section name
.endgroup
Description
Three directives instruct the assembler to make certain sections members of an ELF
group section (see the ELF specification for more information on group sections).
The .group directive begins the group declaration. The group section name designates
the name of the group section. The group type designates the type of the group. The
following types are supported:
0x0
0x1
Regular ELF group
COMDAT ELF group
Duplicate COMDAT (common data) groups are allowed in multiple modules; the linker
keeps only one. Creating such duplicate groups is useful for late instantiation of C++
templates and for providing debugging information.
The .gmember directive designates section name as a member of the group.
The .endgroup directive ends the group declaration.
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.half/.short/.uhalf/.ushort Initialize 16-Bit Integers
.half value1[, ... , valuen ]
Syntax
.short value1[, ... , valuen ]
.uhalf value1[, ... , valuen ]
.ushort value1[, ... , valuen ]
Description
The .half, .uhalf, .short, and .ushort directives place one or more values into
consecutive halfwords in the current section. Each value is placed in a 2-byte memory
location by itself. A value can be either:
• An expression that the assembler evaluates and treats as a 16-bit signed or unsigned
number
• A character string enclosed in double quotes. Each character in a string represents a
separate value and is stored alone in the least significant eight bits of a 16-bit field,
which is padded with 0s.
The assembler truncates values greater than 16 bits.
If you use a label with .half, .short, .uhalf, or .ushort; it points to the location where the
assembler places the first byte.
These directives perform a halfword (16-bit) alignment before data is written to the
section. This guarantees that data resides on a 16-bit boundary.
When you use .half, .short, .uhalf, or .ushort in a .struct/.endstruct sequence, they define
a member's size; they do not initialize memory. For more information, see the
.struct/.endstruct/.tag topic.
Example
In this example, .half is used to place 16-bit values (10, -1, abc, and a) into consecutive
halfwords in memory; .short is used to place 16-bit values (8, -3, def, and b) into
consecutive halfwords in memory. The label STRN has the value 100ch, which is the
location of the first initialized halfword for .short.
1 00000000
2 00001000 0000000A
00001002 0000FFFF
00001004 00000061
00001006 00000062
00001008 00000063
0000100a 00000061
3 0000100c 00000008
0000100e 0000FFFD
00001010 00000064
00001012 00000065
00001014 00000066
00001016 00000062
STRN
.space
.half
100h * 16
10, -1, "abc", 'a'
.short
8, -3, "def", 'b'
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.if/.elseif/.else/.endif Assemble Conditional Blocks
.if condition
Syntax
[.elseif condition]
[.else]
.endif
Description
These directives provide conditional assembly:
The .if directive marks the beginning of a conditional block. The condition is a required
parameter.
• If the expression evaluates to true (nonzero), the assembler assembles the code that
follows the expression (up to a .elseif, .else, or .endif).
• If the expression evaluates to false (0), the assembler assembles code that follows a
.elseif (if present), .else (if present), or .endif (if no .elseif or .else is present).
The .elseif directive identifies a block of code to be assembled when the .if expression is
false (0) and the .elseif expression is true (nonzero). When the .elseif expression is
false, the assembler continues to the next .elseif (if present), .else (if present), or .endif
(if no .elseif or .else is present). The .elseif is optional in a conditional block, and more
than one .elseif can be used. If an expression is false and there is no .elseif, the
assembler continues with the code that follows a .else (if present) or a .endif.
The .else directive identifies a block of code that the assembler assembles when the .if
expression and all .elseif expressions are false (0). The .else directive is optional in the
conditional block; if an expression is false and there is no .else statement, the assembler
continues with the code that follows the .endif. The .elseif and .else directives can be
used in the same conditional assembly block.
The .endif directive terminates a conditional block.
See Section 4.9.2 for information about relational operators.
Example
This example shows conditional assembly:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
120
00000001
00000002
00000003
00000004
SYM1
SYM2
SYM3
SYM4
.set
.set
.set
.set
1
2
3
4
If_4:
.if
.byte
.else
.byte
.endif
SYM4 = SYM2 * SYM2
SYM4
; Equal values
SYM2 * SYM2
; Unequal values
.if
.byte
.else
.byte
.endif
SYM1 <;= 10
10
; Less than / equal
SYM1
; Greater than
.if
.byte
.else
.byte
.endif
SYM3 * SYM2 != SYM4 + SYM2
SYM3 * SYM2
; Unequal value
.if
.byte
.elseif
.byte
.endif
SYM1 = SYM2
SYM1
SYM2 + SYM3 = 5
SYM2 + SYM3
00000000 00000004
If_5:
00000001 0000000A
If_6:
00000002 00000008
If_7:
00000003 00000005
SYM4 + SYM4
Assembler Directives
; Equal values
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.import/.export/.hidden/.protected Set Dynamic Visibility of Global Symbol
.import "symbolname"
Syntax
.export "symbolname"
.hidden "symbolname"
.protected "symbolname"
Description
These directives set the dynamic visibility of a global symbol. Each takes a single symbol
name, optionally enclosed in double-quotes.
• The .import directive sets the visibility of symbolname to STV_IMPORT.
• The .export directive sets the visibility of symbolname to STV_EXPORT.
• The .hidden directive sets the visibility of symbolname to STV_HIDDEN.
• The .protected directive sets the visibility of symbolname to STV_PROTECTED.
See Section 8.12 for an explanation of symbol visibility.
Theses directives are commonly used in the context of dynamic linking. For more about
dynamic linking, see Chapter 14 of The C6000 Embedded Application Binary Interface
Application Report (SPRAB89).
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.int/.unint/.long/.ulong/.word/.uword Initialize 32-Bit Integers
.int value1[, ... , valuen ]
Syntax
.uint value1[, ... , valuen ]
.long value1[, ... , valuen ]
.ulong value1[, ... , valuen ]
.word value1[, ... , valuen ]
.uword value1[, ... , valuen ]
Description
The .int, .unint, .long, .ulong, .word, and .uword directives place one or more values
into consecutive words in the current section. Each value is placed in a 32-bit word by
itself and is aligned on a word boundary. A value can be either:
• An expression that the assembler evaluates and treats as a 32-bit signed or unsigned
number
• A character string enclosed in double quotes. Each character in a string represents a
separate value and is stored alone in the least significant eight bits of a 32-bit field,
which is padded with 0s.
A value can be either an absolute or a relocatable expression. If an expression is
relocatable, the assembler generates a relocation entry that refers to the appropriate
symbol; the linker can then correctly patch (relocate) the reference. This allows you to
initialize memory with pointers to variables or labels.
If you use a label with these directives, it points to the first word that is initialized.
When you use these directives in a .struct/.endstruct sequence, they define a member's
size; they do not initialize memory. See the .struct/.endstruct/.tag topic.
Example 1
This example uses the .int directive to initialize words. Notice that the symbol SYMPTR
puts the symbol's address in the object code and generates a relocatable reference
(indicated by the - character appended to the object word).
1
2
3
4
5
Example 2
00000000
00000000
00000080
00000074
00000078
0000007c
00000080
00000084
00000088
003C12E4 INST:
0000000A
00000080FFFFFFFF
00000084
00000074'
DAT1:
.long
0FFFFABCDh,'A'+100h
This example initializes five words. The symbol WordX points to the first word.
1 00000000
00000004
00000008
0000000c
00000010
122
73h
PAGE, 128
SYMPTR, 3
*++B15[0],A0
10, SYMPTR, -1, 35 + 'a', INST
This example initializes two 32-bit fields and defines DAT1 to point to the first location.
The contents of the resulting 32-bit fields are FFFABCDh and 141h.
1 00000000 FFFFABCD
00000004 00000141
Example 3
.space
.bss
.bss
LDW.D2
.int
00000C80
00004242
FFFFB9BF
0000F410
00000041
;WordX
.word
3200,1+'AB',-'AF',0F410h,'A'
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.label
Create a Load-Time Address Label
.label symbol
Syntax
Description
The .label directive defines a special symbol that refers to the load-time address rather
than the run-time address within the current section. Most sections created by the
assembler have relocatable addresses. The assembler assembles each section as if it
started at 0, and the linker relocates it to the address at which it loads and runs.
For some applications, it is desirable to have a section load at one address and run at a
different address. For example, you may want to load a block of performance-critical
code into slower memory to save space and then move the code to high-speed memory
to run it. Such a section is assigned two addresses at link time: a load address and a run
address. All labels defined in the section are relocated to refer to the run-time address
so that references to the section (such as branches) are correct when the code runs.
See Section 3.5 for more information about run-time relocation.
The .label directive creates a special label that refers to the load-time address. This
function is useful primarily to designate where the section was loaded for purposes of
the code that relocates the section.
Example
This example shows the use of a load-time address label.
sect
".examp"
.label examp_load
start:
<code>
finish:
.label examp_end
; load address of section
; run address of section
; run address of section end
; load address of section end
See Section 8.5.6 for more information about assigning run-time and load-time
addresses in the linker.
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.length/.width
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Set Listing Page Size
.length [page length]
Syntax
.width [page width]
Description
Two directives allow you to control the size of the output listing file.
The .length directive sets the page length of the output listing file. It affects the current
and following pages. You can reset the page length with another .length directive.
• Default length: 60 lines. If you do not use the .length directive or if you use the
.length directive without specifying the page length, the output listing length defaults
to 60 lines.
• Minimum length: 1 line
• Maximum length: 32 767 lines
The .width directive sets the page width of the output listing file. It affects the next line
assembled and the lines following. You can reset the page width with another .width
directive.
• Default width: 132 characters. If you do not use the .width directive or if you use the
.width directive without specifying a page width, the output listing width defaults to
132 characters.
• Minimum width: 80 characters
• Maximum width: 200 characters
The width refers to a full line in a listing file; the line counter value, SPC value, and
object code are counted as part of the width of a line. Comments and other portions of a
source statement that extend beyond the page width are truncated in the listing.
The assembler does not list the .width and .length directives.
Example
The following example shows how to change the page length and width.
********************************************
**
Page length = 65 lines
**
**
Page width = 85 characters
**
********************************************
.length
65
.width
85
********************************************
**
Page length = 55 lines
**
**
Page width = 100 characters
**
********************************************
.length
55
.width
100
124
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.list/.nolist
Start/Stop Source Listing
.list
Syntax
.nolist
Description
Two directives enable you to control the printing of the source listing:
The .list directive allows the printing of the source listing.
The .nolist directive suppresses the source listing output until a .list directive is
encountered. The .nolist directive can be used to reduce assembly time and the source
listing size. It can be used in macro definitions to suppress the listing of the macro
expansion.
The assembler does not print the .list or .nolist directives or the source statements that
appear after a .nolist directive. However, it continues to increment the line counter. You
can nest the .list/.nolist directives; each .nolist needs a matching .list to restore the
listing.
By default, the source listing is printed to the listing file; the assembler acts as if the .list
directive had been used. However, if you do not request a listing file when you invoke
the assembler by including the --asm_listing option on the command line (see
Section 4.3), the assembler ignores the .list directive.
Example
This example shows how the .list and .nolist directives turn the output listing on and off.
The .nolist, the table: .data through .byte lines, and the .list directives do not appear in
the listing file. Also, the line counter is incremented even when source statements are
not listed.
Source file:
.data
.space
.text
ABS
0CCh
A0,A1
.nolist
table:
.data
.word
.byte
-1
0FFh
.list
coeff
.text
MV
.data
.word
A0,A1
00h,0ah,0bh
Listing file:
1
2
3
4
5
13
14
15
16
17
00000000
00000000
00000000
00000000 00800358
.data
.space
.text
ABS
00000004
00000004
000000d1
000000d4
000000d8
000000dc
.text
MV
.data
.word
008001A0
00000000
0000000A
0000000B
coeff
0CCh
A0,A1
A0,A1
00h,0ah,0bh
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.loop/.endloop/.break Assemble Code Block Repeatedly
.loop [count]
Syntax
.break [end-condition]
.endloop
Description
Three directives allow you to repeatedly assemble a block of code:
The .loop directive begins a repeatable block of code. The optional count operand, if
used, must be a well-defined integer expression. The count indicates the number of
loops to be performed (the loop count). If count is omitted, it defaults to 1024. The loop
will be repeated count number of times, unless terminated early by a .break directive.
The optional .break directive terminates a .loop early. You may use .loop without using
.break. The .break directive terminates a .loop only if the end-condition expression is true
(evaluates to nonzero). If the optional end-condition operand is omitted, it defaults to
true. If end-condition is true, the assembler stops repeating the .loop body immediately;
any remaining statements after .break and before .endloop are not assembled. The
assembler resumes assembling with the statement after the .endloop directive. If endcondition is false (evaluates to 0), the loop continues.
The .endloop directive marks the end of a repeatable block of code. When the loop
terminates, whether by a .break directive with a true end-condition or by performing the
loop count number of iterations, the assembler stops repeating the loop body and
resumes assembling with the statement after the .endloop directive.
Example
This example illustrates how these directives can be used with the .eval directive. The
code in the first six lines expands to the code immediately following those six lines.
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3
4
5
6
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
126
COEF
00000000 00000000
00000004 00000064
00000008 000000C8
0000000c 0000012C
00000010 00000190
00000014 000001F4
.eval
.loop
.word
.eval
.break
.endloop
.word
.eval
.break
.word
.eval
.break
.word
.eval
.break
.word
.eval
.break
.word
.eval
.break
.word
.eval
.break
0,x
x*100
x+1, x
x = 6
0*100
0+1, x
1 = 6
1*100
1+1, x
2 = 6
2*100
2+1, x
3 = 6
3*100
3+1, x
4 = 6
4*100
4+1, x
5 = 6
5*100
5+1, x
6 = 6
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.macro/.endm
Define Macro
Syntax
macname .macro [parameter1[, ... , parametern]]
model statements or macro directives
.endm
Description
The .macro and .endm directives are used to define macros.
You can define a macro anywhere in your program, but you must define the macro
before you can use it. Macros can be defined at the beginning of a source file, in an
.include/.copy file, or in a macro library.
macname
.macro
[parameters]
model statements
macro directives
.endm
names the macro. You must place the name in the source
statement's label field.
identifies the source statement as the first line of a macro
definition. You must place .macro in the opcode field.
are optional substitution symbols that appear as operands for the
.macro directive.
are instructions or assembler directives that are executed each
time the macro is called.
are used to control macro expansion.
marks the end of the macro definition.
Macros are explained in further detail in Chapter 6.
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.map/.clearmap
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Assign a Variable to a Register
.map symbol1 / register1 [, symbol2 / register2 , ...]
Syntax
.clearmap
Description
The .map directive is used by the compiler when the input is linear assembly. The
compiler tries to keep your symbolic names for registers defined with .reg by creating
substitution symbols with .map.
The .map directive is similar to .asg, but uses a forward slash instead of a comma; and
allows single quote characters in the symbolic names. For example, this linear assembly
input:
The .clearmap directive is used by the compiler to undefine all current .map substitution
symbols.
See the TMS320C6000 Optimizing Compiler User's Guide for details on using the .map
directive in linear assembly code.
Example
The .map directive is similar to .asg, but uses a forward slash instead of a comma; and
allows single quote characters in the symbolic names. For example, this linear assembly
input:
fn:
.cproc a, b, c
.reg x, y, z
ADD a, b, z
ADD z, c, z
.return z
.endproc
Becomes this assembly code output:
fn:
.map
.map
.map
.map
.map
RET
ADD
ADD
NOP
128
a/A4
b/B4
c/A6
z/A4
z'/A3
.S2
.L1X
.L1
B3
a,b,z'
z',c,z
3
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.mlib
Define Macro Library
.mlib "filename"
Syntax
Description
The .mlib directive provides the assembler with the filename of a macro library. A macro
library is a collection of files that contain macro definitions. The macro definition files are
bound into a single file (called a library or archive) by the archiver.
Each file in a macro library contains one macro definition that corresponds to the name
of the file. The filename of a macro library member must be the same as the macro
name, and its extension must be .asm. The filename must follow host operating system
conventions; it can be enclosed in double quotes. You can specify a full pathname (for
example, c:\320tools\macs.lib). If you do not specify a full pathname, the assembler
searches for the file in the following locations in the order given:
1. The directory that contains the current source file
2. Any directories named with the --include_path assembler option
3. Any directories specified by the C6X_A_DIR environment variable
4. Any directories specified by the C6X_C_DIR environment variable
See Section 4.5 for more information about the --include_path option.
A .mlib directive causes the assembler to open the library specified by filename and
create a table of the library's contents. The assembler stores names of individual library
members in the opcode table as library entries. This redefines any existing opcodes or
macros with the same name. If one of these macros is called, the assembler extracts the
library entry and loads it into the macro table. The assembler expands the library entry
as it does other macros, but it does not place the source code in the listing. Only macros
called from the library are extracted, and they are extracted only once.
See Chapter 6 for more information on macros and macro libraries.
Example
The code creates a macro library that defines two macros, inc1.asm and dec1.asm. The
file inc1.asm contains the definition of inc1 and dec1.asm contains the definition of dec1.
inc1.asm
dec1.asm
* Macro for incrementing
inc1 .macro A
ADD A,1,A
.endm
* Macro for decrementing
dec1 .macro A
SUB A,1,A
.endm
Use the archiver to create a macro library:
ar6x -a mac inc1.asm dec1.asm
Now you can use the .mlib directive to reference the macro library and define the
inc1.asm and dec1.asm macros:
1
1
1
2
3
4 00000000
00000000 000021A0
5
6
7 00000004
00000004 0003E1A2
.mlib
"mac.lib"
* Macro Call
inc1
ADD
A0
A0,1,A0
* Macro Call
dec1
SUB
B0
B0,1,B0
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.mlist/.mnolist
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Start/Stop Macro Expansion Listing
.mlist
Syntax
.mnolist
Description
Two directives enable you to control the listing of macro and repeatable block
expansions in the listing file:
The .mlist directive allows macro and .loop/.endloop block expansions in the listing file.
The .mnolist directive suppresses macro and .loop/.endloop block expansions in the
listing file.
By default, the assembler behaves as if the .mlist directive had been specified.
See Chapter 6 for more information on macros and macro libraries. See the
.loop/.break/.endloop topic for information on conditional blocks.
Example
This example defines a macro named STR_3. The first time the macro is called, the
macro expansion is listed (by default). The second time the macro is called, the macro
expansion is not listed, because a .mnolist directive was assembled. The third time the
macro is called, the macro expansion is again listed because a .mlist directive was
assembled.
1
1
130
1
2
3
4
5 00000000
00000000
00000001
00000002
00000003
00000004
00000005
00000006
00000007
00000008
00000009
0000000a
0000000b
6
7 0000000c
8
9 00000018
00000018
00000019
0000001a
0000001b
0000001c
0000001d
0000001e
0000001f
00000020
00000021
00000022
00000023
STR_3
0000003A
00000070
00000031
0000003A
0000003A
00000070
00000032
0000003A
0000003A
00000070
00000033
0000003A
0000003A
00000070
00000031
0000003A
0000003A
00000070
00000032
0000003A
0000003A
00000070
00000033
0000003A
.macro
P1, P2, P3
.string ":p1:", ":p2:", ":p3:"
.endm
STR_3 "as", "I", "am"
.string ":p1:", ":p2:", ":p3:"
.mnolist
STR_3 "as", "I", "am"
.mlist
STR_3 "as", "I", "am"
.string ":p1:", ":p2:", ":p3:"
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.newblock
Terminate Local Symbol Block
.newblock
Syntax
Description
The .newblock directive undefines any local labels currently defined. Local labels, by
nature, are temporary; the .newblock directive resets them and terminates their scope.
A local label is a label in the form $n, where n is a single decimal digit, or name?, where
name is a legal symbol name. Unlike other labels, local labels are intended to be used
locally, and cannot be used in expressions. They can be used only as operands in 8-bit
jump instructions. Local labels are not included in the symbol table.
After a local label has been defined and (perhaps) used, you should use the .newblock
directive to reset it. The .text, .data, and .sect directives also reset local labels. Local
labels that are defined within an include file are not valid outside of the include file.
See Section 4.8.3 for more information on the use of local labels.
Example
This example shows how the local label $1 is declared, reset, and then declared again.
1
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5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
.global table1, table2
00000000
00000004
00000008
0000000c
00000028!
00000068!
008031A9
010848C0 ||
00000010
00000014
00000018
0000001c
80000212
01003674
0087E1A0
00004000
MVKL
MVK
ZERO
$1:[A1] B
STW
SUB
NOP
table1,A0
MVKH
table1,A0
99, A1
A2
$1
A2, *A0++
A1,1,A1
3
.newblock ; undefine $1
00000020
00000024
00000028
0000002c
00000028!
00000068!
008031A9
010829C0 ||
00000030
00000034
00000038
0000003c
80000212
01003674
0087E1A0
00004000
MVKL
MVKH
MVK
SUB
$1:[A1] B
STW
SUB
NOP
table2,A0
table2,A0
99, A1
A2,1,A2
$1
A2, *A0++
A1,1,A1
3
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.nocmp
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Do Not Utilize 16-Bit Instructions in Section
.nocmp
Syntax
Description
The .nocmp directive instructs the compiler to not utilize 16-bit instructions for the code
section .nocmp appears in. The .nocmp directive can appear anywhere in the section.
Example
In the example, the section one is not compressed, whereas section two is compressed.
.sect "one"
LDW *A4, A5
LDW *B4, A5
.nocmp
NOP 4
ADD A4, A5, A6
ADD B4, B5, B6
NOP
...
.sect "two"
ADD A4, A5, A6
NOP
NOP
...
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.noremark/.remark
Control Remarks
.noremark num
Syntax
.remark [num]
Description
The .noremark directive suppresses the assembler remark identified by num. A remark
is an informational assembler message that is less severe than a warning.
This directive is equivalent to using the -ar[num] assembler option.
The .remark directive re-enables the remark(s) previously suppressed.
Example
This example uses .noremark to turn off remark #5001 and then .remark to turn it back
on again.
Partial source file:
SPLOOP
1
||
SPMASK
CMPYSP
.M2
||
SPKERNEL
DADDSP .S2
1,0
B27:B26,B7:B6,B27:B26
NOP
5
.noremark
B9:B8,B19:B18,B7:B6:B5:B4
5001
SPLOOP
1
||
SPMASK
CMPYSP
.M2
||
SPKERNEL
DADDSP .S2
1,0
B27:B26,B7:B6,B27:B26
NOP
5
.remark
B9:B8,B19:B18,B7:B6:B5:B4
5001
SPLOOP
1
||
SPMASK
CMPYSP
.M2
||
SPKERNEL
DADDSP .S2
1,0
B27:B26,B7:B6,B27:B26
NOP
5
B9:B8,B19:B18,B7:B6:B5:B4
Resulting listing file:
1
2
3
4
5
6
7
8
9
10
11
12
13
14
; Example using .noremark to turn off remark #5001 and
; then .remark to turn it back on again
00000000
0c66
SPLOOP
1
00000002
2c66
00000004 12490f02
||
SPMASK
CMPYSP
00000008 08034001
0000000c 1d1b4b22
||
SPKERNEL
DADDSP .S2
1,0
B27:B26,B7:B6,B27:B26
NOP
5
00000010
8c6e
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.M2
B9:B8,B19:B18,B7:B6:B5:B4
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15
.noremark
5001
16
17 00000012
0c66
SPLOOP
1
18
19 00000014 00030001
SPMASK
20 00000018 12490f02 ||
CMPYSP .M2
B9:B8,B19:B18,B7:B6:B5:B4
21
22 00000020 08034001
SPKERNEL
1,0
23 00000024 1d1b4b22 ||
DADDSP .S2
B27:B26,B7:B6,B27:B26
24
25 00000028
8c6e
NOP
5
26
27
.remark
5001
28
29 0000002a
0c66
SPLOOP
1
"sploopex.asm", REMARK
at line 29: [R5001] SDSCM00012367 potentially triggered
by this
execute packet sequence. SPLOOP must be
30
31 0000002c 00030001
SPMASK
32 00000030 12490f02 ||
CMPYSP .M2
B9:B8,B19:B18,B7:B6:B5:B4
33
34 00000034 08034001
SPKERNEL
1,0
35 00000038 1d1b4b22 ||
DADDSP .S2
B27:B26,B7:B6,B27:B26
36
37 00000040 00008000
NOP
5
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.option
Select Listing Options
.option option1[, option2,. . .]
Syntax
Description
The .option directive selects options for the assembler output listing. The options must
be separated by commas; each option selects a listing feature. These are valid options:
A
turns on listing of all directives and data, and subsequent expansions, macros,
and blocks.
limits the listing of .byte and .char directives to one line.
turns off the listing of certain directives (same effect as .drnolist).
limits the listing of .half and .short directives to one line.
limits the listing of .long directives to one line.
turns off macro expansions in the listing.
turns off listing (performs .nolist).
turns on listing (performs .list).
resets any B, H, L, M, T, and W (turns off the limits of B, H, L, M, T, and W).
limits the listing of .string directives to one line.
limits the listing of .word and .int directives to one line.
produces a cross-reference listing of symbols. You can also obtain a crossreference listing by invoking the assembler with the -asm_listing_cross_reference option (see Section 4.3).
B
D
H
L
M
N
O
R
T
W
X
Options are not case sensitive.
Example
This example shows how to limit the listings of the .byte, .char, .int, long, .word, and
.string directives to one line each.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
00000000
00000003
00000008
0000001c
00000024
0000002c
00000035
00000036
00000037
00000038
00000039
0000003a
0000003c
00000040
00000044
00000048
0000004c
00000050
00000054
00000058
0000005c
000000BD
000000BC
0000000A
AABBCCDD
000015AA
00000052
000000BD
000000B0
00000005
000000BC
000000C0
00000006
0000000A
00000084
00000061
00000062
00000063
AABBCCDD
00000259
000015AA
00000078
****************************************
** Limit the listing of .byte, .char, **
**
.int, .word, and .string **
**
directives to 1 line each.
**
****************************************
.option B, W, T
.byte
-'C', 0B0h, 5
.char
-'D', 0C0h, 6
.int
10, 35 + 'a', "abc"
.long
0AABBCCDDh, 536 + 'A'
.word
5546, 78h
.string "Registers"
****************************************
**
Reset the listing options.
**
****************************************
.option R
.byte
-'C', 0B0h, 5
.char
-'D', 0C0h, 6
.int
10, 35 + 'a', "abc"
.long
0AABBCCDDh, 536 + 'A'
.word
5546, 78h
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23 00000060
00000061
00000062
00000063
00000064
00000065
00000066
00000067
00000068
.page
00000052
00000065
00000067
00000069
00000073
00000074
00000065
00000072
00000073
.string "Registers"
Eject Page in Listing
.page
Syntax
Description
The .page directive produces a page eject in the listing file. The .page directive is not
printed in the source listing, but the assembler increments the line counter when it
encounters the .page directive. Using the .page directive to divide the source listing into
logical divisions improves program readability.
Example
This example shows how the .page directive causes the assembler to begin a new page
of the source listing.
Source file:
Source file (generic)
.title
"**** Page Directive Example ****"
;
.
;
.
;
.
.page
Listing file:
TMS320C6000 Assembler
Version x.xx
Day
Time
Copyright (c) 1996-2011 Texas Instruments Incorporated
**** Page Directive Example ****
2
;
.
3
;
.
4
;
.
TMS320C6000 Assembler
Version x.xx
Day
Time
Copyright (c) 1996-2011 Texas Instruments Incorporated
**** Page Directive Example ****
Year
PAGE
1
PAGE
2
Year
No Errors, No Warnings
136
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.retain / .retainrefs
Conditionally Retain Sections In Object Module Output
.retain["section name"]
Syntax
.retainrefs["section name"]
Description
The .retain directive indicates that the current or specified section is not eligible for
removal via conditional linking. You can also override conditional linking for a given
section with the --retain linker option. You can disable conditional linking entirely with the
--unused_section_elimination=off linker option.
The .retainrefs directive indicates that any sections that refer to the current or specified
section are not eligible for removal via conditional linking. For example, applications may
use an .intvecs section to set up interrupt vectors. The .intvecs section is eligible for
removal during conditional linking by default. You can force the .intvecs section and any
sections that reference it to be retained by applying the .retain and .retainrefs directives
to the .intvecs section.
The section name identifies the section. If the directive is used without a section name, it
applies to the current initialized section. If the directive is applied to an uninitialized
section, the section name is required. The section name must be enclosed in double
quotes. A section name can contain a subsection name in the form section
name:subsection name.
The linker assumes that all sections by default are eligible for removal via conditional
linking. (However, the linker does automatically retain the .reset section.) The .retain
directive is useful for overriding this default conditional linking behavior for sections that
you want to keep included in the link, even if the section is not referenced by any other
section in the link. For example, you could apply a .retain directive to an interrupt
function that you have written in assembly language, but which is not referenced from
any normal entry point in the application.
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Example 1
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This example of an interrupt function that has a .retain directive applied to it.
.sect
".text:interrupts:retain"
.retain
.global _int_func1
;******************************************************************************
;* FUNCTION NAME: int_func1
*
;******************************************************************************
_int_func1:
STW
.D2
FP,*SP++(-88)
; [B_D] |31|
STW
.D2
B3,*SP(80)
; [B_D] |31|
STW
.D2
A4,*SP(24)
; [B_D] |31|
STW
.D2
B2,*SP(84)
; [B_D] |31|
STW
.D2
B9,*SP(76)
; [B_D] |31|
STW
.D2
B8,*SP(72)
; [B_D] |31|
STW
.D2
B7,*SP(68)
; [B_D] |31|
STW
.D2
B6,*SP(64)
; [B_D] |31|
STW
.D2
B5,*SP(60)
; [B_D] |31|
STW
.D2
B4,*SP(56)
; [B_D] |31|
STW
.D2
B1,*SP(52)
; [B_D] |31|
STW
.D2
B0,*SP(48)
; [B_D] |31|
STW
.D2
A7,*SP(36)
; [B_D] |31|
STW
.D2
A6,*SP(32)
; [B_D] |31|
STW
.D2
A5,*SP(28)
; [B_D] |31|
||
CALL
STW
.S1
.D2
_foo
A8,*SP(40)
; [A_S] |32|
; [B_D] |31|
STW
.D2
B4,*+DP(_a_i)
; [B_D] |33|
RET
LDW
.S2
.D2
IRP
*SP(56),B4
; [B_Sb] |34|
; [B_D] |34|
LDW
NOP
.D2
*++SP(88),FP
4
; [B_D] |34|
; [A_L]
...
||
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.sect
Assemble Into Named Section
.sect " section name "
Syntax
.sect " section name " [,{RO|RW}] [,{ALLOC|NOALLOC}]
Description
The .sect directive defines a named section that can be used like the default .text and
.data sections. The .sect directive sets section name to be the current section; the lines
that follow are assembled into the section name section.
The section name identifies the section. The section name must be enclosed in double
quotes. A section name can contain a subsection name in the form section name :
subsection name. See Chapter 2 for more information about sections.
The sections can be marked read-only (RO) or read-write (RW). Also, the sections can
be marked for allocation (ALLOC) or no allocation (NOALLOC). These attributes can be
specified in any order, but only one attribute from each set can be selected. RO conflicts
with RW, and ALLOC conflicts with NOALLOC. If conflicting attributes are specified the
assembler generates an error, for example:
"t.asm", ERROR! at line 1:[E0000] Attribute RO cannot be combined with attr RW
.sect "illegal_sect",RO,RW
Example
This example defines two special-purpose sections, Sym_Defs and Vars, and assembles
code into them.
1
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8
9
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21
22
23
24
25
26
27
00000000
00000000 000005E0
00000004 008425E0
**********************************************
**
Begin assembling into .text section.
**
**********************************************
.text
ZERO
A0
ZERO
A1
00000000
00000000 4048F5C3
00000004 000007D0
00000008 00000001
**********************************************
**
Begin assembling into vars section.
**
**********************************************
.sect
"vars"
pi
.float 3.14
max
.int
2000
min
.int
1
00000008
00000008 010000A8
0000000c 018000A8
**********************************************
**
Resume assembling into .text section. **
**********************************************
.text
MVK
1,A2
MVK
1,A3
0000000c
0000000c 00000019
**********************************************
**
Resume assembling into vars section.
**
**********************************************
.sect
"vars"
count
.short 25
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.set/.equ
Define Assembly-Time Constant
Syntax
symbol .set value
symbol .equ value
Description
The .set and .equ directives equate a constant value to a .set/.equ symbol. The symbol
can then be used in place of a value in assembly source. This allows you to equate
meaningful names with constants and other values. The .set and .equ directives are
identical and can be used interchangeably.
• The symbol is a label that must appear in the label field.
• The value must be a well-defined expression, that is, all symbols in the expression
must be previously defined in the current source module.
Undefined external symbols and symbols that are defined later in the module cannot be
used in the expression. If the expression is relocatable, the symbol to which it is
assigned is also relocatable.
The value of the expression appears in the object field of the listing. This value is not
part of the actual object code and is not written to the output file.
Symbols defined with .set or .equ can be made externally visible with the .def or .global
directive (see the .global/.def/.ref topic). In this way, you can define global absolute
constants.
Example
This example shows how symbols can be assigned with .set and .equ.
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
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19
20
21
22
23
24
25
26
27
140
00000001
00000000 00B802D4
**********************************************
**
Equate symbol AUX_R1 to register A1
**
**
and use it instead of the register.
**
**********************************************
AUX_R1 .set
A1
STH
AUX_R1,*+B14
00000035
00000004 01001AD0
**********************************************
**
Set symbol index to an integer expr.
**
**
and use it as an immediate operand.
**
**********************************************
INDEX
.equ
100/2 +3
ADDK
INDEX, A2
**********************************************
** Set symbol SYMTAB to a relocatable expr. **
**
and use it as a relocatable operand.
**
**********************************************
00000008 0000000A LABEL
.word
10
00000009' SYMTAB .set
LABEL + 1
00000035
0000000c 00000035
**********************************************
**
Set symbol NSYMS equal to the symbol
**
**
INDEX and use it as you would INDEX.
**
**********************************************
NSYMS
.set
INDEX
.word
NSYMS
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.space/.bes
Reserve Space
Syntax
[label] .space size in bytes
[label] .bes
Description
size in bytes
The .space and .bes directives reserve the number of bytes given by size in bytes in the
current section and fill them with 0s. The section program counter is incremented to
point to the word following the reserved space.
When you use a label with the .space directive, it points to the first byte reserved. When
you use a label with the .bes directive, it points to the last byte reserved.
Example
This example shows how memory is reserved with the .space and .bes directives.
1
2
3
4 00000000
5
6
7
8 00000000
9 000000f0 00000100
000000f4 00000200
10
11
12
13 00000000
14 00000000 00000049
00000001 0000006E
00000002 00000020
00000003 0000002E
00000004 00000064
00000005 00000061
00000006 00000074
00000007 00000061
15
16
17
18
19
20 00000008
21 0000006c 0000000F
22 00000070 00000008"
23
24
25
26
27
28 00000087
29 00000088 00000036
30 0000008c 00000087"
*****************************************************
**
Begin assembling into the .text section.
**
*****************************************************
.text
*****************************************************
** Reserve 0F0 bytes (60 words in .text section). **
*****************************************************
.space 0F0h
.word
100h, 200h
*****************************************************
**
Begin assembling into the .data section.
**
*****************************************************
.data
.string "In .data"
*****************************************************
**
Reserve 100 bytes in the .data section;
**
**
RES_1 points to the first word
**
**
that contains reserved bytes.
**
*****************************************************
RES_1: .space 100
.word
15
.word
RES_1
*****************************************************
**
Reserve 20 bytes in the .data section;
**
**
RES_2 points to the last word
**
**
that contains reserved bytes.
**
*****************************************************
RES_2: .bes
20
.word
36h
.word
RES_2
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.sslist/.ssnolist
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Control Listing of Substitution Symbols
.sslist
Syntax
.ssnolist
Description
Two directives allow you to control substitution symbol expansion in the listing file:
The .sslist directive allows substitution symbol expansion in the listing file. The
expanded line appears below the actual source line.
The .ssnolist directive suppresses substitution symbol expansion in the listing file.
By default, all substitution symbol expansion in the listing file is suppressed; the
assembler acts as if the .ssnolist directive had been used.
Lines with the pound (#) character denote expanded substitution symbols.
Example
This example shows code that, by default, suppresses the listing of substitution symbol
expansion, and it shows the .sslist directive assembled, instructing the assembler to list
substitution symbol code expansion.
1
2
3
4
5
6
7
8
9
10
11
12
13
1
1
1
1
1
1
#
1
#
1
1
1
#
00000000
00000004
00000008
addm
00000000
00000000
00000004
00000008
0000000c
00000010
0000006C0080016C00006000
000401E0
0000027C-
14
15
16 00000014
00000014 0000006C00000018 0080016C0000001c 00006000
00000020 000401E0
00000024 0000027C-
.bss
.bss
.bss
x,4
y,4
z,4
.macro
LDW
LDW
NOP
ADD
STW
.endm
src1,src2,dst
*+B14(:src1:), A0
*+B14(:src2:), A1
4
A0,A1,A0
A0,*+B14(:dst:)
addm
LDW
LDW
NOP
ADD
STW
x,y,z
*+B14(x), A0
*+B14(y), A1
4
A0,A1,A0
A0,*+B14(z)
.sslist
addm
LDW
LDW
LDW
LDW
NOP
ADD
STW
STW
x,y,z
*+B14(:src1:), A0
*+B14(x), A0
*+B14(:src2:), A1
*+B14(y), A1
4
A0,A1,A0
A0,*+B14(:dst:)
A0,*+B14(z)
17
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.string/.cstring
Initialize Text
.string {expr1 | "string1"} [, ... , {exprn | "stringn"} ]
Syntax
.cstring {expr1 | "string1"} [, ... , {exprn | "stringn"} ]
Description
The .string and .cstring directives place 8-bit characters from a character string into the
current section. The expr or string can be one of the following:
• An expression that the assembler evaluates and treats as an 8-bit signed number.
• A character string enclosed in double quotes. Each character in a string represents a
separate value, and values are stored in consecutive bytes. The entire string must be
enclosed in quotes.
The .cstring directive adds a NUL character needed by C; the .string directive does not
add a NUL character. In addition, .cstring interprets C escapes (\\ \a \b \f \n \r \t \v
\<octal>).
The assembler truncates any values that are greater than eight bits. Operands must fit
on a single source statement line.
If you use a label, it points to the location of the first byte that is initialized.
When you use .string and .cstring in a .struct/.endstruct sequence, the directive only
defines a member's size; it does not initialize memory. For more information, see the
.struct/.endstruct/.tag topic.
Example
In this example, 8-bit values are placed into consecutive bytes in the current section.
The label Str_Ptr has the value 0h, which is the location of the first initialized byte.
1 00000000
00000001
00000002
00000003
2 00000004
00000005
00000006
00000007
3 00000008
00000009
0000000a
0000000b
0000000c
0000000d
0000000e
0000000f
00000010
00000011
00000012
00000013
00000014
4 00000015
00000041
00000042
00000043
00000044
00000041
00000042
00000043
00000044
00000041
00000075
00000073
00000074
00000069
0000006E
00000048
0000006F
00000075
00000073
00000074
0000006F
0000006E
00000030
Str_Ptr:
.string
"ABCD"
.string
41h, 42h, 43h, 44h
.string
"Austin", "Houston"
.string
36 + 12
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.struct/.endstruct/.tag Declare Structure Type
Syntax
Description
[stag]
.struct
[expr]
[mem0]
[mem1]
.
.
.
element
element
.
.
.
[expr0]
[expr1]
.
.
.
[memn]
.
.
.
.tag stag
.
.
.
[exprn]
.
.
.
[memN]
element
[size]
.endstruct
label
.tag
[exprN]
stag
The .struct directive assigns symbolic offsets to the elements of a data structure
definition. This allows you to group similar data elements together and let the assembler
calculate the element offset. This is similar to a C structure or a Pascal record. The
.struct directive does not allocate memory; it merely creates a symbolic template that can
be used repeatedly.
The .endstruct directive terminates the structure definition.
The .tag directive gives structure characteristics to a label, simplifying the symbolic
representation and providing the ability to define structures that contain other structures.
The .tag directive does not allocate memory. The structure tag (stag) of a .tag directive
must have been previously defined.
Following are descriptions of the parameters used with the .struct, .endstruct, and .tag
directives:
• The stag is the structure's tag. Its value is associated with the beginning of the
structure. If no stag is present, the assembler puts the structure members in the
global symbol table with the value of their absolute offset from the top of the
structure. The stag is optional for .struct, but is required for .tag.
• The expr is an optional expression indicating the beginning offset of the structure.
The default starting point for a structure is 0.
• The memn/N is an optional label for a member of the structure. This label is absolute
and equates to the present offset from the beginning of the structure. A label for a
structure member cannot be declared global.
• The element is one of the following descriptors: .byte, .char, .int, .long, .word,
.double, .half, .short, .string, .float, .field, and .tag. All of these except .tag are typical
directives that initialize memory. Following a .struct directive, these directives
describe the structure element's size. They do not allocate memory. The .tag
directive is a special case because stag must be used (as in the definition of stag).
• The exprn/N is an optional expression for the number of elements described. This
value defaults to 1. A .string element is considered to be one byte in size, and a .field
element is one bit.
• The size is an optional label for the total size of the structure.
Directives that Can Appear in a .struct/.endstruct Sequence
NOTE: The only directives that can appear in a .struct/.endstruct sequence are
element descriptors, conditional assembly directives, and the .align
directive, which aligns the member offsets on word boundaries. Empty
structures are illegal.
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The following examples show various uses of the .struct, .tag, and .endstruct directives.
Example 1
Example 2
Example 3
Example 4
1
2
3
4
5
6 00000000
7
8
9 00000000
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
1
2
3
4
5
6
7
8
00000000
00000004
00000008
real_rec
nom
den
real_len
0080016C-
00000000
00000008
00000010
.struct
.int
.int
.endstruct
LDW
.bss real, real_len
; allocate mem rec
cplx_rec
reali
imagi
cplx_len
.struct
.tag real_rec
.tag real_rec
.endstruct
;
;
;
;
complex
.tag cplx_rec
; assign structure
; attribute
; allocate mem rec
.bss complex, cplx_len
00000004 0100046C-
LDW
stag
member1 = 0
member2 = 2
cplx_len = 4
*+B14(complex.imagi.nom), A2
; access structure
LDW *+B14(complex.reali.den), A2
; access structure
CMPEQ A2, A3, A3
00000008 0100036C0000000c 018C4A78
1
2
00000000
3
00000040
4
00000040
5
00000042
6
00000044
7
00000045
8
9
10 00000000
11
12 00000000 0100106C13
14 00000004 0109E7A0
stag
member1 = 0
member2 = 1
real_len = 2
*+B14(real+real_rec.den), A1
; access structure
00000008
00000000
00000001
00000002
00000003
;
;
;
;
.struct
; no stag puts
; mems into global
; symbol table
X
Y
Z
.byte
.byte
.byte
.endstruct
; create 3 dim
; templates
bit_rec
stream
bit7
bit1
bit5
x_int
bit_len
.struct
.string 64
.field 7
.field 9
.field 10
.byte
.endstruct
; stag
bits
.tag bit_rec
.bss bits, bit_len
LDW
AND
;
;
;
;
;
bit7 = 64
bit9 = 64
bit5 = 64
x_int = 68
length = 72
*+B14(bits.bit7), A2
; load field
0Fh, A2, A2
; mask off garbage
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.symdepend/.weak Affect Symbol Linkage and Visibility
.symdepend dst symbol name[, src symbol name]
Syntax
.weak symbol name
Description
These directives are used to affect symbol linkage and visibility.
The .symdepend directive creates an artificial reference from the section defining src
symbol name to the symbol dst symbol name. This prevents the linker from removing the
section containing dst symbol name if the section defining src symbol name is included
in the output module. If src symbol name is not specified, a reference from the current
section is created.
The .weak directive identifies a symbol that is used in the current module but is defined
in another module. The linker resolves this symbol's definition at link time. Instead of
including a weak symbol in the output file's symbol table by default (as it would for a
global symbol), the linker only includes a weak symbol in the output of a "final" link if the
symbol is required to resolve an otherwise unresolved reference. See Section 2.6.2 for
details about how weak symbols are handled by the linker.
The .weak directive is equivalent to the .ref directive, except that the reference has weak
linkage.
A global symbol is defined in the same manner as any other symbol; that is, it appears
as a label or is defined by the .set, .equ, .bss, or .usect directive. If a global symbol is
defined more than once, the linker issues a multiple-definition error. (The assembler can
provide a similar multiple-definition error for local symbols.) The .weak directive always
creates a symbol table entry for a symbol, whether the module uses the symbol or not;
.symdepend, however, creates an entry only if the module actually uses the symbol.
A symbol can be declared global in either of the following ways:
• If the symbol is not defined in the current module (which includes macro, copy, and
include files), use the .weak directive to tell the assembler that the symbol is defined
in an external module. This prevents the assembler from issuing an unresolved
reference error. At link time, the linker looks for the symbol's definition in other
modules.
• If the symbol is defined in the current module, use the .symdepend directive to
declare that the symbol and its definition can be used externally by other modules.
These types of references are resolved at link time.
For example, use the .weak and .set directives in combination as shown in the following
example, which defines a weak absolute symbol "ext_addr_sym":
ext_addr_sym
.weak
.set
ext_addr_sym
0x12345678
If you assemble such assembly source and include the resulting object file in the link, the
"ext_addr_sym" in this example is available as a weak absolute symbol in a final link. It
is a candidate for removal if the symbol is not referenced elsewhere in the application.
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.tab
Define Tab Size
.tab size
Syntax
Description
The .tab directive defines the tab size. Tabs encountered in the source input are
translated to size character spaces in the listing. The default tab size is eight spaces.
Example
In this example, each of the lines of code following a .tab statement consists of a single
tab character followed by an NOP instruction.
Source file:
; default tab size
NOP
NOP
NOP
.tab 4
NOP
NOP
NOP
.tab 16
NOP
NOP
NOP
Listing file:
1
2
3
4
5
7
8
9
10
12
13
14
00000000 00000000
00000004 00000000
00000008 00000000
0000000c 00000000
00000010 00000000
00000014 00000000
00000018 00000000
0000001c 00000000
00000020 00000000
; default tab size
NOP
NOP
NOP
.tab4
NOP
NOP
NOP
.tab 16
NOP
NOP
NOP
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.text
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Assemble Into the .text Section
.text
Syntax
Description
The .text sets .text as the current section. Lines that follow this directive will be
assembled into the .text section, which usually contains executable code. The section
program counter is set to 0 if nothing has yet been assembled into the .text section. If
code has already been assembled into the .text section, the section program counter is
restored to its previous value in the section.
The .text section is the default section. Therefore, at the beginning of an assembly, the
assembler assembles code into the .text section unless you use a .data or .sect directive
to specify a different section.
For more information about sections, see Chapter 2.
Example
This example assembles code into the .text and .data sections.
1
2
3
4 00000000
5 00000000 00000005
00000001 00000006
6
7
8
9
10 00000000
11 00000000 00000001
12 00000001 00000002
00000002 00000003
13
14
15
16
17 00000002
18 00000002 00000007
00000003 00000008
19
20
21
22
23 00000003
24 00000003 00000004
148
******************************************
** Begin assembling into .data section. **
******************************************
.data
.byte
5,6
******************************************
** Begin assembling into .text section. **
******************************************
.text
.byte
1
.byte
2,3
******************************************
** Resume assembling into .data section.**
******************************************
.data
.byte
7,8
******************************************
** Resume assembling into .text section.**
******************************************
.text
.byte
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.title
Define Page Title
.title "string"
Syntax
Description
The .title directive supplies a title that is printed in the heading on each listing page. The
source statement itself is not printed, but the line counter is incremented.
The string is a quote-enclosed title of up to 64 characters. If you supply more than 64
characters, the assembler truncates the string and issues a warning:
*** WARNING! line x: W0001: String is too long - will be truncated
The assembler prints the title on the page that follows the directive and on subsequent
pages until another .title directive is processed. If you want a title on the first page, the
first source statement must contain a .title directive.
Example
In this example, one title is printed on the first page and a different title is printed on
succeeding pages.
Source file:
.title
.
.
.
.title
.page
;
;
;
"**** Fast Fourier Transforms ****"
"**** Floating-Point Routines ****"
Listing file:
TMS320C6000 Assembler
Version x.xx
Day
Time
Copyright (c) 1996-2011 Texas Instruments Incorporated
**** Fast Fourier Transforms ****
2
;
.
3
;
.
4
;
.
TMS320C6000 Assembler
Version x.xx
Day
Time
Copyright (c) 1996-2011 Texas Instruments Incorporated
**** Floating-Point Routines ****
Year
PAGE
1
PAGE
2
Year
No Errors, No Warnings
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.union/.endunion/.tag Declare Union Type
Syntax
Description
[stag]
.union
[expr]
[mem0 ]
[mem1 ]
.
.
.
element
element
.
.
.
[expr0 ]
[expr1 ]
.
.
.
[memn ]
.
.
.
.tag stag
.
.
.
[memN ]
element
[size]
.endunion
label
.tag
[exprn ]
.
.
.
[exprN ]
stag
The .union directive assigns symbolic offsets to the elements of alternate data structure
definitions to be allocated in the same memory space. This enables you to define
several alternate structures and then let the assembler calculate the element offset. This
is similar to a C union. The .union directive does not allocate any memory; it merely
creates a symbolic template that can be used repeatedly.
A .struct definition can contain a .union definition, and .structs and .unions can be
nested.
The .endunion directive terminates the union definition.
The .tag directive gives structure or union characteristics to a label, simplifying the
symbolic representation and providing the ability to define structures or unions that
contain other structures or unions. The .tag directive does not allocate memory. The
structure or union tag of a .tag directive must have been previously defined.
Following are descriptions of the parameters used with the .struct, .endstruct, and .tag
directives:
• The utag is the union's tag. is the union's tag. Its value is associated with the
beginning of the union. If no utag is present, the assembler puts the union members
in the global symbol table with the value of their absolute offset from the top of the
union. In this case, each member must have a unique name.
• The expr is an optional expression indicating the beginning offset of the union.
Unions default to start at 0. This parameter can only be used with a top-level union. It
cannot be used when defining a nested union.
• The memn/N is an optional label for a member of the union. This label is absolute and
equates to the present offset from the beginning of the union. A label for a union
member cannot be declared global.
• The element is one of the following descriptors: .byte, .char, .int, .long, .word,
.double, .half, .short, .string, .float, and .field. An element can also be a complete
declaration of a nested structure or union, or a structure or union declared by its tag.
Following a .union directive, these directives describe the element's size. They do not
allocate memory.
• The exprn/N is an optional expression for the number of elements described. This
value defaults to 1. A .string element is considered to be one byte in size, and a .field
element is one bit.
• The size is an optional label for the total size of the union.
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Directives that Can Appear in a .union/.endunion Sequence
NOTE: The only directives that can appear in a .union/.endunion sequence are
element descriptors, structure and union tags, and conditional assembly
directives. Empty structures are illegal.
These examples show unions with and without tags.
Example 1
Example 2
1
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0000
4
0000
5
0000
6
0002
7
8 000000
9
10
11 000000 00001
2
3
4
5
6
7
xample
ival
fval
sval
real_len
.global employid
.union
.word
.float
.string
.endunion
;
;
;
;
;
.bss
employid, real_len
employid
.tag
ADD
xample
employid.fval, A
x
y
z
size_u
.long
.float
.word
.endunion
utag
member1 = int
member2 = float
member3 = string
real_len = 2
;allocate memory
; name an instance
; access union element
; utag
0000
0000
0000
0002
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;
;
;
;
member1 = long
member2 = float
member3 = word
real_len = 2
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.usect
Reserve Uninitialized Space
Syntax
symbol .usect "section name", size in bytes[, alignment[, bank offset] ]
Description
The .usect directive reserves space for variables in an uninitialized, named section. This
directive is similar to the .bss directive; both simply reserve space for data and that
space has no contents. However, .usect defines additional sections that can be placed
anywhere in memory, independently of the .bss section.
• The symbol points to the first location reserved by this invocation of the .usect
directive. The symbol corresponds to the name of the variable for which you are
reserving space.
• The section name must be enclosed in double quotes. This parameter names the
uninitialized section. A section name can contain a subsection name in the form
section name : subsection name.
• The size in bytes is an expression that defines the number of bytes that are reserved
in section name.
• The alignment is an optional parameter that ensures that the space allocated to the
symbol occurs on the specified boundary. This boundary must be set to a power of 2.
• The bank offset is an optional parameter that ensures that the space allocated to the
symbol occurs on a specific memory bank boundary. The bank offset value measures
the number of bytes to offset from the alignment specified before assigning the
symbol to that location.
Initialized sections directives (.text, .data, and .sect) tell the assembler to pause
assembling into the current section and begin assembling into another section. A .usect
or .bss directive encountered in the current section is simply assembled, and assembly
continues in the current section.
Variables that can be located contiguously in memory can be defined in the same
specified section; to do so, repeat the .usect directive with the same section name and
the subsequent symbol (variable name).
For more information about sections, see Chapter 2.
Example
152
This example uses the .usect directive to define two uninitialized, named sections, var1
and var2. The symbol ptr points to the first byte reserved in the var1 section. The symbol
array points to the first byte in a block of 100 bytes reserved in var1, and dflag points to
the first byte in a block of 50 bytes in var1. The symbol vec points to the first byte
reserved in the var2 section.
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Figure 5-8 shows how this example reserves space in two uninitialized sections, var1
and var2.
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00000000
00000000 008001A0
***************************************************
**
Assemble into .text section
**
***************************************************
.text
MV
A0,A1
***************************************************
**
Reserve 2 bytes in var1.
**
***************************************************
00000000
ptr
.usect "var1",2
00000004 0100004CLDH
*+B14(ptr),A2
; still in .text
***************************************************
**
Reserve 100 bytes in var1
**
***************************************************
00000002
array
.usect "var1",100
00000008 01800128MVK
array,A3
; still in .text
0000000c 01800068MVKH
array,A3
***************************************************
**
Reserve 50 bytes in var1
**
***************************************************
00000066
dflag
.usect "var1",50
00000010 02003328MVK
dflag,A4
00000014 02000068MVKH
dflag,A4
***************************************************
**
Reserve 100 bytes in var1
**
***************************************************
00000000
vec
.usect "var2",100
00000018 0000002AMVK
vec,B0
; still in .text
0000001c 0000006AMVKH
vec,B0
Figure 5-8. The .usect Directive
Section var1
ptr
2 bytes
array
Section var2
ptr
100 bytes
100 bytes
100 bytes reserved
in var2
dflag
50 bytes
152 bytes reserved
in var1
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.unasg/.undefine
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Turn Off Substitution Symbol
.unasg symbol
Syntax
.undefine symbol
Description
The .unasg and .undefine directives remove the definition of a substitution symbol
created using .asg or .define. The named symbol will removed from the substitution
symbol table from the point of the .undefine or .unasg to the end of the assembly file.
See Section 4.8.10 for more information on substitution symbols.
These directives can be used to remove from the assembly environment any C/C++
macros that may cause a problem. See Chapter 11 for more information about using
C/C++ headers in assembly source.
.var
Use Substitution Symbols as Local Variables
.var sym1 [, sym2 , ... , symn ]
Syntax
Description
The .var directive allows you to use substitution symbols as local variables within a
macro. With this directive, you can define up to 32 local macro substitution symbols
(including parameters) per macro.
The .var directive creates temporary substitution symbols with the initial value of the null
string. These symbols are not passed in as parameters, and they are lost after
expansion.
See Section 4.8.10 for more information on substitution symbols .See Chapter 6 for
information on macros.
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Chapter 6
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Macro Language Description
The TMS320C6000 assembler supports a macro language that enables you to create your own
instructions. This is especially useful when a program executes a particular task several times. The macro
language lets you:
• Define your own macros and redefine existing macros
• Simplify long or complicated assembly code
• Access macro libraries created with the archiver
• Define conditional and repeatable blocks within a macro
• Manipulate strings within a macro
• Control expansion listing
Topic
6.1
6.2
6.3
6.4
6.5
6.6
6.7
6.8
6.9
6.10
...........................................................................................................................
Using Macros ...................................................................................................
Defining Macros ...............................................................................................
Macro Parameters/Substitution Symbols .............................................................
Macro Libraries ................................................................................................
Using Conditional Assembly in Macros ...............................................................
Using Labels in Macros .....................................................................................
Producing Messages in Macros..........................................................................
Using Directives to Format the Output Listing .....................................................
Using Recursive and Nested Macros ..................................................................
Macro Directives Summary ................................................................................
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156
156
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163
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169
170
155
Using Macros
6.1
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Using Macros
Programs often contain routines that are executed several times. Instead of repeating the source
statements for a routine, you can define the routine as a macro, then call the macro in the places where
you would normally repeat the routine. This simplifies and shortens your source program.
If you want to call a macro several times but with different data each time, you can assign parameters
within a macro. This enables you to pass different information to the macro each time you call it. The
macro language supports a special symbol called a substitution symbol, which is used for macro
parameters. See Section 6.3 for more information.
Using a macro is a 3-step process.
Step 1. Define the macro. You must define macros before you can use them in your program. There
are two methods for defining macros:
(a) Macros can be defined at the beginning of a source file or in a copy/include file. See
Section 6.2, Defining Macros, for more information.
(b) Macros can also be defined in a macro library. A macro library is a collection of files in
archive format created by the archiver. Each member of the archive file (macro library)
may contain one macro definition corresponding to the member name. You can access a
macro library by using the .mlib directive. For more information, see Section 6.4.
Step 2. Call the macro. After you have defined a macro, call it by using the macro name as a
mnemonic in the source program. This is referred to as a macro call.
Step 3. Expand the macro. The assembler expands your macros when the source program calls
them. During expansion, the assembler passes arguments by variable to the macro
parameters, replaces the macro call statement with the macro definition, then assembles the
source code. By default, the macro expansions are printed in the listing file. You can turn off
expansion listing by using the .mnolist directive. For more information, see Section 6.8.
When the assembler encounters a macro definition, it places the macro name in the opcode table. This
redefines any previously defined macro, library entry, directive, or instruction mnemonic that has the same
name as the macro. This allows you to expand the functions of directives and instructions, as well as to
add new instructions.
6.2
Defining Macros
You can define a macro anywhere in your program, but you must define the macro before you can use it.
Macros can be defined at the beginning of a source file or in a .copy/.include file (see Copy Source File);
they can also be defined in a macro library. For more information about macro libraries, see Section 6.4.
Macro definitions can be nested, and they can call other macros, but all elements of the macro must be
defined in the same file. Nested macros are discussed in Section 6.9.
A macro definition is a series of source statements in the following format:
macname
.macro
[parameter1 ] [, ... , parametern ]
model statements or macro directives
[.mexit]
.endm
macname
.macro
parameter 1,
parameter n
156
names the macro. You must place the name in the source statement's label field.
Only the first 128 characters of a macro name are significant. The assembler
places the macro name in the internal opcode table, replacing any instruction or
previous macro definition with the same name.
is the directive that identifies the source statement as the first line of a macro
definition. You must place .macro in the opcode field.
are optional substitution symbols that appear as operands for the .macro directive.
Parameters are discussed in Section 6.3.
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model statements
macro directives
.mexit
.endm
are instructions or assembler directives that are executed each time the macro is
called.
are used to control macro expansion.
is a directive that functions as a goto .endm. The .mexit directive is useful when
error testing confirms that macro expansion fails and completing the rest of the
macro is unnecessary.
is the directive that terminates the macro definition.
If you want to include comments with your macro definition but do not want those comments to appear in
the macro expansion, use an exclamation point to precede your comments. If you do want your comments
to appear in the macro expansion, use an asterisk or semicolon. See Section 6.7 for more information
about macro comments.
Example 6-1 shows the definition, call, and expansion of a macro.
Example 6‑1. Macro Definition, Call, and Expansion
Macro definition: The following code defines a macro, sadd4, with four parameters:
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7
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9
sadd4
.macro r1,r2,r3,r4
!
! sadd4 r1, r2 ,r3, r4
! r1 = r1 + r2 + r3 + r4 (saturated)
!
SADD
r1,r2,r1
SADD
r1,r3,r1
SADD
r1,r4,r1
.endm
Macro call: The following code calls the sadd4 macro with four arguments:
10
11 00000000
sadd4
A0,A1,A2,A3
Macro expansion: The following code shows the substitution of the macro definition for the macro call. The
assembler substitutes A0, A1, A2, and A3 for the r1, r2, r3, and r4 parameters of sadd4.
1
1
1
00000000 00040278
00000004 00080278
00000008 000C0278
SADD
SADD
SADD
A0,A1,A0
A0,A2,A0
A0,A3,A0
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Macro Parameters/Substitution Symbols
If you want to call a macro several times with different data each time, you can assign parameters within
the macro. The macro language supports a special symbol, called a substitution symbol, which is used for
macro parameters.
Macro parameters are substitution symbols that represent a character string. These symbols can also be
used outside of macros to equate a character string to a symbol name (see Section 4.8.10).
Valid substitution symbols can be up to 128 characters long and must begin with a letter. The remainder
of the symbol can be a combination of alphanumeric characters, underscores, and dollar signs.
Substitution symbols used as macro parameters are local to the macro they are defined in. You can define
up to 32 local substitution symbols (including substitution symbols defined with the .var directive) per
macro. For more information about the .var directive, see Section 6.3.6.
During macro expansion, the assembler passes arguments by variable to the macro parameters. The
character-string equivalent of each argument is assigned to the corresponding parameter. Parameters
without corresponding arguments are set to the null string. If the number of arguments exceeds the
number of parameters, the last parameter is assigned the character-string equivalent of all remaining
arguments.
If you pass a list of arguments to one parameter or if you pass a comma or semicolon to a parameter, you
must surround these terms with quotation marks.
At assembly time, the assembler replaces the macro parameter/substitution symbol with its corresponding
character string, then translates the source code into object code.
Example 6-2 shows the expansion of a macro with varying numbers of arguments.
Example 6‑2. Calling a Macro With Varying Numbers of Arguments
Macro definition:
Parms
;
;
;
.macro
a,b,c
a = :a:
b = :b:
c = :c:
.endm
Calling the macro:
Parms
100,label
a = 100
b = label
c = ""
Parms
;
;
;
100,label,x,y
;
a = 100
;
b = label
;
c = x,y
Parms
100, , x
a = 100
b = ""
c = x
Parms
;
;
;
"100,200,300",x,y
;
a = 100,200,300
;
b = x
;
c = y
;
;
;
Parms
"""string""",x,y
a = "string"
b = x
c = y
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6.3.1 Directives That Define Substitution Symbols
You can manipulate substitution symbols with the .asg and .eval directives.
• The .asg directive assigns a character string to a substitution symbol.
For the .asg directive, the quotation marks are optional. If there are no quotation marks, the assembler
reads characters up to the first comma and removes leading and trailing blanks. In either case, a
character string is read and assigned to the substitution symbol. The syntax of the .asg directive is:
.asg["]character string["], substitution symbol
Example 6-3 shows character strings being assigned to substitution symbols.
Example 6-3. The .asg Directive
.asg
•
"A4", RETVAL
; return value
The .eval directive performs arithmetic on numeric substitution symbols.
The .eval directive evaluates the expression and assigns the string value of the result to the
substitution symbol. If the expression is not well defined, the assembler generates an error and
assigns the null string to the symbol. The syntax of the .eval directive is:
.eval well-defined expression , substitution symbol
Example 6-4 shows arithmetic being performed on substitution symbols.
Example 6-4. The .eval Directive
.asg
1,counter
.loop 100
.word counter
.eval counter + 1,counter
.endloop
In Example 6-4, the .asg directive could be replaced with the .eval directive (.eval 1, counter) without
changing the output. In simple cases like this, you can use .eval and .asg interchangeably. However, you
must use .eval if you want to calculate a value from an expression. While .asg only assigns a character
string to a substitution symbol, .eval evaluates an expression and then assigns the character string
equivalent to a substitution symbol.
See Assign a Substitution Symbol for more information about the .asg and .eval assembler directives.
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6.3.2 Built-In Substitution Symbol Functions
The following built-in substitution symbol functions enable you to make decisions on the basis of the string
value of substitution symbols. These functions always return a value, and they can be used in
expressions. Built-in substitution symbol functions are especially useful in conditional assembly
expressions. Parameters of these functions are substitution symbols or character-string constants.
In the function definitions shown in Table 6-1, a and b are parameters that represent substitution symbols
or character-string constants. The term string refers to the string value of the parameter. The symbol ch
represents a character constant.
Table 6-1. Substitution Symbol Functions and Return Values
Function
Return Value
$symlen (a)
Length of string a
$symcmp (a,b)
< 0 if a < b; 0 if a = b; > 0 if a > b
$firstch (a,ch)
Index of the first occurrence of character constant ch in string a
$lastch (a,ch)
Index of the last occurrence of character constant ch in string a
$isdefed (a)
1 if string a is defined in the symbol table
0 if string a is not defined in the symbol table
$ismember (a,b)
Top member of list b is assigned to string a
0 if b is a null string
$iscons (a)
1 if string a is a binary constant
2 if string a is an octal constant
3 if string a is a hexadecimal constant
4 if string a is a character constant
5 if string a is a decimal constant
$isname (a)
1 if string a is a valid symbol name
0 if string a is not a valid symbol name
$isreg (a)
(1)
1 if string a is a valid predefined register name
0 if string a is not a valid predefined register name
(1)
For more information about predefined register names, see Section 4.8.6.
Example 6-5 shows built-in substitution symbol functions.
Example 6‑5. Using Built-In Substitution Symbol Functions
pushx .macro list
!
! Push more than one item
! $ismember removes the first item in the list
160
.var
.loop
.break
STW
.endloop
.endm
item
pushx
A0,A1,A2,A3
($ismember(item, list) = 0)
item,*B15--[1]
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6.3.3 Recursive Substitution Symbols
When the assembler encounters a substitution symbol, it attempts to substitute the corresponding
character string. If that string is also a substitution symbol, the assembler performs substitution again. The
assembler continues doing this until it encounters a token that is not a substitution symbol or until it
encounters a substitution symbol that it has already encountered during this evaluation.
In Example 6-6, the x is substituted for z; z is substituted for y; and y is substituted for x. The assembler
recognizes this as infinite recursion and ceases substitution.
Example 6‑6. Recursive Substitution
*
*
.asg
.asg
.asg
MVKL
MVKH
"x",z
"z",y
"y",x
x, A1
x, A1
; declare z and assign z = "x"
; declare y and assign y = "z"
; declare x and assign x = "y"
MVKL
MVKH
x, A1
x, A1
; recursive expansion
; recursive expansion
6.3.4 Forced Substitution
In some cases, substitution symbols are not recognizable to the assembler. The forced substitution
operator, which is a set of colons surrounding the symbol, enables you to force the substitution of a
symbol's character string. Simply enclose a symbol with colons to force the substitution. Do not include
any spaces between the colons and the symbol. The syntax for the forced substitution operator is:
:symbol:
The assembler expands substitution symbols surrounded by colons before expanding other substitution
symbols.
You can use the forced substitution operator only inside macros, and you cannot nest a forced substitution
operator within another forced substitution operator.
Example 6-7 shows how the forced substitution operator is used.
Example 6-7. Using the Forced Substitution Operator
force
PORT:x:
PORT0
PORT1
.
.
.
PORT7
.macro
.loop
.set
.eval
.endloop
.endm
x
8
x*4
x+1, x
.global
force
portbase
.set
.set
0
4
.set
28
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6.3.5 Accessing Individual Characters of Subscripted Substitution Symbols
In a macro, you can access the individual characters (substrings) of a substitution symbol with subscripted
substitution symbols. You must use the forced substitution operator for clarity.
You can access substrings in two ways:
• :symbol (well-defined expression):
This method of subscripting evaluates to a character string with one character.
• :symbol (well-defined expression 1, well-defined expression 2):
In this method, expression1 represents the substring's starting position, and expression2 represents the
substring's length. You can specify exactly where to begin subscripting and the exact length of the
resulting character string. The index of substring characters begins with 1, not 0.
Example 6-8 and Example 6-9 show built-in substitution symbol functions used with subscripted
substitution symbols. In Example 6-8, subscripted substitution symbols redefine the STW instruction so
that it handles immediates. In Example 6-9, the subscripted substitution symbol is used to find a substring
strg1 beginning at position start in the string strg2. The position of the substring strg1 is assigned to the
substitution symbol pos.
Example 6‑8. Using Subscripted Substitution Symbols to Redefine an Instruction
storex
162
.macro
.var
.asg
.if
STW
.elseif
STW
.elseif
MVK
STW
.else
.emsg
.endif
.endm
x
tmp
:x(1):, tmp
$symcmp(tmp,"A") == 0
x,*A15--(4)
$symcmp(tmp,"B") == 0
x,*A15--(4)
$iscons(x)
x,A0
A0,*A15--(4)
storex
storex
10h
A15
"Bad Macro Parameter"
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Example 6‑9. Using Subscripted Substitution Symbols to Find Substrings
substr
.macro
.var
.if
.eval
.endif
.eval
.eval
.eval
.eval
.loop
.break
.asg
.if
.eval
.break
.else
.eval
.endif
.endloop
.endm
start,strg1,strg2,pos
len1,len2,i,tmp
$symlen(start) = 0
1,start
.asg
.asg
substr
.word
0,pos
"ar1 ar2 ar3 ar4",regs
1,"ar2",regs,pos
pos
0,pos
start,i
$symlen(strg1),len1
$symlen(strg2),len2
I = (len2 - len1 + 1)
":strg2(i,len1):",tmp
$symcmp(strg1,tmp) = 0
i,pos
I + 1,i
6.3.6 Substitution Symbols as Local Variables in Macros
If you want to use substitution symbols as local variables within a macro, you can use the .var directive to
define up to 32 local macro substitution symbols (including parameters) per macro. The .var directive
creates temporary substitution symbols with the initial value of the null string. These symbols are not
passed in as parameters, and they are lost after expansion.
.var
sym1 [,sym2 , ... ,symn ]
The .var directive is used in Example 6-8 and Example 6-9.
6.4
Macro Libraries
One way to define macros is by creating a macro library. A macro library is a collection of files that contain
macro definitions. You must use the archiver to collect these files, or members, into a single file (called an
archive). Each member of a macro library contains one macro definition. The files in a macro library must
be unassembled source files. The macro name and the member name must be the same, and the macro
filename's extension must be .asm. For example:
Macro Name
Filename in Macro Library
simple
simple.asm
add3
add3.asm
You can access the macro library by using the .mlib assembler directive (described in Define Macro
Library). The syntax is:
.mlib filename
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Using Conditional Assembly in Macros
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When the assembler encounters the .mlib directive, it opens the library named by filename and creates a
table of the library's contents. The assembler enters the names of the individual members within the library
into the opcode tables as library entries; this redefines any existing opcodes or macros that have the same
name. If one of these macros is called, the assembler extracts the entry from the library and loads it into
the macro table.
The assembler expands the library entry the same way it expands other macros. See Section 6.1 for how
the assembler expands macros. You can control the listing of library entry expansions with the .mlist
directive. For information about the .mlist directive, see Section 6.8 and Start/Stop Macro Expansion
Listing. Only macros that are actually called from the library are extracted, and they are extracted only
once.
You can use the archiver to create a macro library by including the desired files in an archive. A macro
library is no different from any other archive, except that the assembler expects the macro library to
contain macro definitions. The assembler expects only macro definitions in a macro library; putting object
code or miscellaneous source files into the library may produce undesirable results. For information about
creating a macro library archive, see Section 7.1.
6.5
Using Conditional Assembly in Macros
The conditional assembly directives are .if/.elseif/.else/.endif and .loop/ .break/.endloop. They can be
nested within each other up to 32 levels deep. The format of a conditional block is:
.if well-defined expression
[.elseif well-defined expression]
[.else]
.endif
The .elseif and .else directives are optional in conditional assembly. The .elseif directive can be used
more than once within a conditional assembly code block. When .elseif and .else are omitted and when
the .if expression is false (0), the assembler continues to the code following the .endif directive. See
Assemble Conditional Blocks for more information on the .if/ .elseif/.else/.endif directives.
The .loop/.break/.endloop directives enable you to assemble a code block repeatedly. The format of a
repeatable block is:
.loop [well-defined expression]
[.break [well-defined expression]]
.endloop
The .loop directive's optional well-defined expression evaluates to the loop count (the number of loops to
be performed). If the expression is omitted, the loop count defaults to 1024 unless the assembler
encounters a .break directive with an expression that is true (nonzero). See Assemble Conditional Blocks
Repeatedly for more information on the .loop/.break/.endloop directives.
The .break directive and its expression are optional in repetitive assembly. If the expression evaluates to
false, the loop continues. The assembler breaks the loop when the .break expression evaluates to true or
when the .break expression is omitted. When the loop is broken, the assembler continues with the code
after the .endloop directive. For more information, see Section 5.7.
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Example 6-10, Example 6-11, and Example 6-12 show the .loop/.break/ .endloop directives, properly
nested conditional assembly directives, and built-in substitution symbol functions used in a conditional
assembly code block.
Example 6‑10. The .loop/.break/.endloop Directives
.asg
.loop
1,x
.break
(x == 10)
; if x == 10, quit loop/break with expression
.eval
x+1,x
.endloop
Example 6‑11. Nested Conditional Assembly Directives
.asg
.loop
1,x
.if
.break
.endif
(x == 10)
(x == 10)
; if x == 10, quit loop
; force break
.eval
x+1,x
.endloop
Example 6‑12. Built-In Substitution Symbol Functions in a Conditional Assembly Code Block
MACK3
!
!
.macro src1, src2, sum, k
dst = dst + k * (src1 * src2)
.if
MPY
NOP
ADD
.else
MPY
MVK
MPY
NOP
ADD
.endif
k = 0
src1, src2, src2
src2, sum, sum
src1,src2,src2
k,src1
src1,src2,src2
src2,sum,sum
.endm
MACK3
MACK3
A0,A1,A3,0
A0,A1,A3,100
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Using Labels in Macros
6.6
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Using Labels in Macros
All labels in an assembly language program must be unique. This includes labels in macros. If a macro is
expanded more than once, its labels are defined more than once. Defining a label more than once is
illegal. The macro language provides a method of defining labels in macros so that the labels are unique.
Simply follow each label with a question mark, and the assembler replaces the question mark with a
period followed by a unique number. When the macro is expanded, you do not see the unique number in
the listing file. Your label appears with the question mark as it did in the macro definition. You cannot
declare this label as global. See Section 4.8.3 for more about labels.
The syntax for a unique label is:
label ?
Example 6-13 shows unique label generation in a macro. The maximum label length is shortened to allow
for the unique suffix. For example, if the macro is expanded fewer than 10 times, the maximum label
length is 126 characters. If the macro is expanded from 10 to 99 times, the maximum label length is 125.
The label with its unique suffix is shown in the cross-listing file. To obtain a cross-listing file, invoke the
assembler with the --cross_reference option (see Section 4.3).
Example 6‑13. Unique Labels in a Macro
1
2
3
4
5
6
7
8
9
10
11
12 00000000
1
1
1
1
1
1
1
00000000
00000004
00000008
0000000c
00000010
00000014
min
||
[y]
x,y,z
MV
CMPLT
B
NOP
MV
y,z
x,y,y
l?
5
x,z
l?
.endm
010401A1
00840AF8
80000292
00008000
010001A0
LABEL
||
[A1]
MIN
A0,A1,A2
MV
CMPLT
B
NOP
MV
A1,A2
A0,A1,A1
l?
5
A0,A2
l?
VALUE
.TMS320C60
.tms320C60
l$1$
166
.macro
00000001
00000001
00000014'
DEFN
REF
0
0
12
12
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Producing Messages in Macros
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6.7
Producing Messages in Macros
The macro language supports three directives that enable you to define your own assembly-time error and
warning messages. These directives are especially useful when you want to create messages specific to
your needs. The last line of the listing file shows the error and warning counts. These counts alert you to
problems in your code and are especially useful during debugging.
.emsg
.mmsg
.wmsg
sends error messages to the listing file. The .emsg directive generates errors in the same
manner as the assembler, incrementing the error count and preventing the assembler from
producing an object file.
sends assembly-time messages to the listing file. The .mmsg directive functions in the same
manner as the .emsg directive but does not set the error count or prevent the creation of an
object file.
sends warning messages to the listing file. The .wmsg directive functions in the same
manner as the .emsg directive, but it increments the warning count and does not prevent the
generation of an object file.
Macro comments are comments that appear in the definition of the macro but do not show up in the
expansion of the macro. An exclamation point in column 1 identifies a macro comment. If you want your
comments to appear in the macro expansion, precede your comment with an asterisk or semicolon.
Example 6-14 shows user messages in macros and macro comments that do not appear in the macro
expansion.
For more information about the .emsg, .mmsg, and .wmsg assembler directives, see Define Messages.
Example 6‑14. Producing Messages in a Macro
TEST
.macro x,y
!
! This macro checks for the correct number of parameters.
! It generates an error message if x and y are not present.
!
! The first line tests for proper input.
!
.if
($symlen(x) + ||$symlen(y) == 0)
.emsg
"ERROR --missing parameter in call to TEST"
.mexit
.else
.
.
.endif
.if
.
.
.endif
.endm
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Using Directives to Format the Output Listing
6.8
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Using Directives to Format the Output Listing
Macros, substitution symbols, and conditional assembly directives may hide information. You may need to
see this hidden information, so the macro language supports an expanded listing capability.
By default, the assembler shows macro expansions and false conditional blocks in the list output file. You
may want to turn this listing off or on within your listing file. Four sets of directives enable you to control
the listing of this information:
•
Macro and loop expansion listing
.mlist
expands macros and .loop/.endloop blocks. The .mlist directive prints all code
encountered in those blocks.
suppresses the listing of macro expansions and .loop/ .endloop blocks.
.mnolist
For macro and loop expansion listing, .mlist is the default.
168
•
False conditional block listing
.fclist
causes the assembler to include in the listing file all conditional blocks that do not
generate code (false conditional blocks). Conditional blocks appear in the listing
exactly as they appear in the source code.
.fcnolist
suppresses the listing of false conditional blocks. Only the code in conditional blocks
that actually assemble appears in the listing. The .if, .elseif, .else, and .endif directives
do not appear in the listing.
For false conditional block listing, .fclist is the default.
•
Substitution symbol expansion listing
.sslist
expands substitution symbols in the listing. This is useful for debugging the expansion
of substitution symbols. The expanded line appears below the actual source line.
.ssnolist
turns off substitution symbol expansion in the listing.
For substitution symbol expansion listing, .ssnolist is the default.
•
Directive listing
.drlist
causes the assembler to print to the listing file all directive lines.
.drnolist
suppresses the printing of certain directives in the listing file. These directives are
.asg, .eval, .var, .sslist, .mlist, .fclist, .ssnolist, .mnolist, .fcnolist, .emsg, .wmsg,
.mmsg, .length, .width, and .break.
For directive listing, .drlist is the default.
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Using Recursive and Nested Macros
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6.9
Using Recursive and Nested Macros
The macro language supports recursive and nested macro calls. This means that you can call other
macros in a macro definition. You can nest macros up to 32 levels deep. When you use recursive macros,
you call a macro from its own definition (the macro calls itself).
When you create recursive or nested macros, you should pay close attention to the arguments that you
pass to macro parameters because the assembler uses dynamic scoping for parameters. This means that
the called macro uses the environment of the macro from which it was called.
Example 6-15 shows nested macros. The y in the in_block macro hides the y in the out_block macro. The
x and z from the out_block macro, however, are accessible to the in_block macro.
Example 6‑15. Using Nested Macros
in_block
.macro y,a
.
.endm
; visible parameters are y,a and x,z from the calling macro
out_block .macro
x,y,z
.
; visible parameters are x,y,z
.
in_block x,y ; macro call with x and y as arguments
.
.
.endm
out_block
; macro call
Example 6-16 shows recursive and fact macros. The fact macro produces assembly code necessary to
calculate the factorial of n, where n is an immediate value. The result is placed in the A1 register . The fact
macro accomplishes this by calling fact1, which calls itself recursively.
Example 6‑16. Using Recursive Macros
.fcnolist
fact1
.macro n
.if n == 1
MVK globcnt, A1
; Leave the answer in the A1 register.
.else
.eval 1, temp
; Compute the decrement of symbol n.
.eval globcnt*temp, globcnt
; Multiply to get a new result.
fact1 temp
; Recursive call.
.endif
.endm
fact
.macro n
.if ! $iscons(n)
.emsg "Parm not a constant"
.elseif n < 1
MVK 0, A1
; Test that input is a constant.
; Type check input.
.else
.var temp
.asg n, globcnt
fact1 n
; Perform recursive procedure
.endif
.endm
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6.10 Macro Directives Summary
The directives listed in Table 6-2 through Table 6-6 can be used with macros. The .macro, .mexit, .endm
and .var directives are valid only with macros; the remaining directives are general assembly language
directives.
Table 6-2. Creating Macros
See
Mnemonic and Syntax
Description
Macro Use
Directive
.endm
End macro definition
Section 6.2
.endm
Define macro by macname
Section 6.2
.macro
.mexit
Go to .endm
Section 6.2
Section 6.2
.mlib filename
Identify library containing macro definitions
Section 6.4
.mlib
macname .macro
[parameter1 ][,... , parametern ]
Table 6-3. Manipulating Substitution Symbols
See
Mnemonic and Syntax
Description
Macro Use
Directive
.asg ["]character string["], substitution symbol
Assign character string to substitution symbol
Section 6.3.1
.asg
.eval well-defined expression, substitution symbol
Perform arithmetic on numeric substitution symbols
Section 6.3.1
.eval
.var
Define local macro symbols
Section 6.3.6
.var
sym1 [, sym2 , ..., symn ]
Table 6-4. Conditional Assembly
See
Mnemonic and Syntax
Description
Macro Use
Directive
.break [well-defined expression]
Optional repeatable block assembly
Section 6.5
.break
.endif
End conditional assembly
Section 6.5
.endif
.endloop
End repeatable block assembly
Section 6.5
.endloop
.else
Optional conditional assembly block
Section 6.5
.else
.elseif well-defined expression
Optional conditional assembly block
Section 6.5
.elseif
.if well-defined expression
Begin conditional assembly
Section 6.5
.if
.loop [well-defined expression]
Begin repeatable block assembly
Section 6.5
.loop
Table 6-5. Producing Assembly-Time Messages
See
Mnemonic and Syntax
Description
Macro Use
Directive
.emsg
Send error message to standard output
Section 6.7
.emsg
.mmsg
Send assembly-time message to standard output
Section 6.7
.mmsg
.wmsg
Send warning message to standard output
Section 6.7
.wmsg
Table 6-6. Formatting the Listing
See
Mnemonic and Syntax
Description
Macro Use
Directive
.fclist
Allow false conditional code block listing (default)
Section 6.8
.fclist
.fcnolist
Suppress false conditional code block listing
Section 6.8
.fcnolist
.mlist
Allow macro listings (default)
Section 6.8
.mlist
.mnolist
Suppress macro listings
Section 6.8
.mnolist
.sslist
Allow expanded substitution symbol listing
Section 6.8
.sslist
.ssnolist
Suppress expanded substitution symbol listing (default)
Section 6.8
.ssnolist
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Chapter 7
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Archiver Description
The TMS320C6000 archiver lets you combine several individual files into a single archive file. For
example, you can collect several macros into a macro library. The assembler searches the library and
uses the members that are called as macros by the source file. You can also use the archiver to collect a
group of object files into an object library. The linker includes in the library the members that resolve
external references during the link. The archiver allows you to modify a library by deleting, replacing,
extracting, or adding members.
Topic
...........................................................................................................................
7.1
7.2
7.3
7.4
7.5
Archiver Overview ............................................................................................
The Archiver's Role in the Software Development Flow ........................................
Invoking the Archiver ........................................................................................
Archiver Examples............................................................................................
Library Information Archiver Description.............................................................
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Page
172
173
174
175
176
171
Archiver Overview
7.1
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Archiver Overview
You can build libraries from any type of files. Both the assembler and the linker accept archive libraries as
input; the assembler can use libraries that contain individual source files, and the linker can use libraries
that contain individual object files.
One of the most useful applications of the archiver is building libraries of object modules. For example,
you can write several arithmetic routines, assemble them, and use the archiver to collect the object files
into a single, logical group. You can then specify the object library as linker input. The linker searches the
library and includes members that resolve external references.
You can also use the archiver to build macro libraries. You can create several source files, each of which
contains a single macro, and use the archiver to collect these macros into a single, functional group. You
can use the .mlib directive during assembly to specify that macro library to be searched for the macros
that you call. Chapter 6 discusses macros and macro libraries in detail, while this chapter explains how to
use the archiver to build libraries.
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7.2
The Archiver's Role in the Software Development Flow
Figure 7-1 shows the archiver's role in the software development process. The shaded portion highlights
the most common archiver development path. Both the assembler and the linker accept libraries as input.
Figure 7-1. The Archiver in the TMS320C6000 Software Development Flow
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Invoking the Archiver
7.3
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Invoking the Archiver
To invoke the archiver, enter:
ar6x[-]command [options] libname [filename1 ... filenamen ]
ar6x
[-]command
options
libname
filenames
is the command that invokes the archiver.
tells the archiver how to manipulate the existing library members and any specified. A
command can be preceded by an optional hyphen. You must use one of the following
commands when you invoke the archiver, but you can use only one command per
invocation. The archiver commands are as follows:
@ uses the contents of the specified file instead of command line entries. You can
use this command to avoid limitations on command line length imposed by the
host operating system. Use a ; at the beginning of a line in the command file to
include comments. (See Example 7-1 for an example using an archiver command
file.)
a
adds the specified files to the library. This command does not replace an existing
member that has the same name as an added file; it simply appends new
members to the end of the archive.
d
deletes the specified members from the library.
r
replaces the specified members in the library. If you do not specify filenames, the
archiver replaces the library members with files of the same name in the current
directory. If the specified file is not found in the library, the archiver adds it instead
of replacing it.
t
prints a table of contents of the library. If you specify filenames, only those files
are listed. If you do not specify any filenames, the archiver lists all the members in
the specified library.
x
extracts the specified files. If you do not specify member names, the archiver
extracts all library members. When the archiver extracts a member, it simply
copies the member into the current directory; it does not remove it from the library.
In addition to one of the commands, you can specify options. To use options, combine
them with a command; for example, to use the a command and the s option, enter -as
or as. The hyphen is optional for archiver options only. These are the archiver options:
-q (quiet) suppresses the banner and status messages.
-s prints a list of the global symbols that are defined in the library. (This option is
valid only with the a, r, and d commands.)
-u replaces library members only if the replacement has a more recent modification
date. You must use the r command with the -u option to specify which members to
replace.
-v (verbose) provides a file-by-file description of the creation of a new library from an
old library and its members.
names the archive library to be built or modified. If you do not specify an extension for
libname, the archiver uses the default extension .lib.
names individual files to be manipulated. These files can be existing library members or
new files to be added to the library. When you enter a filename, you must enter a
complete filename including extension, if applicable.
Naming Library Members
NOTE:
174
It is possible (but not desirable) for a library to contain several members with the same
name. If you attempt to delete, replace, or extract a member whose name is the same as
another library member, the archiver deletes, replaces, or extracts the first library member
with that name.
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Archiver Examples
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7.4
Archiver Examples
The following are examples of typical archiver operations:
• If you want to create a library called function.lib that contains the files sine.obj, cos.obj, and flt.obj,
enter:
ar6x -a function sine.obj cos.obj flt.obj
The archiver responds as follows:
==> new archive 'function.lib' ==> building new archive 'function.lib'
•
You can print a table of contents of function.lib with the -t command, enter:
ar6x -t function
The archiver responds as follows:
FILE NAME
---------------sine.obj
cos.obj
flt.obj
•
SIZE
----300
300
300
DATE
-----------------------Wed Jun 15 10:00:24 2011
Wed Jun 15 10:00:30 2011
Wed Jun 15 09:59:56 2011
If you want to add new members to the library, enter:
ar6x -as function atan.obj
The archiver responds as follows:
==>
==>
==>
==>
==>
•
symbol defined: '_sin'
symbol defined: '_cos'
symbol defined: '_tan'
symbol defined: '_atan
building archive 'function.lib'
Because this example does not specify an extension for the libname, the archiver adds the files to the
library called function.lib. If function.lib does not exist, the archiver creates it. (The -s option tells the
archiver to list the global symbols that are defined in the library.)
If you want to modify a library member, you can extract it, edit it, and replace it. In this example,
assume there is a library named macros.lib that contains the members push.asm, pop.asm, and
swap.asm.
ar6x -x macros push.asm
The archiver makes a copy of push.asm and places it in the current directory; it does not remove
push.asm from the library. Now you can edit the extracted file. To replace the copy of push.asm in the
library with the edited copy, enter:
ar6x -r macros push.asm
•
If you want to use a command file, specify the command filename after the -@ command. For
example:
ar6x -@modules.cmd
The archiver responds as follows:
==>
building archive 'modules.lib'
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Archiver Examples
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Example 7-1 is the modules.cmd command file. The r command specifies that the filenames given in
the command file replace files of the same name in the modules.lib library. The -u option specifies that
these files are replaced only when the current file has a more recent revision date than the file that is
in the library.
Example 7‑1. Archiver Command File
; Command file to replace members of the
;
modules library with updated files
; Use r command and u option:
ru
; Specify library name:
modules.lib
; List filenames to be replaced if updated:
align.asm
bss.asm
data.asm
text.asm
sect.asm
clink.asm
copy.asm
double.asm
drnolist.asm
emsg.asm
end.asm
7.5
Library Information Archiver Description
Section 7.1 explains how to use the archiver to create libraries of object files for use in the linker of one or
more applications. You can have multiple versions of the same object file libraries, each built with different
sets of build options. For example, you might have different versions of your object file library for big and
little endian, for different architecture revisions, or for different ABIs depending on the typical build
environments of client applications. However, if you have several versions of a library, it can be
cumbersome to keep track of which version of the library needs to be linked in for a particular application.
When several versions of a single library are available, the library information archiver can be used to
create an index library of all of the object file library versions. This index library is used in the linker in
place of a particular version of your object file library. The linker looks at the build options of the
application being linked, and uses the specified index library to determine which version of your object file
library to include in the linker. If one or more compatible libraries were found in the index library, the most
suitable compatible library is linked in for your application.
7.5.1 Invoking the Library Information Archiver
To invoke the library information archiver, enter:
libinfo6x [options] -o=libname libname1 [libname2 ... libnamen ]
libinfo6x
options
libnames
176
is the command that invokes the library information archiver.
changes the default behavior of the library information archiver. These options are:
-o libname
specifies the name of the index library to create or update. This option is
required.
-u
updates any existing information in the index library specified with the -o
option instead of creating a new index.
names individual object file libraries to be manipulated. When you enter a libname, you
must enter a complete filename including extension, if applicable.
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7.5.2 Library Information Archiver Example
Consider these object file libraries that all have the same members, but are built with different build
options:
Object File Library Name
Build Options
mylib_64plus_be.lib
-mv6400+ --endian=big
mylib_64plus_le.lib
-mv6400+ --endian=little
mylib_6740_le.lib
-mv6740 --endian=little
mylib_6600_be.lib
-mv6600 --endian=big
Using the library information archiver, you can create an index library called mylib.lib from the above
libraries:
libinfo6x -o mylib.lib mylib_6600_be.lib mylib_6600_le.lib
You can now specify mylib.lib as a library for the linker of an application. The linker uses the index library
to choose the appropriate version of the library to use. If the --issue_remarks option is specified before the
--run_linker option, the linker reports which library was chosen.
• Example 1 (ISA 64plus, little endian):
cl6x -mv64plus --endian=little --issue_remarks main.c -z -l lnk.cmd ./mylib.lib
<Linking>
remark: linking in "mylib_64plus_le.lib" in place of "mylib.lib"
•
Example 2 (ISA 6600, big endian):
cl6x -mv6600 --endian=big --issue_remarks main.c -z -l lnk.cmd ./mylib.lib
<Linking>
remark: linking in "mylib_6600_be.lib" in place of "mylib.lib"
7.5.3 Listing the Contents of an Index Library
The archiver’s -t option can be used on an index library to list the archives indexed by an index library:
ar6x t mylib.lib
SIZE
DATE
------------------------------119
Wed Feb 03 12:45:22 2010
119
Wed Feb 03 12:45:22 2010
119
Wed Feb 03 12:45:22 2010
119
Wed Feb 03 12:45:22 2010
0
Wed Sep 30 12:45:22 2009
FILE NAME
----------------mylib_6600_be.lib
mylib_6600_le.lib
mylib_64plus_be.lib
mylib_64plus_le.lib
__TI_$$LIBINFO
The indexed object file libraries have an additional .libinfo extension in the archiver listing. The
__TI_$$LIBINFO member is a special member that designates mylib.lib as an index library, rather than a
regular library.
If the archiver’s -d command is used on an index library to delete a .libinfo member, the linker will no
longer choose the corresponding library when the index library is specified.
Using any other archiver option with an index library, or using -d to remove the __TI_$$LIBINFO member,
results in undefined behavior, and is not supported.
7.5.4 Requirements
You must follow these requirements to use library index files:
• At least one application object file must appear on the linker command line before the index library.
• Each object file library specified as input to the library information archiver must only contain object file
members that are built with the same build options.
• The linker expects the index library and all of the libraries it indexes to be in a single directory.
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Chapter 8
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Linker Description
The TMS320C6000 linker creates a static executable or dynamic object module by combining object
modules. This chapter describes the linker options, directives, and statements used to create static
executables and dynamic object modules. Object libraries, command files, and other key concepts are
discussed as well.
The concept of sections is basic to linker operation; Chapter 2 includes a detailed discussion of sections.
Topic
8.1
8.2
8.3
8.4
8.5
8.6
8.7
8.8
8.9
8.10
8.11
8.12
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Linker Overview ...............................................................................................
The Linker's Role in the Software Development Flow ............................................
Invoking the Linker ...........................................................................................
Linker Options .................................................................................................
Linker Command Files ......................................................................................
Linker Symbols ................................................................................................
Default Placement Algorithm .............................................................................
Linker-Generated Copy Tables ...........................................................................
Partial (Incremental) Linking ..............................................................................
Linking C/C++ Code ..........................................................................................
Linker Example ................................................................................................
Dynamic Linking with the C6000 Code Generation Tools ......................................
Linker Description
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244
257
258
260
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8.1
Linker Overview
The TMS320C6000 linker allows you to allocate output sections efficiently in the memory map. As the
linker combines object files, it performs the following tasks:
• Allocates sections into the target system's configured memory
• Relocates symbols and sections to assign them to final addresses
• Resolves undefined external references between input files
The linker command language controls memory configuration, output section definition, and address
binding. The language supports expression assignment and evaluation. You configure system memory by
defining and creating a memory model that you design. Two powerful directives, MEMORY and
SECTIONS, allow you to:
• Allocate sections into specific areas of memory
• Combine object file sections
• Define or redefine global symbols at link time
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The Linker's Role in the Software Development Flow
8.2
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The Linker's Role in the Software Development Flow
Figure 8-1 illustrates the linker's role in the software development process. The linker accepts several
types of files as input, including object files, command files, libraries, and partially linked files. The linker
creates an executable object module that can be downloaded to one of several development tools or
executed by a TMS320C6000 device.
Figure 8-1. The Linker in the TMS320C6000 Software Development Flow
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8.3
Invoking the Linker
The general syntax for invoking the linker is:
cl6x --run_linker [options] filename1 .... filenamen
cl6x --run_linker
options
filename 1, filename n
is the command that invokes the linker. The --run_linker option's short form is
-z.
can appear anywhere on the command line or in a linker command file.
(Options are discussed in Section 8.4.)
can be object files, linker command files, or archive libraries. The default
extension for all input files is .obj; any other extension must be explicitly
specified. The linker can determine whether the input file is an object or ASCII
file that contains linker commands. The default output filename is a.out, unless
you use the --output_file option to name the output file.
There are two methods for invoking the linker:
• Specify options and filenames on the command line. This example links two files, file1.obj and file2.obj,
and creates an output module named link.out.
cl6x --run_linker file1.obj file2.obj --output_file=link.out
•
Put filenames and options in a linker command file. Filenames that are specified inside a linker
command file must begin with a letter. For example, assume the file linker.cmd contains the following
lines:
--output_file=link.out file1.obj file2.obj
Now you can invoke the linker from the command line; specify the command filename as an input file:
cl6x --run_linker linker.cmd
When you use a command file, you can also specify other options and files on the command line. For
example, you could enter:
cl6x --run_linker --map_file=link.map linker.cmd file3.obj
The linker reads and processes a command file as soon as it encounters the filename on the
command line, so it links the files in this order: file1.obj, file2.obj, and file3.obj. This example creates an
output file called link.out and a map file called link.map.
For information on invoking the linker for C/C++ files, see Section 8.10.
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Linker Options
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Linker Options
Linker options control linking operations. They can be placed on the command line or in a command file.
Linker options must be preceded by a hyphen (-). Options can be separated from arguments (if they have
them) by an optional space.
Table 8-1. Basic Options Summary
Option
Alias
Description
Section
--run_linker
-z
Enables linking
Section 8.3
--output_file
-o
Names the executable output module. The default filename is a.out.
Section 8.4.23
--map_file
-m
Produces a map or listing of the input and output sections, including holes, and Section 8.4.18
places the listing in filename
--stack_size
-stack
Sets C system stack size to size bytes and defines a global symbol that
specifies the stack size. Default = 1K bytes
Section 8.4.28
--heap_size
-heap
Sets heap size (for the dynamic memory allocation in C) to size bytes and
defines a global symbol that specifies the heap size. Default = 1K bytes
Section 8.4.14
Table 8-2. File Search Path Options Summary
Option
Alias
Description
Section
--library
-l
Names an archive library or link command filename as linker input
Section 8.4.16
--search_path
-i
Alters library-search algorithms to look in a directory named with pathname
before looking in the default location. This option must appear before the -library option.
Section 8.4.16.1
--priority
-priority
Satisfies unresolved references by the first library that contains a definition for
that symbol
Section 8.4.16.3
--reread_libs
-x
Forces rereading of libraries, which resolves back references
Section 8.4.16.3
Disables the automatic selection of a run-time-support library
Section 8.4.8
--disable_auto_rts
Table 8-3. Command File Preprocessing Options Summary
Option
Description
Section
--define
Alias
Predefines name as a preprocessor macro.
Section 8.4.10
--undefine
Removes the preprocessor macro name.
Section 8.4.10
--disable_pp
Disables preprocessing for command files
Section 8.4.10
Table 8-4. Diagnostic Options Summary
Option
Description
Section
--diag_error
Alias
Categorizes the diagnostic identified by num as an error
Section 8.4.7
--diag_remark
Categorizes the diagnostic identified by num as a remark
Section 8.4.7
--diag_suppress
Suppresses the diagnostic identified by num
Section 8.4.7
--diag_warning
Categorizes the diagnostic identified by num as a warning
Section 8.4.7
Displays a diagnostic's identifiers along with its text
Section 8.4.7
Treats warnings as errors
Section 8.4.7
--issue_remarks
Issues remarks (nonserious warnings)
Section 8.4.7
--no_demangle
Disables demangling of symbol names in diagnostics
Section 8.4.20
--no_warnings
Suppresses warning diagnostics (errors are still issued)
Section 8.4.7
--set_error_limit
Sets the error limit to num. The linker abandons linking after this number of
errors. (The default is 100.)
Section 8.4.7
Provides verbose diagnostics that display the original source with line-wrap
Section 8.4.7
Displays a message when an undefined output section is created
Section 8.4.33
--display_error_number
--emit_warnings_as_errors
-pdew
--verbose_diagnostics
--warn_sections
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Table 8-5. Linker Output Options Summary
Option
Alias
Description
Section
--absolute_exe
-a
Produces an absolute, executable module. This is the default; if neither -absolute_exe nor --relocatable is specified, the linker acts as if --absolute_exe
were specified.
Section 8.4.3.1
--ecc:data_error
Inject the specified errors into the output file for testing
Section 8.4.11
Section 8.5.9
--ecc:ecc_error
Inject the specified errors into the Error Correcting Code (ECC) for testing
Section 8.4.11
Section 8.5.9
--mapfile_contents
Controls the information that appears in the map file.
Section 8.4.19
--relocatable
-r
Produces a nonexecutable, relocatable output module
Section 8.4.3.2
--rom
-r
Create a ROM object
--xml_link_info
Generates a well-formed XML file containing detailed information about the
result of a link
Section 8.4.34
Table 8-6. Symbol Management Options Summary
Option
Alias
Description
Section
--entry_point
-e
Defines a global symbol that specifies the primary entry point for the output
module
Section 8.4.12
--globalize
Changes the symbol linkage to global for symbols that match pattern
Section 8.4.17
--hide
Hides global symbols that match pattern
Section 8.4.15
--localize
Changes the symbol linkage to local for symbols that match pattern
Section 8.4.17
--make_global
-g
Makes symbol global (overrides -h)
--make_static
-h
Makes all global symbols static
Section 8.4.17.1
--no_symtable
-s
Strips symbol table information and line number entries from the output
module
Section 8.4.22
Retains a list of sections that otherwise would be discarded
Section 8.4.26
Scans all libraries for duplicate symbol definitions
Section 8.4.27
Maps symbol references to a symbol definition of a different name
Section 8.4.30
Places an unresolved external symbol into the output module's symbol table
Section 8.4.32
Reveals (un-hides) global symbols that match pattern
Section 8.4.15
--retain
--scan_libraries
-scanlibs
--symbol_map
--undef_sym
-u
--unhide
Table 8-7. Run-Time Environment Options Summary
Option
Alias
Description
Section
--arg_size
--args
Allocates memory to be used by the loader to pass arguments
Section 8.4.4
--fill_value
-f
Sets default fill values for holes within output sections; fill_value is a 32-bit
constant
Section 8.4.13
Causes the linker to choose a thread-safe version of the RTS library when
auto-selecting an RTS library or resolving a reference to libc.a, even if none of
the input object files contain the TI build attribute placed by the --multithread
compiler option. If you used the --openmp compiler option to create any of the
object files, the --multithread option is enabled automatically.
Section 8.4.8
--multithread
--ram_model
-cr
Initializes variables at load time
Section 8.4.25
--rom_model
-c
Autoinitializes variables at run time
Section 8.4.25
Generates far call trampolines; on by default
Section 8.4.31
--trampolines
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Table 8-8. Link-Time Optimization Options Summary
Option
Description
Section
--cinit_compression
[=compression_kind]
Alias
Specifies the type of compression to apply to the c auto initialization data
(default is rle)
Section 8.4.5
--compress_dwarf
Aggressively reduces the size of DWARF information from input object files
Section 8.4.6
--copy_compression
[=compression_kind]
Compresses data copied by linker copy tables
Section 8.4.5
--unused_section_elimination
Eliminates sections that are not needed in the executable module; on by
default
Section 8.4.9
Table 8-9. Dynamic Linking Options Summary
Option
Description
Section
--dsbt_index
Alias
Specifies the Data Segment Base Table (DSBT) index to be assumed for the
dynamic shared object or dynamic library being linked
Section 8.12.4.3
--dsbt_size
Specifies the number of entries to be reserved for the Data Segment Base
Table (DSBT)
Section 8.12.4.3
--dynamic
Generates a bare-metal dynamic executable or library (argument is optional; if
no argument is specified, then a dynamic executable (exe) is generated)
Section 8.12.4.3
--export
Exports the specified function symbol (sym)
Section 8.12.3.1
--fini
Specifies function symbol (sym) of the termination code
Section 8.12.4.3
--import
Imports the specified symbol
Section 8.12.4.1
--init
Specifies the function symbol (sym) of the initialization code
Section 8.12.4.3
--linux
Generates code for Linux
Section 8.12.4.3
--pic
Generates position independent addressing for a shared object. Default is
near.
Section 8.12.4.3
--rpath
Adds specified directory to the beginning of the dynamic library search path
Section 8.12.4.3
--runpath
Adds specified directory to the end of the dynamic library search path
Section 8.12.4.3
--shared
Generates an ELF dynamically shared object (DSO)
Section 8.12.4.3
--soname
Specifies the name to be associated with this linked dynamic output; this name Section 8.12.4.3
is stored in the file's dynamic table
--sysv
Generates SysV ELF output file
Section 8.12.4.3
Table 8-10. Miscellaneous Options Summary
Option
Alias
Description
Section
--linker_help
-help
Displays information about syntax and available options
–
--minimize_trampolines
Selects the trampoline minimization algorithm (argument is optional; algoriithm
is postorder by default)
Section 8.4.31.2
--preferred_order
Prioritizes placement of functions
Section 8.4.24
--strict_compatibility
Performs more conservative and rigorous compatibility checking of input object Section 8.4.29
files
--trampoline_min_spacing
When trampoline reservations are spaced more closely than the specified limit, Section 8.4.31.3
tries to make them adjacent
--zero_init
Controls preinitialization of uninitialized variables. Default is on.
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8.4.1 Wildcards in File, Section, and Symbol Patterns
The linker allows file, section, and symbol names to be specified using the asterisk (*) and question mark
(?) wildcards. Using * matches any number of characters and using ? matches a single character. Using
wildcards can make it easier to handle related objects, provided they follow a suitable naming convention.
For example:
mp3*.obj
task?.o*
/* matches anything .obj that begins with mp3
*/
/* matches task1.obj, task2.obj, taskX.o55, etc. */
SECTIONS
{
.fast_code: { *.obj(*fast*) }
> FAST_MEM
.vectors : { vectors.obj(.vector:part1:*) > 0xFFFFFF00
.str_code : { rts*.lib<str*.obj>(.text) } > S1ROM
}
8.4.2 Specifying C/C++ Symbols with Linker Options
Tthe link-time symbol is the same as the C/C++ identifier name. The compiler does not prepend an
underscore to the beginning of C/C++ identifiers.
See Section 8.6.1 for information about referring to linker symbols in C/C++ code.
8.4.3 Relocation Capabilities (--absolute_exe and --relocatable Options)
The linker performs relocation, which is the process of adjusting all references to a symbol when the
symbol's address changes (Section 2.7).
The linker supports two options (--absolute_exe and --relocatable) that allow you to produce an absolute
or a relocatable output module. The linker also supports a third option (-ar) that allows you to produce an
executable, relocatable output module.
When the linker encounters a file that contains no relocation or symbol table information, it issues a
warning message (but continues executing). Relinking an absolute file can be successful only if each input
file contains no information that needs to be relocated (that is, each file has no unresolved references and
is bound to the same virtual address that it was bound to when the linker created it).
8.4.3.1
Producing an Absolute Output Module (--absolute_exe option)
When you use the --absolute_exe option without the --relocatable option, the linker produces an absolute,
executable output module. Absolute files contain no relocation information. Executable files contain the
following:
• Special symbols defined by the linker (see Section 8.5.10.4)
• An header that describes information such as the program entry point
• No unresolved references
The following example links file1.obj and file2.obj and creates an absolute output module called a.out:
cl6x --run_linker --absolute_exe file1.obj file2.obj
The --absolute_exe and --relocatable Options
NOTE: If you do not use the --absolute_exe or the --relocatable option, the linker acts as if you
specified --absolute_exe.
8.4.3.2
Producing a Relocatable Output Module (--relocatable option)
When you use the --relocatable option, the linker retains relocation entries in the output module. If the
output module is relocated (at load time) or relinked (by another linker execution), use --relocatable to
retain the relocation entries.
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The linker produces a file that is not executable when you use the --relocatable option without the -absolute_exe option. A file that is not executable does not contain special linker symbols or an optional
header. The file can contain unresolved references, but these references do not prevent creation of an
output module.
This example links file1.obj and file2.obj and creates a relocatable output module called a.out:
cl6x --run_linker --relocatable file1.obj file2.obj
The output file a.out can be relinked with other object files or relocated at load time. (Linking a file that will
be relinked with other files is called partial linking. For more information, see Section 8.9.)
8.4.3.3
Producing an Executable, Relocatable Output Module (-ar Option)
If you invoke the linker with both the --absolute_exe and --relocatable options, the linker produces an
executable, relocatable object module. The output file contains the special linker symbols, an optional
header, and all resolved symbol references; however, the relocation information is retained.
This example links file1.obj and file2.obj to create an executable, relocatable output module called xr.out:
cl6x --run_linker -ar file1.obj file2.obj --output_file=xr.out
8.4.4 Allocate Memory for Use by the Loader to Pass Arguments (--arg_size Option)
The --arg_size option instructs the linker to allocate memory to be used by the loader to pass arguments
from the command line of the loader to the program. The syntax of the --arg_size option is:
--arg_size= size
The size is the number of bytes to be allocated in target memory for command-line arguments.
By default, the linker creates the __c_args__ symbol and sets it to -1. When you specify --arg_size=size,
the following occur:
• The linker creates an uninitialized section named .args of size bytes.
• The __c_args__ symbol contains the address of the .args section.
The loader and the target boot code use the .args section and the __c_args__ symbol to determine
whether and how to pass arguments from the host to the target program. See the TMS320C6000
Optimizing Compiler User's Guide for information about the loader.
8.4.5 Compression (--cinit_compression and --copy_compression Option)
By default, the linker does not compress data. These two options specify compression through the linker.
The --cinit_compression option specifies the compression type the linker applies to the C autoinitialization
data. The default is rle.
Overlays can be managed by using linker-generated copy tables. To save ROM space the linker can
compress the data copied by the copy tables. The compressed data is decompressed during copy. The -copy_compression option controls the compression of the copy data tables.
The syntax for the options are:
--cinit_compression[=compression_kind]
--copy_compression[=compression_kind]
The compression_kind can be one of the following types:
• off. Don't compress the data.
• rle. Compress data using Run Length Encoding (the default if nocompression_kind is specified).
• lzss. Compress data using Lempel-Ziv Storer and Symanski compression.
See Section 8.8.5 for more information about compression.
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8.4.6 Compress DWARF Information (--compress_dwarf Option)
The --compress_dwarf option aggressively reduces the size of DWARF information by eliminating
duplicate information from input object files. The --compress_dwarf option eliminates duplicate information
that could not be removed through the use of ELF COMDAT groups. (See the ELF specification for
information on COMDAT groups.)
8.4.7 Control Linker Diagnostics
The linker uses certain C/C++ compiler options to control linker-generated diagnostics. The diagnostic
options must be specified before the --run_linker option.
--diag_error=num
--diag_remark=num
--diag_suppress=num
--diag_warning=num
--display_error_number
--emit_warnings_as_
errors
--issue_remarks
--no_warnings
--set_error_limit=num
--verbose_diagnostics
Categorize the diagnostic identified by num as an error. To find the numeric
identifier of a diagnostic message, use the --display_error_number option first
in a separate link. Then use --diag_error=num to recategorize the diagnostic
as an error. You can only alter the severity of discretionary diagnostics.
Categorize the diagnostic identified by num as a remark. To find the numeric
identifier of a diagnostic message, use the --display_error_number option first
in a separate link. Then use --diag_remark=num to recategorize the
diagnostic as a remark. You can only alter the severity of discretionary
diagnostics.
Suppress the diagnostic identified by num. To find the numeric identifier of a
diagnostic message, use the --display_error_number option first in a
separate link. Then use --diag_suppress=num to suppress the diagnostic.
You can only suppress discretionary diagnostics.
Categorize the diagnostic identified by num as a warning. To find the numeric
identifier of a diagnostic message, use the --display_error_number option first
in a separate link. Then use --diag_warning=num to recategorize the
diagnostic as a warning. You can only alter the severity of discretionary
diagnostics.
Display a diagnostic's numeric identifier along with its text. Use this option in
determining which arguments you need to supply to the diagnostic
suppression options (--diag_suppress, --diag_error, --diag_remark, and -diag_warning). This option also indicates whether a diagnostic is
discretionary. A discretionary diagnostic is one whose severity can be
overridden. A discretionary diagnostic includes the suffix -D; otherwise, no
suffix is present. See the TMS320C6000 Optimizing Compiler User's Guide
for more information on understanding diagnostic messages.
Treat all warnings as errors. This option cannot be used with the -no_warnings option. The --diag_remark option takes precedence over this
option. This option takes precedence over the --diag_warning option.
Issue remarks (nonserious warnings), which are suppressed by default.
Suppress warning diagnostics (errors are still issued).
Set the error limit to num, which can be any decimal value. The linker
abandons linking after this number of errors. (The default is 100.)
Provide verbose diagnostics that display the original source with line-wrap
and indicate the position of the error in the source line
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8.4.8 Automatic Library Selection (--disable_auto_rts and --multithread Options)
The --disable_auto_rts option disables the automatic selection of a run-time-support (RTS) library. See the
TMS320C6000 Optimizing Compiler User's Guide for details on the automatic selection process.
The --multithread option can be used for multithreaded applications that do not use OpenMP. This option
causes the linker to choose a thread-safe version of the RTS library when auto-selecting an RTS library or
resolving a reference to libc.a, even if none of the input object files contain the TI build attribute placed by
the --multithread compiler option. If you used the --openmp compiler option to create any of the object
files, the --multithread option is enabled automatically. See the TMS320C6000 Optimizing Compiler User's
Guide for details on OpenMP and other multithreaded applications.
8.4.9 Do Not Remove Unused Sections (--unused_section_elimination Option)
In order to minimize the foot print, the ELF linker does not include a section that is not needed to resolve
any references in the final executable. Use --unused_section_elimination=off to disable this optimization.
The syntax for the option is:
--unused_section_elimination[=on|off]
The linker default behavior is equivalent to --unused_section_elimination=on.
8.4.10 Linker Command File Preprocessing (--disable_pp, --define and --undefine Options)
The linker preprocesses linker command files using a standard C preprocessor. Therefore, the command
files can contain well-known preprocessing directives such as #define, #include, and #if / #endif.
Three linker options control the preprocessor:
--disable_pp
--define=name[=val]
--undefine=name
Disables preprocessing for command files
Predefines name as a preprocessor macro
Removes the macro name
The compiler has --define and --undefine options with the same meanings. However, the linker options are
distinct; only --define and --undefine options specified after --run_linker are passed to the linker. For
example:
cl6x --define=FOO=1 main.c --run_linker --define=BAR=2 lnk.cmd
The linker sees only the --define for BAR; the compiler only sees the --define for FOO.
When one command file #includes another, preprocessing context is carried from parent to child in the
usual way (that is, macros defined in the parent are visible in the child). However, when a command file is
invoked other than through #include, either on the command line or by the typical way of being named in
another command file, preprocessing context is not carried into the nested file. The exception to this is -define and --undefine options, which apply globally from the point they are encountered. For example:
--define GLOBAL
#define LOCAL
#include "incfile.cmd"
nestfile.cmd
/* sees GLOBAL and LOCAL */
/* only sees GLOBAL
*/
Two cautions apply to the use of --define and --undefine in command files. First, they have global effect as
mentioned above. Second, since they are not actually preprocessing directives themselves, they are
subject to macro substitution, probably with unintended consequences. This effect can be defeated by
quoting the symbol name. For example:
--define MYSYM=123
--undefine MYSYM
--undefine "MYSYM"
188
/* expands to --undefine 123 (!) */
/* ahh, that's better
*/
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The linker uses the same search paths to find #include files as it does to find libraries. That is, #include
files are searched in the following places:
1. If the #include file name is in quotes (rather than <brackets>), in the directory of the current file
2. In the list of directories specified with --Iibrary options or environment variables (see Section 8.4.16)
There are two exceptions: relative pathnames (such as "../name") always search the current directory; and
absolute pathnames (such as "/usr/tools/name") bypass search paths entirely.
The linker provides the built-in macro definitions listed in Table 8-11. The availability of these macros
within the linker is determined by the command-line options used, not the build attributes of the files being
linked. If these macros are not set as expected, confirm that your project's command line uses the correct
compiler option settings.
Table 8-11. Predefined C6000 Macro Names
Macro Name
Description
_ _DATE_ _
Expands to the compilation date in the form mmm dd yyyy
_ _FILE_ _
Expands to the current source filename
_ _TI_COMPILER_VERSION_ _
Defined to a 7-9 digit integer, depending on if X has 1, 2, or 3 digits. The number does
not contain a decimal. For example, version 3.2.1 is represented as 3002001. The
leading zeros are dropped to prevent the number being interpreted as an octal.
_ _TI_EABI_ _
Defined to 1 if EABI is enabled; otherwise, it is undefined.
_ _TIME_ _
Expands to the compilation time in the form "hh:mm:ss"
__TMS320C6X__
Always defined
__TMS320C6600__
Defined to 1 if --silicon_version=6600; otherwise it is undefined.
__TMS320C6740__
Defined to 1 if --silicon_version=6740; otherwise it is undefined.
__TMS320C64_PLUS__
Defined to 1 if --silicon_version=6400+; otherwise it is undefined.
__TMS320C6400_PLUS__
Defined to 1 if --silicon_version=6400+; otherwise it is undefined; an alternate macro for
__TMS320C64_PLUS__
__DSBT__
Defined to 1 if --dsbt is specified (to use Dynamic Segment Base Table); otherwise it is
undefined.
8.4.11 Error Correcting Code Testing (--ecc Options)
Error Correcting Codes (ECC) can be generated and placed in separate sections through the linker
command file. ECC uses extra bits to allow errors to be detected and/or corrected by a device. The ECC
support provided by the linker is compatible with the ECC support in TI Flash memory on various TI
devices. TI Flash memory uses a modified Hamming(72,64) code, which uses 8 parity bits for every 64
bits. Check the documentation for your Flash memory to see if ECC is supported. (ECC for read-write
memory is handled completely in hardware at run time.)
See Section 8.5.9 for details on linker command file syntax for ECC support.
To test ECC error detection and handling, you can use two command-line options that inject bit errors into
the linked executable. These options let you specify an address where an error should appear and a
bitmask of bits in the code/data at that address to flip. You can specify the address of the error absolutely
or as an offset from a symbol.
When a data error is injected, the ECC parity bits for the data are calculated as if the error were not
present. This simulates bit errors that might actually occur and test ECC's ability to correct different levels
of errors.
The --ecc:data_error option injects errors into the load image at the specified location. The syntax is:
--ecc:data_error=(symbol+offset|address)[,page],bitmask
The address is the location of the minimum addressable unit where the error is to be injected. A
symbol+offset can be used to specify the location of the error to be injected with a signed offset from that
symbol. The page number is needed to make the location non-ambiguous if the address occurs on
multiple memory pages. The bitmask is a mask of the bits to flip; its width should be the width of an
addressable unit.
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For example, the following command line flips the least-significant bit in the byte at the address 0x100,
making it inconsistent with the ECC parity bits for that byte:
cl6x test.c --ecc:data_error=0x100,0x01 -z -o test.out
The following command flips two bits in the third byte of the code for main():
cl6x test.c --ecc:data_error=main+2,0x42 -z -o test.out
The --ecc:ecc_error option injects errors into the ECC parity bits that correspond to the specified
location. Note that the ecc_error option can therefore only specify locations inside ECC input ranges,
whereas the data_error option can also specify errors in the ECC output memory ranges. The syntax is:
--ecc:ecc_error=(symbol+offset|address)[,page],bitmask
The parameters for this option are the same as for --ecc:data_error, except that the bitmask must be
exactly 8 bits. Mirrored copies of the affected ECC byte will also contain the same injected error.
An error injected into an ECC byte with --ecc:ecc_error may cause errors to be detected at run time in any
of the 8 data bytes covered by that ECC byte.
For example, the following command flips every bit in the ECC byte that contains the parity information for
the byte at 0x200:
cl6x test.c --ecc:ecc_error=0x200,0xff -z -o test.out
The linker disallows injecting errors into memory ranges that are neither an ECC range nor the input range
for an ECC range. The compiler can only inject errors into initialized sections.
8.4.12 Define an Entry Point (--entry_point Option)
The memory address at which a program begins executing is called the entry point. When a loader loads
a program into target memory, the program counter (PC) must be initialized to the entry point; the PC then
points to the beginning of the program.
The linker can assign one of four values to the entry point. These values are listed below in the order in
which the linker tries to use them. If you use one of the first three values, it must be an external symbol in
the symbol table.
• The value specified by the --entry_point option. The syntax is:
--entry_point= global_symbol
where global_symbol defines the entry point and must be defined as an external symbol of the input
files. The external symbol name of C or C++ objects may be different than the name as declared in the
source language; refer to the TMS320C6000 Optimizing Compiler User's Guide.
• The value of symbol _c_int00 (if present). The _c_int00 symbol must be the entry point if you are
linking code produced by the C compiler.
• The value of symbol _main (if present)
• 0 (default value)
This example links file1.obj and file2.obj. The symbol begin is the entry point; begin must be defined as
external in file1 or file2.
cl6x --run_linker --entry_point=begin file1.obj file2.obj
See Section 8.6.1 for information about referring to linker symbols in C/C++ code.
8.4.13 Set Default Fill Value (--fill_value Option)
The --fill_value option fills the holes formed within output sections. The syntax for the option is:
--fill_value= value
The argument value is a 32-bit constant (up to eight hexadecimal digits). If you do not use --fill_value, the
linker uses 0 as the default fill value.
This example fills holes with the hexadecimal value ABCDABCD:
cl6x --run_linker --fill_value=0xABCDABCD file1.obj file2.obj
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8.4.14 Define Heap Size (--heap_size Option)
The C/C++ compiler uses an uninitialized section called .sysmem for the C run-time memory pool used by
malloc(). You can set the size of this memory pool at link time by using the --heap_size option. The syntax
for the --heap_size option is:
--heap_size= size
The size must be a constant. This example defines a 4K byte heap:
cl6x --run_linker --heap_size=0x1000 /* defines a 4k heap (.sysmem section)*/
The linker creates the .sysmem section only if there is a .sysmem section in an input file.
The linker also creates a global symbol __TI_SYSMEM_SIZE and assigns it a value equal to the size of
the heap. The default size is 1K bytes. See Section 8.6.1 for information about referring to linker symbols
in C/C++ code. For more about C/C++ linking, see Section 8.10.
8.4.15 Hiding Symbols
Symbol hiding prevents the symbol from being listed in the output file's symbol table. While localization is
used to prevent name space clashes in a link unit, symbol hiding is used to obscure symbols which should
not be visible outside a link unit. Such symbol’s names appear only as empty strings or “no name” in
object file readers. The linker supports symbol hiding through the --hide and --unhide options.
The syntax for these options are:
--hide=' pattern '
--unhide=' pattern '
The pattern is a string with optional wildcards ? or *. Use ? to match a single character and use * to match
zero or more characters.
The --hide option hides global symbols with a linkname matching the pattern. It hides symbols matching
the pattern by changing the name to an empty string. A global symbol that is hidden is also localized.
The --unhide option reveals (un-hides) global symbols that match the pattern that are hidden by the --hide
option. The --unhide option excludes symbols that match pattern from symbol hiding provided the pattern
defined by --unhide is more restrictive than the pattern defined by --hide.
These options have the following properties:
• The --hide and --unhide options can be specified more than once on the command line.
• The order of --hide and --unhide has no significance.
• A symbol is matched by only one pattern defined by either --hide or --unhide.
• A symbol is matched by the most restrictive pattern. Pattern A is considered more restrictive than
Pattern B, if Pattern A matches a narrower set than Pattern B.
• It is an error if a symbol matches patterns from --hide and --unhide and one does not supersede the
other. Pattern A supersedes pattern B if A can match everything B can and more. If Pattern A
supersedes Pattern B, then Pattern B is said to more restrictive than Pattern A.
• These options affect final and partial linking.
In map files these symbols are listed under the Hidden Symbols heading.
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8.4.16 Alter the Library Search Algorithm (--library Option, --search_path Option, and
C6X_C_DIR Environment Variable)
Usually, when you want to specify a file as linker input, you simply enter the filename; the linker looks for
the file in the current directory. For example, suppose the current directory contains the library object.lib. If
this library defines symbols that are referenced in the file file1.obj, this is how you link the files:
cl6x --run_linker file1.obj object.lib
If you want to use a file that is not in the current directory, use the --library linker option. The --library
option's short form is -l. The syntax for this option is:
--library=[pathname] filename
The filename is the name of an archive, an object file, or linker command file. You can specify up to 128
search paths.
The --library option is not required when one or more members of an object library are specified for input
to an output section. For more information about allocating archive members, see Section 8.5.5.5.
You can augment the linker's directory search algorithm by using the --search_path linker option or the
C6X_C_DIR environment variable. The linker searches for object libraries and command files in the
following order:
1. It searches directories named with the --search_path linker option. The --search_path option must
appear before the --Iibrary option on the command line or in a command file.
2. It searches directories named with C6X_C_DIR.
3. If C6X_C_DIR is not set, it searches directories named with the assembler's C6X_A_DIR environment
variable.
4. It searches the current directory.
8.4.16.1 Name an Alternate Library Directory (--search_path Option)
The --search_path option names an alternate directory that contains input files. The --search_path option's
short form is -I. The syntax for this option is:
--search_path= pathname
The pathname names a directory that contains input files.
When the linker is searching for input files named with the --library option, it searches through directories
named with --search_path first. Each --search_path option specifies only one directory, but you can have
several --search_path options per invocation. When you use the --search_path option to name an
alternate directory, it must precede any --library option used on the command line or in a command file.
For example, assume that there are two archive libraries called r.lib and lib2.lib that reside in ld and ld2
directories. The table below shows the directories that r.lib and lib2.lib reside in, how to set environment
variable, and how to use both libraries during a link. Select the row for your operating system:
192
Operating System
Enter
UNIX (Bourne shell)
cl6x --run_linker f1.obj f2.obj --search_path=/ld --search_path=/ld2
--library=r.lib --library=lib2.lib
Windows
cl6x --run_linker f1.obj f2.obj --search_path=\ld --search_path=\ld2
--library=r.lib --library=lib2.lib
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8.4.16.2 Name an Alternate Library Directory (C6X_C_DIR Environment Variable)
An environment variable is a system symbol that you define and assign a string to. The linker uses an
environment variable named C6X_C_DIR to name alternate directories that contain object libraries. The
command syntaxes for assigning the environment variable are:
Operating System
Enter
UNIX (Bourne shell)
C6X_C_DIR=" pathname1; pathname2; . . . "; export C6X_C_DIR
Windows
set C6X_C_DIR= pathname1 ; pathname2 ; . . .
The pathnames are directories that contain input files. Use the --library linker option on the command line
or in a command file to tell the linker which library or linker command file to search for. The pathnames
must follow these constraints:
• Pathnames must be separated with a semicolon.
• Spaces or tabs at the beginning or end of a path are ignored. For example the space before and after
the semicolon in the following is ignored:
set C6X_C_DIR= c:\path\one\to\tools ; c:\path\two\to\tools
•
Spaces and tabs are allowed within paths to accommodate Windows directories that contain spaces.
For example, the pathnames in the following are valid:
set C6X_C_DIR=c:\first path\to\tools;d:\second path\to\tools
In the example below, assume that two archive libraries called r.lib and lib2.lib reside in ld and ld2
directories. The table below shows how to set the environment variable, and how to use both libraries
during a link. Select the row for your operating system:
Operating System
Invocation Command
UNIX (Bourne shell)
C6X_C_DIR="/ld ;/ld2"; export C6X_C_DIR;
cl6x --run linker f1.obj f2.obj --library=r.lib --library=lib2.lib
Windows
C6X_C_DIR=\ld;\ld2
cl6x --run linker f1.obj f2.obj --library=r.lib --library=lib2.lib
The environment variable remains set until you reboot the system or reset the variable by entering:
Operating System
Enter
UNIX (Bourne shell)
unset C6X_C_DIR
Windows
set C6X_C_DIR=
The assembler uses an environment variable named C6X_A_DIR to name alternate directories that
contain copy/include files or macro libraries. If C6X_C_DIR is not set, the linker searches for object
libraries in the directories named with C6X_A_DIR. For information about C6X_A_DIR, see Section 4.5.2.
For more information about object libraries, see Section 8.6.3.
8.4.16.3 Exhaustively Read and Search Libraries (--reread_libs and --priority Options)
There are two ways to exhaustively search for unresolved symbols:
• Reread libraries if you cannot resolve a symbol reference (--reread_libs).
• Search libraries in the order that they are specified (--priority).
The linker normally reads input files, including archive libraries, only once when they are encountered on
the command line or in the command file. When an archive is read, any members that resolve references
to undefined symbols are included in the link. If an input file later references a symbol defined in a
previously read archive library, the reference is not resolved.
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With the --reread_libs option, you can force the linker to reread all libraries. The linker rereads libraries
until no more references can be resolved. Linking using --reread_libs may be slower, so you should use it
only as needed. For example, if a.lib contains a reference to a symbol defined in b.lib, and b.lib contains a
reference to a symbol defined in a.lib, you can resolve the mutual dependencies by listing one of the
libraries twice, as in:
cl6x --run_linker --library=a.lib --library=b.lib --library=a.lib
or you can force the linker to do it for you:
cl6x --run_linker --reread_libs --library=a.lib --library=b.lib
The --priority option provides an alternate search mechanism for libraries. Using --priority causes each
unresolved reference to be satisfied by the first library that contains a definition for that symbol. For
example:
objfile
lib1
lib2
references A
defines B
defines A, B; obj defining A references B
% cl6x --run_linker objfile lib1 lib2
Under the existing model, objfile resolves its reference to A in lib2, pulling in a reference to B, which
resolves to the B in lib2.
Under --priority, objfile resolves its reference to A in lib2, pulling in a reference to B, but now B is resolved
by searching the libraries in order and resolves B to the first definition it finds, namely the one in lib1.
The --priority option is useful for libraries that provide overriding definitions for related sets of functions in
other libraries without having to provide a complete version of the whole library.
For example, suppose you want to override versions of malloc and free defined in the rts6600_elf.lib
without providing a full replacement for rts6600_elf.lib. Using --priority and linking your new library before
rts6600_elf.lib guarantees that all references to malloc and free resolve to the new library.
The --priority option is intended to support linking programs with SYS/BIOS where situations like the one
illustrated above occur.
8.4.17 Change Symbol Localization
Symbol localization changes symbol linkage from global to local (static). This is used to obscure global
symbols in a library which should not be visible outside the library, but must be global because they are
accessed by several modules in the library. The linker supports symbol localization through the --localize
and --globalize linker options.
The syntax for these options are:
--localize=' pattern '
--globalize=' pattern '
The pattern is a string with optional wildcards ? or *. Use ? to match a single character and use * to match
zero or more characters.
The --localize option changes the symbol linkage to local for symbols matching the pattern.
The --globalize option changes the symbol linkage to global for symbols matching the pattern. The -globalize option only affects symbols that are localized by the --localize option. The --globalize option
excludes symbols that match the pattern from symbol localization, provided the pattern defined by -globalize is more restrictive than the pattern defined by --localize.
See Section 8.4.2 for information about using C/C++ identifiers in linker options such as --localize and -globalize.
These options have the following properties:
• The --localize and --globalize options can be specified more than once on the command line.
• The order of --localize and --globalize options has no significance.
• A symbol is matched by only one pattern defined by either --localize or --globalize.
• A symbol is matched by the most restrictive pattern. Pattern A is considered more restrictive than
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•
•
Pattern B, if Pattern A matches a narrower set than Pattern B.
It is an error if a symbol matches patterns from --localize and --globalize and if one does not supersede
other. Pattern A supersedes pattern B if A can match everything B can, and some more. If Pattern A
supersedes Pattern B, then Pattern B is said to more restrictive than Pattern A.
These options affect final and partial linking.
In map files these symbols are listed under the Localized Symbols heading.
8.4.17.1 Make All Global Symbols Static (--make_static Option)
The --make_static option makes all global symbols static. Static symbols are not visible to externally linked
modules. By making global symbols static, global symbols are essentially hidden. This allows external
symbols with the same name (in different files) to be treated as unique.
The --make_static option effectively nullifies all .global assembler directives. All symbols become local to
the module in which they are defined, so no external references are possible. For example, assume
file1.obj and file2.obj both define global symbols called EXT. By using the --make_static option, you can
link these files without conflict. The symbol EXT defined in file1.obj is treated separately from the symbol
EXT defined in file2.obj.
cl6x --run_linker --make_static file1.obj file2.obj
The --make_static option makes all global symbols static. If you have a symbol that you want to remain
global and you use the --make_static option, you can use the --make_global option to declare that symbol
to be global. The --make_global option overrides the effect of the --make_static option for the symbol that
you specify. The syntax for the --make_global option is:
--make_global= global_symbol
8.4.18 Create a Map File (--map_file Option)
The syntax for the --map_file option is:
--map_file= filename
The linker map describes:
• Memory configuration
• Input and output section allocation
• Linker-generated copy tables
• Trampolines
• The addresses of external symbols after they have been relocated
• Hidden and localized symbols
The map file contains the name of the output module and the entry point; it can also contain up to three
tables:
• A table showing the new memory configuration if any nondefault memory is specified (memory
configuration). The table has the following columns; this information is generated on the basis of the
information in the MEMORY directive in the linker command file:
– Name. This is the name of the memory range specified with the MEMORY directive.
– Origin. This specifies the starting address of a memory range.
– Length. This specifies the length of a memory range.
– Unused. This specifies the total amount of unused (available) memory in that memory area.
– Attributes. This specifies one to four attributes associated with the named range:
R
W
X
I
specifies
specifies
specifies
specifies
that the
that the
that the
that the
memory
memory
memory
memory
can
can
can
can
be read.
be written to.
contain executable code.
be initialized.
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•
•
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For more information about the MEMORY directive, see Section 8.5.4.
A table showing the linked addresses of each output section and the input sections that make up the
output sections (section placement map). This table has the following columns; this information is
generated on the basis of the information in the SECTIONS directive in the linker command file:
– Output section. This is the name of the output section specified with the SECTIONS directive.
– Origin. The first origin listed for each output section is the starting address of that output section.
The indented origin value is the starting address of that portion of the output section.
– Length. The first length listed for each output section is the length of that output section. The
indented length value is the length of that portion of the output section.
– Attributes/input sections. This lists the input file or value associated with an output section. If the
input section could not be allocated, the map file will indicate this with "FAILED TO ALLOCATE".
For more information about the SECTIONS directive, see Section 8.5.5.
A table showing each external symbol and its address sorted by symbol name.
A table showing each external symbol and its address sorted by symbol address.
The following example links file1.obj and file2.obj and creates a map file called map.out:
cl6x --run_linker file1.obj file2.obj --map_file=map.out
Example 8-26 shows an example of a map file.
8.4.19 Managing Map File Contents (--mapfile_contents Option)
The --mapfile_contents option assists with managing the content of linker-generated map files. The syntax
for the --mapfile_contents option is:
--mapfile_contents= filter[, filter]
When the --map_file option is specified, the linker produces a map file containing information about
memory usage, placement information about sections that were created during a link, details about linkergenerated copy tables, and symbol values.
The --mapfile_contents option provides a mechanism for you to control what information is included in or
excluded from a map file. When you specify --mapfile_contents=help from the command line, a help
screen listing available filter options is displayed. The following filter options are available:
Attribute
Description
Default State
copytables
Copy tables
On
entry
Entry point
On
load_addr
Display load addresses
Off
memory
Memory ranges
On
modules
Module view
On
sections
Sections
On
sym_defs
Defined symbols per file
Off
sym_dp
Symbols sorted by data page
On
sym_name
Symbols sorted by name
On
sym_runaddr
Symbols sorted by run address
On
all
Enables all attributes
none
Disables all attributes
The --mapfile_contents option controls display filter settings by specifying a comma-delimited list of display
attributes. When prefixed with the word no, an attribute is disabled instead of enabled. For example:
--mapfile_contents=copytables,noentry
--mapfile_contents=all,nocopytables
--mapfile_contents=none,entry
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By default, those sections that are currently included in the map file when the --map_file option is specified
are included. The filters specified in the --mapfile_contents options are processed in the order that they
appear in the command line. In the third example above, the first filter, none, clears all map file content.
The second filter, entry, then enables information about entry points to be included in the generated map
file. That is, when --mapfile_contents=none,entry is specified, the map file contains only information about
entry points.
The load_addr and sym_defs attributes are both disabled by default.
If you turn on the load_addr filter, the map file includes the load address of symbols that are included in
the symbol list in addition to the run address (if the load address is different from the run address).
You can use the sym_defs filter to include information sorted on a file by file basis. You may find it useful
to replace the sym_name, sym_dp, and sym_runaddr sections of the map file with the sym_defs section
by specifying the following --mapfile_contents option:
--mapfile_contents=nosym_name,nosym_dp,nosym_runaddr,sym_defs
By default, information about global symbols defined in an application are included in tables sorted by
name, data page, and run address. If you use the --mapfile_contents=sym_defs option, static variables
are also listed.
8.4.20 Disable Name Demangling (--no_demangle)
By default, the linker uses demangled symbol names in diagnostics. For example:
undefined symbol
ANewClass::getValue()
first referenced in file
test.obj
The --no_demangle option disables the demangling of symbol names in diagnostics. For example:
undefined symbol
_ZN9ANewClass8getValueEv
first referenced in file
test.obj
8.4.21 Merging of Symbolic Debugging Information
By default, the linker eliminates duplicate entries of symbolic debugging information. Such duplicate
information is commonly generated when a C program is compiled for debugging. For example:
-[ header.h ]typedef struct
{
<define some structure members>
} XYZ;
-[ f1.c ]#include "header.h"
...
-[ f2.c ]#include "header.h"
...
When these files are compiled for debugging, both f1.obj and f2.obj have symbolic debugging entries to
describe type XYZ. For the final output file, only one set of these entries is necessary. The linker
eliminates the duplicate entries automatically.
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8.4.22 Strip Symbolic Information (--no_symtable Option)
The --no_symtable option creates a smaller output module by omitting symbol table information and line
number entries. The --no_sym_table option is useful for production applications when you do not want to
disclose symbolic information to the consumer.
This example links file1.obj and file2.obj and creates an output module, stripped of line numbers and
symbol table information, named nosym.out:
cl6x --run_linker --output_file=nosym.out --no_symtable file1.obj file2.obj
Using the --no_symtable option limits later use of a symbolic debugger.
Stripping Symbolic Information
NOTE: The --no_symtable option is deprecated. To remove symbol table information, use the strip6x
utility as described in Section 9.4.
8.4.23 Name an Output Module (--output_file Option)
The linker creates an output module when no errors are encountered. If you do not specify a filename for
the output module, the linker gives it the default name a.out. If you want to write the output module to a
different file, use the --output_file option. The syntax for the --output_file option is:
--output_file= filename
The filename is the new output module name.
This example links file1.obj and file2.obj and creates an output module named run.out:
cl6x --run_linker --output_file=run.out file1.obj file2.obj
8.4.24 Prioritizing Function Placement (--preferred_order Option)
The compiler prioritizes the placement of a function relative to others based on the order in which -preferred_order options are encountered during the linker invocation. The syntax is:
--preferred_order=function specification
Refer to the TMS320C6000 Optimizing Compiler User's Guide for details on the program cache layout
tool, which is impacted by --preferred_option.
8.4.25 C Language Options (--ram_model and --rom_model Options)
The --ram_model and --rom_model options cause the linker to use linking conventions that are required by
the C compiler.
• The --ram_model option tells the linker to initialize variables at load time.
• The --rom_model option tells the linker to autoinitialize variables at run time.
For more information, see Section 8.10, Section 3.3.2.1, and Section 3.3.2.2.
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8.4.26 Retain Discarded Sections (--retain Option)
When --unused_section_elimination is on, the ELF linker does not include a section in the final link if it is
not needed in the executable to resolve references. The --retain option tells the linker to retain a list of
sections that would otherwise not be retained. This option accepts the wildcards '*' and '?'. When
wildcards are used, the argument should be in quotes. The syntax for this option is:
--retain=sym_or_scn_spec
The --retain option take one of the following forms:
• --retain= symbol_spec
Specifying the symbol format retains sections that define symbol_spec. For example, this code retains
sections that define symbols that start with init:
--retain='init*'
•
You cannot specify --retain='*'.
--retain= file_spec(scn_spec[, scn_spec, ...]
Specifying the file format retains sections that match one or more scn_spec from files matching the
file_spec. For example, this code retains .intvec sections from all input files:
--retain='*(.int*)'
•
You can specify --retain='*(*)' to retain all sections from all input files. However, this does not prevent
sections from library members from being optimized out.
--retain= ar_spec<mem_spec, [mem_spec, ...>(scn_spec[, scn_spec, ...]
Specifying the archive format retains sections matching one or more scn_spec from members
matching one or more mem_spec from archive files matching ar_spec. For example, this code retains
the .text sections from printf.obj in the rts64plus_eabi.lib library:
--retain=rts64plus_eabi.lib<printf.obj>(.text)
If the library is specified with the --library option (--library=rts64plus_eabi.lib) the library search path is
used to search for the library. You cannot specify '*<*>(*)'.
8.4.27 Scan All Libraries for Duplicate Symbol Definitions (--scan_libraries)
The --scan_libraries option scans all libraries during a link looking for duplicate symbol definitions to those
symbols that are actually included in the link. The scan does not consider absolute symbols or symbols
defined in COMDAT sections. The --scan_libraries option helps determine those symbols that were
actually chosen by the linker over other existing definitions of the same symbol in a library.
The library scanning feature can be used to check against unintended resolution of a symbol reference to
a definition when multiple definitions are available in the libraries.
8.4.28 Define Stack Size (--stack_size Option)
The TMS320C6000 C/C++ compiler uses an uninitialized section, .stack, to allocate space for the run-time
stack. You can set the size of this section in bytes at link time with the --stack_size option. The syntax for
the --stack_size option is:
--stack_size= size
The size must be a constant and is in bytes. This example defines a 4K byte stack:
cl6x --run_linker --stack_size=0x1000 /* defines a 4K heap (.stack section)*/
If you specified a different stack size in an input section, the input section stack size is ignored. Any
symbols defined in the input section remain valid; only the stack size is different.
When the linker defines the .stack section, it also defines a global symbol, __TI_STACK_SIZE, and
assigns it a value equal to the size of the section. The default software stack size is 1K bytes. See
Section 8.6.1 for information about referring to linker symbols in C/C++ code.
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8.4.29 Enforce Strict Compatibility (--strict_compatibility Option)
The linker performs more conservative and rigorous compatibility checking of input object files when you
specify the --strict_compatibility option. Using this option guards against additional potential compatibility
issues, but may signal false compatibility errors when linking in object files built with an older toolset, or
with object files built with another compiler vendor's toolset. To avoid issues with legacy libraries, the -strict_compatibility option is turned off by default.
8.4.30 Mapping of Symbols (--symbol_map Option)
Symbol mapping allows a symbol reference to be resolved by a symbol with a different name. Symbol
mapping allows functions to be overridden with alternate definitions. This feature can be used to patch in
alternate implementations, which provide patches (bug fixes) or alternate functionality. The syntax for the -symbol_map option is:
--symbol_map= refname=defname
For example, the following code makes the linker resolve any references to foo by the definition
foo_patch:
--symbol_map='foo=foo_patch'
8.4.31 Generate Far Call Trampolines (--trampolines Option)
The C6000 device has PC-relative call and PC-relative branch instructions whose range is smaller than
the entire address space. When these instructions are used, the destination address must be near enough
to the instruction that the difference between the call and the destination fits in the available encoding bits.
If the called function is too far away from the calling function, the linker generates an error.
The alternative to a PC-relative call is an absolute call, which is often implemented as an indirect call: load
the called address into a register, and call that register. This is often undesirable because it takes more
instructions (speed- and size-wise) and requires an extra register to contain the address.
By default, the compiler generates near calls. The --trampolines option causes the linker to generate a
trampoline code section for each call that is linked out-of-range of its called destination. The trampoline
code section contains a sequence of instructions that performs a transparent long branch to the original
called address. Each calling instruction that is out-of-range from the called function is redirected to the
trampoline.
For example, in a section of C code the bar function calls the foo function. The compiler generates this
code for the function:
bar:
...
call
...
foo
; call the function "foo"
If the foo function is placed out-of-range from the call to foo that is inside of bar, then with --trampolines
the linker changes the original call to foo into a call to foo_trampoline as shown:
bar:
...
call
...
foo_trampoline
; call a trampoline for foo
The above code generates a trampoline code section called foo_trampoline, which contains code that
executes a long branch to the original called function, foo. For example:
foo_trampoline:
branch_long
foo
Trampolines can be shared among calls to the same called function. The only requirement is that all calls
to the called function be linked near the called function's trampoline.
The syntax for this option is:
--trampolines[=on|off]
The default setting is on. For C6000, trampolines are turned on by default.
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When the linker produces a map file (the --map_file option) and it has produced one or more trampolines,
then the map file will contain statistics about what trampolines were generated to reach which functions. A
list of calls for each trampoline is also provided in the map file.
The Linker Assumes B15 Contains the Stack Pointer
NOTE: Assembly language programmers must be aware that the linker assumes B15 contains the
stack pointer. The linker must save and restore values on the stack in trampoline code that it
generates. If you do not use B15 as the stack pointer, you should use the linker option that
disables trampolines, --trampolines=off. Otherwise, trampolines could corrupt memory and
overwrite register values.
8.4.31.1 Advantages and Disadvantages of Using Trampolines
The advantage of using trampolines is that you can treat all calls as near calls, which are faster and more
efficient. You will only need to modify those calls that don't reach. In addition, there is little need to
consider the relative placement of functions that call each other. Cases where calls must go through a
trampoline are less common than near calls.
While generating far call trampolines provides a more straightforward solution, trampolines have the
disadvantage that they are somewhat slower than directly calling a function. They require both a call and a
branch. Additionally, while inline code could be tailored to the environment of the call, trampolines are
generated in a more general manner, and may be slightly less efficient than inline code.
An alternative method to creating a trampoline code section for a call that cannot reach its called function
is to actually modify the source code for the call. In some cases this can be done without affecting the size
of the code. However, in general, this approach is extremely difficult, especially when the size of the code
is affected by the transformation.
8.4.31.2 Minimizing the Number of Trampolines Required (--minimize_trampolines Option)
The --minimize_trampolines option attempts to place sections so as to minimize the number of far call
trampolines required, possibly at the expense of optimal memory packing. The syntax is:
--minimize_trampolines=postorder
The argument selects a heuristic to use. The postorder heuristic attempts to place functions before their
callers, so that the PC-relative offset to the callee is known when the caller is placed. By placing the callee
first, its address is known when the caller is placed so the linker can definitively know if a trampoline is
required.
8.4.31.3 Making Trampoline Reservations Adjacent (--trampoline_min_spacing Option)
When a call is placed and the callee's address is unknown, the linker must provisionally reserve space for
a far call trampoline in case the callee turns out to be too far away. Even if the callee ends up being close
enough, the trampoline reservation can interfere with optimal placement for very large code sections.
When trampoline reservations are spaced more closely than the specified limit, use the -trampoline_min_spacing option to try to make them adjacent. The syntax is:
--trampoline_min_spacing=size
A higher value minimizes fragmentation, but may result in more trampolines. A lower value may reduce
trampolines, at the expense of fragmentation and linker running time. Specifying 0 for this option disables
coalescing. The default is 16K.
8.4.31.4 Carrying Trampolines From Load Space to Run Space
It is sometimes useful to load code in one location in memory and run it in another. The linker provides the
capability to specify separate load and run allocations for a section. The burden of actually copying the
code from the load space to the run space is left to you.
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A copy function must be executed before the real function can be executed in its run space. To facilitate
this copy function, the assembler provides the .label directive, which allows you to define a load-time
address. These load-time addresses can then be used to determine the start address and size of the code
to be copied. However, this mechanism will not work if the code contains a call that requires a trampoline
to reach its called function. This is because the trampoline code is generated at link time, after the loadtime addresses associated with the .label directive have been defined. If the linker detects the definition of
a .label symbol in an input section that contains a trampoline call, then a warning is generated.
To solve this problem, you can use the START(), END(), and SIZE() operators (see Section 8.5.10.7).
These operators allow you to define symbols to represent the load-time start address and size inside the
linker command file. These symbols can be referenced by the copy code, and their values are not
resolved until link time, after the trampoline sections have been allocated.
Here is an example of how you could use the START() and SIZE() operators in association with an output
section to copy the trampoline code section along with the code containing the calls that need trampolines:
SECTIONS
{ .foo : load = ROM, run = RAM, start(foo_start), size(foo_size)
{ x.obj(.text) }
.text: {} > ROM
.far : { --library=rts.lib(.text) } > FAR_MEM
}
A function in x.obj contains an run-time-support call. The run-time-support library is placed in far memory
and so the call is out-of-range. A trampoline section will be added to the .foo output section by the linker.
The copy code can refer to the symbols foo_start and foo_size as parameters for the load start address
and size of the entire .foo output section. This allows the copy code to copy the trampoline section along
with the original x.obj code in .text from its load space to its run space.
See Section 8.6.1 for information about referring to linker symbols in C/C++ code.
8.4.32 Introduce an Unresolved Symbol (--undef_sym Option)
The --undef_sym option introduces the linkname for an unresolved symbol into the linker's symbol table.
This forces the linker to search a library and include the member that defines the symbol. The linker must
encounter the --undef_sym option before it links in the member that defines the symbol. The syntax for the
--undef_sym option is:
--undef_sym= symbol
For example, suppose a library named rts6600_elf.lib contains a member that defines the symbol symtab;
none of the object files being linked reference symtab. However, suppose you plan to relink the output
module and you want to include the library member that defines symtab in this link. Using the --undef_sym
option as shown below forces the linker to search rts6600_elf.lib for the member that defines symtab and
to link in the member.
cl6x --run_linker --undef_sym=symtab file1.obj file2.obj rts6600_elf.lib
If you do not use --undef_sym, this member is not included, because there is no explicit reference to it in
file1.obj or file2.obj.
8.4.33 Display a Message When an Undefined Output Section Is Created (--warn_sections)
In a linker command file, you can set up a SECTIONS directive that describes how input sections are
combined into output sections. However, if the linker encounters one or more input sections that do not
have a corresponding output section defined in the SECTIONS directive, the linker combines the input
sections that have the same name into an output section with that name. By default, the linker does not
display a message to tell you that this occurred.
You can use the --warn_sections option to cause the linker to display a message when it creates a new
output section.
For more information about the SECTIONS directive, see Section 8.5.5. For more information about the
default actions of the linker, see Section 8.7.
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8.4.34 Generate XML Link Information File (--xml_link_info Option)
The linker supports the generation of an XML link information file through the --xml_link_info=file option.
This option causes the linker to generate a well-formed XML file containing detailed information about the
result of a link. The information included in this file includes all of the information that is currently produced
in a linker generated map file. See Appendix B for specifics on the contents of the generated XML file.
8.4.35 Zero Initialization (--zero_init Option)
The C and C++ standards require that global and static variables that are not explicitly initialized must be
set to 0 before program execution. The C/C++ compiler supports preinitialization of uninitialized variables
by default. To turn this off, specify the linker option --zero_init=off.
The syntax for the --zero_init option is:
--zero_init[={on|off}]
Disabling Zero Initialization Not Recommended
NOTE:
In general, this option it is not recommended. If you turn off zero initialization, automatic
initialization of uninitialized global and static objects to zero will not occur. You are then
expected to initialize these variables to zero in some other manner.
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Linker Command Files
Linker command files allow you to put linker options and directives in a file; this is useful when you invoke
the linker often with the same options and directives. Linker command files are also useful because they
allow you to use the MEMORY and SECTIONS directives to customize your application. You must use
these directives in a command file; you cannot use them on the command line.
Linker command files are ASCII files that contain one or more of the following:
• Input filenames, which specify object files, archive libraries, or other command files. (If a command file
calls another command file as input, this statement must be the last statement in the calling command
file. The linker does not return from called command files.)
• Linker options, which can be used in the command file in the same manner that they are used on the
command line
• The MEMORY and SECTIONS linker directives. The MEMORY directive defines the target memory
configuration (see Section 8.5.4). The SECTIONS directive controls how sections are built and
allocated (see Section 8.5.5.)
• Assignment statements, which define and assign values to global symbols
To invoke the linker with a command file, enter the cl6x --run_linker command and follow it with the name
of the command file:
cl6x --run_linker command_filename
The linker processes input files in the order that it encounters them. If the linker recognizes a file as an
object file, it links the file. Otherwise, it assumes that a file is a command file and begins reading and
processing commands from it. Command filenames are case sensitive, regardless of the system used.
Example 8-1 shows a sample linker command file called link.cmd.
Example 8‑1. Linker Command File
a.obj
b.obj
--output_file=prog.out
--map_file=prog.map
/*
/*
/*
/*
First input filename
Second input filename
Option to specify output file
Option to specify map file
*/
*/
*/
*/
The sample file in Example 8-1 contains only filenames and options. (You can place comments in a
command file by delimiting them with /* and */.) To invoke the linker with this command file, enter:
cl6x --run_linker link.cmd
You can place other parameters on the command line when you use a command file:
cl6x --run_linker --relocatable link.cmd c.obj d.obj
The linker processes the command file as soon as it encounters the filename, so a.obj and b.obj are
linked into the output module before c.obj and d.obj.
You can specify multiple command files. If, for example, you have a file called names.lst that contains
filenames and another file called dir.cmd that contains linker directives, you could enter:
cl6x --run_linker names.lst dir.cmd
One command file can call another command file; this type of nesting is limited to 16 levels. If a command
file calls another command file as input, this statement must be the last statement in the calling command
file.
Blanks and blank lines are insignificant in a command file except as delimiters. This also applies to the
format of linker directives in a command file. Example 8-2 shows a sample command file that contains
linker directives.
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Example 8‑2. Command File With Linker Directives
a.obj b.obj c.obj
--output_file=prog.out
--map_file=prog.map
/* Input filenames
/* Options
*/
*/
MEMORY
{
FAST_MEM:
SLOW_MEM:
}
/* MEMORY directive
*/
SECTIONS
{
.text:
.data:
.bss:
}
origin = 0x0100
origin = 0x7000
length = 0x0100
length = 0x1000
/* SECTIONS directive
*/
> SLOW_MEM
> SLOW_MEM
> FAST_MEM
For more information, see Section 8.5.4 for the MEMORY directive, and Section 8.5.5 for the SECTIONS
directive.
8.5.1 Reserved Names in Linker Command Files
The following names (in both uppercase and lowercase) are reserved as keywords for linker directives. Do
not use them as symbol or section names in a command file.
ADDRESS_MASK
ALGORITHM
ALIGN
ATTR
BLOCK
COMPRESSION
COPY
DSECT
ECC
END
f
FILL
GROUP
HAMMING_MASK
HIGH
INPUT_PAGE
INPUT_RANGE
l (lowercase L)
LEN
LENGTH
LOAD
LOAD_END
LOAD_SIZE
LOAD_START
MEMORY
MIRRORING
NOINIT
NOLOAD
o
ORG
ORIGIN
PAGE
PALIGN
PARITY_MASK
RUN
RUN_END
RUN_SIZE
RUN_START
SECTIONS
SIZE
START
TABLE
TYPE
UNION
UNORDERED
VFILL
In addition, any section names used by the TI tools are reserved from being used as the prefix for other
names, unless the section will be a subsection of the section name used by the TI tools. For example,
section names may not begin with .debug.
8.5.2 Constants in Linker Command Files
You can specify constants with either of two syntax schemes: the scheme used for specifying decimal,
octal, or hexadecimal constants (but not binary constants) used in the assembler (see Section 4.7) or the
scheme used for integer constants in C syntax.
Examples:
Format
Decimal
Octal
Hexadecimal
Assembler format
32
40q
020h
C format
32
040
0x20
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8.5.3 Accessing Files and Libraries from a Linker Command File
Many applications use custom linker command files (or LCFs) to control the placement of code and data in
target memory. For example, you may want to place a specific data object from a specific file into a
specific location in target memory. This is simple to do using the available LCF syntax to reference the
desired object file or library. However, a problem that many developers run into when they try to do this is
a linker generated "file not found" error when accessing an object file or library from inside the LCF that
has been specified earlier in the command-line invocation of the linker. Most often, this error occurs
because the syntax used to access the file on the linker command-line does not match the syntax that is
used to access the same file in the LCF.
Consider a simple example. Imagine that you have an application that requires a table of constants called
"app_coeffs" to be defined in a memory area called "DDR". Assume also that the "app_coeffs" data object
is defined in a .data section that resides in an object file, app_coeffs.obj. app_coeffs.obj is then included in
the object file library app_data.lib. In your LCF, you can control the placement of the "app_coeffs" data
object as follows:
SECTIONS
{
...
.coeffs: { app_data.lib<app_coeffs.obj>(.data) } > DDR
...
}
Now assume that the app_data.lib object library resides in a sub-directory called "lib" relative to where you
are building the application. In order to gain access to app_data.lib from the build command-line, you can
use a combination of the –i and –l options to set up a directory search path which the linker can use to
find the app_data.lib library:
%> cl6x <compile options/files> -z -i ./lib -l app_data.lib mylnk.cmd <link options/files>
The –i option adds the lib sub-directory to the directory search path and the –l option instructs the linker to
look through the directories in the directory search path to find the app_data.lib library. However, if you do
not update the reference to app_data.lib in mylnk.cmd, the linker will fail to find the app_data.lib library and
generate a "file not found" error. The reason is that when the linker encounters the reference to
app_data.lib inside the SECTIONS directive, there is no –l option preceding the reference. Therefore, the
linker tries to open app_data.lib in the current working directory.
In essence, the linker has a few different ways of opening files:
• If there is a path specified, the linker will look for the file in the specified location. For an absolute path,
the linker will try to open the file in the specified directory. For a relative path, the linker will follow the
specified path starting from the current working directory and try to open the file at that location.
• If there is no path specified, the linker will try to open the file in the current working directory.
• If a –l option precedes the file reference, then the linker will try to find and open the referenced file in
one of the directories in the directory search path. The directory search path is set up via –i options
and environment variables (like C_DIR and C6X_C_DIR).
As long as a file is referenced in a consistent manner on the command line and throughout any applicable
LCFs, the linker will be able to find and open your object files and libraries.
Returning to the earlier example, you can insert a –l option in front of the reference to app_data.lib in
mylnk.cmd to ensure that the linker will find and open the app_data.lib library when the application is built:
SECTIONS
{
...
.coeffs: { -l app_data.lib<app_coeffs.obj>(.data) } > DDR
...
}
Another benefit to using the –l option when referencing a file from within an LCF is that if the location of
the referenced file changes, you can modify the directory search path to incorporate the new location of
the file (using –i option on the command line, for example) without having to modify the LCF.
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8.5.4 The MEMORY Directive
The linker determines where output sections are allocated into memory; it must have a model of target
memory to accomplish this. The MEMORY directive allows you to specify a model of target memory so
that you can define the types of memory your system contains and the address ranges they occupy. The
linker maintains the model as it allocates output sections and uses it to determine which memory locations
can be used for object code.
The memory configurations of TMS320C6000 systems differ from application to application. The
MEMORY directive allows you to specify a variety of configurations. After you use MEMORY to define a
memory model, you can use the SECTIONS directive to allocate output sections into defined memory.
For more information, see Section 2.5.
8.5.4.1
Default Memory Model
If you do not use the MEMORY directive, the linker uses a default memory model that is based on the
TMS320C6000 architecture. This model assumes that the full 32-bit address space (232 locations) is
present in the system and available for use. For more information about the default memory model, see
Section 8.7.
8.5.4.2
MEMORY Directive Syntax
The MEMORY directive identifies ranges of memory that are physically present in the target system and
can be used by a program. Each range has several characteristics:
• Name
• Starting address
• Length
• Optional set of attributes
• Optional fill specification
When you use the MEMORY directive, be sure to identify all memory ranges that are available for the
program to access at run time. Memory defined by the MEMORY directive is configured; any memory that
you do not explicitly account for with MEMORY is unconfigured. The linker does not place any part of a
program into unconfigured memory. You can represent nonexistent memory spaces by simply not
including an address range in a MEMORY directive statement.
The MEMORY directive is specified in a command file by the word MEMORY (uppercase), followed by a
list of memory range specifications enclosed in braces. The MEMORY directive in Example 8-3 defines a
system that has 4K bytes of fast external memory at address 0x0000 0000, 2K bytes of slow external
memory at address 0x0000 1000 and 4K bytes of slow external memory at address 0x1000 0000. It also
demonstrates the use of memory range expressions as well as start/end/size address operators (see
Section 8.5.4.3).
Example 8-3. The MEMORY Directive
/********************************************************/
/*
Sample command file with MEMORY directive
*/
/********************************************************/
file1.obj file2.obj
/*
Input files
*/
--output_file=prog.out
/*
Options
*/
#define BUFFER 0
MEMORY
{
FAST_MEM (RX): origin = 0x00000000
length = 0x00001000 + BUFFER
SLOW_MEM (RW): origin = end(FAST_MEM) length = 0x00001800 - size(FAST_MEM)
EXT_MEM (RX): origin = 0x10000000
length = size(FAST_MEM)
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The general syntax for the MEMORY directive is:
MEMORY
{
name 1 [( attr )] : origin = expression , length = expression [, fill = constant]
.
.
name n [( attr )] : origin = expression , length = expression [, fill = constant]
}
name
names a memory range. A memory name can be one to 64 characters; valid characters
include A-Z, a-z, $, ., and _. The names have no special significance to the linker; they
simply identify memory ranges. Memory range names are internal to the linker and are not
retained in the output file or in the symbol table. All memory ranges must have unique
names and must not overlap.
specifies one to four attributes associated with the named range. Attributes are optional;
when used, they must be enclosed in parentheses. Attributes restrict the allocation of
output sections into certain memory ranges. If you do not use any attributes, you can
allocate any output section into any range with no restrictions. Any memory for which no
attributes are specified (including all memory in the default model) has all four attributes.
Valid attributes are:
R
specifies that the memory can be read.
W
specifies that the memory can be written to.
X
specifies that the memory can contain executable code.
I
specifies that the memory can be initialized.
specifies the starting address of a memory range; enter as origin, org, or o. The value,
specified in bytes, is a 32-bit integer constant expression, which can be decimal, octal, or
hexadecimal.
specifies the length of a memory range; enter as length, len, or l. The value, specified in
bytes, is a 32-bit integer constant expression, which can be decimal, octal, or hexadecimal.
specifies a fill character for the memory range; enter as fill or f. Fills are optional. The value
is an integer constant and can be decimal, octal, or hexadecimal. The fill value is used to
fill areas of the memory range that are not allocated to a section. (See Section 8.5.9.3 for
virtual filling of memory ranges when using Error Correcting Code (ECC).)
attr
origin
length
fill
Filling Memory Ranges
NOTE: If you specify fill values for large memory ranges, your output file will be very large because
filling a memory range (even with 0s) causes raw data to be generated for all unallocated
blocks of memory in the range.
The following example specifies a memory range with the R and W attributes and a fill constant of
0FFFFFFFFh:
MEMORY
{
RFILE (RW) : o = 0x00000020, l = 0x00001000, f = 0xFFFFFFFF
}
You normally use the MEMORY directive in conjunction with the SECTIONS directive to control placement
of output sections. For more information about the SECTIONS directive, see Section 8.5.5.
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8.5.4.3
Expressions and Address Operators
Memory range origin and length can use expressions of integer constants with the following operators:
Binary operators:
Unary operators:
* / % + - << >> == =
< <= > >= & | && ||
- ~ !
Expressions are evaluated using standard C operator precedence rules.
No checking is done for overflow or underflow, however, expressions are evaluated using a larger integer
type.
Preprocess directive #define constants can be used in place of integer constants. Global symbols cannot
be used in Memory Directive expressions.
Three address operators reference memory range properties from prior memory range entries:
START(MR)
SIZE(MR)
END(MR)
Returns start address for previously defined memory range MR.
Returns size of previously defined memory range MR.
Returns end address for previously defined memory range MR.
Example 8-4. Origin and Length as Expressions
/********************************************************/
/*
Sample command file with MEMORY directive
*/
/********************************************************/
file1.obj file2.obj
/*
Input files
*/
--output_file=prog.out
/*
Options
*/
#define ORIGIN 0x00000000
#define BUFFER 0x00000200
#define CACHE 0x0001000
MEMORY
{
FAST_MEM (RX): origin = ORIGIN + CACHE length = 0x00001000 + BUFFER
SLOW_MEM (RW): origin = end(FAST_MEM) length = 0x00001800 - size(FAST_MEM)
EXT_MEM (RX): origin = 0x10000000
length = size(FAST_MEM) - CACHE
8.5.5 The SECTIONS Directive
After you use MEMORY to specify the target system's memory model, you can use SECTIONS to place
output sections into specific named memory ranges or into memory that has specific attributes. For
example, you could allocate the .text and .data sections into the area named FAST_MEM and allocate the
.bss section into the area named SLOW_MEM.
The SECTIONS directive controls your sections in the following ways:
• Describes how input sections are combined into output sections
• Defines output sections in the executable program
• Allows you to control where output sections are placed in memory in relation to each other and to the
entire memory space (Note that the memory placement order is not simply the sequence in which
sections occur in the SECTIONS directive.)
• Permits renaming of output sections
For more information, see Section 2.5, Section 2.7, and Section 2.4.6. Subsections allow you to
manipulate sections with greater precision.
If you do not specify a SECTIONS directive, the linker uses a default algorithm for combining and
allocating the sections. Section 8.7 describes this algorithm in detail.
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SECTIONS Directive Syntax
The SECTIONS directive is specified in a command file by the word SECTIONS (uppercase), followed by
a list of output section specifications enclosed in braces.
The general syntax for the SECTIONS directive is:
SECTIONS
{
name : [property [, property] [, property] . . . ]
name : [property [, property] [, property] . . . ]
name : [property [, property] [, property] . . . ]
}
Each section specification, beginning with name, defines an output section. (An output section is a section
in the output file.) Section names can refer to sections, subsections, or archive library members. (See
Section 8.5.5.4 for information on multi-level subsections.) After the section name is a list of properties
that define the section's contents and how the section is allocated. The properties can be separated by
optional commas. Possible properties for a section are as follows:
•
Load allocation defines where in memory the section is to be loaded. See Section 3.5,
Section 3.1.1, and Section 8.5.6.
Syntax:
load = allocation
or
> allocation
•
Run allocation defines where in memory the section is to be run.
Syntax:
run = allocation
or
run > allocation
•
Input sections defines the input sections (object files) that constitute the output section. See
Section 8.5.5.3.
Syntax:
{ input_sections }
•
Section type defines flags for special section types. See Section 8.5.8.
Syntax:
type = COPY
or
type = DSECT
or
type = NOLOAD
•
Fill value defines the value used to fill uninitialized holes. See Section 8.5.11.
Syntax:
fill = value
Example 8-5 shows a SECTIONS directive in a sample linker command file.
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Example 8-5. The SECTIONS Directive
/**************************************************/
/* Sample command file with SECTIONS directive
*/
/**************************************************/
file1.obj
file2.obj
/* Input files
*/
--output_file=prog.out
/* Options
*/
SECTIONS
{
.text:
load = EXT_MEM, run = 0x00000800
.const:
load = FAST_MEM
.bss:
load = SLOW_MEM
.vectors:
load = 0x00000000
{
t1.obj(.intvec1)
t2.obj(.intvec2)
endvec = .;
}
.data:alpha: align = 16
.data:beta: align = 16
}
Figure 8-2 shows the output sections defined by the SECTIONS directive in Example 8-5 (.vectors, .text,
.const, .bss, .data:alpha, and .data:beta) and shows how these sections are allocated in memory using the
MEMORY directive given in Example 8-3.
Figure 8-2. Section Placement Defined by Example 8-5
0x00000000
FAST_MEM
- Bound at 0x00000000
The .vectors section is composed of the .intvec1
section from t1.obj and the .intvec2 section from
t2.obj.
- Allocated in FAST_MEM
The .const section combines the .const sections
from file1.obj and file2.obj.
.bss
- Allocated in SLOW_MEM
The .bss section combines the .bss sections from
file1.obj and file2.obj.
.data:alpha
- Aligned on 16-byte
boundary
.data:beta
- Aligned on 16-byte
boundary
The .data:alpha subsection combines the .data:alpha subsections from file1.obj and file2.obj. The
.data:beta subsection combines the .data:beta
subsections from file1.obj and file2.obj. The linker
places the subsections anywhere there is space for
them (in SLOW_MEM in this illustration) and aligns
each on a 16-byte boundary.
.vectors
.const
0x00001000
SLOW_MEM
0x00001800
- Empty range of memory
as defined in above
0x10000000
EXT_MEM
.text
- Allocated in EXT_MEM
The .text section combines the .text sections from
file1.obj and file2.obj. The linker combines all sections named .text into this section. The application
must relocate the section to run at 0x00000800.
0x10001000
- Empty range of memory
as defined in above
0xFFFFFFFF
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Section Allocation and Placement
The linker assigns each output section two locations in target memory: the location where the section will
be loaded and the location where it will be run. Usually, these are the same, and you can think of each
section as having only a single address. The process of locating the output section in the target's memory
and assigning its address(es) is called placement. For more information about using separate load and
run placement, see Section 8.5.6.
If you do not tell the linker how a section is to be allocated, it uses a default algorithm to place the section.
Generally, the linker puts sections wherever they fit into configured memory. You can override this default
placement for a section by defining it within a SECTIONS directive and providing instructions on how to
allocate it.
You control placement by specifying one or more allocation parameters. Each parameter consists of a
keyword, an optional equal sign or greater-than sign, and a value optionally enclosed in parentheses. If
load and run placement are separate, all parameters following the keyword LOAD apply to load
placement, and those following the keyword RUN apply to run placement. The allocation parameters are:
Binding
allocates a section at a specific address.
.text: load = 0x1000
Named
memory
allocates the section into a range defined in the MEMORY directive with the specified
name (like SLOW_MEM) or attributes.
.text: load > SLOW_MEM
Alignment
uses the align or palign keyword to specify the section must start on an address boundary.
.text: align = 0x100
Blocking
uses the block keyword to specify the section must fit between two address aligned to the
blocking factor. If a section is too large, it starts on an address boundary.
.text: block(0x100)
For the load (usually the only) allocation, use a greater-than sign and omit the load keyword:
.text: > SLOW_MEM
.text: {...} > SLOW_MEM
.text: > 0x4000
If more than one parameter is used, you can string them together as follows:
.text: > SLOW_MEM align 16
Or if you prefer, use parentheses for readability:
.text: load = (SLOW_MEM align(16))
You can also use an input section specification to identify the sections from input files that are combined
to form an output section. See Section 8.5.5.3.
Additional information about controlling the order in which code and data are placed in memory is provided
in the FAQ topic on section placement.
8.5.5.2.1 Binding
You can set the starting address for an output section by following the section name with an address:
.text: 0x00001000
This example specifies that the .text section must begin at location 0x1000. The binding address must be
a 32-bit constant.
Output sections can be bound anywhere in configured memory (assuming there is enough space), but
they cannot overlap. If there is not enough space to bind a section to a specified address, the linker issues
an error message.
Binding is Incompatible With Alignment and Named Memory
NOTE: You cannot bind a section to an address if you use alignment or named memory. If you try to
do this, the linker issues an error message.
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8.5.5.2.2 Named Memory
You can allocate a section into a memory range that is defined by the MEMORY directive (see
Section 8.5.4). This example names ranges and links sections into them:
MEMORY
{
SLOW_MEM (RIX) : origin = 0x00000000,
FAST_MEM (RWIX) : origin = 0x03000000,
}
SECTIONS
{
.text
.data
.bss
}
:
:
:
length = 0x00001000
length = 0x00000300
> SLOW_MEM
> FAST_MEM ALIGN(128)
> FAST_MEM
In this example, the linker places .text into the area called SLOW_MEM. The .data and .bss output
sections are allocated into FAST_MEM. You can align a section within a named memory range; the .data
section is aligned on a 128-byte boundary within the FAST_MEM range.
Similarly, you can link a section into an area of memory that has particular attributes. To do this, specify a
set of attributes (enclosed in parentheses) instead of a memory name. Using the same MEMORY directive
declaration, you can specify:
SECTIONS
{
.text: > (X)
.data: > (RI)
.bss : > (RW)
}
/* .text --> executable memory
/* .data --> read or init memory
/* .bss --> read or write memory
*/
*/
*/
In this example, the .text output section can be linked into either the SLOW_MEM or FAST_MEM area
because both areas have the X attribute. The .data section can also go into either SLOW_MEM or
FAST_MEM because both areas have the R and I attributes. The .bss output section, however, must go
into the FAST_MEM area because only FAST_MEM is declared with the W attribute.
You cannot control where in a named memory range a section is allocated, although the linker uses lower
memory addresses first and avoids fragmentation when possible. In the preceding examples, assuming no
conflicting assignments exist, the .text section starts at address 0. If a section must start on a specific
address, use binding instead of named memory.
8.5.5.2.3 Controlling Placement Using The HIGH Location Specifier
The linker allocates output sections from low to high addresses within a designated memory range by
default. Alternatively, you can cause the linker to allocate a section from high to low addresses within a
memory range by using the HIGH location specifier in the SECTION directive declaration. You might use
the HIGH location specifier in order to keep RTS code separate from application code, so that small
changes in the application do not cause large changes to the memory map.
For example, given this MEMORY directive:
MEMORY
{
RAM
FLASH
VECTORS
RESET
}
:
:
:
:
origin
origin
origin
origin
=
=
=
=
0x0200,
0x1100,
0xFFE0,
0xFFFE,
length
length
length
length
=
=
=
=
0x0800
0xEEE0
0x001E
0x0002
and an accompanying SECTIONS directive:
SECTIONS
{
.bss
.sysmem
.stack
}
: {} > RAM
: {} > RAM
: {} > RAM (HIGH)
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The HIGH specifier used on the .stack section placement causes the linker to attempt to allocate .stack
into the higher addresses within the RAM memory range. The .bss and .sysmem sections are allocated
into the lower addresses within RAM. Example 8-6 illustrates a portion of a map file that shows where the
given sections are allocated within RAM for a typical program.
Example 8-6. Linker Placement With the HIGH Specifier
.bss
0
00000200
00000200
0000031a
000003a2
0000041a
00000460
00000468
0000046c
0000046e
00000270
0000011a
00000088
00000078
00000046
00000008
00000004
00000002
00000002
UNINITIALIZED
rtsxxx.lib : defs.obj (.bss)
: trgdrv.obj (.bss)
: lowlev.obj (.bss)
: exit.obj (.bss)
: memory.obj (.bss)
: _lock.obj (.bss)
: fopen.obj (.bss)
hello.obj (.bss)
.sysmem
0
00000470
00000470
00000120
00000004
UNINITIALIZED
rtsxxx .lib : memory.obj (.sysmem)
.stack
0
000008c0
000008c0
00000140
00000002
UNINITIALIZED
rtsxxx .lib : boot.obj (.stack)
As shown in Example 8-6 , the .bss and .sysmem sections are allocated at the lower addresses of RAM
(0x0200 - 0x0590) and the .stack section is allocated at address 0x08c0, even though lower addresses
are available.
Without using the HIGH specifier, the linker allocation would result in the code shown in Example 8-7
The HIGH specifier is ignored if it is used with specific address binding or automatic section splitting (>>
operator).
Example 8-7. Linker Placement Without HIGH Specifier
.bss
0
00000200
00000200
0000031a
000003a2
0000041a
00000460
00000468
0000046c
0000046e
00000270
0000011a
00000088
00000078
00000046
00000008
00000004
00000002
00000002
UNINITIALIZED
rtsxxx.lib : defs.obj (.bss)
: trgdrv.obj (.bss)
: lowlev.obj (.bss)
: exit.obj (.bss)
: memory.obj (.bss)
: _lock.obj (.bss)
: fopen.obj (.bss)
hello.obj (.bss)
.stack
0
00000470
00000470
00000140
00000002
UNINITIALIZED
rtsxxx.lib : boot.obj (.stack)
.sysmem
0
000005b0
000005b0
00000120
00000004
UNINITIALIZED
rtsxxx.lib : memory.obj (.sysmem)
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8.5.5.2.4 Alignment and Blocking
You can tell the linker to place an output section at an address that falls on an n-byte boundary, where n
is a power of 2, by using the align keyword. For example, the following code allocates .text so that it falls
on a 32-byte boundary:
.text: load = align(32)
Blocking is a weaker form of alignment that allocates a section anywhere within a block of size n. The
specified block size must be a power of 2. For example, the following code allocates .bss so that the entire
section is contained in a single 128-byte block or begins on that boundary:
bss: load = block(0x0080)
You can use alignment or blocking alone or in conjunction with a memory area, but alignment and
blocking cannot be used together.
8.5.5.2.5 Alignment With Padding
As with align, you can tell the linker to place an output section at an address that falls on an n-byte
boundary, where n is a power of 2, by using the palign keyword. In addition, palign ensures that the size
of the section is a multiple of its placement alignment restrictions, padding the section size up to such a
boundary, as needed.
For example, the following code lines allocate .text on a 2-byte boundary within the PMEM area. The .text
section size is guaranteed to be a multiple of 2 bytes. Both statements are equivalent:
.text: palign(2) {} > PMEM
.text: palign = 2 {} > PMEM
If the linker adds padding to an initialized output section then the padding space is also initialized. By
default, padding space is filled with a value of 0 (zero). However, if a fill value is specified for the output
section then any padding for the section is also filled with that fill value. For example, consider the
following section specification:
.mytext: palign(8), fill = 0xffffffff {} > PMEM
In this example, the length of the .mytext section is 6 bytes before the palign operator is applied. The
contents of .mytext are as follows:
addr
---0000
0002
0004
content
------0x1234
0x1234
0x1234
After the palign operator is applied, the length of .mytext is 8 bytes, and its contents are as follows:
addr
---0000
0002
0004
0006
content
------0x1234
0x1234
0x1234
0xffff
The size of .mytext has been bumped to a multiple of 8 bytes and the padding created by the linker has
been filled with 0xff.
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The fill value specified in the linker command file is interpreted as a 16-bit constant. If you specify this
code:
.mytext: palign(8), fill = 0xff {} > PMEM
The fill value assumed by the linker is 0x00ff, and .mytext will then have the following contents:
addr
---0000
0002
0004
0006
content
------0x1234
0x1234
0x1234
0x00ff
If the palign operator is applied to an uninitialized section, then the size of the section is bumped to the
appropriate boundary, as needed, but any padding created is not initialized.
The palign operator can also take a parameter of power2. This parameter tells the linker to add padding to
increase the section's size to the next power of two boundary. In addition, the section is aligned on that
power of 2 as well. For example, consider the following section specification:
.mytext: palign(power2) {} > PMEM
Assume that the size of the .mytext section is 120 bytes and PMEM starts at address 0x10020. After
applying the palign(power2) operator, the .mytext output section will have the following properties:
name
------.mytext
216
addr
---------0x00010080
size
----0x80
align
----128
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8.5.5.3
Specifying Input Sections
An input section specification identifies the sections from input files that are combined to form an output
section. In general, the linker combines input sections by concatenating them in the order in which they
are specified. However, if alignment or blocking is specified for an input section, all of the input sections
within the output section are ordered as follows:
• All aligned sections, from largest to smallest
• All blocked sections, from largest to smallest
• All other sections, from largest to smallest
The size of an output section is the sum of the sizes of the input sections that it comprises.
Example 8-8 shows the most common type of section specification; note that no input sections are listed.
Example 8-8. The Most Common Method of Specifying Section Contents
SECTIONS
{
.text:
.data:
.bss:
}
In Example 8-8, the linker takes all the .text sections from the input files and combines them into the .text
output section. The linker concatenates the .text input sections in the order that it encounters them in the
input files. The linker performs similar operations with the .data and .bss sections. You can use this type of
specification for any output section.
You can explicitly specify the input sections that form an output section. Each input section is identified by
its filename and section name. If the filename is hyphenated (or contains special characters), enclose it
within quotes:
SECTIONS
{
.text :
/* Build .text output section
{
f1.obj(.text)
/* Link .text section from f1.obj
f2.obj(sec1)
/* Link sec1 section from f2.obj
"f3-new.obj"
/* Link ALL sections from f3-new.obj
f4.obj"(.text,sec2) /* Link .text and sec2 from f4.obj
}
}
*/
*/
*/
*/
*/
It is not necessary for input sections to have the same name as each other or as the output section they
become part of. If a file is listed with no sections,all of its sections are included in the output section. If any
additional input sections have the same name as an output section but are not explicitly specified by the
SECTIONS directive, they are automatically linked in at the end of the output section. For example, if the
linker found more .text sections in the preceding example and these .text sections were not specified
anywhere in the SECTIONS directive, the linker would concatenate these extra sections after f4.obj(sec2).
The specifications in Example 8-8 are actually a shorthand method for the following:
SECTIONS
{
.text: { *(.text) }
.data: { *(.data) }
.bss: { *(.bss) }
}
The specification *(.text) means the unallocated .text sections from all input files. This format is useful if:
• You want the output section to contain all input sections that have a specified name, but the output
section name is different from the input sections' name.
• You want the linker to allocate the input sections before it processes additional input sections or
commands within the braces.
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The following example illustrates the two purposes above:
SECTIONS
{
.text
:
{
abc.obj(xqt)
*(.text)
.data
:
}
{
*(.data)
fil.obj(table)
}
}
In this example, the .text output section contains a named section xqt from file abc.obj, which is followed
by all the .text input sections. The .data section contains all the .data input sections, followed by a named
section table from the file fil.obj. This method includes all the unallocated sections. For example, if one of
the .text input sections was already included in another output section when the linker encountered
*(.text), the linker could not include that first .text input section in the second output section.
Each input section acts as a prefix and gathers longer-named sections. For example, the pattern *(.data)
matches .dataspecial. This mechanism enables the use of subsections, which are described in the
following section.
8.5.5.4
Using Multi-Level Subsections
Subsections can be identified with the base section name and one or more subsection names separated
by colons. For example, A:B and A:B:C name subsections of the base section A. In certain places in a
linker command file specifying a base name, such as A, selects the section A as well as any subsections
of A, such as A:B or A:C:D.
A name such as A:B can specify a (sub)section of that name as well as any (multi-level) subsections
beginning with that name, such as A:B:C, A:B:OTHER, etc. All subsections of A:B are also subsections of
A. A and A:B are supersections of A:B:C. Among a group of supersections of a subsection, the nearest
supersection is the supersection with the longest name. Thus, among {A, A:B} the nearest supersection of
A:B:C:D is A:B. With multiple levels of subsections, the constraints are the following:
1. When specifying input sections within a file (or library unit) the section name selects an input section
of the same name and any subsections of that name.
2. Input sections that are not explicitly allocated are allocated in an existing output section of the same
name or in the nearest existing supersection of such an output section. An exception to this rule is that
during a partial link (specified by the --relocatable linker option) a subsection is allocated only to an
existing output section of the same name.
3. If no such output section described in 2) is defined, the input section is put in a newly created output
section with the same name as the base name of the input section
Consider linking input sections with the following names:
europe:north:norway
europe:central:france
europe:north:sweden
europe:central:germany
europe:north:finland
europe:central:denmark
europe:north:iceland
europe:south:spain
europe:south:italy
europe:south:malta
This SECTIONS specification allocates the input sections as indicated in the comments:
SECTIONS {
nordic: {*(europe:north)
*(europe:central:denmark)} /* the nordic countries */
central: {*(europe:central)}
/* france, germany
*/
therest: {*(europe)}
/* spain, italy, malta */
}
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This SECTIONS specification allocates the input sections as indicated in the comments:
SECTIONS {
islands: {*(europe:south:malta)
*(europe:north:iceland)}
europe:north:finland : {}
europe:north
: {}
europe:central
: {}
europe:central:france: {}
/*
/*
/*
/*
/*
malta, iceland
finland
norway, sweden
germany, denmark
france
*/
*/
*/
*/
*/
/* (italy, spain) go into a linker-generated output section "europe" */
}
Upward Compatibility of Multi-Level Subsections
NOTE: Existing linker commands that use the existing single-level subsection features and which do
not contain section names containing multiple colon characters continue to behave as
before. However, if section names in a linker command file or in the input sections supplied
to the linker contain multiple colon characters, some change in behavior could be possible.
You should carefully consider the impact of the rules for multiple levels to see if it affects a
particular system link.
8.5.5.5
Specifying Library or Archive Members as Input to Output Sections
You can specify one or more members of an object library or archive for input to an output section.
Consider this SECTIONS directive:
Example 8-9. Archive Members to Output Sections
SECTIONS
{
boot
{
>
BOOT1
--library=rtsXX.lib<boot.obj> (.text)
--library=rtsXX.lib<exit.obj strcpy.obj> (.text)
}
.rts
{
>
BOOT2
--library=rtsXX.lib (.text)
}
.text
{
>
RAM
* (.text)
}
}
In Example 8-9, the .text sections of boot.obj, exit.obj, and strcpy.obj are extracted from the run-timesupport library and placed in the .boot output section. The remainder of the run-time-support library object
that is referenced is allocated to the .rts output section. Finally, the remainder of all other .text sections are
to be placed in section .text.
An archive member or a list of members is specified by surrounding the member name(s) with angle
brackets < and > after the library name. Any object files separated by commas or spaces from the
specified archive file are legal within the angle brackets.
The --library option (which normally implies a library path search be made for the named file following the
option) listed before each library in Example 8-9 is optional when listing specific archive members inside <
>. Using < > implies that you are referring to a library.
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To collect a set of the input sections from a library in one place, use the --library option within the
SECTIONS directive. For example, the following collects all the .text sections from rts6600_elf.lib into the
.rtstest section:
SECTIONS
{
.rtstest { --library=rts6600_elf.lib(.text) } > RAM
}
SECTIONS Directive Effect on --priority
NOTE: Specifying a library in a SECTIONS directive causes that library to be entered in the list of
libraries that the linker searches to resolve references. If you use the --priority option, the first
library specified in the command file will be searched first.
8.5.5.6
Allocation Using Multiple Memory Ranges
The linker allows you to specify an explicit list of memory ranges into which an output section can be
allocated. Consider the following example:
MEMORY
{
P_MEM1
P_MEM2
P_MEM3
P_MEM4
}
SECTIONS
{
.text
}
:
:
:
:
origin
origin
origin
origin
=
=
=
=
0x02000,
0x04000,
0x06000,
0x08000,
length
length
length
length
=
=
=
=
0x01000
0x01000
0x01000
0x01000
: { } > P_MEM1 | P_MEM2 | P_MEM4
The | operator is used to specify the multiple memory ranges. The .text output section is allocated as a
whole into the first memory range in which it fits. The memory ranges are accessed in the order specified.
In this example, the linker first tries to allocate the section in P_MEM1. If that attempt fails, the linker tries
to place the section into P_MEM2, and so on. If the output section is not successfully allocated in any of
the named memory ranges, the linker issues an error message.
With this type of SECTIONS directive specification, the linker can seamlessly handle an output section
that grows beyond the available space of the memory range in which it is originally allocated. Instead of
modifying the linker command file, you can let the linker move the section into one of the other areas.
8.5.5.7
Automatic Splitting of Output Sections Among Non-Contiguous Memory Ranges
The linker can split output sections among multiple memory ranges for efficient allocation. Use the >>
operator to indicate that an output section can be split, if necessary, into the specified memory ranges:
MEMORY
{
P_MEM1 : origin
P_MEM2 : origin
P_MEM3 : origin
P_MEM4 : origin
}
SECTIONS
{
.text: { *(.text)
}
=
=
=
=
0x2000,
0x4000,
0x6000,
0x8000,
length
length
length
length
=
=
=
=
0x1000
0x1000
0x1000
0x1000
} >> P_MEM1 | P_MEM2 | P_MEM3 | P_MEM4
In this example, the >> operator indicates that the .text output section can be split among any of the listed
memory areas. If the .text section grows beyond the available memory in P_MEM1, it is split on an input
section boundary, and the remainder of the output section is allocated to P_MEM2 | P_MEM3 | P_MEM4.
The | operator is used to specify the list of multiple memory ranges.
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You can also use the >> operator to indicate that an output section can be split within a single memory
range. This functionality is useful when several output sections must be allocated into the same memory
range, but the restrictions of one output section cause the memory range to be partitioned. Consider the
following example:
MEMORY
{
RAM :
}
origin = 0x1000,
length = 0x8000
SECTIONS
{
.special: { f1.obj(.text) } load = 0x4000
.text: { *(.text) } >> RAM
}
The .special output section is allocated near the middle of the RAM memory range. This leaves two
unused areas in RAM: from 0x1000 to 0x4000, and from the end of f1.obj(.text) to 0x8000. The
specification for the .text section allows the linker to split the .text section around the .special section and
use the available space in RAM on either side of .special.
The >> operator can also be used to split an output section among all memory ranges that match a
specified attribute combination. For example:
MEMORY
{
P_MEM1 (RWX) : origin = 0x1000,
P_MEM2 (RWI) : origin = 0x4000,
}
length = 0x2000
length = 0x1000
SECTIONS
{
.text: { *(.text) } >> (RW)
}
The linker attempts to allocate all or part of the output section into any memory range whose attributes
match the attributes specified in the SECTIONS directive.
This SECTIONS directive has the same effect as:
SECTIONS
{
.text: { *(.text) } >> P_MEM1 | P_MEM2}
}
Certain sections should not be split:
• Certain sections created by the compiler, including
– The .cinit section, which contains the autoinitialization table for C/C++ programs
– The .pinit section, which contains the list of global constructors for C++ programs
– The .bss section, which defines global variables
• An output section with an input section specification that includes an expression to be evaluated. The
expression may define a symbol that is used in the program to manage the output section at run time.
• An output section that has a START(), END(), OR SIZE() operator applied to it. These operators
provide information about a section's load or run address, and size. Splitting the section may
compromise the integrity of the operation.
• The run allocation of a UNION. (Splitting the load allocation of a UNION is allowed.)
If you use the >> operator on any of these sections, the linker issues a warning and ignores the operator.
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8.5.6 Placing a Section at Different Load and Run Addresses
At times, you may want to load code into one area of memory and run it in another. For example, you may
have performance-critical code in slow external memory. The code must be loaded into slow external
memory, but it would run faster in fast external memory.
The linker provides a simple way to accomplish this. You can use the SECTIONS directive to direct the
linker to allocate a section twice: once to set its load address and again to set its run address. For
example:
.fir: load = SLOW_MEM, run = FAST_MEM
Use the load keyword for the load address and the run keyword for the run address.
See Section 3.5 for an overview on run-time relocation.
The application must copy the section from its load address to its run address; this does not happen
automatically when you specify a separate run address. (The TABLE operator instructs the linker to
produce a copy table; see Section 8.8.4.1.)
8.5.6.1
Specifying Load and Run Addresses
The load address determines where a loader places the raw data for the section. Any references to the
section (such as labels in it) refer to its run address. See Section 3.1.1 for an overview of load and run
addresses.
If you provide only one allocation (either load or run) for a section, the section is allocated only once and
loads and runs at the same address. If you provide both allocations, the section is allocated as if it were
two sections of the same size. This means that both allocations occupy space in the memory map and
cannot overlay each other or other sections. (The UNION directive provides a way to overlay sections; see
Section 8.5.7.2.)
If either the load or run address has additional parameters, such as alignment or blocking, list them after
the appropriate keyword. Everything related to allocation after the keyword load affects the load address
until the keyword run is seen, after which, everything affects the run address. The load and run allocations
are completely independent, so any qualification of one (such as alignment) has no effect on the other.
You can also specify run first, then load. Use parentheses to improve readability.
The examples that follow specify load and run addresses.
In this example, align applies only to load:
.data: load = SLOW_MEM, align = 32, run = FAST_MEM
The following example uses parentheses, but has effects that are identical to the previous example:
.data: load = (SLOW_MEM align 32), run = FAST_MEM
The following example aligns FAST_MEM to 32 bits for run allocations and aligns all load allocations to 16
bits:
.data: run
= FAST_MEM, align 32, load = align 16
For more information on run-time relocation see Section 3.5.
Uninitialized sections (such as .bss) are not loaded, so their only significant address is the run address.
The linker allocates uninitialized sections only once: if you specify both run and load addresses, the linker
warns you and ignores the load address. Otherwise, if you specify only one address, the linker treats it as
a run address, regardless of whether you call it load or run.
This example specifies load and run addresses for an uninitialized section:
.bss: load = 0x1000, run = FAST_MEM
A warning is issued, load is ignored, and space is allocated in FAST_MEM. All of the following examples
have the same effect. The .bss section is allocated in FAST_MEM.
.dbss: load = FAST_MEM
.bss: run = FAST_MEM
.bss: > FAST_MEM
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8.5.6.2
Referring to the Load Address by Using the .label Directive
Normally, any reference to a symbol refers to its run-time address. However, it may be necessary at run
time to refer to a load-time address. Specifically, the code that copies a section from its load address to its
run address must have access to the load address. The .label directive defines a special symbol that
refers to the section's load address. Thus, whereas normal symbols are relocated with respect to the run
address, .label symbols are relocated with respect to the load address. See Create a Load-Time Address
Label for more information on the .label directive.
Example 8-10 and Example 8-11 show the use of the .label directive to copy a section from its load
address in SLOW_MEM to its run address in FAST_MEM. Figure 8-3 illustrates the run-time execution of
Example 8-10.
If you use the table operator, the .label directive is not needed. See Section 8.8.4.1.
Example 8-10. Moving a Function from Slow to Fast Memory at Run Time
.sect ".fir"
.align 4
.label fir_src
fir
; insert code here
.label
.text
MVKL
MVKH
MVKL
MVKH
MVKL
MVKH
SUB
loop:
[!A1]
fir_end
fir_src, A4
fir_src, A4
fir_end, A5
fir_end, A5
fir, A6
fir, A6
A5, A4, A1
B
done
LDW
*A4+ +, B3
NOP
4
; branch occurs
STW
B3, *A6+ +
SUB
A1, 4, A1
B
loop
NOP
5
; branch occurs
done:
B
fir
NOP
5
; call occurs
Example 8-11. Linker Command File for Example 8-10
/*
PARTIAL LINKER COMMAND FILE FOR FIR EXAMPLE
*/
MEMORY
{
FAST_MEM : origin = 0x00001000, length = 0x00001000
SLOW_MEM : origin = 0x10000000, length = 0x00001000
}
SECTIONS
{
.text: load = FAST_MEM
.fir: load = SLOW_MEM, run FAST_MEM
}
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Figure 8-3. Run-Time Execution of Example 8-10
0x00000000
FAST_MEM
.text
fir (relocated
to run here)
0x00001000
0x10000000
SLOW_MEM
fir (loads here)
0x10001000
0xFFFFFFFF
See Section 8.6.1 for information about referring to linker symbols in C/C++ code.
8.5.7 Using GROUP and UNION Statements
Two SECTIONS statements allow you to organize or conserve memory: GROUP and UNION. Grouping
sections causes the linker to allocate them contiguously in memory. Unioning sections causes the linker to
allocate them to the same run address.
8.5.7.1
Grouping Output Sections Together
The SECTIONS directive's GROUP option forces several output sections to be allocated contiguously and
in the order listed, unless the UNORDERED operator is used. For example, assume that a section named
term_rec contains a termination record for a table in the .data section. You can force the linker to allocate
.data and term_rec together:
Example 8-12. Allocate Sections Together
SECTIONS
{
.text
/*
.bss
/*
GROUP 0x00001000 :
{
.data
/*
term_rec
/*
}
}
Normal output section
Normal output section
/* Specify a group of sections
*/
*/
*/
First section in the group
*/
Allocated immediately after .data */
You can use binding, alignment, or named memory to allocate a GROUP in the same manner as a single
output section. In the preceding example, the GROUP is bound to address 0x1000. This means that .data
is allocated at 0x1000, and term_rec follows it in memory.
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You Cannot Specify Addresses for Sections Within a GROUP
NOTE: When you use the GROUP option, binding, alignment, or allocation into named memory can
be specified for the group only. You cannot use binding, named memory, or alignment for
sections within a group.
8.5.7.2
Overlaying Sections With the UNION Statement
For some applications, you may want to allocate more than one section that occupies the same address
during run time. For example, you may have several routines you want in fast external memory at different
stages of execution. Or you may want several data objects that are not active at the same time to share a
block of memory. The UNION statement within the SECTIONS directive provides a way to allocate several
sections at the same run-time address.
In Example 8-13, the .bss sections from file1.obj and file2.obj are allocated at the same address in
FAST_MEM. In the memory map, the union occupies as much space as its largest component. The
components of a union remain independent sections; they are simply allocated together as a unit.
Example 8-13. The UNION Statement
SECTIONS
{
.text: load = SLOW_MEM
UNION: run = FAST_MEM
{
.bss:part1: { file1.obj(.bss) }
.bss:part2: { file2.obj(.bss) }
}
.bss:part3: run = FAST_MEM { globals.obj(.bss) }
}
Allocation of a section as part of a union affects only its run address. Under no circumstances can
sections be overlaid for loading. If an initialized section is a union member (an initialized section, such as
.text, has raw data), its load allocation must be separately specified. See Example 8-14.
Example 8-14. Separate Load Addresses for UNION Sections
UNION run = FAST_MEM
{
.text:part1: load = SLOW_MEM, { file1.obj(.text) }
.text:part2: load = SLOW_MEM, { file2.obj(.text) }
}
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Figure 8-4. Memory Allocation Shown in Example 8-13 and Example 8-14
FAST_MEM
.bss:part2
.bss:part1
Sections can run
as a union. This
is run-time allocation only.
.bss:part3
.text 2 (run)
Copies at
run time
.text 1 (run)
.bss:part3
SLOW_MEM
.text
FAST_MEM
SLOW_MEM
Sections cannot
load as a union
.text 1 (load)
.text 2 (load)
Since the .text sections contain raw data, they cannot load as a union, although they can be run as a
union. Therefore, each requires its own load address. If you fail to provide a load allocation for an
initialized section within a UNION, the linker issues a warning and allocates load space anywhere it can in
configured memory.
Uninitialized sections are not loaded and do not require load addresses.
The UNION statement applies only to allocation of run addresses, so it is meaningless to specify a load
address for the union itself. For purposes of allocation, the union is treated as an uninitialized section: any
one allocation specified is considered a run address, and if both run and load addresses are specified, the
linker issues a warning and ignores the load address.
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8.5.7.3
Nesting UNIONs and GROUPs
The linker allows arbitrary nesting of GROUP and UNION statements with the SECTIONS directive. By
nesting GROUP and UNION statements, you can express hierarchical overlays and groupings of sections.
Example 8-15 shows how two overlays can be grouped together.
Example 8-15. Nesting GROUP and UNION Statements
SECTIONS
{
GROUP 0x1000 :
{
UNION:
{
mysect1:
mysect2:
}
UNION:
{
mysect3:
mysect4:
}
}
}
run = FAST_MEM
load = SLOW_MEM
load = SLOW_MEM
load = SLOW_MEM
load = SLOW_MEM
For this example, the linker performs the following allocations:
• The four sections (mysect1, mysect2, mysect3, mysect4) are assigned unique, non-overlapping load
addresses. The name you defined with the .label directive is used in the SLOW_MEM memory region.
This assignment is determined by the particular load allocations given for each section.
• Sections mysect1 and mysect2 are assigned the same run address in FAST_MEM.
• Sections mysect3 and mysect4 are assigned the same run address in FAST_MEM.
• The run addresses of mysect1/mysect2 and mysect3/mysect4 are allocated contiguously, as directed
by the GROUP statement (subject to alignment and blocking restrictions).
To refer to groups and unions, linker diagnostic messages use the notation:
GROUP_n UNION_n
where n is a sequential number (beginning at 1) that represents the lexical ordering of the group or union
in the linker control file without regard to nesting. Groups and unions each have their own counter.
8.5.7.4
Checking the Consistency of Allocators
The linker checks the consistency of load and run allocations specified for unions, groups, and sections.
The following rules are used:
• Run allocations are only allowed for top-level sections, groups, or unions (sections, groups, or unions
that are not nested under any other groups or unions). The linker uses the run address of the top-level
structure to compute the run addresses of the components within groups and unions.
• The linker does not accept a load allocation for UNIONs.
• The linker does not accept a load allocation for uninitialized sections.
• In most cases, you must provide a load allocation for an initialized section. However, the linker does
not accept a load allocation for an initialized section that is located within a group that already defines
a load allocator.
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•
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As a shortcut, you can specify a load allocation for an entire group, to determine the load allocations
for every initialized section or subgroup nested within the group. However, a load allocation is
accepted for an entire group only if all of the following conditions are true:
– The group is initialized (that is, it has at least one initialized member).
– The group is not nested inside another group that has a load allocator.
– The group does not contain a union containing initialized sections.
If the group contains a union with initialized sections, it is necessary to specify the load allocation for
each initialized section nested within the group. Consider the following example:
SECTIONS
{
GROUP: load = SLOW_MEM, run = SLOW_MEM
{
.text1:
UNION:
{
.text2:
.text3:
}
}
}
The load allocator given for the group does not uniquely specify the load allocation for the elements
within the union: .text2 and .text3. In this case, the linker issues a diagnostic message to request that
these load allocations be specified explicitly.
8.5.7.5
Naming UNIONs and GROUPs
You can give a name to a UNION or GROUP by entering the name in parentheses after the declaration.
For example:
GROUP(BSS_SYSMEM_STACK_GROUP)
{
.bss
:{}
.sysmem :{}
.stack :{}
} load=D_MEM, run=D_MEM
The name you defined is used in diagnostics for easy identification of the problem LCF area. For example:
warning: LOAD placement ignored for "BSS_SYSMEM_STACK_GROUP": object is uninitialized
UNION(TEXT_CINIT_UNION)
{
.const :{}load=D_MEM, table(table1)
.pinit :{}load=D_MEM, table(table1)
}run=P_MEM
warning:table(table1) operator ignored: table(table1) has already been applied to a section
in the "UNION(TEXT_CINIT_UNION)" in which ".pinit" is a descendant
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8.5.8 Special Section Types (DSECT, COPY, NOLOAD, and NOINIT)
You can assign the following special types to output sections: DSECT, COPY, NOLOAD, and NOINIT.
These types affect the way that the program is treated when it is linked and loaded. You can assign a type
to a section by placing the type after the section definition. For example:
SECTIONS
{
sec1:
sec2:
sec3:
sec4:
}
•
•
•
•
load
load
load
load
=
=
=
=
0x00002000,
0x00004000,
0x00006000,
0x00008000,
type
type
type
type
=
=
=
=
DSECT
COPY
NOLOAD
NOINIT
{f1.obj}
{f2.obj}
{f3.obj}
{f4.obj}
The DSECT type creates a dummy section with the following characteristics:
– It is not included in the output section memory allocation. It takes up no memory and is not included
in the memory map listing.
– It can overlay other output sections, other DSECTs, and unconfigured memory.
– Global symbols defined in a dummy section are relocated normally. They appear in the output
module's symbol table with the same value they would have if the DSECT had actually been
loaded. These symbols can be referenced by other input sections.
– Undefined external symbols found in a DSECT cause specified archive libraries to be searched.
– The section's contents, relocation information, and line number information are not placed in the
output module.
In the preceding example, none of the sections from f1.obj are allocated, but all the symbols are
relocated as though the sections were linked at address 0x2000. The other sections can refer to any of
the global symbols in sec1.
A COPY section is similar to a DSECT section, except that its contents and associated information are
written to the output module. The .cinit section that contains initialization tables for the TMS320C6000
C/C++ compiler has this attribute under the run-time initialization model.
A NOLOAD section differs from a normal output section in one respect: the section's contents,
relocation information, and line number information are not placed in the output module. The linker
allocates space for the section, and it appears in the memory map listing.
A NOINIT section is not C auto-initialized by the linker. It is your responsibility to initialize this section
as needed.
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8.5.9 Configuring Error Correcting Code (ECC) with the Linker
Error Correcting Codes (ECC) can be generated and placed in separate sections through the linker
command file. ECC uses extra bits to allow errors to be detected and/or corrected by a device. The ECC
support provided by the linker is compatible with the ECC support in TI Flash memory on various TI
devices. TI Flash memory uses a modified Hamming(72,64) code, which uses 8 parity bits for every 64
bits. Check the documentation for your Flash memory to see if ECC is supported. (ECC for read-write
memory is handled completely in hardware at run time.)
See Section 8.4.11 for command-line options that introduce bit errors into code that has a corresponding
ECC section or into the ECC parity bits themselves. You can use these options to test your ECC error
handling code.
ECC can be generated during linking. The ECC data is included in the resulting object file, alongside code
and data, as a data section located at the appropriate address. No extra ECC generation step is required
after compilation, and the ECC can be uploaded to the device along with everything else.
You can control the generation of ECC data using the ECC specifier in the memory map (Section 8.5.9.1)
and the ECC directive (Section 8.5.9.2).
8.5.9.1
Using the ECC Specifier in the Memory Map
To generate ECC, add a separate memory range to your memory map to hold ECC data and to indicate
which memory range contains the Flash data that corresponds to this ECC data. If you have multiple
memory ranges for Flash data, you should add a separate ECC memory range for each Flash data range.
The definition of an ECC memory range can also provide parameters for how to generate the ECC data.
The memory map for a device supporting Flash ECC may look something like this:
MEMORY {
VECTORS
FLASH0
FLASH1
STACKS
RAM
ECC_VEC
ECC_FLA0
ECC_FLA1
}
:
:
:
:
:
:
:
:
origin=0x00000000
origin=0x00000020
origin=0x00180000
origin=0x08000000
origin=0x08000500
origin=0xf0400000
origin=0xf0400004
origin=0xf0430000
length=0x000020
length=0x17FFE0
length=0x180000
length=0x000500
length=0x03FB00
length=0x000004 ECC={ input_range=VECTORS }
length=0x02FFFC ECC={ input_range=FLASH0 }
length=0x030000 ECC={ input_range=FLASH1 }
The specification syntax for ECC memory ranges is as follows:
MEMORY {
<memory specifier1> : <memory attributes> [ vfill=<fill value> ]
<memory specifier2> : <memory attributes> ECC = {
input_range = <memory specifier1>
[ algorithm
= <algorithm name> ]
[ fill
= [ true, false ] ]
}
}
The "ECC" specifier attached to the ECC memory ranges indicates the data memory range that the ECC
range covers. The ECC specifier supports the following parameters:
input_range = <memory
range>
algorithm = <ECC algorithm
name>
fill = true | false
230
The data memory range covered by this ECC data range. Required.
The name of an ECC algorithm defined later in the command file using
the ECC directive. Optional if only one algorithm is defined. (See
Section 8.5.9.2.)
Whether to generate ECC data for holes in the initialized data of the input
range. The default is "true". Using fill=false produces behavior similar to
the nowECC tool. The input range can be filled normally or using a virtual
fill (see Section 8.5.9.3).
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8.5.9.2
Using the ECC Directive
In addition to specifying ECC memory ranges in the memory map, the linker command file must specify
parameters for the algorithm that generates ECC data. You might need multiple ECC algorithm
specifications if you have multiple Flash devices.
Each TI device supporting Flash ECC has exactly one set of valid values for these parameters. The linker
command files provided with Code Composer Studio include the ECC parameters necessary for ECC
support on the Flash memory accessible by the device. Documentation is provided here for completeness.
You specify algorithm parameters with the top-level ECC directive in the linker command file. The
specification syntax is as follows:
ECC {
<algorithm name> : parity_mask = <8-bit integer>
mirroring
= [ F021, F035 ]
address_mask = <32-bit mask>
}
For example:
MEMORY {
FLASH0 : origin=0x00000020 length=0x17FFE0
ECC_FLA0 : origin=0xf0400004 length=0x02FFFC ECC={ input_range=FLASH0
algorithm=F021 }
}
ECC { F021 : parity_mask = 0xfc
mirroring = F021 }
This ECC directive accepts the following attributes:
algorithm_name
address_mask = <32-bit
mask>
parity_mask = <8-bit mask>
mirroring = F021 | F035
8.5.9.3
Specify the name you would like to use for referencing the algorithm.
This mask determines which bits of the address of each 64-bit piece of
memory are used in the calculation of the ECC byte for that memory.
Default is 0xffffffff, so that all bits of the address are used. (Note that the
ECC algorithm itself ignores the lowest bits, which are always zero for a
correctly-aligned input block.)
This mask determines which ECC bits encode even parity and which bits
encode odd parity. Default is 0, meaning that all bits encode even parity.
This setting determines the order of the ECC bytes and their duplication
pattern for redundancy. Default is F021.
Using the VFILL Specifier in the Memory Map
Normally, specifying a fill value for a MEMORY range creates initialized data sections to cover any
previously uninitialized areas of memory. To generate ECC data for an entire memory range, the linker
either needs to have initialized data in the entire range, or needs to know what value uninitialized memory
areas will have at run time.
In cases where you want to generate ECC for an entire memory range, but do not want to initialize the
entire range by specifying a fill value, you can use the "vfill" specifier instead of a "fill" specifier to virtually
fill the range:
MEMORY {
FLASH : origin=0x0000
}
length=0x4000
vfill=0xffffffff
The vfill specifier is functionally equivalent to omitting a fill specifier, except that it allows ECC data to be
generated for areas of the input memory range that remain uninitialized. This has the benefit of reducing
the size of the resulting object file.
The vfill specifier has no effect other than in ECC data generation. It cannot be specified along with a fill
specifier, since that would introduce ambiguity.
If fill is specified in the ECC specifier, but vfill is not specified, vfill defaults to 0xff.
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8.5.10 Assigning Symbols at Link Time
Linker assignment statements allow you to define external (global) symbols and assign values to them at
link time. You can use this feature to initialize a variable or pointer to an allocation-dependent value. See
Section 8.6.1 for information about referring to linker symbols in C/C++ code.
8.5.10.1 Syntax of Assignment Statements
The syntax of assignment statements in the linker is similar to that of assignment statements in the C
language:
symbol
symbol
symbol
symbol
symbol
=
+=
-=
*=
/=
expression;
expression;
expression;
expression;
expression;
assigns the value of expression to symbol
adds the value of expression to symbol
subtracts the value of expression from symbol
multiplies symbol by expression
divides symbol by expression
The symbol should be defined externally. If it is not, the linker defines a new symbol and enters it into the
symbol table. The expression must follow the rules defined in Section 8.5.10.3. Assignment statements
must terminate with a semicolon.
The linker processes assignment statements after it allocates all the output sections. Therefore, if an
expression contains a symbol, the address used for that symbol reflects the symbol's address in the
executable output file.
For example, suppose a program reads data from one of two tables identified by two external symbols,
Table1 and Table2. The program uses the symbol cur_tab as the address of the current table. The
cur_tab symbol must point to either Table1 or Table2. You could accomplish this in the assembly code,
but you would need to reassemble the program to change tables. Instead, you can use a linker
assignment statement to assign cur_tab at link time:
prog.obj
cur_tab = Table1;
/* Input file
*/
/* Assign cur_tab to one of the tables */
8.5.10.2 Assigning the SPC to a Symbol
A special symbol, denoted by a dot (.), represents the current value of the section program counter (SPC)
during allocation. The SPC keeps track of the current location within a section. The linker's . symbol is
analogous to the assembler's $ symbol. The . symbol can be used only in assignment statements within a
SECTIONS directive because . is meaningful only during allocation and SECTIONS controls the allocation
process. (See Section 8.5.5.)
The . symbol refers to the current run address, not the current load address, of the section.
For example, suppose a program needs to know the address of the beginning of the .data section. By
using the .global directive (see Identify Global Symbols), you can create an external undefined variable
called Dstart in the program. Then, assign the value of . to Dstart:
SECTIONS
{
.text:
.data:
.bss :
}
{}
{Dstart = .;}
{}
This defines Dstart to be the first linked address of the .data section. (Dstart is assigned before .data is
allocated.) The linker relocates all references to Dstart.
A special type of assignment assigns a value to the . symbol. This adjusts the SPC within an output
section and creates a hole between two input sections. Any value assigned to . to create a hole is relative
to the beginning of the section, not to the address actually represented by the . symbol. Holes and
assignments to . are described in Section 8.5.11.
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8.5.10.3 Assignment Expressions
These rules apply to linker expressions:
• Expressions can contain global symbols, constants, and the C language operators listed in Table 8-12.
• All numbers are treated as long (32-bit) integers.
• Constants are identified by the linker in the same way as by the assembler. That is, numbers are
recognized as decimal unless they have a suffix (H or h for hexadecimal and Q or q for octal). C
language prefixes are also recognized (0 for octal and 0x for hex). Hexadecimal constants must begin
with a digit. No binary constants are allowed.
• Symbols within an expression have only the value of the symbol's address. No type-checking is
performed.
• Linker expressions can be absolute or relocatable. If an expression contains any relocatable symbols
(and 0 or more constants or absolute symbols), it is relocatable. Otherwise, the expression is absolute.
If a symbol is assigned the value of a relocatable expression, it is relocatable; if it is assigned the value
of an absolute expression, it is absolute.
The linker supports the C language operators listed in Table 8-12 in order of precedence. Operators in the
same group have the same precedence. Besides the operators listed in Table 8-12, the linker also has an
align operator that allows a symbol to be aligned on an n-byte boundary within an output section (n is a
power of 2). For example, the following expression aligns the SPC within the current section on the next
16-byte boundary. Because the align operator is a function of the current SPC, it can be used only in the
same context as . —that is, within a SECTIONS directive.
. = align(16);
Table 8-12. Groups of Operators Used in Expressions (Precedence)
Group 1 (Highest Precedence)
!
~
-
Logical NOT
Bitwise NOT
Negation
*
/
%
Multiplication
Division
Modulus
+
-
Addition
Subtraction
>>
<<
Arithmetic right shift
Arithmetic left shift
Group 6
&
Bitwise AND
Group 2
Group 7
|
Bitwise OR
Group 3
Group 8
&&
Logical AND
Group 4
Group 9
||
Group 5
==
!=
>
<
<=
>=
Logical OR
Group 10 (Lowest Precedence)
Equal to
Not equal to
Greater than
Less than
Less than or equal to
Greater than or equal to
=
+=
-=
*=
/=
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Assignment
A+=B
A-=B
A*=B
A/=B
is
is
is
is
equivalent
equivalent
equivalent
equivalent
to
to
to
to
A=A+B
A=A-B
A=A*B
A=A/B
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8.5.10.4 Symbols Defined by the Linker
The linker automatically defines several symbols based on which sections are used in your assembly
source. A program can use these symbols at run time to determine where a section is linked. Since these
symbols are external, they appear in the linker map. Each symbol can be accessed in any assembly
language module if it is declared with a .global directive (see Identify Global Symbols). You must have
used the corresponding section in a source module for the symbol to be created. Values are assigned to
these symbols as follows:
.text
etext
.data
edata
.bss
end
is assigned the first address of the .text output section.
(It marks the beginning of executable code.)
is assigned the first address following the .text output section.
(It marks the end of executable code.)
is assigned the first address of the .data output section.
(It marks the beginning of initialized data tables.)
is assigned the first address following the .data output section.
(It marks the end of initialized data tables.)
is assigned the first address of the .bss output section.
(It marks the beginning of uninitialized data.)
is assigned the first address following the .bss output section.
(It marks the end of uninitialized data.)
The following symbols are defined only for C/C++ support when the --ram_model or --rom_model option is
used.
__TI_STACK_END
__TI_STACK_SIZE
__TI_STATIC_BASE
__TI_SYSMEM_SIZE
is assigned the end of the .stack size.
is assigned the size of the .stack section for.
is assigned the value to be loaded into the data pointer register (DP)
at boot time. This is typically the start of the first section containing a
definition of a symbol that is referenced via near-DP addressing.
is assigned the size of the .sysmem section.
See Section 8.6.1 for information about referring to linker symbols in C/C++ code.
8.5.10.5 Assigning Exact Start, End, and Size Values of a Section to a Symbol
The code generation tools currently support the ability to load program code in one area of (slow) memory
and run it in another (faster) area. This is done by specifying separate load and run addresses for an
output section or group in the linker command file. Then execute a sequence of instructions (the copying
code in Example 8-10) that moves the program code from its load area to its run area before it is needed.
There are several responsibilities that a programmer must take on when setting up a system with this
feature. One of these responsibilities is to determine the size and run-time address of the program code to
be moved. The current mechanisms to do this involve use of the .label directives in the copying code. A
simple example is illustrated in Example 8-10.
This method of specifying the size and load address of the program code has limitations. While it works
fine for an individual input section that is contained entirely within one source file, this method becomes
more complicated if the program code is spread over several source files or if the programmer wants to
copy an entire output section from load space to run space.
Another problem with this method is that it does not account for the possibility that the section being
moved may have an associated far call trampoline section that needs to be moved with it.
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8.5.10.6 Why the Dot Operator Does Not Always Work
The dot operator (.) is used to define symbols at link-time with a particular address inside of an output
section. It is interpreted like a PC. Whatever the current offset within the current section is, that is the
value associated with the dot. Consider an output section specification within a SECTIONS directive:
outsect:
{
s1.obj(.text)
end_of_s1
= .;
start_of_s2 = .;
s2.obj(.text)
end_of_s2 = .;
}
This statement creates three symbols:
• end_of_s1—the end address of .text in s1.obj
• start_of_s2—the start address of .text in s2.obj
• end_of_s2—the end address of .text in s2.obj
Suppose there is padding between s1.obj and s2.obj created as a result of alignment. Then start_of_s2 is
not really the start address of the .text section in s2.obj, but it is the address before the padding needed to
align the .text section in s2.obj. This is due to the linker's interpretation of the dot operator as the current
PC. It is also true because the dot operator is evaluated independently of the input sections around it.
Another potential problem in the above example is that end_of_s2 may not account for any padding that
was required at the end of the output section. You cannot reliably use end_of_s2 as the end address of
the output section. One way to get around this problem is to create a dummy section immediately after the
output section in question. For example:
GROUP
{
outsect:
{
start_of_outsect = .;
...
}
dummy: { size_of_outsect = . - start_of_outsect; }
}
8.5.10.7 Address and Dimension Operators
Six operators allow you to define symbols for load-time and run-time addresses and sizes:
LOAD_START( sym )
START( sym )
LOAD_END( sym )
END( sym )
LOAD_SIZE( sym )
SIZE( sym )
RUN_START( sym )
RUN_END( sym )
RUN_SIZE(sym )
Defines sym with the load-time start address of related allocation unit
Defines sym with the load-time end address of related allocation unit
Defines sym with the load-time size of related allocation unit
Defines sym with the run-time start address of related allocation unit
Defines sym with the run-time end address of related allocation unit
Defines sym with the run-time size of related allocation unit
Linker Command File Operator Equivalencies -NOTE: LOAD_START() and START() are equivalent, as are LOAD_END()/END() and
LOAD_SIZE()/SIZE(). The LOAD names are recommended for clarity.
These address and dimension operators can be associated with several different kinds of allocation units,
including input items, output sections, GROUPs, and UNIONs. The following sections provide some
examples of how the operators can be used in each case.
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These symbols defined by the linker can be accessed at runtime using the _symval operator, which is
essentially a cast operation. For example, suppose your linker command file contains the following:
.text: RUN_START(text_run_start), RUN_SIZE(text_run_size) { *(.text) }
Your C program can access these symbols as follows:
extern char text_run_start, text_run_size;
printf(".text load start is %lx\n", _symval(&text_run_start));
printf(".text load size is %lx\n", _symval(&text_run_size));
See Section 8.6.1 for more information about referring to linker symbols in C/C++ code.
8.5.10.7.1 Input Items
Consider an output section specification within a SECTIONS directive:
outsect:
{
s1.obj(.text)
end_of_s1
= .;
start_of_s2 = .;
s2.obj(.text)
end_of_s2 = .;
}
This can be rewritten using the START and END operators as follows:
outsect:
{
s1.obj(.text) { END(end_of_s1) }
s2.obj(.text) { START(start_of_s2), END(end_of_s2) }
}
The values of end_of_s1 and end_of_s2 will be the same as if you had used the dot operator in the
original example, but start_of_s2 would be defined after any necessary padding that needs to be added
between the two .text sections. Remember that the dot operator would cause start_of_s2 to be defined
before any necessary padding is inserted between the two input sections.
The syntax for using these operators in association with input sections calls for braces { } to enclose the
operator list. The operators in the list are applied to the input item that occurs immediately before the list.
8.5.10.7.2 Output Section
The START, END, and SIZE operators can also be associated with an output section. Here is an example:
outsect: START(start_of_outsect), SIZE(size_of_outsect)
{
<list of input items>
}
In this case, the SIZE operator defines size_of_outsect to incorporate any padding that is required in the
output section to conform to any alignment requirements that are imposed.
The syntax for specifying the operators with an output section does not require braces to enclose the
operator list. The operator list is simply included as part of the allocation specification for an output
section.
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8.5.10.7.3 GROUPs
Here is another use of the START and SIZE operators in the context of a GROUP specification:
GROUP
{
outsect1: { ... }
outsect2: { ... }
} load = ROM, run = RAM, START(group_start), SIZE(group_size);
This can be useful if the whole GROUP is to be loaded in one location and run in another. The copying
code can use group_start and group_size as parameters for where to copy from and how much is to be
copied. This makes the use of .label in the source code unnecessary.
8.5.10.7.4 UNIONs
The RUN_SIZE and LOAD_SIZE operators provide a mechanism to distinguish between the size of a
UNION's load space and the size of the space where its constituents are going to be copied before they
are run. Here is an example:
UNION: run = RAM, LOAD_START(union_load_addr),
LOAD_SIZE(union_ld_sz), RUN_SIZE(union_run_sz)
{
.text1: load = ROM, SIZE(text1_size) { f1.obj(.text) }
.text2: load = ROM, SIZE(text2_size) { f2.obj(.text) }
}
Here union_ld_sz is going to be equal to the sum of the sizes of all output sections placed in the union.
The union_run_sz value is equivalent to the largest output section in the union. Both of these symbols
incorporate any padding due to blocking or alignment requirements.
8.5.11 Creating and Filling Holes
The linker provides you with the ability to create areas within output sections that have nothing linked into
them. These areas are called holes. In special cases, uninitialized sections can also be treated as holes.
This section describes how the linker handles holes and how you can fill holes (and uninitialized sections)
with values.
8.5.11.1 Initialized and Uninitialized Sections
There are two rules to remember about the contents of output sections. An output section contains either:
• Raw data for the entire section
• No raw data
A section that has raw data is referred to as initialized. This means that the object file contains the actual
memory image contents of the section. When the section is loaded, this image is loaded into memory at
the section's specified starting address. The .text and .data sections always have raw data if anything was
assembled into them. Named sections defined with the .sect assembler directive also have raw data.
By default, the .bss section (see Reserve Space in the .bss Section) and sections defined with the .usect
directive (see Reserve Uninitialized Space) have no raw data (they are uninitialized). They occupy space
in the memory map but have no actual contents. Uninitialized sections typically reserve space in fast
external memory for variables. In the object file, an uninitialized section has a normal section header and
can have symbols defined in it; no memory image, however, is stored in the section.
8.5.11.2 Creating Holes
You can create a hole in an initialized output section. A hole is created when you force the linker to leave
extra space between input sections within an output section. When such a hole is created, the linker must
supply raw data for the hole.
Holes can be created only within output sections. Space can exist between output sections, but such
space is not a hole. To fill the space between output sections, see Section 8.5.4.2.
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To create a hole in an output section, you must use a special type of linker assignment statement within
an output section definition. The assignment statement modifies the SPC (denoted by .) by adding to it,
assigning a greater value to it, or aligning it on an address boundary. The operators, expressions, and
syntaxes of assignment statements are described in Section 8.5.10.
The following example uses assignment statements to create holes in output sections:
SECTIONS
{
outsect:
{
file1.obj(.text)
. += 0x0100
/* Create a hole with size 0x0100 */
file2.obj(.text)
. = align(16); /* Create a hole to align the SPC */
file3.obj(.text)
}
}
The output section outsect is built as follows:
1. The .text section from file1.obj is linked in.
2. The linker creates a 256-byte hole.
3. The .text section from file2.obj is linked in after the hole.
4. The linker creates another hole by aligning the SPC on a 16-byte boundary.
5. Finally, the .text section from file3.obj is linked in.
All values assigned to the . symbol within a section refer to the relative address within the section. The
linker handles assignments to the . symbol as if the section started at address 0 (even if you have
specified a binding address). Consider the statement . = align(16) in the example. This statement
effectively aligns the file3.obj .text section to start on a 16-byte boundary within outsect. If outsect is
ultimately allocated to start on an address that is not aligned, the file3.obj .text section will not be aligned
either.
The . symbol refers to the current run address, not the current load address, of the section.
Expressions that decrement the . symbol are illegal. For example, it is invalid to use the -= operator in an
assignment to the . symbol. The most common operators used in assignments to the . symbol are += and
align.
If an output section contains all input sections of a certain type (such as .text), you can use the following
statements to create a hole at the beginning or end of the output section.
.text:
.data:
{
{
.+= 0x0100; }
*(.data)
. += 0x0100; }
/* Hole at the beginning */
/* Hole at the end
*/
Another way to create a hole in an output section is to combine an uninitialized section with an initialized
section to form a single output section. In this case, the linker treats the uninitialized section as a hole and
supplies data for it. The following example illustrates this method:
SECTIONS
{
outsect:
{
file1.obj(.text)
file1.obj(.bss)
}
}
/* This becomes a hole */
Because the .text section has raw data, all of outsect must also contain raw data. Therefore, the
uninitialized .bss section becomes a hole.
Uninitialized sections become holes only when they are combined with initialized sections. If several
uninitialized sections are linked together, the resulting output section is also uninitialized.
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8.5.11.3 Filling Holes
When a hole exists in an initialized output section, the linker must supply raw data to fill it. The linker fills
holes with a 32-bit fill value that is replicated through memory until it fills the hole. The linker determines
the fill value as follows:
1. If the hole is formed by combining an uninitialized section with an initialized section, you can specify a
fill value for the uninitialized section. Follow the section name with an = sign and a 32-bit constant. For
example:
SECTIONS
{ outsect:
{
file1.obj(.text)
file2.obj(.bss)= 0xFF00FF00
}
}
/* Fill this hole with 0xFF00FF00 */
2. You can also specify a fill value for all the holes in an output section by supplying the fill value after the
section definition:
SECTIONS
{ outsect:fill = 0xFF00FF00
{
. += 0x0010;
file1.obj(.text)
file1.obj(.bss)
}
}
/* Fills holes with 0xFF00FF00 */
/* This creates a hole
*/
/* This creates another hole
*/
3. If you do not specify an initialization value for a hole, the linker fills the hole with the value specified
with the --fill_value option (see Section 8.4.13). For example, suppose the command file link.cmd
contains the following SECTIONS directive:
SECTIONS { .text: { .= 0x0100; } /* Create a 100 word hole */ }
Now invoke the linker with the --fill_value option:
cl6x --run_linker --fill_value=0xFFFFFFFF link.cmd
This fills the hole with 0xFFFFFFFF.
4. If you do not invoke the linker with the --fill_value option or otherwise specify a fill value, the linker fills
holes with 0s.
Whenever a hole is created and filled in an initialized output section, the hole is identified in the link map
along with the value the linker uses to fill it.
8.5.11.4 Explicit Initialization of Uninitialized Sections
You can force the linker to initialize an uninitialized section by specifying an explicit fill value for it in the
SECTIONS directive. This causes the entire section to have raw data (the fill value). For example:
SECTIONS
{
.bss: fill = 0x12341234 /* Fills .bss with 0x12341234 */
}
Filling Sections
NOTE: Because filling a section (even with 0s) causes raw data to be generated for the entire
section in the output file, your output file will be very large if you specify fill values for large
sections or holes.
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Linker Symbols
This section provides information about using and resolving linker symbols.
8.6.1 Using Linker Symbols in C/C++ Applications
Linker symbols have a name and a value. The value is a 32-bit unsigned integer, even if it represents a
pointer value on a target that has pointers smaller than 32 bits.
The most common kind of symbol is generated by the compiler for each function and variable. The value
represents the target address where that function or variable is located. When you refer to the symbol by
name in the linker command file or in an assembly file, you get that 32-bit integer value.
However, in C and C++ names mean something different. If you have a variable named x that contains
the value Y, and you use the name "x" in your C program, you are actually referring to the contents of
variable x. If "x" is used on the right-hand side of an expression, the compiler fetches the value Y. To
realize this variable, the compiler generates a linker symbol named x with the value &x. Even though the
C/C++ variable and the linker symbol have the same name, they don't represent the same thing. In C, x is
a variable name with the address &x and content Y. For linker symbols, x is an address, and that address
contains the value Y.
Because of this difference, there are some tricks to referring to linker symbols in C code. The basic
technique is to cause the compiler to creating a "fake" C variable or function and take its address. The
details differ depending on the type of linker symbol.
Linker symbols that represent a function address: In C code, declare the function as an extern
function. Then, refer to the value of the linker symbol using the same name. This works because function
pointers "decay" to their address value when used without adornment. For example:
extern void _c_int00(void);
printf("_c_int00 %lx\n", (unsigned long)&_c_int00);
Suppose your linker command file defines the following linker symbol:
func_sym=printf+100;
Your C application can refer to this symbol as follows:
extern void func_sym(void);
printf("func_sym %lx\n", _symval(&func_sym)); /* these two are equivalent */
printf("func_sym %lx\n", (unsigned long)&func_sym);
Linker symbols that represent a data address: In C code, declare the variable as an extern variable.
Then, refer to the value of the linker symbol using the & operator. Because the variable is at a valid data
address, we know that a data pointer can represent the value.
Suppose your linker command file defines the following linker symbols:
data_sym=.data+100;
xyz=12345
Your C application can refer to these symbols as follows:
extern char data_sym;
extern int xyz;
printf("data_sym %lx\n", _symval(&data_sym));
printf("data_sym %p\n", &data_sym);
/* these two are equivalent */
myvar = &xyz;
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Linker symbols for an arbitrary address: In C code, declare this as an extern symbol. The type does
not matter. If you are using GCC extensions, declare it as "extern void". If you are not using GCC
extensions, declare it as "extern char". Then, refer to the value of the linker symbol mySymbol as
_symval(&mySymbol). You must use the _symval operator, which is equivalent to a cast, because the 32bit value of the linker symbol could be wider than a data pointer. The compiler treats _symval(&mySymbol)
in a special way that can represent all 32 bits, even when pointers are 16 bits. Targets that have 32-bit
pointers can usually use &mySymbol instead of the _symval operator. However, the portable way to
access such linker symbols across TI targets is to use _symval(&mySymbol).
Suppose your linker command file defines the following linker symbol:
abs_sym=0x12345678;
Your C application can refer to this symbol as follows:
extern char abs_sym;
printf("abs_sym %lx\n", _symval(&abs_sym));
8.6.2 Declaring Weak Symbols
In a linker command file, an assignment expression outside a MEMORY or SECTIONS directive can be
used to define a linker-defined symbol. To define a weak symbol in a linker command file, use the "weak"
operator in an assignment expression to designate that the symbol as eligible for removal from the output
file's symbol table if it is not referenced. For example, you can define "ext_addr_sym" as follows:
weak(ext_addr_sym) = 0x12345678;
When the linker command file is used to perform the final link, then "ext_addr_sym" is presented to the
linker as a weak absolute symbol; it will not be included in the resulting output file if the symbol is not
referenced.
See Section 2.6.2 for details about how weak symbols are handled by the linker.
8.6.3 Resolving Symbols with Object Libraries
An object library is a partitioned archive file that contains object files as members. Usually, a group of
related modules are grouped together into a library. When you specify an object library as linker input, the
linker includes any members of the library that define existing unresolved symbol references. You can use
the archiver to build and maintain libraries. Section 7.1 contains more information about the archiver.
Using object libraries can reduce link time and the size of the executable module. Normally, if an object
file that contains a function is specified at link time, the file is linked whether the function is used or not;
however, if that same function is placed in an archive library, the file is included only if the function is
referenced.
The order in which libraries are specified is important, because the linker includes only those members
that resolve symbols that are undefined at the time the library is searched. The same library can be
specified as often as necessary; it is searched each time it is included. Alternatively, you can use the -reread_libs option to reread libraries until no more references can be resolved (see Section 8.4.16.3). A
library has a table that lists all external symbols defined in the library; the linker searches through the table
until it determines that it cannot use the library to resolve any more references.
The following examples link several files and libraries, using these assumptions:
• Input files f1.obj and f2.obj both reference an external function named clrscr.
• Input file f1.obj references the symbol origin.
• Input file f2.obj references the symbol fillclr.
• Member 0 of library libc.lib contains a definition of origin.
• Member 3 of library liba.lib contains a definition of fillclr.
• Member 1 of both libraries defines clrscr.
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If you enter:
cl6x --run_linker f1.obj f2.obj liba.lib libc.lib
then:
• Member 1 of liba.lib satisfies the f1.obj and f2.obj references to clrscr because the library is searched
and the definition of clrscr is found.
• Member 0 of libc.lib satisfies the reference to origin.
• Member 3 of liba.lib satisfies the reference to fillclr.
If, however, you enter:
cl6x --run_linker f1.obj f2.obj libc.lib liba.lib
then the references to clrscr are satisfied by member 1 of libc.lib.
If none of the linked files reference symbols defined in a library, you can use the --undef_sym option to
force the linker to include a library member. (See Section 8.4.32.) The next example creates an undefined
symbol rout1 in the linker's global symbol table:
cl6x --run_linker --undef_sym=rout1 libc.lib
If any member of libc.lib defines rout1, the linker includes that member.
Library members are allocated according to the SECTIONS directive default allocation algorithm; see
Section 8.5.5.
Section 8.4.16 describes methods for specifying directories that contain object libraries.
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8.7
Default Placement Algorithm
The MEMORY and SECTIONS directives provide flexible methods for building, combining, and allocating
sections. However, any memory locations or sections you choose not to specify must still be handled by
the linker. The linker uses algorithms to build and allocate sections in coordination with any specifications
you do supply.
If you do not use the MEMORY and SECTIONS directives, the linker allocates output sections as though
the memory map and section definitions were as shown in Example 8-16 were specified.
Example 8‑16. Default Allocation for TMS320C6000 Devices
MEMORY
{
RAM
}
: origin = 0x00000001, length = 0xFFFFFFFE
SECTIONS
{
.text :
.const :
.data :
.bss
:
.cinit :
.pinit :
.stack :
.far
:
.sysmem:
.switch:
.cio
:
}
ALIGN(32)
ALIGN(8)
ALIGN(8)
ALIGN(8)
ALIGN(4)
ALIGN(4)
ALIGN(8)
ALIGN(8)
ALIGN(8)
ALIGN(4)
ALIGN(4)
{}
{}
{}
{}
{}
{}
{}
{}
{}
{}
{}
>
>
>
>
>
>
>
>
>
>
>
RAM
RAM
RAM
RAM
RAM
RAM
RAM
RAM
RAM
RAM
RAM
;
;
;
;
;
;
;
cflag
cflag
cflag
cflag
cflag
cflag
cflag
option
option
option
option
option
option
option
only
only
only
only
only
only
only
Also see Section 2.5.1 for information about default memory allocation.
All .text input sections are concatenated to form a .text output section in the executable output file, and all
.data input sections are combined to form a .data output section.
If you use a SECTIONS directive, the linker performs no part of this default allocation. Instead, allocation
is performed according to the rules specified by the SECTIONS directive and the general algorithm
described next in Section 8.7.1.
8.7.1 How the Allocation Algorithm Creates Output Sections
An output section can be formed in one of two ways:
Method 1 As the result of a SECTIONS directive definition
Method 2 By combining input sections with the same name into an output section that is not defined in
a SECTIONS directive
If an output section is formed as a result of a SECTIONS directive, this definition completely determines
the section's contents. (See Section 8.5.5 for examples of how to define an output section's content.)
If an output section is formed by combining input sections not specified by a SECTIONS directive, the
linker combines all such input sections that have the same name into an output section with that name.
For example, suppose the files f1.obj and f2.obj both contain named sections called Vectors and that the
SECTIONS directive does not define an output section for them. The linker combines the two Vectors
sections from the input files into a single output section named Vectors, allocates it into memory, and
includes it in the output file.
By default, the linker does not display a message when it creates an output section that is not defined in
the SECTIONS directive. You can use the --warn_sections linker option (see Section 8.4.33) to cause the
linker to display a message when it creates a new output section.
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After the linker determines the composition of all output sections, it must allocate them into configured
memory. The MEMORY directive specifies which portions of memory are configured. If there is no
MEMORY directive, the linker uses the default configuration as shown in Example 8-16. (See
Section 8.5.4 for more information on configuring memory.)
8.7.2 Reducing Memory Fragmentation
The linker's allocation algorithm attempts to minimize memory fragmentation. This allows memory to be
used more efficiently and increases the probability that your program will fit into memory. The algorithm
comprises these steps:
1. Each output section for which you supply a specific binding address is placed in memory at that
address.
2. Each output section that is included in a specific, named memory range or that has memory attribute
restrictions is allocated. Each output section is placed into the first available space within the named
area, considering alignment where necessary.
3. Any remaining sections are allocated in the order in which they are defined. Sections not defined in a
SECTIONS directive are allocated in the order in which they are encountered. Each output section is
placed into the first available memory space, considering alignment where necessary.
If you want to control the order in which code and data are placed in memory, see the FAQ topic on
section placement.
8.8
Linker-Generated Copy Tables
The linker supports extensions to the linker command file syntax that enable the following:
• Make it easier for you to copy objects from load-space to run-space at boot time
• Make it easier for you to manage memory overlays at run time
• Allow you to split GROUPs and output sections that have separate load and run addresses
8.8.1 Using Copy Tables for Boot Loading
In some embedded applications, there is a need to copy or download code and/or data from one location
to another at boot time before the application actually begins its main execution thread. For example, an
application may have its code and/or data in FLASH memory and need to copy it into on-chip memory
before the application begins execution.
One way to develop such an application is to create a copy table in assembly code that contains three
elements for each block of code or data that needs to be moved from FLASH to on-chip memory at boot
time:
• The load address
• The run address
• The size
The process you follow to develop such an application might look like this:
1. Build the application to produce a .map file that contains the load and run addresses of each section
that has a separate load and run placement.
2. Edit the copy table (used by the boot loader) to correct the load and run addresses as well as the size
of each block of code or data that needs to be moved at boot time.
3. Build the application again, incorporating the updated copy table.
4. Run the application.
This process puts a heavy burden on you to maintain the copy table (by hand, no less). Each time a piece
of code or data is added or removed from the application, you must repeat the process in order to keep
the contents of the copy table up to date.
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8.8.2 Using Built-in Link Operators in Copy Tables
You can avoid some of this maintenance burden by using the LOAD_START(), RUN_START(), and
SIZE() operators that are already part of the linker command file syntax . For example, instead of building
the application to generate a .map file, the linker command file can be annotated:
SECTIONS
{
.flashcode: { app_tasks.obj(.text) }
load = FLASH, run = PMEM,
LOAD_START(_flash_code_ld_start),
RUN_START(_flash_code_rn_start),
SIZE(_flash_code_size)
...
}
In this example, the LOAD_START(), RUN_START(), and SIZE() operators instruct the linker to create
three symbols:
Symbol
Description
_flash_code_ld_start
Load address of .flashcode section
_flash_code_rn_start
Run address of .flashcode section
_flash_code_size
Size of .flashcode section
These symbols can then be referenced from the copy table. The actual data in the copy table will be
updated automatically each time the application is linked. This approach removes step 1 of the process
described in Section 8.8.1.
While maintenance of the copy table is reduced markedly, you must still carry the burden of keeping the
copy table contents in sync with the symbols that are defined in the linker command file. Ideally, the linker
would generate the boot copy table automatically. This would avoid having to build the application twice
and free you from having to explicitly manage the contents of the boot copy table.
For more information on the LOAD_START(), RUN_START(), and SIZE() operators, see Section 8.5.10.7.
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8.8.3 Overlay Management Example
Consider an application that contains a memory overlay that must be managed at run time. The memory
overlay is defined using a UNION in the linker command file as illustrated in Example 8-17:
Example 8-17. Using a UNION for Memory Overlay
SECTIONS
{
...
UNION
{
GROUP
{
.task1: { task1.obj(.text) }
.task2: { task2.obj(.text) }
} load = ROM, LOAD_START(_task12_load_start), SIZE(_task12_size)
GROUP
{
.task3: { task3.obj(.text) }
.task4: { task4.obj(.text) }
} load = ROM, LOAD_START(_task34_load_start), SIZE(_task_34_size)
} run = RAM, RUN_START(_task_run_start)
...
}
The application must manage the contents of the memory overlay at run time. That is, whenever any
services from .task1 or .task2 are needed, the application must first ensure that .task1 and .task2 are
resident in the memory overlay. Similarly for .task3 and .task4.
To affect a copy of .task1 and .task2 from ROM to RAM at run time, the application must first gain access
to the load address of the tasks (_task12_load_start), the run address (_task_run_start), and the size
(_task12_size). Then this information is used to perform the actual code copy.
8.8.4 Generating Copy Tables With the table() Operator
The linker supports extensions to the linker command file syntax that enable you to do the following:
• Identify any object components that may need to be copied from load space to run space at some
point during the run of an application
• Instruct the linker to automatically generate a copy table that contains (at least) the load address, run
address, and size of the component that needs to be copied
• Instruct the linker to generate a symbol specified by you that provides the address of a linkergenerated copy table. For instance, Example 8-17 can be written as shown in Example 8-18:
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Example 8-18. Produce Address for Linker Generated Copy Table
SECTIONS
{
...
UNION
{
GROUP
{
.task1: { task1.obj(.text) }
.task2: { task2.obj(.text) }
} load = ROM, table(_task12_copy_table)
GROUP
{
.task3: { task3.obj(.text) }
.task4: { task4.obj(.text) }
} load = ROM, table(_task34_copy_table)
} run = RAM
...
}
Using the SECTIONS directive from Example 8-18 in the linker command file, the linker generates two
copy tables named: _task12_copy_table and _task34_copy_table. Each copy table provides the load
address, run address, and size of the GROUP that is associated with the copy table. This information is
accessible from application source code using the linker-generated symbols, _task12_copy_table and
_task34_copy_table, which provide the addresses of the two copy tables, respectively.
Using this method, you need not worry about the creation or maintenance of a copy table. You can
reference the address of any copy table generated by the linker in C/C++ or assembly source code,
passing that value to a general purpose copy routine, which will process the copy table and affect the
actual copy.
8.8.4.1
The table() Operator
You can use the table() operator to instruct the linker to produce a copy table. A table() operator can be
applied to an output section, a GROUP, or a UNION member. The copy table generated for a particular
table() specification can be accessed through a symbol specified by you that is provided as an argument
to the table() operator. The linker creates a symbol with this name and assigns it the address of the copy
table as the value of the symbol. The copy table can then be accessed from the application using the
linker-generated symbol.
Each table() specification you apply to members of a given UNION must contain a unique name. If a
table() operator is applied to a GROUP, then none of that GROUP's members may be marked with a
table() specification. The linker detects violations of these rules and reports them as warnings, ignoring
each offending use of the table() specification. The linker does not generate a copy table for erroneous
table() operator specifications.
Copy tables can be generated automatically; see Section 8.8.4. The table operator can be used with
compression; see Section 8.8.5.
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Boot-Time Copy Tables
The linker supports a special copy table name, BINIT (or binit), that you can use to create a boot-time
copy table. This table is handled before the .cinit section is used to initialize variables at startup. For
example, the linker command file for the boot-loaded application described in Section 8.8.2 can be
rewritten as follows:
SECTIONS
{
.flashcode: { app_tasks.obj(.text) }
load = FLASH, run = PMEM,
table(BINIT)
...
}
For this example, the linker creates a copy table that can be accessed through a special linker-generated
symbol, __binit__, which contains the list of all object components that need to be copied from their load
location to their run location at boot-time. If a linker command file does not contain any uses of
table(BINIT), then the __binit__ symbol is given a value of -1 to indicate that a boot-time copy table does
not exist for a particular application.
You can apply the table(BINIT) specification to an output section, GROUP, or UNION member. If used in
the context of a UNION, only one member of the UNION can be designated with table(BINIT). If applied to
a GROUP, then none of that GROUP's members may be marked with table(BINIT).The linker detects
violations of these rules and reports them as warnings, ignoring each offending use of the table(BINIT)
specification.
8.8.4.3
Using the table() Operator to Manage Object Components
If you have several pieces of code that need to be managed together, then you can apply the same table()
operator to several different object components. In addition, if you want to manage a particular object
component in multiple ways, you can apply more than one table() operator to it. Consider the linker
command file excerpt in Example 8-19:
Example 8-19. Linker Command File to Manage Object Components
SECTIONS
{
UNION
{
.first: { a1.obj(.text), b1.obj(.text), c1.obj(.text) }
load = EMEM, run = PMEM, table(BINIT), table(_first_ctbl)
.second: { a2.obj(.text), b2.obj(.text) }
load = EMEM, run = PMEM, table(_second_ctbl)
}
.extra: load = EMEM, run = PMEM, table(BINIT)
...
}
In this example, the output sections .first and .extra are copied from external memory (EMEM) into
program memory (PMEM) at boot time while processing the BINIT copy table. After the application has
started executing its main thread, it can then manage the contents of the overlay using the two overlay
copy tables named: _first_ctbl and _second_ctbl.
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8.8.4.4
Linker-Generated Copy Table Sections and Symbols
The linker creates and allocates a separate input section for each copy table that it generates. Each copy
table symbol is defined with the address value of the input section that contains the corresponding copy
table.
The linker generates a unique name for each overlay copy table input section. For example,
table(_first_ctbl) would place the copy table for the .first section into an input section called
.ovly:_first_ctbl. The linker creates a single input section, .binit, to contain the entire boot-time copy table.
Example 8-20 illustrates how you can control the placement of the linker-generated copy table sections
using the input section names in the linker command file.
Example 8-20. Controlling the Placement of the Linker-Generated Copy Table Sections
SECTIONS
{
UNION
{
.first: { a1.obj(.text), b1.obj(.text), c1.obj(.text) }
load = EMEM, run = PMEM, table(BINIT), table(_first_ctbl)
.second: { a2.obj(.text), b2.obj(.text) }
load = EMEM, run = PMEM, table(_second_ctbl)
}
.extra: load = EMEM, run = PMEM, table(BINIT)
...
.ovly: { } > BMEM
.binit: { } > BMEM
}
For the linker command file in Example 8-20, the boot-time copy table is generated into a .binit input
section, which is collected into the .binit output section, which is mapped to an address in the BMEM
memory area. The _first_ctbl is generated into the .ovly:_first_ctbl input section and the _second_ctbl is
generated into the .ovly:_second_ctbl input section. Since the base names of these input sections match
the name of the .ovly output section, the input sections are collected into the .ovly output section, which is
then mapped to an address in the BMEM memory area.
If you do not provide explicit placement instructions for the linker-generated copy table sections, they are
allocated according to the linker's default placement algorithm.
The linker does not allow other types of input sections to be combined with a copy table input section in
the same output section. The linker does not allow a copy table section that was created from a partial link
session to be used as input to a succeeding link session.
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Splitting Object Components and Overlay Management
It is possible to split sections that have separate load and run placement instructions. The linker can
access both the load address and run address of every piece of a split object component. Using the
table() operator, you can tell the linker to generate this information into a copy table. The linker gives each
piece of the split object component a COPY_RECORD entry in the copy table object.
For example, consider an application which has seven tasks. Tasks 1 through 3 are overlaid with tasks 4
through 7 (using a UNION directive). The load placement of all of the tasks is split among four different
memory areas (LMEM1, LMEM2, LMEM3, and LMEM4). The overlay is defined as part of memory area
PMEM. You must move each set of tasks into the overlay at run time before any services from the set are
used.
You can use table() operators in combination with splitting operators, >>, to create copy tables that have
all the information needed to move either group of tasks into the memory overlay as shown in Example 821.
Example 8-21. Creating a Copy Table to Access a Split Object Component
SECTIONS
{
UNION
{
.task1to3: { *(.task1), *(.task2), *(.task3) }
load >> LMEM1 | LMEM2 | LMEM4, table(_task13_ctbl)
GROUP
{
.task4:
.task5:
.task6:
.task7:
{
{
{
{
*(.task4)
*(.task5)
*(.task6)
*(.task7)
}
}
}
}
} load >> LMEM1 | LMEM3 | LMEM4, table(_task47_ctbl)
} run = PMEM
...
.ovly: > LMEM4
}
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Example 8-22 illustrates a possible driver for such an application.
Example 8-22. Split Object Component Driver
#include <cpy_tbl.h>
extern far COPY_TABLE task13_ctbl;
extern far COPY_TABLE task47_ctbl;
extern void task1(void);
...
extern void task7(void);
main()
{
...
copy_in(&task13_ctbl);
task1();
task2();
task3();
...
copy_in(&task47_ctbl);
task4();
task5();
task6();
task7();
...
}
You must declare a COPY_TABLE object as far to allow the overlay copy table section placement to be
independent from the other sections containing data objects (such as .bss).
The contents of the .task1to3 section are split in the section's load space and contiguous in its run space.
The linker-generated copy table, _task13_ctbl, contains a separate COPY_RECORD for each piece of the
split section .task1to3. When the address of _task13_ctbl is passed to copy_in(), each piece of .task1to3
is copied from its load location into the run location.
The contents of the GROUP containing tasks 4 through 7 are also split in load space. The linker performs
the GROUP split by applying the split operator to each member of the GROUP in order. The copy table for
the GROUP then contains a COPY_RECORD entry for every piece of every member of the GROUP.
These pieces are copied into the memory overlay when the _task47_ctbl is processed by copy_in().
The split operator can be applied to an output section, GROUP, or the load placement of a UNION or
UNION member. The linker does not permit a split operator to be applied to the run placement of either a
UNION or of a UNION member. The linker detects such violations, emits a warning, and ignores the
offending split operator usage.
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8.8.5 Compression
When automatically generating copy tables, the linker provides a way to compress the load-space data.
This can reduce the read-only memory foot print. This compressed data can be decompressed while
copying the data from load space to run space.
You can specify compression in two ways:
• The linker command line option --copy_compression=compression_kind can be used to apply the
specified compression to any output section that has a table() operator applied to it.
• The table() operator accepts an optional compression parameter. The syntax is: .
table( name , compression= compression_kind )
The compression_kind can be one of the following types:
– off. Don't compress the data.
– rle. Compress data using Run Length Encoding.
– lzss. Compress data using Lempel-Ziv-Storer-Szymanski compression.
A table() operator without the compression keyword uses the compression kind specified using the
command line option --copy_compression.
When you choose compression, it is not guaranteed that the linker will compress the load data. The linker
compresses load data only when such compression reduces the overall size of the load space. In some
cases even if the compression results in smaller load section size the linker does not compress the data if
the decompression routine offsets for the savings.
For example, assume RLE compression reduces the size of section1 by 30 bytes. Also assume the RLE
decompression routine takes up 40 bytes in load space. By choosing to compress section1 the load space
is increased by 10 bytes. Therefore, the linker will not compress section1. On the other hand, if there is
another section (say section2) that can benefit by more than 10 bytes from applying the same
compression then both sections can be compressed and the overall load space is reduced. In such cases
the linker compresses both the sections.
You cannot force the linker to compress the data when doing so does not result in savings.
You cannot compress the decompression routines or any member of a GROUP containing .cinit.
8.8.5.1
Compressed Copy Table Format
The copy table format is the same irrespective of the compression_kind. The size field of the copy record
is overloaded to support compression. Figure 8-5 illustrates the compressed copy table layout.
Figure 8-5. Compressed Copy Table
Rec size
Rec cnt
Load address
Run address
Size (0 if load data is compressed)
In Figure 8-5, if the size in the copy record is non-zero it represents the size of the data to be copied, and
also means that the size of the load data is the same as the run data. When the size is 0, it means that
the load data is compressed.
8.8.5.2
Compressed Section Representation in the Object File
The linker creates a separate input section to hold the compressed data. Consider the following table()
operation in the linker command file.
SECTIONS
{
.task1: load = ROM, run = RAM, table(_task1_table)
}
The output object file has one output section named .task1 which has different load and run addresses.
This is possible because the load space and run space have identical data when the section is not
compressed.
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Alternatively, consider the following:
SECTIONS
{
.task1: load = ROM, run = RAM, table(_task1_table, compression=rle)
}
If the linker compresses the .task1 section then the load space data and the run space data are different.
The linker creates the following two sections:
• .task1 : This section is uninitialized. This output section represents the run space image of section
task1.
• .task1.load : This section is initialized. This output section represents the load space image of the
section task1. This section usually is considerably smaller in size than .task1 output section.
The linker allocates load space for the .task1.load input section in the memory area that was specified for
load placement for the .task1 section. There is only a single load section to represent the load placement
of .task1 - .task1.load. If the .task1 data had not been compressed, there would be two allocations for the
.task1 input section: one for its load placement and another for its run placement.
8.8.5.3
Compressed Data Layout
The compressed load data has the following layout:
8-bit index
Compressed data
The first 8 bits of the load data are the handler index. This handler index is used to index into a handler
table to get the address of a handler function that knows how to decode the data that follows. The handler
table is a list of 32-bit function pointers as shown in Figure 8-6.
Figure 8-6. Handler Table
_TI_Handler_Table_Base:
32-bit handler address 1
32-bit handler address N
_TI_Handler_Table_Limit:
The linker creates a separate output section for the load and run space. For example, if .task1.load is
compressed using RLE, the handler index points to an entry in the handler table that has the address of
the run-time-support routine __TI_decompress_rle().
8.8.5.4
Run-Time Decompression
During run time you call the run-time-support routine copy_in() to copy the data from load space to run
space. The address of the copy table is passed to this routine. First the routine reads the record count.
Then it repeats the following steps for each record:
1. Read load address, run address and size from record.
2. If size is zero go to step 5.
3. Call memcpy passing the run address, load address and size.
4. Go to step 1 if there are more records to read.
5. Read the first byte from the load address. Call this index.
6. Read the handler address from (&__TI_Handler_Base)[index].
7. Call the handler and pass load address + 1 and run address.
8. Go to step 1 if there are more records to read.
The routines to handle the decompression of load data are provided in the run-time-support library.
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8.8.5.5
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Compression Algorithms
The following subsections provide information about decompression algorithms for the RLE and LZSS
formats. To see example decompression algorithms, refer to the following functions in the Run-Time
Support library:
• RLE: The __TI_decompress_rle() function in the copy_decompress_rle.c file.
• LZSS: The __TI_decompress_lzss() function in the copy_decompress_lzss.c file.
Additional information about compression algorithms can be found in the C6000 Embedded Application
Binary Interface Application Report (SPRAB89) EABI specification.
Run Length Encoding (RLE):
8-bit index
Initialization data compressed using run length encoding
The data following the 8-bit index is compressed using run length encoded (RLE) format. C6000 uses a
simple run length encoding that can be decompressed using the following algorithm:
1. Read the first byte, Delimiter (D).
2. Read the next byte (B).
3. If B != D, copy B to the output buffer and go to step 2.
4. Read the next byte (L).
(a) If L == 0, then length is either a 16-bit or 24-bit value, or we’ve reached the end of the data, read
next byte (L).
(i) If L == 0, length is a 24-bit value or the end of the data is reached, read next byte (L).
(i) If L == 0, the end of the data is reached, go to step 7.
(ii) Else L <<= 16, read next two bytes into lower 16 bits of L to complete 24-bit value for L.
(ii) Else L <<= 8, read next byte into lower 8 bits of L to complete 16-bit value for L.
(b) Else if L > 0 and L < 4, copy D to the output buffer L times. Go to step 2.
(c) Else, length is 8-bit value (L).
5. Read the next byte (C); C is the repeat character.
6. Write C to the output buffer L times; go to step 2.
7. End of processing.
The C6000 run-time support library has a routine __TI_decompress_rle24() to decompress data
compressed using RLE. The first argument to this function is the address pointing to the byte after the 8bit index. The second argument is the run address from the C auto initialization record.
RLE Decompression Routine
NOTE: The previous decompression routine, __TI_decompress_rle(), is included in the run-timesupport library for decompressing RLE encodings that are generated by older versions of the
linker.
Lempel-Ziv-Storer-Szymanski Compression (LZSS):
8-bit index
Data compressed using LZSS
The data following the 8-bit index is compressed using LZSS compression. The C6000 run-time-support
library has the routine __TI_decompress_lzss() to decompress the data compressed using LZSS. The first
argument to this function is the address pointing to the byte after the 8-bit Index, and the second argument
is the run address from the C auto initialization record.
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8.8.6 Copy Table Contents
To use a copy table generated by the linker, you must know the contents of the copy table. This
information is included in a run-time-support library header file, cpy_tbl.h, which contains a C source
representation of the copy table data structure that is generated by the linker. Example 8-23 shows the
copy table header file.
Example 8-23. TMS320C6000 cpy_tbl.h File
/****************************************************************************/
/* cpy_tbl.h
*/
/*
*/
/* Copyright (c) 2011 Texas Instruments Incorporated
*/
/*
*/
/* Specification of copy table data structures which can be automatically
*/
/* generated by the linker (using the table() operator in the LCF).
*/
/*
*/
/****************************************************************************/
/****************************************************************************/
/* Copy Record Data Structure
*/
/****************************************************************************/
typedef struct copy_record
{
unsigned int load_addr;
unsigned int run_addr;
unsigned int size;
} COPY_RECORD;
/****************************************************************************/
/* Copy Table Data Structure
*/
/****************************************************************************/
typedef struct copy_table
{
unsigned short rec_size;
unsigned short num_recs;
COPY_RECORD
recs[1];
} COPY_TABLE;
/****************************************************************************/
/* Prototype for general purpose copy routine.
*/
/****************************************************************************/
extern void copy_in(COPY_TABLE *tp);
#ifdef __cplusplus
} /* extern "C" namespace std */
#ifndef _CPP_STYLE_HEADER
using std::COPY_RECORD;
using std::COPY_TABLE;
using std::copy_in;
#endif /* _CPP_STYLE_HEADER */
#endif /* __cplusplus */
#endif /* !_CPY_TBL */
For each object component that is marked for a copy, the linker creates a COPY_RECORD object for it.
Each COPY_RECORD contains at least the following information for the object component:
• The load address
• The run address
• The size
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The linker collects all COPY_RECORDs that are associated with the same copy table into a
COPY_TABLE object. The COPY_TABLE object contains the size of a given COPY_RECORD, the
number of COPY_RECORDs in the table, and the array of COPY_RECORDs in the table. For instance, in
the BINIT example in Section 8.8.4.2, the .first and .extra output sections will each have their own
COPY_RECORD entries in the BINIT copy table. The BINIT copy table will then look like this:
COPY_TABLE __binit__ = { 12, 2,
{ <load address of .first>,
<run address of .first>,
<size of .first> },
{ <load address of .extra>,
<run address of .extra>,
<size of .extra> } };
8.8.7 General Purpose Copy Routine
The cpy_tbl.h file in Example 8-23 also contains a prototype for a general-purpose copy routine, copy_in(),
which is provided as part of the run-time-support library. The copy_in() routine takes a single argument:
the address of a linker-generated copy table. The routine then processes the copy table data object and
performs the copy of each object component specified in the copy table.
The copy_in() function definition is provided in the cpy_tbl.c run-time-support source file shown in
Example 8-24.
Example 8-24. Run-Time-Support cpy_tbl.c File
/****************************************************************************/
/* cpy_tbl.c
*/
/*
*/
/* Copyright (c) 2011 Texas Instruments Incorporated
*/
/*
*/
/* General purpose copy routine. Given the address of a link-generated
*/
/* COPY_TABLE data structure, effect the copy of all object components
*/
/* that are designated for copy via the corresponding LCF table() operator. */
/*
*/
/****************************************************************************/
#include <cpy_tbl.h>
#include <string.h>
typedef void (*handler_fptr)(const unsigned char *in, unsigned char *out);
/****************************************************************************/
/* COPY_IN()
*/
/****************************************************************************/
void copy_in(COPY_TABLE *tp)
{
unsigned short I;
for (I = 0; I < tp->num_recs; I++)
{
COPY_RECORD crp = tp->recs[i];
unsigned char *ld_addr = (unsigned char *)crp.load_addr;
unsigned char *rn_addr = (unsigned char *)crp.run_addr;
if (crp.size)
{
/*------------------------------------------------------------------*/
/* Copy record has a non-zero size so the data is not compressed.
*/
/* Just copy the data.
*/
/*------------------------------------------------------------------*/
memcpy(rn_addr, ld_addr, crp.size);
}
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Example 8-24. Run-Time-Support cpy_tbl.c File (continued)
#ifdef __TI_EABI__
else if (HANDLER_TABLE)
{
/*------------------------------------------------------------------*/
/* Copy record has size zero so the data is compressed. The first
*/
/* byte of the load data has the handler index. Use this index with */
/* the handler table to get the handler for this data. Then call
*/
/* the handler by passing the load and run address.
*/
/*------------------------------------------------------------------*/
unsigned char index = *((unsigned char *)ld_addr++);
handler_fptr hndl = (handler_fptr)(&HANDLER_TABLE)[index];
(*hndl)((const unsigned char *)ld_addr, (unsigned char *)rn_addr);
}
#endif
}
}
8.9
Partial (Incremental) Linking
An output file that has been linked can be linked again with additional modules. This is known as partial
linking or incremental linking. Partial linking allows you to partition large applications, link each part
separately, and then link all the parts together to create the final executable program.
Follow these guidelines for producing a file that you will relink:
• The intermediate files produced by the linker must have relocation information. Use the --relocatable
option when you link the file the first time. (See Section 8.4.3.2.)
• Intermediate files must have symbolic information. By default, the linker retains symbolic information in
its output. Do not use the --no_sym_table option if you plan to relink a file, because --no_sym_table
strips symbolic information from the output module. (See Section 8.4.22.)
• Intermediate link operations should be concerned only with the formation of output sections and not
with allocation. All allocation, binding, and MEMORY directives should be performed in the final link.
Since the ELF object file format is used, input sections are not combined into output sections during a
partial link unless a matching SECTIONS directive is specified in the link step command file.
• If the intermediate files have global symbols that have the same name as global symbols in other files
and you want them to be treated as static (visible only within the intermediate file), you must link the
files with the --make_static option (see Section 8.4.17.1).
• If you are linking C code, do not use --ram_model or --rom_model until the final linker. Every time you
invoke the linker with the --ram_model or --rom_model option, the linker attempts to create an entry
point. (See Section 8.4.25, Section 3.3.2.1, and Section 3.3.2.2.)
The following example shows how you can use partial linking:
Step 1:
Link the file file1.com; use the --relocatable option to retain relocation information in the
output file tempout1.out.
cl6x --run_linker --relocatable --output_file=tempout1 file1.com
file1.com contains:
SECTIONS
{
ss1:
{
f1.obj
f2.obj
.
.
.
fn.obj
}
}
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Linking C/C++ Code
Step 2:
www.ti.com
Link the file file2.com; use the --relocatable option to retain relocation information in the
output file tempout2.out.
cl6x --run_linker --relocatable --output_file=tempout2 file2.com
file2.com contains:
SECTIONS
{
ss2:
{
g1.obj
g2.obj
.
.
.
gn.obj
}
}
Step 3:
Link tempout1.out and tempout2.out.
cl6x --run_linker --map_file=final.map -output_file=final.out tempout1.out tempout2.out
8.10 Linking C/C++ Code
The C/C++ compiler produces assembly language source code that can be assembled and linked. For
example, a C program consisting of modules prog1, prog2, etc., can be assembled and then linked to
produce an executable file called prog.out:
cl6x --run_linker --rom_model -output_file prog.out prog1.obj prog2.obj ... rts6600_elf.lib
The --rom_model option tells the linker to use special conventions that are defined by the C/C++
environment.
The archive libraries shipped by TI contain C/C++ run-time-support functions.
C, C++, and mixed C and C++ programs can use the same run-time-support library. Run-time-support
functions and variables that can be called and referenced from both C and C++ will have the same
linkage.
For more information about the TMS320C6000 C/C++ language, including the run-time environment and
run-time-support functions, see the TMS320C6000 Optimizing Compiler User's Guide.
8.10.1 Run-Time Initialization
All C/C++ programs must be linked with code to initialize and execute the program, called a bootstrap
routine, also known as the boot.obj object module. The symbol _c_int00 is defined as the program entry
point and is the start of the C boot routine in boot.obj; referencing _c_int00 ensures that boot.obj is
automatically linked in from the run-time-support library. When a program begins running, it executes
boot.obj first. The boot.obj symbol contains code and data for initializing the run-time environment and
performs the following tasks:
• Sets up the system stack and configuration registers
• Processes the run-time .cinit initialization table and autoinitializes global variables (when the linker is
invoked with the --rom_model option)
• Disables interrupts and calls _main
The run-time-support object libraries contain boot.obj. You can:
• Use the archiver to extract boot.obj from the library and then link the module in directly.
• Include the appropriate run-time-support library as an input file (the linker automatically extracts
boot.obj when you use the --ram_model or --rom_model option).
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8.10.2 Object Libraries and Run-Time Support
The TMS320C6000 Optimizing Compiler User's Guide describes additional run-time-support functions that
are included in rts.src. If your program uses any of these functions, you must link the appropriate run-timesupport library with your object files.
You can also create your own object libraries and link them. The linker includes and links only those
library members that resolve undefined references.
8.10.3 Setting the Size of the Stack and Heap Sections
The C/C++ language uses two uninitialized sections called .sysmem and .stack for the memory pool used
by the malloc( ) functions and the run-time stacks, respectively. You can set the size of these by using the
--heap_size or --stack_size option and specifying the size of the section as a 4-byte constant immediately
after the option. If the options are not used, the default size of the heap is 1K bytes and the default size of
the stack is 1K bytes.
See Section 8.4.14 for setting heap sizes and Section 8.4.28 for setting stack sizes.
8.10.4 Initializing and AutoInitialzing Variables at Run Time
Autoinitializing variables at run time is the default method of autoinitialization. To use this method, invoke
the linker with the --rom_model option. See Section 3.3.2.1 for details.
Initialization of variables at load time enhances performance by reducing boot time and by saving the
memory used by the initialization tables. To use this method, invoke the linker with the --ram_model
option. See Section 3.3.2.2 for details.
See Section 3.3.2.3 for information about the steps that are performed when you invoke the linker with the
--ram_model or --rom_model option.
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8.11 Linker Example
This example links three object files named demo.obj, filter.obj, tables.obj, and lex.obj and creates a
program called demo.out.
Assume that target memory has the following program memory configuration:
Address Range
0x00000020 to 0x00210000
0x00400000 to 0x01400000
0x01400000 to 0x01800000
0x02000000 to 0x03000000
0x03000000 to 0x04000000
0x80000000 to 0x82000000
Contents
PMEM
EXT0
EXT1
EXT2
EXT3
BMEM
The output sections are constructed in the following manner:
• Executable code, contained in the .text sections of demo.obj, filters.obj, and lex.obj, as well as
executable code from the RTS library, are linked into program memory PMEM.
• Two data objects are defined in tables.obj. Each is placed in its own output section: .tableA and
.tableB. When the program is loaded, both the .tableA and .tableB output sections are linked into
separate locations in the BMEM area. However, run-time access to these tables refers to the run-time
location indicated by the symbol "filter_matrix", which is defined as the start address of the UNION
containing both .tableA and .tableB. This location is linked into the EXT1 memory area. At run-time, the
application is responsible for copying either .tableA or .tableB from its load location in BMEM to its run
location in EXT1 before attempting to access data from the table that was copied. The linker supports
the copy table mechanisms described in Section 8.8 to help facilitate this action.
• All data objects that are accessed using DP-relative addressing are collected into a group consisting of
the .neardata, .rodata, and .bss output sections. This group is linked into the BMEM memory area.
• Since the demo.out program uses command line arguments that must be specified when demo.out is
loaded and run, the application must reserve space for passing command-line arguments to the
program in the .args section. The amount of space allocated for the .args section is indicated in the '-args 0x1000' option near the top of the linker command file. The .args output section is then linked into
the BMEM memory area. Support for processing command-line arguments is provided in the boot
routine contained in the RTS library that will be linked into the demo.out program.
• The size of the software stack is indicated by the "--stack 0x6000" option near the top of the linker
command file. Likewise, the size of the heap, from which memory can be dynamically allocated at runtime, is indicated via the "--heap 0x3000" option near the top of the linker command file. Both the
.stack and .sysmem (which contains the heap) output sections are linked into the BMEM memory area.
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Example 8-25 shows the linker command file for this example. Example 8-26 shows the map file.
Example 8‑25. Linker Command File, mylnk.cmd
/****************************************************************************/
/*** Specify Linker Options
***/
/****************************************************************************/
-c
--heap 0x3000
--stack 0x6000
--args 0x1000
--output_file=demo.out
--map_file=demo.map
/* Name the output file
/* Create an output map file
*/
*/
-u filter_table_A
-u filter_table_B
/****************************************************************************/
/*** Specify the Input Files
***/
/****************************************************************************/
demo.obj
tables.obj
filter.obj
lex.obj
/****************************************************************************/
/*** Specify Runtime Support Library to be linked in
***/
/****************************************************************************/
-l libc.a
/****************************************************************************/
/*** Specify the Memory Configuration
***/
/****************************************************************************/
MEMORY
{
PMEM:
o = 00000020h
l = 0020ffe0h
EXT0:
o = 00400000h
l = 01000000h
EXT1:
o = 01400000h
l = 00400000h
EXT2:
o = 02000000h
l = 01000000h
EXT3:
o = 03000000h
l = 01000000h
BMEM:
o = 80000000h
l = 02000000h
}
/****************************************************************************/
/* Specify the Output Sections ***/
/****************************************************************************/
SECTIONS
{
.text :
> PMEM
UNION
{
.tableA: { tables.obj(.tableA) } load > BMEM, table(tableA_cpy)
.tableB: { tables.obj(.tableB) } load > BMEM, table(tableB_cpy)
} RUN = EXT1, RUN_START(filter_matrix)
GROUP
{
.neardata:
.rodata:
.bss:
} > EXT2
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Example 8‑25. Linker Command File, mylnk.cmd (continued)
.stack:
.args :
.cinit:
.cio:
.const:
.data:
.switch:
.sysmem:
.far:
.fardata:
.ppinfo:
>
>
>
>
>
>
>
>
>
>
>
BMEM
BMEM
BMEM
BMEM
BMEM
BMEM
BMEM
BMEM
BMEM
BMEM
BMEM
}
/****************************************************************************/
/*** End of Command File ***/
/****************************************************************************/
Invoke the linker by entering the following command:
cl6x --run_linker mylnk.cmd
This creates the map file shown in Example 8-26 and an output file called demo.out that can be run on a
TMS320C6000.
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Example 8‑26. Output Map File, demo.map
OUTPUT FILE NAME:
<demo.out>
EENTRY POINT SYMBOL: "_c_int00"
address: 00007a00
MEMORY CONFIGURATION
name
---------------------PMEM
EXT0
EXT1
EXT2
EXT3
BMEM
origin
-------00000020
00400000
01400000
02000000
03000000
80000000
length
--------0020ffe0
01000000
00400000
01000000
01000000
02000000
used
-------00008080
00000000
00000030
0000001c
00000000
0000a9d4
unused
-------00207f60
01000000
003fffd0
00ffffe4
01000000
01ff562c
attr
---RWIX
RWIX
RWIX
RWIX
RWIX
RWIX
fill
--------
SEGMENT ALLOCATION MAP
run origin
---------00000020
00000020
00008080
01400000
01400000
01400000
01400000
02000000
02000000
80000000
80000000
80006000
80009000
80009000
8000a000
8000a398
8000a398
8000a620
8000a620
8000a768
8000a888
8000a888
8000a920
8000a920
load origin
----------00000020
00000020
00008080
8000a8c0
8000a8c0
8000a8f0
8000a8f0
02000000
02000000
80000000
80000000
80006000
80009000
80009000
8000a000
8000a398
8000a398
8000a620
8000a620
8000a768
8000a888
8000a888
8000a920
8000a920
length
---------00008080
00008060
00000020
00000030
00000030
00000030
00000030
0000001c
0000001c
00009000
00006000
00003000
00001398
00001000
00000398
00000288
00000288
00000268
00000148
00000120
00000038
00000038
000000b4
000000b4
init length
----------00008080
00008060
00000020
00000030
00000030
00000030
00000030
00000000
00000000
00000000
00000000
00000000
00001000
00001000
00000000
00000288
00000288
00000000
00000000
00000000
00000038
00000038
000000b4
000000b4
attrs
----r-x
r-x
r-rwrwrwrwrwrwrwrwrwrwrwrwr-r-rwrwrwr-r-r-r--
members
------.text
.ovly
.tableA
.tableB
.neardata
.stack
.sysmem
.args
.fardata
.const
.far
.cio
.switch
.cinit
SECTION ALLOCATION MAP
output
section
-------.text
page
---0
origin
---------00000020
00000020
000005e0
00000ba0
00001140
000015a0
attributes/
length
input sections
---------- ---------------00008060
000005c0
rts6740_elf.lib
000005c0
000005a0
00000460
00000380
02000000
02000000
0000001c
0000001c
:
:
:
:
:
divd.obj (.text:__c6xabi_divd)
_printfi.obj (.text:_getarg_diouxp)
_printfi.obj (.text:_setfield)
_printfi.obj (.text:__TI_printfi)
fputs.obj (.text:fputs)
...
.neardata
*
0
UNINITIALIZED
lex.obj (.neardata)
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Example 8‑26. Output Map File, demo.map (continued)
.rodata
0
0200001c
00000000
UNINITIALIZED
.bss
0
0200001c
00000000
UNINITIALIZED
.stack
0
80000000
80000000
80000008
00006000
00000008
00005ff8
UNINITIALIZED
rts6740_elf.lib : boot.obj (.stack)
--HOLE--
.sysmem
0
80006000
80006000
80006008
00003000
00000008
00002ff8
UNINITIALIZED
rts6740_elf.lib : memory.obj (.sysmem)
--HOLE--
.args
0
80009000
80009000
00001000
00001000
--HOLE-- [fill = 0]
...
.tableA
0
8000a8c0
8000a8c0
00000030
00000030
RUN ADDR = 01400000
tables.obj (.tableA)
.tableB
0
8000a8f0
8000a8f0
00000030
00000030
RUN ADDR = 01400000
tables.obj (.tableB)
...
LINKER GENERATED COPY TABLES
tableA_cpy @ 00008080 records: 1, size/record: 12, table size: 16
.tableA: load addr=8000a8c0, load size=00000030, run addr=01400000,
run size=00000030, compression=none
tableB_cpy @ 00008090 records: 1, size/record: 12, table size: 16
.tableB: load addr=8000a8f0, load size=00000030, run addr=01400000,
run size=00000030, compression=none
__TI_cinit_table @ 8000a9bc records: 3, size/record: 8, table size: 24
.fardata: load addr=8000a920, load size=00000072 bytes, run addr=8000a000,
run size=00000398 bytes, compression=rle
.neardata: load addr=8000a994, load size=00000014 bytes, run addr=02000000,
run size=0000001c bytes, compression=rle
.far: load addr=8000a9b4, load size=00000008 bytes, run addr=8000a620,
run size=00000148 bytes, compression=zero_init
LINKER GENERATED HANDLER TABLE
__TI_handler_table @ 8000a9a8 records: 3, size/record: 4, table size: 12
index: 0, handler: __TI_decompress_rle24
index: 1, handler: __TI_decompress_none
index: 2, handler: __TI_zero_init
GLOBAL SYMBOLS: SORTED ALPHABETICALLY BY Name
address
name
---------00007fc0 C$$EXIT
00007700 C$$IO$$
000071c0 HOSTclose
00005d20 HOSTlseek
...
00008080 __TI_table_tableA_cpy
00008090 __TI_table_tableB_cpy
...
[121 symbols]
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8.12 Dynamic Linking with the C6000 Code Generation Tools
The C6000 v7.2 Code Generation Tools (CGT) support dynamic linking. If you are not already familiar with
the EABI support in the C6000 compiler, please see the C6000 Embedded Application Binary Interface
Application Report (SPRAB89).
The compiler generates object files in ELF object file format. The C6000 CGT makes use of the industrystandard dynamic linking mechanisms that are detailed in the ELF Specification (Tool Interface Standard).
8.12.1 Static vs Dynamic Linking
Static linking is the traditional process of combining relocatable object files and static libraries into a static
link unit: either an ELF executable file (.exe) or an ELF shared object (.so). The term object is used to
refer generically to either.
8.12.1.1 Code Size Reduction
A program consists of exactly one executable file (also commonly known as a client application) and any
additional shared objects (such as libraries) that it depends on to satisfy any undefined references. If
multiple executables depend on the same library, they can share a single copy of its code (hence the
“shared” in “shared object”), thereby significantly reducing the memory requirements of the system.
A dynamic shared object (DSO), as the name implies, can be shared among several applications that may
be running one-at-a-time in a single threaded environment, or at the same time in a multi-threaded
environment. Rather than making a separate copy of the DSO code in memory for each application that
needs to use it, a single version of the code can reside in one location (like ROM) where references to its
functions can be resolved as the executables and other DSOs that use it are loaded and dynamically
linked.
8.12.1.2 Binding Time
In a conventionally linked static executable, symbols are bound to addresses and library code is bound to
the executable at link-time, so the library that the executable is bound to at link-time is the one that it will
always use, regardless of changes or defect fixes that are made to the library.
In a static shared library, symbols are still bound to addresses at link-time, but the library code is not
bound to the executable that uses the library until run-time.
With a dynamic shared library, decisions about binding library symbols to addresses and resolving symbol
references between a dynamic shared library and the other objects that use it (or are used by it) are
delayed until actual load-time. This allows you to load a shared library when its services are needed, and
unload it when its services are not needed. Thus, making more effective use of limited target memory
space.
8.12.1.3 Modular Development
Dynamically linking encourages modular development. The interface for a dynamic shared object is
explicitly defined via the importing and exporting of global symbols. A cleanly defined interface for a
dynamic shared object will tend to improve the cohesion of the code that implements the services
provided by a given dynamic object.
8.12.1.4 Recommended Reading
For a more detailed discussion of the benefits and disadvantages of using dynamic executables and
dynamic shared objects, please refer to available literature on the subject, including John R. Levine's
excellent book Linkers & Loaders (ISBN-13: 978-1-55860-496-4).
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8.12.2 Bare-Metal Dynamic Linking Model
The bare-metal dynamic linking model is intended to support an application environment in which a Real
Time Operating System (RTOS) is loaded and running on a DSP processor.
8.12.2.1 Consider a Static DSP Application
First, consider an example of a basic DSP run-time model. If the RTOS and the applications that use it are
built as a single static executable, the resulting system will look something like this:
Figure 8-7. A Basic DSP Run-Time Model
DSP Memory
Application Tasks
Drivers
RTOS
(DSPBIOS)
DSP
In this scenario, the DSP application is a single static executable file that contains: the RTOS, any
required driver functions, and all tasks that the application needs to carry out. All of the addresses in the
static executable are bound at link-time, they cannot be relocated at load-time. Execution of the DSP
application will proceed from the application's entry point.
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8.12.2.2 Make it Dynamic
In a dynamic linking system you can build dynamic modules that are loaded and relocated by a dynamic
loader at run time. The dynamic loader can also perform dynamic symbol resolution: resolving symbol
references from dynamic modules with the symbol definitions from other dynamic modules. The dynamic
linking model supports the creation of such dynamic modules. In particular, it supports creating dynamic
executables and dynamic libraries.
A
•
•
•
•
•
•
dynamic executable:
Will have a dynamic segment
Can export/import symbols
Is optionally relocatable (can contain dynamic relocations)
Must have an entry point
Can be created using -c/-cr compiler options
Must use far DP or absolute addressing to access imported data, but can use near DP addressing to
access its own data
A
•
•
•
•
•
•
dynamic library:
Will have a dynamic segment
Can export/import symbols
Is relocatable
Does not require an entry point
Cannot be created using -c/-cr compiler option
Must use far DP or absolute addressing to access its own data as well as data that it imports from
other modules
Figure 8-8. Dynamic Linking Model
DSP Memory
DSP Dynamic Lib
Dynamically
Loaded Task
DSP Dynamic Exe
DSP Dynamic Lib
DSP Dynamic Exe
Application Tasks
Loader
GPP File
System
Drivers
RTOS
(DSPBIOS)
GPP OS
GPP
DSP
If we convert the earlier RTOS example into a dynamic system, the RTOS part of the system is still built
like an executable and is assumed to be loaded by traditional means (bootstrap loader) and set running on
the DSP by a host application.
Application tasks can be built as dynamic libraries that can then be loaded by the dynamic loader and
linked against the RTOS that is already loaded and running on the DSP. In this scenario, the RTOS is a
dynamic executable and is also sometimes referred to as the base image. The dynamic library is
dynamically linked against the RTOS base image at load time.
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In Figure 8-8, the dynamic loader is running on a General Purpose Processor (GPP) and is able to interact
with the user to load and unload dynamic library components onto the DSP as needed. Another scenario
is to load the dynamic loader as part of the RTOS base image executable:
Figure 8-9. Base Image Executable
DSP Memory
DSP Dynamic Lib
Dynamically
Loaded Task
DSP Dynamic Exe
Application Tasks
I/O
DSP Dynamic Lib
Drivers
Loader
RTOS
(DSPBIOS)
DSP
An example of this scenario is the reference implementation of the C6000 dynamic loader. It is written to
be built and run as a dynamic executable base image itself. It contains an interactive user interface which
allows the user to identify their own base image, load and link dynamic libraries against that base image,
and then execute a function that is defined in the dynamic library. For more details about the reference
implementation of the dynamic loader, please see the Dynamic Loader wiki article at
http://processors.wiki.ti.com/index.php/C6000_Dynamic_Loader.
8.12.2.3 Symbol Resolution
A dynamic library in a dynamic DSP application can utilize services that are provided by the RTOS. These
functions in the RTOS that are callable from a dynamic library must be exported when the RTOS is built.
Similarly, a dynamic library must import any function or data object symbols that are part of the RTOS
when the dynamic library is built.
Exported symbols in a dynamic object, dynA, are available for use by any other dynamic object that links
with dynA. When a dynamic object imports a symbol, it is asserting that when the object is loaded, the
definition of that symbol must be contained in a dynamic object that is already loaded or one that is
required to be loaded. The symbol importing and exporting mechanisms lie at the core of how dynamic
objects are designed to interact with each other. This subject is explored in more detail in
Section 8.12.4.1.
8.12.3 Building a Dynamic Executable
A dynamic executable is essentially a statically linked executable file that contains extra information in the
form of a dynamic segment that can be used when a dynamic library is loaded and needs symbols that
are defined in the dynamic executable.
In the sample system described here, the reference implementation of the dynamic loader (dl6x.6x) is built
as a base image. This base image also contains the basic I/O functions and some run-time-support (RTS)
functions. The base image should export these I/O and RTS functions. These symbols will then become
available to a dynamic library when it is dynamically loaded and linked against the dynamic executable.
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8.12.3.1 Exporting Symbols
To accomplish exporting of symbols, there are two methods available:
• Recommended: Declare exported symbols explicitly in the source of the dynamic executable using
__declspec(dllexport).
For example, if you want to export exp_func from the dynamic executable, you can declare it in your
source as follows:
__declspec(dllexport) int exp_func();
•
Use the --export option at link time. You can specify one or more symbols to be exported with -export=symbol on the linker command line or in a linker command file. For example, you could export
exp_func() at link time with:
cl6x ... -z --dynamic=exe --export=exp_func ...
In general, to build a dynamic executable, you must specify --dynamic=exe or --dynamic on the linker
command line or in a linker command file. Consider the build of the dl6x.6x file described in the
Dynamic Loader wiki article at http://processors.wiki.ti.com/index.php/C6000_Dynamic_Loader as an
example of how to build a dynamic executable or base image:
cl6x ... -z *.obj ... --dynamic --export=printf ...
In this example, the --dynamic option indicates that the result of the link is going to be a dynamic
executable. The --export=printf indicates that the printf() run-time-support function is exported by the
dynamic executable and, if imported by a dynamic library, can be called at run time by the functions
defined in the dynamic library.
8.12.4 Building a Dynamic Library
A dynamic library is a shared object that contains dynamic information in the form of a dynamic segment.
It is relocatable and can import symbols from other ELF dynamic objects that it links against and it can
also export symbols that it defines itself.
8.12.4.1 Importing/Exporting Symbols
Importing and exporting of symbols can be accomplished in two ways, similarly to how it can be done in
dynamic executables:
• Recommended: Declare exported and/or imported symbols explicitly in the source code of the
dynamic library using __declspec(dllexport) for exported symbols and __declspec(dllimport) for
imported symbols.
For example, if you want to export a function, red_fish(), and import another function, blue_fish(), you
could specify this in a source file as follows:
__declspec(dllexport) long red_fish();
__declspec(dllimport) int blue_fish();
•
You can also specify symbols to be imported or exported on the linker command line (or in a linker
command file) using --import=symbol or "--export=symbol.
So at link time, you might say:
cl6x ... -z --dynamic=lib --export=red_fish --import=blue_fish
blue.dll -o red.dll
This informs the linker that the definition of red_fish() will be in the red.dll dynamic library and that we
can find and use the definition of blue_fish() in blue.dll.
In general, to build a dynamic library, you must specify --dynamic=lib on the linker command line or in a
linker command file. In addition, if any symbols are imported from other dynamic objects, then those
dynamic objects must be specified on the linker command line when the dynamic library is built. This is
sometimes referred to as static binding.
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8.12.4.2 A Simple Example - hello.dll
This section describes a simple walk-through of the process used to build, load, and run a function that is
defined in a dynamic library.
• First compile this simple "Hello World" source:
hello.c:
#include <stdio.h>
__declspec(dllexport) int start();
int start()
{
printf("Hello World\n");
return 0;
}
•
Then build a dynamic library called hello.dll:
cl6x -mv6400+ hello.c -z --import=printf --dynamic=lib -o hello.dll
dl6x.6x -e start
•
Now, load the dynamic loader using a loader that supports C6000 ELF executable object files. Then
start the dynamic loader running. When using the reference implementation of the dynamic loader
(RIDL), you will see the RIDL prompt come up and then you need to issue the following commands:
RIDL> base_image dl6x.6x
RIDL> load hello.dll
RIDL> execute
You should see the "Hello World" message displayed and then control will return to the RIDL prompt.
To terminate the dynamic loader you can enter the exit command from the RIDL prompt.
For more details, see the Dynamic Loader wiki article
(http://processors.wiki.ti.com/index.php/C6000_Dynamic_Loader).
8.12.4.3 Summary of Compiler and Linker Options
This is a brief summary of the compiler and linker options that are related to support for the Dynamic
Linking Model in the C6000 CGT.
Table 8-13. Compiler Options For Dynamic Linking
Option
Description
--dsbt
Generates addressing via Dynamic Segment Base Table
--export_all_cpp_vtbl
Exports C++ virtual tables by default
--import_undef[=off|on]
Specifies that all global symbol references that are not defined in a module are imported. Default
is on.
--import_helper_functions
Specifies that all compiler generated calls to run-time-support functions are treated as calls to
imported functions. See Section 8.12.5.
--inline_plt[=off|on]
Inlines the import function call stub. Default is on.
--linux
Generates code for Linux.
--pic[=off|on]
Generates position independent addressing for a shared object. Default is near.
--visibility={hidden|
default|protected}
Specifies a default visibility to be assumed for global symbols. See Section 8.12.5.
–wchar_t
Generates 32-bit wchar_t type. By default the compiler generates 16-bit wchar_t.
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Table 8-14. Linker Options For Dynamic Linking
Option
Description
--dsbt_index=int
Requests a specific Data Segment Base Table (DSBT) index to be associated with the current output file. If the
DSBT model is being used, and you do not request a specific DSBT index for the output file, then a DSBT
index is assigned to the module at load time.
--dsbt_size=int
Specifies the size of the Data Segment Base Table (DSBT) for the current output file, in words. If the DSBT
model is being used, this option can be used to override the default DSBT size (8 words).
--dynamic[=exe]
Specifies that the result of a link will be a dynamic executable. See Section 8.12.3.1.
--dynamic=lib
Specifies that the result of a link will be a dynamic library. See Section 8.12.4.1.
--export=symbol
Specifies that symbol is exported by the ELF object that is generated for this link.
--fini=symbol
Specifies the symbol name of the termination code for the output file currently being linked.
--import=symbol
Specifies that symbol is imported by the ELF object that is generated for this link.
--init=symbol
Specifies the symbol name of the initialization code for the output file currently being linked.
--rpath=dir
Adds a directory to the beginning of the dynamic library search path.
--runpath=dir
Adds a directory to the end of the dynamic library search path.
--shared
Generates a dynamically shared object.
--soname=string
Specifies shared object name to be used to identify this ELF object to the any downstream ELF object
consumers.
--sysv
Generates SysV ELF output file.
8.12.5 Symbol Import/Export
In a dynamic linking system you can build dynamic modules that are loaded and relocated by a dynamic
loader at run time. The dynamic loader can also perform dynamic symbol resolution: resolve references
from dynamic modules with the definitions from other dynamic objects.
Only symbols explicitly imported or exported have dynamic linkage and participate in dynamic linking.
Normal global symbols don't participate in dynamic symbol resolution. A symbol is exported if it is visible
from a module during dynamic symbol resolution. A dynamic object is a dynamic library or a dynamic
executable. Such a dynamic object imports a symbol when its symbol references are resolved by
definitions from another dynamic object. The dynamic object that has the definition and makes it visible is
said to export the symbol.
8.12.5.1 ELF Symbols
ELF symbols have two attributes that contribute to static and dynamic symbol binding:
• Symbol Binding - symbol’s scope with respect to other files
• Symbol Visibility - symbol’s scope with respect to other run-time components (dynamic executable or
dynamic libraries)
A more detailed discussion of the symbol binding and visibility characteristics can be found in the ELF
Specification (Tool Interface Standard).
8.12.5.1.1 Symbol Binding Attribute Values
• STB_LOCAL
– Indicates that a symbol is not visible outside the module where it is defined.
– Any local references to the symbol will be resolved by the definition in the current module.
• STB_GLOBAL
– Indicates that a symbol is visible to all files being combined during the link step
– Any references to a global symbol that are left unresolved will result in a link-time error
• STB_WEAK
– Indicates that a symbol is visible to all files being combined during a link step.
– Global symbol definition takes precedence over corresponding weak symbol def.
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8.12.5.1.2 ELF Symbol Visibility
GLOBAL/WEAK symbols can have any of the following visibility attributes:
• STV_DEFAULT
– Symbol definition is visible outside the defining component.
– Symbol definition can be preempted.
– Symbol references can be resolved by definition outside the referenced component.
• STV_PROTECTED
– Symbol definition is visible outside the defining component.
– Symbol definition cannot be preempted.
– Symbol reference must be resolved by a definition in the same component.
• STV_HIDDEN
– Symbol definition is not visible outside its own component.
– Symbol reference must be resolved by a definition in the same component.
8.12.5.2 Controlling Import/Export of Symbols
Symbols can be imported/exported by using:
• Source Code Annotations
• ELF Linkage Macros
• Compiler Options
• Linker Options
8.12.5.2.1 Source Code Annotations (Recommended)
A global symbol can be imported or exported by adding a __declspec() symbol annotation to the source
file.
• Export Using __declspec(dllexport)
__declspec(dllexport) int foo() { }
•
__declspec(dllexport) can be applied to both symbol declarations and symbol definitions.
Import Using __declspec(dllimport)
__declspec(dllimport) int bar();
•
•
•
272
__declspec(dllimport) can be applied to a symbol declaration.
The compiler generates a warning if __declspec(dllimport) is applied to a symbol definition.
Typically an API is exported by a module and is imported by another module. __declspec() can be
added to the API header file
The linker uses the most restrictive visibility for symbols. For example, consider if the following were
true:
– foo() is declared with __declspec(dllimport) in a.c
– foo() is declared plain (no __declspec()) in b.c
– a.c and b.c are compiled into ab.dll
Then, the symbol, foo, is not imported in ab.dll and the linker reports an error indicating that the
reference to foo() is unresolved.
Some of the benefits of using the __declspec() approach include:
– It enables the compiler to generate more optimal code.
– The optimizer does not optimize out exported symbols.
– The source code becomes a self-documenting in specifying the API for a given module, making it
easier to read and maintain.
– It can be used in the Dynamic Linking Model
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8.12.5.2.2 Import/Export Using ELF Linkage Macros (elf_linkage.h)
The C6000 compiler provides a header file, elf_linkage.h, in the include sub-directory of the installed
toolset. The elf_linkage.h file defines several macros that can be used to control symbol visibility:
• TI_IMPORT symbol declaration
This macro imports the declared symbol. The TI_IMPORT macro cannot be applied to symbol
definitions.
TI_IMPORT int foo(void);
extern TI_IMPORT long global_variable;
•
TI_EXPORT symbol definition|symbol declaration
This macro exports the symbol that is being declared or defined. The source module that makes use of
this macro must contain a definition of the symbol.
TI_EXPORT int foo(void);
TI_EXPORT long global_variable;
•
TI_PATCHABLE symbol definition
This macro makes the definition of the symbol visible outside of the source module that uses it. Other
modules can import the defined symbol. Also, a reference to the symbol can be patched (or redirected) to a different definition of the symbol if needed. The compiler will generate an indirect call to a
function that has been marked as patchable. This technique is also sometimes called symbol
preemption.
TI_PATCHABLE int foo(void);
TI_PATCHABLE long global_variable;
•
•
•
TI_DEFAULT symbol definition|symbol declaration
This macro specifies that the symbol in question can be either imported or exported. The definition of
the symbol is visible outside the module. Other modules can import the symbol definition. Any
references to the symbol can also be patched.
TI_PROTECTED symbol definition|symbol declaration
This macro specifies that the symbol in question is visible outside of the module. Other modules can
import the symbol definition. However, a reference to the symbol can never be patched (symbol is nonpreemptable).
TI_HIDDEN symbol definition|symbol declaration
The definition of the symbol is not visible outside the module that defines it.
8.12.5.2.3 Import/Export Using Compiler Options
The following compiler options can be used to control the symbol visibility of global symbols. The symbols
using source code annotations to control the visibility are not affected by these compiler options.
• --visibility=default visibility
The --visibility option specifies the default visibility for global symbols. This option does not affect the
visibility of symbols that use the __declspec() or TI_xxx macros to specify a visibility in the source
code. The default visibility is one of the following:
– hidden - Global symbols are not imported or exported. This is the default compiler behavior.
– default - All global symbols are imported, exported, and patchable.
– protected - All global symbols are exported.
• --import_undef
The --import_undef option makes all of the global symbol references imported. This option can be
combined with the --visibility option. For example, the following option combination makes all
definitions exported and all references imported:
--import_undef --visibility=protected
The --import_undef option takes precedence over the --visibility option.
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--import_helper_functions
The compiler generates calls to functions that are defined in the run-time-support library. For example,
to perform unsigned long division in user code, the compiler generates a call to __c6xabi_divul. Since
there is no declaration and you do not call these functions directly, the __declspec() annotation cannot
be used. This prevents you from importing such functions from the run-time-support library that is built
as a dynamic library. To address this issue, the compiler supports the --import_helper_functions option.
When specified on the compiler command line, for each run-time-support function that is called by the
compiler, that function symbol will be imported.
8.12.5.2.4 Import/Export Using Linker Options
To import or export a symbol when the source code cannot be updated with a __declspec() annotation,
the following linker options can be used:
• --import=symbol
This option adds symbol to the dynamic symbol table as an imported reference. At link-time, the static
linker searches through any object libraries that are included in the link to make sure that a definition of
symbol is available.
If a definition of symbol is included in the current link, then the --import option is ignored with a
warning.
• --export=symbol
This option adds symbol to the dynamic symbol table as an exported definition. At link-time, if the are
any objects that contain an unresolved external reference to symbol when the object that exports
symbol is encountered, then the object that contains the exported definition is included in the link.
If the --export=symbol option is used on the compile of an object that does not have a definition of
symbol in it, then the compiler generates an error.
The --import and --export Options
NOTE: The --import and --export options cannot be used when building a Linux executable or DSO.
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Chapter 9
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Object File Utilities
This chapter describes how to invoke the following utilities:
• The object file display utility prints the contents of object files, executable files, and/or archive
libraries in both text and XML formats.
• The disassembler accepts object files and executable files as input and produces an assembly listing
as output. This listing shows assembly instructions, their opcodes, and the section program counter
values.
• The name utility prints a list of names defined and referenced in an object file, executable files, and/or
archive libraries.
• The strip utility removes symbol table and debugging information from object and executable files.
Topic
9.1
9.2
9.3
9.4
...........................................................................................................................
Invoking
Invoking
Invoking
Invoking
the
the
the
the
Object File Display Utility ................................................................
Disassembler ................................................................................
Name Utility...................................................................................
Strip Utility ....................................................................................
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276
277
278
278
275
Invoking the Object File Display Utility
9.1
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Invoking the Object File Display Utility
The object file display utility, ofd6x, prints the contents of object files (.obj), executable files (.out), and/or
archive libraries (.lib) in both text and XML formats. Hidden symbols are listed as no name, while localized
symbols are listed like any other local symbol.
To invoke the object file display utility, enter the following:
ofd6x [options] input filename [input filename]
ofd6x
input filename
options
276
is the command that invokes the object file display utility.
names the object file (.obj), executable file (.out), or archive library (.lib) source file.
The filename must contain an extension.
identify the object file display utility options that you want to use. Options are not case
sensitive and can appear anywhere on the command line following the command.
Precede each option with a hyphen.
-cg
Prints function stack usage and callee information in XML
format. While the XML output may be accessed by a
developer, this option was primarily designed to be used
by tools such as Code Composer Studio to display an
application’s worst case stack usage.
--dwarf_display=attributes Controls the DWARF display filter settings by specifying a
comma-delimited list of attributes. When prefixed with no,
an attribute is disabled instead of enabled.
Examples:
--dwarf_display=nodabbrev,nodline
--dwarf_display=all,nodabbrev
--dwarf_display=none,dinfo,types
The ordering of attributes is important (see --obj_display).
The list of available display attributes can be obtained by
invoking ofd6x --dwarf_display=help.
-g
Appends DWARF debug information to program output.
-h
Displays help
-o=filename
Sends program output to filename rather than to the
screen.
--obj_display attributes
Controls the object file display filter settings by specifying
a comma-delimited list of attributes. When prefixed with
no, an attribute is disabled instead of enabled.
Examples:
--obj_display=rawdata,nostrings
--obj_display=all,norawdata
--obj_display=none,header
The ordering of attributes is important. For instance, in "-obj_display=none,header", ofd6x disables all output, then
re-enables file header information. If the attributes are
specified in the reverse order, (header,none), the file
header is enabled, the all output is disabled, including the
file header. Thus, nothing is printed to the screen for the
given files. The list of available display attributes can be
obtained by invoking ofd6x --obj_display=help.
-v
Prints verbose text output.
-x
Displays output in XML format.
--xml_indent=num
Sets the number of spaces to indent nested XML tags.
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If an archive file is given as input to the object file display utility, each object file member of the archive is
processed as if it was passed on the command line. The object file members are processed in the order in
which they appear in the archive file.
If the object file display utility is invoked without any options, it displays information about the contents of
the input files on the console screen.
Object File Display Format
NOTE: The object file display utility produces data in a text format by default. This data is not
intended to be used as input to programs for further processing of the information. XML
format should be used for mechanical processing.
9.2
Invoking the Disassembler
The disassembler, dis6x, examines the output of the assembler or linker. This utility accepts an object file
or executable file as input and writes the disassembled object code to standard output or a specified file.
To invoke the disassembler, enter the following:
dis6x [options] input filename[.] [output filename]
dis6x
options
input
filename[.ext]
output filename
is the command that invokes the disassembler.
identifies the name utility options you want to use. Options are not case sensitive and
can appear anywhere on the command line following the invocation. Precede each
option with a hyphen (-). The name utility options are as follows:
-a
disables the printing of branch destination addresses along with labels.
-b
displays data as bytes instead of words.
-c
dumps the object file information.
-d
disables display of data sections.
-h
shows the current help screen.
-i
disassembles .data sections as instructions.
-l
disassembles data sections as text.
-n
suppresses FP header information for C64x+ Compact FPs.
-o##
disassembles single word ## or 0x## then exits.
-q
(quiet mode) suppresses the banner and all progress information.
-qq
(super quiet mode) suppresses all headers.
-s
suppresses printing of address and data words.
-t
suppresses the display of text sections in the listing.
-v
displays family of the target.
is the name of the input file. If the optional extension is not specified, the file is
searched for in this order:
1. infile
2. infile.out, an executable file
3. infile.obj, an object file
is the name of the optional output file to which the disassembly will be written. If an
output filename is not specified, the disassembly is written to standard output.
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9.3
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Invoking the Name Utility
The name utility, nm6x, prints the list of names defined and referenced in an object file, executable file, or
archive library. It also prints the symbol value and an indication of the kind of symbol. Hidden symbols are
listed as "".
To invoke the name utility, enter the following:
nm6x [-options] [input filenames]
nm6x
input filename
options
9.4
is the command that invokes the name utility.
is an object file (.obj), executable file (.out), or archive library (.lib).
identifies the name utility options you want to use. Options are not case sensitive and
can appear anywhere on the command line following the invocation. Precede each
option with a hyphen (-). The name utility options are as follows:
-a
prints all symbols.
-f
prepends file name to each symbol.
-g
prints only global symbols.
-h
shows the current help screen.
-l
produces a detailed listing of the symbol information.
-n
sorts symbols numerically rather than alphabetically.
-o file
outputs to the given file.
-p
causes the name utility to not sort any symbols.
-q
(quiet mode) suppresses the banner and all progress information.
-r
sorts symbols in reverse order.
-s
lists symbols in the dynamic symbol table for an ELF object module.
-u
only prints undefined symbols.
Invoking the Strip Utility
The strip utility, strip6x, removes symbol table and debugging information from object and executable files.
To invoke the strip utility, enter the following:
strip6x [-p] input filename [input filename]
strip6x
input filename
options
is the command that invokes the strip utility.
is an object file (.obj) or an executable file (.out).
identifies the strip utility options you want to use. Options are not case sensitive and can
appear anywhere on the command line following the invocation. Precede each option
with a hyphen (-). The strip utility option is as follows:
-o filename writes the stripped output to filename.
-p
removes all information not required for execution. This option causes more
information to be removed than the default behavior, but the object file is
left in a state that cannot be linked. This option should be used only with
static executable or dynamic object module files.
When the strip utility is invoked without the -o option, the input object files are replaced with the stripped
version.
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Chapter 10
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Hex Conversion Utility Description
The TMS320C6000 assembler and linker create object files which are in binary formats that encourage
modular programming and provide powerful and flexible methods for managing code segments and target
system memory.
Most EPROM programmers do not accept object files as input. The hex conversion utility converts an
object file into one of several standard ASCII hexadecimal formats, suitable for loading into an EPROM
programmer. The utility is also useful in other applications requiring hexadecimal conversion of an object
file (for example, when using debuggers and loaders).
The hex conversion utility can produce these output file formats:
• ASCII-Hex, supporting 32-bit addresses
• Extended Tektronix (Tektronix)
• Intel MCS-86 (Intel)
• Motorola Exorciser (Motorola-S), supporting 16-bit addresses
• Texas Instruments SDSMAC (TI-Tagged), supporting 16-bit addresses
• Texas Instruments TI-TXT format, supporting 16-bit addresses
Topic
...........................................................................................................................
10.1
10.2
10.3
10.4
10.5
10.6
10.7
10.8
10.9
10.10
10.11
10.12
The Hex Conversion Utility's Role in the Software Development Flow ....................
Invoking the Hex Conversion Utility ....................................................................
Understanding Memory Widths ..........................................................................
The ROMS Directive ..........................................................................................
The SECTIONS Directive ...................................................................................
The Load Image Format (--load_image Option) .....................................................
Excluding a Specified Section ............................................................................
Assigning Output Filenames ..............................................................................
Image Mode and the --fill Option .........................................................................
Controlling the ROM Device Address.................................................................
Control Hex Conversion Utility Diagnostics ........................................................
Description of the Object Formats .....................................................................
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10.1 The Hex Conversion Utility's Role in the Software Development Flow
Figure 10-1 highlights the role of the hex conversion utility in the software development process.
Figure 10-1. The Hex Conversion Utility in the TMS320C6000 Software Development Flow
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10.2 Invoking the Hex Conversion Utility
There are two basic methods for invoking the hex conversion utility:
• Specify the options and filenames on the command line. The following example converts the file
firmware.out into TI-Tagged format, producing two output files, firm.lsb and firm.msb.
hex6x -t firmware -o firm.lsb -o firm.msb
hex6x --ti_tagged firmware --outfile=firm.lsb --outfile=firm.msb
•
Specify the options and filenames in a command file. You can create a file that stores command
line options and filenames for invoking the hex conversion utility. The following example invokes the
utility using a command file called hexutil.cmd:
hex6x hexutil.cmd
In addition to regular command line information, you can use the hex conversion utility ROMS and
SECTIONS directives in a command file.
10.2.1 Invoking the Hex Conversion Utility From the Command Line
To invoke the hex conversion utility, enter:
hex6x [options] filename
hex6x
options
filename
is the command that invokes the hex conversion utility.
supplies additional information that controls the hex conversion process. You can use
options on the command line or in a command file. Table 10-1 lists the basic options.
• All options are preceded by a hyphen and are not case sensitive.
• Several options have an additional parameter that must be separated from the option
by at least one space.
• Options with multi-character names must be spelled exactly as shown in this
document; no abbreviations are allowed.
• Options are not affected by the order in which they are used. The exception to this rule
is the --quiet option, which must be used before any other options.
names an object file or a command file (for more information, see Section 10.2.2).
Table 10-1. Basic Hex Conversion Utility Options
Option
Alias
Description
See
General Options
--byte
-byte
Number output locations by bytes rather than by target
addressing
--entrypoint=addr
-e
Specify the entry point address or global symbol at which to
begin execution after boot loading
--exclude={fname(sname) |
sname}
-exclude
If the filename (fname) is omitted, all sections matching
sname will be excluded.
Section 10.7
--fill=value
-fill
Fill holes with value
Section 10.9.2
--help
-options, -h
Display the syntax for invoking the utility and list available
options. If the option is followed by another option or phrase,
detailed information about that option or phrase is displayed.
Section 10.2.2
For example, to see information about options associated with
generating a boot table, use --help boot.
--image
-image
Select image mode
Section 10.9.1
--linkerfill
-linkerfill
Include linker fill sections in images
--
--map=filename
-map
Generate a map file
Section 10.4.2
--memwidth=value
-memwidth
Define the system memory word width (default 32 bits)
Section 10.3.2
--order={L|M}
-order
Specify data ordering (endianness)
Section 10.3.4
--outfile=filename
-o
Specify an output filename
Section 10.8
--
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Table 10-1. Basic Hex Conversion Utility Options (continued)
Option
Alias
Description
See
--quiet
-q
Run quietly (when used, it must appear before other options)
Section 10.2.2
--romwidth=value
-romwidth
Specify the ROM device width (default depends on format
used). This option is ignored for the TI-TXT and TI-Tagged
formats.
Section 10.3.3
--zero
-zero, -z
Reset the address origin to 0 in image mode
Section 10.9.3
Diagnostic Options
--diag_error=id
Categorizes the diagnostic identified by id as an error
Section 10.11
--diag_remark=id
Categorizes the diagnostic identified by id as a remark
Section 10.11
--diag_suppress=id
Suppresses the diagnostic identified by id
Section 10.11
--diag_warning=id
Categorizes the diagnostic identified by id as a warning
Section 10.11
--display_error_number
Displays a diagnostic's identifiers along with its text
Section 10.11
--issue_remarks
Issues remarks (nonserious warnings)
Section 10.11
--no_warnings
Suppresses warning diagnostics (errors are still issued)
Section 10.11
--set_error_limit=count
Sets the error limit to count. The linker abandons linking after
this number of errors. (The default is 100.)
Section 10.11
--boot
-boot
Convert all initialized sections into bootable form (use instead
of a SECTIONS directive)
--bootorg=addr
-bootorg
Specify origin address of the boot loader table
--bootsection=section
-bootsection
Specify which section contains the boot routine and where it
should be placed
Boot Table Options
Output Options
--ascii
-a
Select ASCII-Hex
Section 10.12.1
--intel
-i
Select Intel
Section 10.12.2
--motorola=1
-m1
Select Motorola-S1
Section 10.12.3
--motorola=2
-m2
Select Motorola-S2
Section 10.12.3
--motorola=3
-m3
Select Motorola-S3 (default -m option)
Section 10.12.3
--tektronix
-x
Select Tektronix (default format when no output option is
specified)
Section 10.12.4
--ti_tagged
-t
Select TI-Tagged
Section 10.12.5
Select TI-Txt
Section 10.12.6
--ti_txt
Load Image Options
282
--load_image
Select load image
Section 10.6
--section_name_prefix=string
Specify the section name prefix for load image object files
Section 10.6
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10.2.2 Invoking the Hex Conversion Utility With a Command File
A command file is useful if you plan to invoke the utility more than once with the same input files and
options. It is also useful if you want to use the ROMS and SECTIONS hex conversion utility directives to
customize the conversion process.
Command files are ASCII files that contain one or more of the following:
• Options and filenames. These are specified in a command file in exactly the same manner as on the
command line.
• ROMS directive. The ROMS directive defines the physical memory configuration of your system as a
list of address-range parameters. (See Section 10.4.)
• SECTIONS directive. The hex conversion utility SECTIONS directive specifies which sections from the
object file are selected. (See Section 10.5.)
• Comments. You can add comments to your command file by using the /* and */ delimiters. For
example:
/*
This is a comment.
*/
To invoke the utility and use the options you defined in a command file, enter:
hex6x command_filename
You can also specify other options and files on the command line. For example, you could invoke the
utility by using both a command file and command line options:
hex6x firmware.cmd --map=firmware.mxp
The order in which these options and filenames appear is not important. The utility reads all input from the
command line and all information from the command file before starting the conversion process. However,
if you are using the -q option, it must appear as the first option on the command line or in a command file.
The --help option displays the syntax for invoking the compiler and lists available options. If the --help
option is followed by another option or phrase, detailed information about the option or phrase is
displayed. For example, to see information about options associated with generating a boot table use -help boot.
The --quiet option suppresses the hex conversion utility's normal banner and progress information.
• Assume that a command file named firmware.cmd contains these lines:
firmware.out
--ti_tagged
--outfile=firm.lsb
--outfile=firm.msb
/*
/*
/*
/*
input file
TI-Tagged
output file
output file
*/
*/
*/
*/
You can invoke the hex conversion utility by entering:
hex6x firmware.cmd
•
This example shows how to convert a file called appl.out into eight hex files in Intel format. Each output
file is one byte wide and 4K bytes long.
appl.out
--intel
--map=appl.mxp
/* input file
*/
/* Intel format */
/* map file
*/
ROMS
{
ROW1: origin=0x00000000 len=0x4000 romwidth=8
files={ appl.u0 appl.u1 app1.u2 appl.u3 }
ROW2: origin=0x00004000 len=0x4000 romwidth=8
files={ app1.u4 appl.u5 appl.u6 appl.u7 }
}
SECTIONS
{
.text, .data, .cinit, .sect1, .vectors, .const:
}
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10.3 Understanding Memory Widths
The hex conversion utility makes your memory architecture more flexible by allowing you to specify
memory and ROM widths. To use the hex conversion utility, you must understand how the utility treats
word widths. Three widths are important in the conversion process:
• Target width
• Memory width
• ROM width
The terms target word, memory word, and ROM word refer to a word of such a width.
Figure 10-2 illustrates the separate and distinct phases of the hex conversion utility's process flow.
Figure 10-2. Hex Conversion Utility Process Flow
Input file
Phase I
The raw data in the object file
is grouped into words according
to the size specified by the
--memwidth option.
Phase II
The memwidth-sized words are
broken up according to the size
specified by the --romwidth option
and are written to a file(s)
according to the specified format
(i.e., Intel, Tektronix, etc.).
Raw data in object files is
represented in the target’s
addressable units. For the
C6000, this is 32 bits.
Output file(s)
10.3.1 Target Width
Target width is the unit size (in bits) of the target processor's word. The width is fixed for each target and
cannot be changed. The TMS320C6000 targets have a width of 32 bits.
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10.3.2 Specifying the Memory Width
Memory width is the physical width (in bits) of the memory system. Usually, the memory system is
physically the same width as the target processor width: a 32-bit processor has a 32-bit memory
architecture. However, some applications require target words to be broken into multiple, consecutive, and
narrower memory words.
By default, the hex conversion utility sets memory width to the target width (in this case, 32 bits).
You can change the memory width (except for TI-TXT format) by:
• Using the --memwidth option. This changes the memory width value for the entire file.
• Setting the memwidth parameter of the ROMS directive. This changes the memory width value for the
address range specified in the ROMS directive and overrides the --memwidth option for that range.
See Section 10.4.
For both methods, use a value that is a power of 2 greater than or equal to 8.
You should change the memory width default value of 32 only when you need to break single target words
into consecutive, narrower memory words.
TI-TXT Format is 8 Bits Wide
NOTE: You cannot change the memory width of the TI-TXT format. The TI-TXT hex format supports
an 8-bit memory width only.
Figure 10-3 demonstrates how the memory width is related to object file data.
Figure 10-3. Object File Data and Memory Widths
Source file
.word
.word
0 A A B B CCDD h
011223344h
Object file data (assumed to be in little-endian format)
AA
BB
CC
DD
11
22
33
44
Memory widths (variable)
Data after
phase I
of hex6x
--memwidth=32 (default)
--memwidth=16
--memwidth=8
A A B B CCDD
CCDD
DD
11223344
AABB
CC
3344
BB
1122
AA
44
33
22
11
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10.3.3 Partitioning Data Into Output Files
ROM width determines how the hex conversion utility partitions the data into output files. ROM width
specifies the physical width (in bits) of each ROM device and corresponding output file (usually one byte
or eight bits). After the object file data is mapped to the memory words, the memory words are broken into
one or more output files. The number of output files is determined by the following formulas:
• If memory width ≥ ROM width:
number of files = memory width ÷ ROM width
• If memory width < ROM width:
number of files = 1
For example, for a memory width of 32, you could specify a ROM width value of 32 and get a single
output file containing 32-bit words. Or you can use a ROM width value of 16 to get two files, each
containing 16 bits of each word.
The default ROM width that the hex conversion utility uses depends on the output format:
• All hex formats except TI-Tagged are configured as lists of 8-bit bytes; the default ROM width for these
formats is 8 bits.
• TI-Tagged is a 16-bit format; the default ROM width for TI-Tagged is 16 bits.
The TI-Tagged Format is 16 Bits Wide
NOTE: You cannot change the ROM width of the TI-Tagged format. The TI-Tagged format supports
a 16-bit ROM width only.
TI-TXT Format is 8 Bits Wide
NOTE: You cannot change the ROM width of the TI-TXT format. The TI-TXT hex format supports
only an 8-bit ROM width.
You can change ROM width (except for TI-Tagged and TI-TXT formats) by:
• Using the --romwidth option. This option changes the ROM width value for the entire object file.
• Setting the romwidth parameter of the ROMS directive. This parameter changes the ROM width value
for a specific ROM address range and overrides the --romwidth option for that range. See
Section 10.4.
For both methods, use a value that is a power of 2 greater than or equal to 8.
If you select a ROM width that is wider than the natural size of the output format, the utility simply writes
multibyte fields into the file. The --romwidth option is ignored for the TI-TXT and TI-Tagged formats.
Figure 10-4 illustrates how the object file data, memory, and ROM widths are related to one another.
Memory width and ROM width are used only for grouping the object file data; they do not represent
values. Thus, the byte ordering of the object file data is maintained throughout the conversion process. To
refer to the partitions within a memory word, the bits of the memory word are always numbered from right
to left as follows:
--memwidth=32
A A B B C C D D 1 1 2 2 3 3 4 4
31
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Figure 10-4. Data, Memory, and ROM Widths
Source file
.word
.word
0 A A B B CCDD h
011223344h
Object file data (assumed to be in little-endian format)
AA
BB
CC
DD
11
22
33
44
Memory widths (variable)
--memwidth=32
--memwidth=16
--memwidth=8
A A B B CCDD
CCDD
DD
11223344
AABB
CC
3344
BB
1122
AA
Data after
phase I
of hex6x
44
33
22
11
Output files
--romwidth=8
Data after
phase II
of hex6x
--outfile=file.b0
DD 4 4
--outfile=file.b1
CC 3 3
--outfile=file.b2
BB 2 2
--outfile=file.b3
AA 1 1
--romwidth=16
--outfile=file.wrd CCDD A A B B 3 3 4 4 1 1 2 2
--romwidth=8
--outfile=file.b0
DD B B 4 4
22
--outfile=file.b1
CC A A 3 3
11
--romwidth=8
--outfile=file.byt
DDCC B B A A 4 4 3 3 2 2 1 1
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10.3.4 Specifying Word Order for Output Words
There are two ways to split a wide word into consecutive memory locations in the same hex conversion
utility output file:
• --order=M specifies big-endian ordering, in which the most significant part of the wide word occupies
the first of the consecutive locations.
• --order=L specifies little-endian ordering, in which the least significant part of the wide word occupies
the first of the consecutive locations.
By default, the utility uses little-endian format. Unless your boot loader program expects big-endian format,
avoid using --order=M.
When the -order Option Applies
NOTE:
•
•
This option applies only when you use a memory width with a value of 32 (-memwidth32). Otherwise, the hex utility does not have access to the entire 32-bit word
and cannot perform the byte swapping necessary to change the endianness; --order is
ignored.
This option does not affect the way memory words are split into output files. Think of the
files as a set: the set contains a least significant file and a most significant file, but there
is no ordering over the set. When you list filenames for a set of files, you always list the
least significant first, regardless of the --order option.
10.4 The ROMS Directive
The ROMS directive specifies the physical memory configuration of your system as a list of address-range
parameters.
Each address range produces one set of files containing the hex conversion utility output data that
corresponds to that address range. Each file can be used to program one single ROM device.
The ROMS directive is similar to the MEMORY directive of the TMS320C6000 linker: both define the
memory map of the target address space. Each line entry in the ROMS directive defines a specific
address range. The general syntax is:
ROMS
{
romname :
romname :
[origin=value,] [length=value,] [romwidth=value,]
[memwidth=value,] [fill=value]
[files={ filename 1, filename 2, ...}]
[origin=value,] [length=value,] [romwidth=value,]
[memwidth=value,] [fill=value]
[files={ filename 1, filename 2, ...}]
...
}
ROMS
romname
origin
288
begins the directive definition.
identifies a memory range. The name of the memory range can be one to eight
characters in length. The name has no significance to the program; it simply identifies
the range, except when the output is for a load image in which case it denotes the
section name. (Duplicate memory range names are allowed.)
specifies the starting address of a memory range. It can be entered as origin, org, or o.
The associated value must be a decimal, octal, or hexadecimal constant. If you omit
the origin value, the origin defaults to 0. The following table summarizes the notation
you can use to specify a decimal, octal, or hexadecimal constant:
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Constant
Notation
Example
Hexadecimal
0x prefix or h suffix
0x77 or 077h
Octal
0 prefix
077
Decimal
No prefix or suffix
77
length
romwidth
memwidth
fill
files
specifies the length of a memory range as the physical length of the ROM device. It
can be entered as length, len, or l. The value must be a decimal, octal, or hexadecimal
constant. If you omit the length, it defaults to the length of the entire address space.
specifies the physical ROM width of the range in bits (see Section 10.3.3). Any value
you specify here overrides the --romwidth option. The value must be a decimal, octal,
or hexadecimal constant that is a power of 2 greater than or equal to 8.
specifies the memory width of the range in bits (see Section 10.3.2). Any value you
specify here overrides the --memwidth option. The value must be a decimal, octal, or
hexadecimal constant that is a power of 2 greater than or equal to 8. When using the
memwidth parameter, you must also specify the paddr parameter for each section in
the SECTIONS directive. (See Section 10.5.)
specifies a fill value to use for the range. In image mode, the hex conversion utility
uses this value to fill any holes between sections in a range. A hole is an area between
the input sections that comprises an output section that contains no actual code or
data. The fill value must be a decimal, octal, or hexadecimal constant with a width
equal to the target width. Any value you specify here overrides the --fill option. When
using fill, you must also use the --image command line option. (See Section 10.9.2.)
identifies the names of the output files that correspond to this range. Enclose the list of
names in curly braces and order them from least significant to most significant output
file, where the bits of the memory word are numbered from right to left. The number of
file names must equal the number of output files that the range generates. To calculate
the number of output files, see Section 10.3.3. The utility warns you if you list too many
or too few filenames.
Unless you are using the --image option, all of the parameters that define a range are optional; the
commas and equal signs are also optional. A range with no origin or length defines the entire address
space. In image mode, an origin and length are required for all ranges.
Ranges must not overlap and must be listed in order of ascending address.
10.4.1 When to Use the ROMS Directive
If you do not use a ROMS directive, the utility defines a single default range that includes the entire
address space. This is equivalent to a ROMS directive with a single range without origin or length.
Use the ROMS directive when you want to:
• Program large amounts of data into fixed-size ROMs. When you specify memory ranges
corresponding to the length of your ROMs, the utility automatically breaks the output into blocks that fit
into the ROMs.
• Restrict output to certain segments. You can also use the ROMS directive to restrict the conversion
to a certain segment or segments of the target address space. The utility does not convert the data
that falls outside of the ranges defined by the ROMS directive. Sections can span range boundaries;
the utility splits them at the boundary into multiple ranges. If a section falls completely outside any of
the ranges you define, the utility does not convert that section and issues no messages or warnings.
Thus, you can exclude sections without listing them by name with the SECTIONS directive. However, if
a section falls partially in a range and partially in unconfigured memory, the utility issues a warning and
converts only the part within the range.
•
Use image mode. When you use the --image option, you must use a ROMS directive. Each range is
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filled completely so that each output file in a range contains data for the whole range. Holes before,
between, or after sections are filled with the fill value from the ROMS directive, with the value specified
with the --fill option, or with the default value of 0.
10.4.2 An Example of the ROMS Directive
The ROMS directive in Example 10-1 shows how 16K bytes of 16-bit memory could be partitioned for two
8K-byte 8-bit EPROMs. Figure 10-5 illustrates the input and output files.
Example 10-1. A ROMS Directive Example
infile.out
--image
--memwidth 16
ROMS
{
EPROM1: org = 0x00004000, len = 0x2000, romwidth = 8
files = { rom4000.b0, rom4000.b1}
EPROM2: org = 0x00006000, len = 0x2000, romwidth = 8,
fill = 0xFF00FF00,
files = { rom6000.b0, rom6000.b1}
}
Figure 10-5. The infile.out File Partitioned Into Four Output Files
The map file (specified with the --map option) is advantageous when you use the ROMS directive with
multiple ranges. The map file shows each range, its parameters, names of associated output files, and a
list of contents (section names and fill values) broken down by address. Example 10-2 is a segment of the
map file resulting from the example in Example 10-1.
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Example 10-2. Map File Output From Example 10-1 Showing Memory Ranges
----------------------------------------------------00004000..00005fff Page=0 Width=8 "EPROM1"
----------------------------------------------------OUTPUT FILES:
rom4000.b0
[b0..b7]
rom4000.b1
[b8..b15]
CONTENTS: 00004000..0000487f .text
00004880..00005b7f FILL = 00000000
00005b80..00005fff .data
----------------------------------------------------00006000..00007fff Page=0 Width=8 "EPROM2"
----------------------------------------------------OUTPUT FILES:
rom6000.b0
[b0..b7]
rom6000.b1
[b8..b15]
CONTENTS: 00006000..0000633f .data
00006340..000066ff FILL = ff00ff00
00006700..00007c7f .table
00007c80..00007fff FILL = ff00ff00
EPROM1 defines the address range from 0x00004000 through 0x00005FFF with the following sections:
This section ...
Has this range ...
.text
0x00004000 through 0x0000487F
.data
0x00005B80 through 0x00005FFF
The rest of the range is filled with 0h (the default fill value), converted into two output files:
• rom4000.b0 contains bits 0 through 7
• rom4000.b1 contains bits 8 through 15
EPROM2 defines the address range from 0x00006000 through 0x00007FFF with the following sections:
This section ...
Has this range ...
.data
0x00006000 through 0x0000633F
.table
0x00006700 through 0x00007C7F
The rest of the range is filled with 0xFF00FF00 (from the specified fill value). The data from this range is
converted into two output files:
• rom6000.b0 contains bits 0 through 7
• rom6000.b1 contains bits 8 through 15
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10.5 The SECTIONS Directive
You can convert specific sections of the object file by name with the hex conversion utility SECTIONS
directive. You can also specify those sections that you want to locate in ROM at a different address than
the load address specified in the linker command file. If you:
• Use a SECTIONS directive, the utility converts only the sections that you list in the directive and
ignores all other sections in the object file.
• Do not use a SECTIONS directive, the utility converts all initialized sections that fall within the
configured memory.
Uninitialized sections are never converted, whether or not you specify them in a SECTIONS directive.
Sections Generated by the C/C++ Compiler
NOTE: The TMS320C6000 C/C++ compiler automatically generates these sections:
•
Initialized sections: .text, .const, .cinit, and .switch
•
Uninitialized sections: .bss, .stack, and .sysmem
Use the SECTIONS directive in a command file. (See Section 10.2.2.) The general syntax is:
SECTIONS
{
oname(sname)[:] [paddr=value]
oname(sname)[:] [paddr= boot]
oname(sname)[:] [boot]
...
}
SECTIONS
oname
sname
paddr=value
boot
begins the directive definition.
identifies the object filename the section is located within. The filename is optional
when only a single input file is given, but required otherwise.
identifies a section in the input file. If you specify a section that does not exist, the
utility issues a warning and ignores the name.
specifies the physical ROM address at which this section should be located. This value
overrides the section load address given by the linker. This value must be a decimal,
octal, or hexadecimal constant. It can also be the word boot (to indicate a boot table
section for use with a boot loader). If your file contains multiple sections, and if one
section uses a paddr parameter, then all sections must use a paddr parameter.
configures a section for loading by a boot loader. This is equivalent to using
paddr=boot. Boot sections have a physical address determined by the location of the
boot table. The origin of the boot table is specified with the --bootorg option.
For more similarity with the linker's SECTIONS directive, you can use colons after the section names (in
place of the equal sign on the boot keyboard). For example, the following statements are equivalent:
SECTIONS { .text: .data: boot }
SECTIONS { .text: .data = boot }
In the example below, the object file contains six initialized sections: .text, .data, .const, .vectors, .coeff,
and .tables. Suppose you want only .text and .data to be converted. Use a SECTIONS directive to specify
this:
SECTIONS { .text: .data: }
To configure both of these sections for boot loading, add the boot keyword:
SECTIONS { .text = boot .data = boot }
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Using the --boot Option and the SECTIONS Directive
NOTE: When you use the SECTIONS directive with the boot table (--boot) option, the --boot option
is ignored. You must explicitly specify any boot sections in the SECTIONS directive. For
more information about --boot and other command line options associated with boot tables,
see Section 10.2.
10.6 The Load Image Format (--load_image Option)
A load image is an object file which contains the load addresses and initialized sections of one or more
executable files. The load image object file can be used for ROM masking or can be relinked in a
subsequent link step.
10.6.1 Load Image Section Formation
The load image sections are formed by collecting the initialized sections from the input executables. There
are two ways the load image sections are formed:
• Using the ROMS Directive. Each memory range that is given in the ROMS directive denotes a load
image section. The romname is the section name. The origin and length parameters are required. The
memwidth, romwidth, and files parameters are invalid and are ignored.
When using the ROMS directive and the load_image option, the --image option is required.
• Default Load Image Section Formation. If no ROMS directive is given, the load image sections are
formed by combining contiguous initialized sections in the input executables. Sections with gaps
smaller than the target word size are considered contiguous.
The default section names are image_1, image_2, ... If another prefix is desired, the -section_name_prefix=prefix option can be used.
10.6.2 Load Image Characteristics
All load image sections are initialized data sections. In the absence of a ROMS directive, the load/run
address of the load image section is the load address of the first input section in the load image section. If
the SECTIONS directive was used and a different load address was given using the paddr parameter, this
address will be used.
The load image format always creates a single load image object file. The format of the load image object
file is determined based on the input files. The file is not marked executable and does not contain an entry
point. The default load image object file name is ti_load_image.obj. This can be changed using the -outfile option. Only one --outfile option is valid when creating a load image, all other occurrences are
ignored.
Concerning Load Image Format
NOTE: These options are invalid when creating a load image:
•
•
•
•
•
--memwidth
--romwidth
--order
--zero
--byte
If a boot table is being created, either using the SECTIONS directive or the --boot option, the
ROMS directive must be used.
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10.7 Excluding a Specified Section
The --exclude section_name option can be used to inform the hex utility to ignore the specified section. If
a SECTIONS directive is used, it overrides the --exclude option.
For example, if a SECTIONS directive containing the section name mysect is used and an --exclude
mysect is specified, the SECTIONS directive takes precedence and mysect is not excluded.
The --exclude option has a limited wildcard capability. The * character can be placed at the beginning or
end of the name specifier to indicate a suffix or prefix, respectively. For example, --exclude sect*
disqualifies all sections that begin with the characters sect.
If you specify the --exclude option on the command line with the * wildcard, use quotes around the section
name and wildcard. For example, --exclude"sect*". Using quotes prevents the * from being interpreted by
the hex conversion utility. If --exclude is in a command file, do not use quotes.
If multiple object files are given, the object file in which the section to be excluded can be given in the form
oname(sname). If the object filename is not provided, all sections matching the section name are
excluded. Wildcards cannot be used for the filename, but can appear within the parentheses.
10.8 Assigning Output Filenames
When the hex conversion utility translates your object file into a data format, it partitions the data into one
or more output files. When multiple files are formed by splitting memory words into ROM words, filenames
are always assigned in order from least to most significant, where bits in the memory words are numbered
from right to left. This is true, regardless of target or endian ordering.
The hex conversion utility follows this sequence when assigning output filenames:
1. It looks for the ROMS directive. If a file is associated with a range in the ROMS directive and you
have included a list of files (files = {. . .}) on that range, the utility takes the filename from the list.
For example, assume that the target data is 32-bit words being converted to four files, each eight bits
wide. To name the output files using the ROMS directive, you could specify:
ROMS
{
RANGE1: romwidth=8, files={ xyz.b0 xyz.b1 xyz.b2 xyz.b3 }
}
The utility creates the output files by writing the least significant bits to xyz.b0 and the most significant
bits to xyz.b3.
2. It looks for the --outfile options. You can specify names for the output files by using the --outfile
option. If no filenames are listed in the ROMS directive and you use --outfile options, the utility takes
the filename from the list of --outfile options. The following line has the same effect as the example
above using the ROMS directive:
--outfile=xyz.b0 --outfile=xyz.b1 --outfile=xyz.b2 --outfile=xyz.b3
If both the ROMS directive and --outfile options are used together, the ROMS directive overrides the -outfile options.
3. It assigns a default filename. If you specify no filenames or fewer names than output files, the utility
assigns a default filename. A default filename consists of the base name from the input file plus a 2- to
3-character extension. The extension has three parts:
(a) A format character, based on the output format (see Section 10.12):
a
i
m
t
x
294
for ASCII-Hex
for Intel
for Motorola-S
for TI-Tagged
for Tektronix
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(b) The range number in the ROMS directive. Ranges are numbered starting with 0. If there is no
ROMS directive, or only one range, the utility omits this character.
(c) The file number in the set of files for the range, starting with 0 for the least significant file.
For example, assume a.out is for a 32-bit target processor and you are creating Intel format output.
With no output filenames specified, the utility produces four output files named a.i0, a.i1, a.i2, a.i3.
If you include the following ROMS directive when you invoke the hex conversion utility, you would have
eight output files:
ROMS
{
range1: o = 0x00001000 l = 0x1000
range2: o = 0x00002000 l = 0x1000
}
These output files ...
Contain data in these locations ...
a.i00, a.i01, a.i02, a.i03
0x00001000 through 0x00001FFF
a.i10, a.i11, a.i12, a.i13
0x00002000 through 0x00002FFF
10.9 Image Mode and the --fill Option
This section points out the advantages of operating in image mode and describes how to produce output
files with a precise, continuous image of a target memory range.
10.9.1 Generating a Memory Image
With the --image option, the utility generates a memory image by completely filling all of the mapped
ranges specified in the ROMS directive.
An object file consists of blocks of memory (sections) with assigned memory locations. Typically, all
sections are not adjacent: there are holes between sections in the address space for which there is no
data. When such a file is converted without the use of image mode, the hex conversion utility bridges
these holes by using the address records in the output file to skip ahead to the start of the next section. In
other words, there may be discontinuities in the output file addresses. Some EPROM programmers do not
support address discontinuities.
In image mode, there are no discontinuities. Each output file contains a continuous stream of data that
corresponds exactly to an address range in target memory. Any holes before, between, or after sections
are filled with a fill value that you supply.
An output file converted by using image mode still has address records, because many of the
hexadecimal formats require an address on each line. However, in image mode, these addresses are
always contiguous.
Defining the Ranges of Target Memory
NOTE: If you use image mode, you must also use a ROMS directive. In image mode, each output
file corresponds directly to a range of target memory. You must define the ranges. If you do
not supply the ranges of target memory, the utility tries to build a memory image of the entire
target processor address space. This is potentially a huge amount of output data. To prevent
this situation, the utility requires you to explicitly restrict the address space with the ROMS
directive.
10.9.2 Specifying a Fill Value
The --fill option specifies a value for filling the holes between sections. The fill value must be specified as
an integer constant following the --fill option. The width of the constant is assumed to be that of a word on
the target processor. For example, specifying --fill=0x0FFF. The constant value is not sign extended.
The hex conversion utility uses a default fill value of 0 if you do not specify a value with the fill option. The
--fill option is valid only when you use --image; otherwise, it is ignored.
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10.9.3 Steps to Follow in Using Image Mode
Step 1:
Step 2:
Define the ranges of target memory with a ROMS directive. See Section 10.4.
Invoke the hex conversion utility with the --image option. You can optionally use the --zero
option to reset the address origin to 0 for each output file. If you do not specify a fill value
with the ROMS directive and you want a value other than the default of 0, use the --fill option.
10.10 Controlling the ROM Device Address
The hex conversion utility output address field corresponds to the ROM device address. The EPROM
programmer burns the data into the location specified by the hex conversion utility output file address field.
The hex conversion utility offers some mechanisms to control the starting address in ROM of each
section. However, many EPROM programmers offer direct control of the location in ROM in which the
data is burned.
Depending on whether or not you are using the boot loader, the hex conversion utility output file
controlling mechanisms are different.
Non-boot loader mode. The address field of the hex conversion utility output file is controlled by the
following mechanisms listed from low to high priority:
1. The linker command file. By default, the address field of the hex conversion utility output file is the
load address (as given in the linker command file).
2. The paddr parameter of the SECTIONS directive. When the paddr parameter is specified for a
section, the hex conversion utility bypasses the section load address and places the section in the
address specified by paddr.
3. The --zero option. When you use the --zero option, the utility resets the address origin to 0 for each
output file. Since each file starts at 0 and counts upward, any address records represent offsets from
the beginning of the file (the address within the ROM) rather than actual target addresses of the data.
You must use the --zero option in conjunction with the --image option to force the starting address in
each output file to be zero. If you specify the --zero option without the --image option, the utility issues
a warning and ignores the --zero option.
Boot-Loader Mode. When the boot loader is used, the hex conversion utility places the different sections
that are in the boot table into consecutive memory locations. Each section becomes a boot table block
whose destination address is equal to the linker-assigned section load address.
In a boot table, the address field of the hex conversion utility output file is not related to the section load
addresses assigned by the linker. The address fields of the boot table are simply offsets to the beginning
of the table. The section load addresses assigned by the linker will be encoded into the boot table along
with the size of the section and the data contained within the section. These addresses will be used to
store the data into memory during the boot load process.
The beginning of the boot table defaults to the linked load address of the first bootable section in the input
file, unless you use one of the following mechanisms, listed here from low to high priority. Higher priority
mechanisms override the values set by low priority options in an overlapping range.
1. The ROM origin specified in the ROMS directive. The hex conversion utility places the boot table at
the origin of the first memory range in a ROMS directive.
2. The --bootorg option. The hex conversion utility places the boot table at the address specified by the
--bootorg option if you select boot loading from memory.
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10.11 Control Hex Conversion Utility Diagnostics
The hex conversion utility uses certain C/C++ compiler options to control hex-converter-generated
diagnostics.
--diag_error=id
--diag_remark=id
--diag_suppress=id
--diag_warning=id
--display_error_number
--issue_remarks
--no_warnings
--set_error_limit=count
--verbose_diagnostics
Categorizes the diagnostic identified by id as an error. To determine the
numeric identifier of a diagnostic message, use the --display_error_number
option first in a separate link. Then use --diag_error=id to recategorize the
diagnostic as an error. You can only alter the severity of discretionary
diagnostics.
Categorizes the diagnostic identified by id as a remark. To determine the
numeric identifier of a diagnostic message, use the --display_error_number
option first in a separate link. Then use --diag_remark=id to recategorize the
diagnostic as a remark. You can only alter the severity of discretionary
diagnostics.
Suppresses the diagnostic identified by id. To determine the numeric
identifier of a diagnostic message, use the --display_error_number option first
in a separate link. Then use --diag_suppress=id to suppress the diagnostic.
You can only suppress discretionary diagnostics.
Categorizes the diagnostic identified by id as a warning. To determine the
numeric identifier of a diagnostic message, use the --display_error_number
option first in a separate link. Then use --diag_warning=id to recategorize the
diagnostic as a warning. You can only alter the severity of discretionary
diagnostics.
Displays a diagnostic's numeric identifier along with its text. Use this option in
determining which arguments you need to supply to the diagnostic
suppression options (--diag_suppress, --diag_error, --diag_remark, and -diag_warning). This option also indicates whether a diagnostic is
discretionary. A discretionary diagnostic is one whose severity can be
overridden. A discretionary diagnostic includes the suffix -D; otherwise, no
suffix is present. See the TMS320C6000 Optimizing Compiler User's Guide
for more information on understanding diagnostic messages.
Issues remarks (nonserious warnings), which are suppressed by default.
Suppresses warning diagnostics (errors are still issued).
Sets the error limit to count, which can be any decimal value. The linker
abandons linking after this number of errors. (The default is 100.)
Provides verbose diagnostics that display the original source with line-wrap
and indicate the position of the error in the source line
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10.12 Description of the Object Formats
The hex conversion utility has options that identify each format. Table 10-2 specifies the format options.
They are described in the following sections.
• You need to use only one of these options on the command line. If you use more than one option, the
last one you list overrides the others.
• The default format is Tektronix (--tektronix option).
Table 10-2. Options for Specifying Hex Conversion Formats
Option
Alias
Format
Address Bits
Default Width
--ascii
-a
ASCII-Hex
16
8
--intel
-i
Intel
32
8
--motorola=1
-m1
Motorola-S1
16
8
--motorola=2
-m2
Motorola-S2
24
8
--motorola=3
-m3
Motorola-S3
32
8
--ti-tagged
-t
TI-Tagged
16
16
TI_TXT
8
8
Tektronix
32
8
--ti_txt
--tektronix
-x
Address bits determine how many bits of the address information the format supports. Formats with 16bit addresses support addresses up to 64K only. The utility truncates target addresses to fit in the number
of available bits.
The default width determines the default output width of the format. You can change the default width by
using the --romwidth option or by using the romwidth parameter in the ROMS directive. You cannot
change the default width of the TI-Tagged format, which supports a 16-bit width only.
10.12.1 ASCII-Hex Object Format (--ascii Option)
The ASCII-Hex object format supports 32-bit addresses. The format consists of a byte stream with bytes
separated by spaces. Figure 10-6 illustrates the ASCII-Hex format.
Figure 10-6. ASCII-Hex Object Format
Nonprintable
start code
Address
Nonprintable
end code
^B $AXXXXXXXX,
XX XX XX XX XX XX XX XX XX XX. . .^C
Data byte
The file begins with an ASCII STX character (ctrl-B, 02h) and ends with an ASCII ETX character (ctrl-C,
03h). Address records are indicated with $AXXXXXXX, in which XXXXXXXX is a 8-digit (16-bit)
hexadecimal address. The address records are present only in the following situations:
• When discontinuities occur
• When the byte stream does not begin at address 0
You can avoid all discontinuities and any address records by using the --image and --zero options. This
creates output that is simply a list of byte values.
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10.12.2 Intel MCS-86 Object Format (--intel Option)
The Intel object format supports 16-bit addresses and 32-bit extended addresses. Intel format consists of
a 9-character (4-field) prefix (which defines the start of record, byte count, load address, and record type),
the data, and a 2-character checksum suffix.
The 9-character prefix represents three record types:
Record Type
Description
00
Data record
01
End-of-file record
04
Extended linear address record
Record type00, the data record, begins with a colon ( : ) and is followed by the byte count, the address of
the first data byte, the record type (00), and the checksum. The address is the least significant 16 bits of a
32-bit address; this value is concatenated with the value from the most recent 04 (extended linear
address) record to create a full 32-bit address. The checksum is the 2s complement (in binary form) of the
preceding bytes in the record, including byte count, address, and data bytes.
Record type 01, the end-of-file record, also begins with a colon ( : ), followed by the byte count, the
address, the record type (01), and the checksum.
Record type 04, the extended linear address record, specifies the upper 16 address bits. It begins with a
colon ( : ), followed by the byte count, a dummy address of 0h, the record type (04), the most significant
16 bits of the address, and the checksum. The subsequent address fields in the data records contain the
least significant bytes of the address.
Figure 10-7 illustrates the Intel hexadecimal object format.
Figure 10-7. Intel Hexadecimal Object Format
Start
character
Address
Extended linear
address record
Most significant 16 bits
Data
records
:00000001FF
Byte Record
count type
Checksum
End-of-file
record
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10.12.3 Motorola Exorciser Object Format (--motorola Option)
The Motorola S1, S2, and S3 formats support 16-bit, 24-bit, and 32-bit addresses, respectively. The
formats consist of a start-of-file (header) record, data records, and an end-of-file (termination) record.
Each record consists of five fields: record type, byte count, address, data, and checksum. The three
record types are:
Record Type
Description
S0
Header record
S1
Code/data record for 16-bit addresses (S1 format)
S2
Code/data record for 24-bit addresses (S2 format)
S3
Code/data record for 32-bit addresses (S3 format)
S7
Termination record for 32-bit addresses (S3 format)
S8
Termination record for 24-bit addresses (S2 format)
S9
Termination record for 16-bit addresses (S1 format)
The byte count is the character pair count in the record, excluding the type and byte count itself.
The checksum is the least significant byte of the 1s complement of the sum of the values represented by
the pairs of characters making up the byte count, address, and the code/data fields.
Figure 10-8 illustrates the Motorola-S object format.
Figure 10-8. Motorola-S Format
Record
type
Address
Checksum
S00600004844521B
Header record
S31A0001FFEB000000000000000000000000000000000000000000FA
S70500000000FA
Data records
Byte count
Checksum
Termination
record
Address for S3 records
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10.12.4 Extended Tektronix Object Format (--tektronix Option)
The Tektronix object format supports 32-bit addresses and has two types of records:
Data records
Termination records
contains the header field, the load address, and the object code.
signifies the end of a module.
The header field in the data record contains the following information:
Number of ASCII
Characters
Item
Description
%
1
Data type is Tektronix format
Block length
2
Number of characters in the record, minus the %
Block type
1
6 = data record
8 = termination record
Checksum
2
A 2-digit hex sum modulo 256 of all values in the record except the % and the
checksum itself.
The load address in the data record specifies where the object code will be located. The first digit
specifies the address length; this is always 8. The remaining characters of the data record contain the
object code, two characters per byte.
Figure 10-9 illustrates the Tektronix object format.
Figure 10-9. Extended Tektronix Object Format
Checksum: 21h =
0+
Block length
1ah = 26
Header
character
1+5+6+8+1+0+0+0+0+0+0+
2+0+2+0+2+0+2+0+2+0+2+
0
Object code: 6 bytes
%15621810000000202020202020
Load address: 10000000h
Block type: 6
(data)
Length of
load address
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10.12.5 Texas Instruments SDSMAC (TI-Tagged) Object Format (--ti_tagged Option)
The Texas Instruments SDSMAC (TI-Tagged) object format supports 16-bit addresses, including start-offile record, data records, and end-of-file record. Each data records consists of a series of small fields and
is signified by a tag character:
Tag Character
Description
K
Followed by the program identifier
7
Followed by a checksum
8
Followed by a dummy checksum (ignored)
9
Followed by a 16-bit load address
B
Followed by a data word (four characters)
F
Identifies the end of a data record
*
Followed by a data byte (two characters)
Figure 10-10 illustrates the tag characters and fields in TI-Tagged object format.
Figure 10-10. TI-Tagged Object Format
Start-of-file
record
Program
Load
address
Tag characters
identifier
BFFFFBFFFFBFFFFBFFFFBFFFFBFFFFBFFFFBFFFFBFFFFBFFFF7F245F
:
End-of-file
record
Data
words
Data
records
Checksum
If any data fields appear before the first address, the first field is assigned address 0000h. Address fields
may be expressed but not required for any data byte. The checksum field, preceded by the tag character
7, is the 2s complement of the sum of the 8-bit ASCII values of characters, beginning with the first tag
character and ending with the checksum tag character (7 or 8). The end-of-file record is a colon ( : ).
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10.12.6 TI-TXT Hex Format (--ti_txt Option)
The TI-TXT hex format supports 16-bit hexadecimal data. It consists of section start addresses, data byte,
and an end-of-file character. These restrictions apply:
• The number of sections is unlimited.
• Each hexadecimal start address must be even.
• Each line must have 16 data bytes, except the last line of a section.
• Data bytes are separated by a single space.
• The end-of-file termination tag q is mandatory.
The data record contains the following information:
Item
Description
@ADDR
Hexadecimal start address of a section
DATAn
Hexadecimal data byte
q
End-of-file termination character
Figure 10-11. TI-TXT Object Format
Section
start
Data
bytes
Section
start
@ADDR1
DATA01 DATA02 ........ DATA16
DATA17 DATA32 ........ DATA32
DATAm ........ DATAn
@ADDR2
DATA01 .................... DATAn
q
Data
bytes
End-of-line
character
Example 10-3. TI-TXT Object Format
@F000
31 40 00 03 B2 40 80 5A 20 01 D2 D3 22 00 D2 E3
21 00 3F 40 E8 FD 1F 83 FE 23 F9 3F
@FFFE
00 F0
Q
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Chapter 11
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Sharing C/C++ Header Files With Assembly Source
You can use the .cdecls assembler directive to share C headers containing declarations and prototypes
between C and assembly code. Any legal C/C++ can be used in a .cdecls block and the C/C++
declarations will cause suitable assembly to be generated automatically, allowing you to reference the
C/C++ constructs in assembly code.
Topic
11.1
11.2
11.3
11.4
304
...........................................................................................................................
Overview of the .cdecls Directive .......................................................................
Notes on C/C++ Conversions .............................................................................
Notes on C++ Specific Conversions ....................................................................
Special Assembler Support ...............................................................................
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11.1 Overview of the .cdecls Directive
The .cdecls directive allows programmers in mixed assembly and C/C++ environments to share C headers
containing declarations and prototypes between the C and assembly code. Any legal C/C++ can be used
in a .cdecls block and the C/C++ declarations will cause suitable assembly to be generated automatically.
This allows the programmer to reference the C/C++ constructs in assembly code — calling functions,
allocating space, and accessing structure members — using the equivalent assembly mechanisms. While
function and variable definitions are ignored, most common C/C++ elements are converted to assembly:
enumerations, (non function-like) macros, function and variable prototypes, structures, and unions.
See the .cdecls directive description for details on the syntax of the .cdecls assembler directive.
The .cdecls directive can appear anywhere in an assembly source file, and can occur multiple times within
a file. However, the C/C++ environment created by one .cdecls is not inherited by a later .cdecls; the
C/C++ environment starts over for each .cdecls instance.
For example, the following code causes the warning to be issued:
.cdecls C,NOLIST
%{
#define ASMTEST 1
%}
.cdecls C,NOLIST
%{
#ifndef ASMTEST
#warn "ASMTEST not defined!"
#endif
%}
/* will be issued */
Therefore, a typical use of the .cdecls block is expected to be a single usage near the beginning of the
assembly source file, in which all necessary C/C++ header files are included.
Use the compiler --include_path=path options to specify additional include file paths needed for the header
files used in assembly, as you would when compiling C files.
Any C/C++ errors or warnings generated by the code of the .cdecls are emitted as they normally would for
the C/C++ source code. C/C++ errors cause the directive to fail, and any resulting converted assembly is
not included.
C/C++ constructs that cannot be converted, such as function-like macros or variable definitions, cause a
comment to be output to the converted assembly file. For example:
; ASM HEADER WARNING - variable definition 'ABCD' ignored
The prefix ASM HEADER WARNING appears at the beginning of each message. To see the warnings,
either the WARN parameter needs to be specified so the messages are displayed on STDERR, or else
the LIST parameter needs to be specified so the warnings appear in the listing file, if any.
Finally, note that the converted assembly code does not appear in the same order as the original C/C++
source code and C/C++ constructs may be simplified to a normalized form during the conversion process,
but this should not affect their final usage.
11.2 Notes on C/C++ Conversions
The following sections describe C and C++ conversion elements that you need to be aware of when
sharing header files with assembly source.
11.2.1 Comments
Comments are consumed entirely at the C level, and do not appear in the resulting converted assembly
file.
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11.2.2 Conditional Compilation (#if/#else/#ifdef/etc.)
Conditional compilation is handled entirely at the C level during the conversion step. Define any necessary
macros either on the command line (using the compiler --define=name=value option) or within a .cdecls
block using #define. The #if, #ifdef, etc. C/C++ directives are not converted to assembly .if, .else, .elseif,
and .endif directives.
11.2.3 Pragmas
Pragmas found in the C/C++ source code cause a warning to be generated as they are not converted.
They have no other effect on the resulting assembly file. See the .cdecls topic for the WARN and
NOWARN parameter discussion for where these warnings are created.
11.2.4 The #error and #warning Directives
These preprocessor directives are handled completely by the compiler during the parsing step of
conversion. If one of these directives is encountered, the appropriate error or warning message is emitted.
These directives are not converted to .emsg or .wmsg in the assembly output.
11.2.5 Predefined symbol _ _ASM_HEADER_ _
The C/C++ macro _ _ASM_HEADER_ _ is defined in the compiler while processing code within .cdecls.
This allows you to make changes in your code, such as not compiling definitions, during the .cdecls
processing.
Be Careful With the _ _ASM_HEADER_ _ Macro
NOTE: You must be very careful not to use this macro to introduce any changes in the code that
could result in inconsistencies between the code processed while compiling the C/C++
source and while converting to assembly.
11.2.6 Usage Within C/C++ asm( ) Statements
The .cdecls directive is not allowed within C/C++ asm( ) statements and will cause an error to be
generated.
11.2.7 The #include Directive
The C/C++ #include preprocessor directive is handled transparently by the compiler during the conversion
step. Such #includes can be nested as deeply as desired as in C/C++ source. The assembly directives
.include and .copy are not used or needed within a .cdecls. Use the command line --include_path option to
specify additional paths to be searched for included files, as you would for C compilation.
11.2.8 Conversion of #define Macros
Only object-like macros are converted to assembly. Function-like macros have no assembly
representation and so cannot be converted. Pre-defined and built-in C/C++ macros are not converted to
assembly (i.e., __FILE__, __TIME__, __TI_COMPILER_VERSION__, etc.). For example, this code is
converted to assembly because it is an object-like macro:
#define NAME Charley
This code is not converted to assembly because it is a function-like macro:
#define MAX(x,y) (x>y ? x : y)
Some macros, while they are converted, have no functional use in the containing assembly file. For
example, the following results in the assembly substitution symbol FOREVER being set to the value
while(1), although this has no useful use in assembly because while(1) is not legal assembly code.
#define FOREVER while(1)
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Macro values are not interpreted as they are converted. For example, the following results in the
assembler substitution symbol OFFSET being set to the literal string value 5+12 and not the value 17.
This happens because the semantics of the C/C++ language require that macros are evaluated in context
and not when they are parsed.
#define OFFSET 5+12
Because macros in C/C++ are evaluated in their usage context, C/C++ printf escape sequences such as
\n are not converted to a single character in the converted assembly macro. See Section 11.2.11 for
suggestions on how to use C/C++ macro strings.
Macros are converted using the .define directive (see Section 11.4.2), which functions similarly to the .asg
assembler directive. The exception is that .define disallows redefinitions of register symbols and
mnemonics to prevent the conversion from corrupting the basic assembly environment. To remove a
macro from the assembly scope, .undef can be used following the .cdecls that defines it (see
Section 11.4.3).
The macro functionality of # (stringize operator) is only useful within functional macros. Since functional
macros are not supported by this process, # is not supported either. The concatenation operator ## is only
useful in a functional context, but can be used degenerately to concatenate two strings and so it is
supported in that context.
11.2.9 The #undef Directive
Symbols undefined using the #undef directive before the end of the .cdecls are not converted to assembly.
11.2.10 Enumerations
Enumeration members are converted to .enum elements in assembly. For example:
enum state { ACTIVE=0x10, SLEEPING=0x01, INTERRUPT=0x100, POWEROFF, LAST};
is converted to the following assembly code:
state
ACTIVE
SLEEPING
NTERRUPT
POWEROFF
LAST
.enum
.emember
.emember
.emember
.emember
.emember
.endenum
16
1
256
257
258
The members are used via the pseudo-scoping created by the .enum directive.
The usage is similar to that for accessing structure members, enum_name.member.
This pseudo-scoping is used to prevent enumeration member names from corrupting other symbols within
the assembly environment.
11.2.11 C Strings
Because C string escapes such as \n and \t are not converted to hex characters 0x0A and 0x09 until their
use in a string constant in a C/C++ program, C macros whose values are strings cannot be represented
as expected in assembly substitution symbols. For example:
#define MSG "\tHI\n"
becomes, in assembly:
.define """\tHI\n""",MSG ; 6 quoted characters! not 5!
When used in a C string context, you expect this statement to be converted to 5 characters (tab, H, I,
newline, NULL), but the .string assembler directive does not know how to perform the C escape
conversions.
You can use the .cstring directive to cause the escape sequences and NULL termination to be properly
handled as they would in C/C++. Using the above symbol MSG with a .cstring directive results in 5
characters of memory being allocated, the same characters as would result if used in a C/C++ strong
context. (See Section 11.4.7 for the .cstring directive syntax.)
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11.2.12 C/C++ Built-In Functions
The C/C++ built-in functions, such as sizeof( ), are not translated to their assembly counterparts, if any, if
they are used in macros. Also, their C expression values are not inserted into the resulting assembly
macro because macros are evaluated in context and there is no active context when converting the
macros to assembly.
Suitable functions such as $sizeof( ) are available in assembly expressions. However, as the basic types
such as int/char/float have no type representation in assembly, there is no way to ask for $sizeof(int), for
example, in assembly.
11.2.13 Structures and Unions
C/C++ structures and unions are converted to assembly .struct and .union elements. Padding and ending
alignments are added as necessary to make the resulting assembly structure have the same size and
member offsets as the C/C++ source. The primary purpose is to allow access to members of C/C++
structures, as well as to facilitate debugging of the assembly code. For nested structures, the assembly
.tag feature is used to refer to other structures/unions.
The alignment is also passed from the C/C++ source so that the assembly symbol is marked with the
same alignment as the C/C++ symbol. (See Section 11.2.3 for information about pragmas, which may
attempt to modify structures.) Because the alignment of structures is stored in the assembly symbol, builtin assembly functions like $sizeof( ) and $alignof( ) can be used on the resulting structure name symbol.
When using unnamed structures (or unions) in typedefs, such as:
typedef struct { int a_member; } mystrname;
This is really a shorthand way of writing:
struct temporary_name { int a_member; };
typedef temporary_name mystrname;
The conversion processes the above statements in the same manner: generating a temporary name for
the structure and then using .define to output a typedef from the temporary name to the user name. You
should use your mystrname in assembly the same as you would in C/C++, but do not be confused by the
assembly structure definition in the list, which contains the temporary name. You can avoid the temporary
name by specifying a name for the structure, as in:
typedef struct a_st_name { ... } mystrname;
If a shorthand method is used in C to declare a variable with a particular structure, for example:
extern struct a_name { int a_member; } a_variable;
Then after the structure is converted to assembly, a .tag directive is generated to declare the structure of
the external variable, such as:
_a_variable .tag a_st_name
This allows you to refer to _a_variable.a_member in your assembly code.
11.2.14 Function/Variable Prototypes
Non-static function and variable prototypes (not definitions) will result in a .global directive being generated
for each symbol found.
See Section 11.3.1 for C++ name mangling issues.
Function and variable definitions will result in a warning message being generated (see the
WARN/NOWARN parameter discussion for where these warnings are created) for each, and they will not
be represented in the converted assembly.
The assembly symbol representing the variable declarations will not contain type information about those
symbols. Only a .global will be issued for them. Therefore, it is your responsibility to ensure the symbol is
used appropriately.
See Section 11.2.13 for information on variables names which are of a structure/union type.
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11.2.15 C Constant Suffixes
The C constant suffixes u, l, and f are passed to the assembly unchanged. The assembler will ignore
these suffixes if used in assembly expressions.
11.2.16 Basic C/C++ Types
Only complex types (structures and unions) in the C/C++ source code are converted to assembly. Basic
types such as int, char, or float are not converted or represented in assembly beyond any existing .int,
.char, .float, etc. directives that previously existed in assembly.
Typedefs of basic types are therefore also not represented in the converted assembly.
11.3 Notes on C++ Specific Conversions
The following sections describe C++ specific conversion elements that you need to be aware of when
sharing header files with assembly source.
11.3.1 Name Mangling
Symbol names may be mangled in C++ source files. When mangling occurs, the converted assembly will
use the mangled names to avoid symbol name clashes. You can use the demangler (dem6x) to demangle
names and identify the correct symbols to use in assembly.
To defeat name mangling in C++ for symbols where polymorphism (calling a function of the same name
with different kinds of arguments) is not required, use the following syntax:
extern "C" void somefunc(int arg);
The above format is the short method for declaring a single function. To use this method for multiple
functions, you can also use the following syntax:
extern "C"
{
void somefunc(int arg);
int anotherfunc(int arg);
...
}
11.3.2 Derived Classes
Derived classes are only partially supported when converting to assembly because of issues related to
C++ scoping which does not exist in assembly. The greatest difference is that base class members do not
automatically become full (top-level) members of the derived class. For example:
---------------------------------------------------------class base
{
public:
int b1;
};
class derived : public base
{
public:
int d1;
}
In C++ code, the class derived would contain both integers b1 and d1. In the converted assembly
structure "derived", the members of the base class must be accessed using the name of the base class,
such as derived.__b_base.b1 rather than the expected derived.b1.
A non-virtual, non-empty base class will have __b_ prepended to its name within the derived class to
signify it is a base class name. That is why the example above is derived.__b_base.b1 and not simply
derived.base.b1.
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11.3.3 Templates
No support exists for templates.
11.3.4 Virtual Functions
No support exists for virtual functions, as they have no assembly representation.
11.4 Special Assembler Support
11.4.1 Enumerations (.enum/.emember/.endenum)
The following directives support a pseudo-scoping for enumerations:
ENUM_NAME
MEMBER1
MEMBER2
...
.enum
.emember [value]
.emember [value]
.endenum
The .enum directive begins the enumeration definition and .endenum terminates it.
The enumeration name (ENUM_NAME) cannot be used to allocate space; its size is reported as zero.
The format to use the value of a member is ENUM_NAME.MEMBER, similar to a structure member
usage.
The .emember directive optionally accepts the value to set the member to, just as in C/C++. If not
specified, the member takes a value one more than the previous member. As in C/C++, member names
cannot be duplicated, although values can be. Unless specified with .emember, the first enumeration
member will be given the value 0 (zero), as in C/C++.
The .endenum directive cannot be used with a label, as structure .endstruct directives can, because the
.endenum directive has no value like the .endstruct does (containing the size of the structure).
Conditional compilation directives (.if/.else/.elseif/.endif) are the only other non-enumeration code allowed
within the .enum/.endenum sequence.
11.4.2 The .define Directive
The .define directive functions in the same manner as the .asg directive, except that .define disallows
creation of a substitution symbol that has the same name as a register symbol or mnemonic. It does not
create a new symbol name space in the assembler, rather it uses the existing substitution symbol name
space. The syntax for the directive is:
.define substitution string , substitution symbol name
The .define directive is used to prevent corruption of the assembly environment when converting C/C++
headers.
11.4.3 The .undefine/.unasg Directives
The .undef directive is used to remove the definition of a substitution symbol created using .define or .asg.
This directive will remove the named symbol from the substitution symbol table from the point of the .undef
to the end of the assembly file. The syntax for these directives is:
.undefine substitution symbol name
.unasg substitution symbol name
This can be used to remove from the assembly environment any C/C++ macros that may cause a
problem.
Also see Section 11.4.2, which covers the .define directive.
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11.4.4 The $defined( ) Built-In Function
The $defined directive returns true/1 or false/0 depending on whether the name exists in the current
substitution symbol table or the standard symbol table. In essence $defined returns TRUE if the
assembler has any user symbol in scope by that name. This differs from $isdefed in that $isdefed only
tests for NON-substitution symbols. The syntax is:
$defined( substitution symbol name )
A statement such as ".if $defined(macroname)" is then similar to the C code "#ifdef macroname".
See Section 11.4.2 and Section 11.4.3 for the use of .define and .undef in assembly.
11.4.5 The $sizeof Built-In Function
The assembly built-in function $sizeof( ) can be used to query the size of a structure in assembly. It is an
alias for the already existing $structsz( ). The syntax is:
$sizeof( structure name )
The $sizeof function can then be used similarly to the C built-in function sizeof( ).
The assembler's $sizeof( ) built-in function cannot be used to ask for the size of basic C/C++ types, such
as $sizeof(int), because those basic type names are not represented in assembly. Only complex types are
converted from C/C++ to assembly.
Also see Section 11.2.12, which notes that this conversion does not happen automatically if the C/C++
sizeof( ) built-in function is used within a macro.
11.4.6 Structure/Union Alignment and $alignof( )
The assembly .struct and .union directives take an optional second argument which can be used to
specify a minimum alignment to be applied to the symbol name. This is used by the conversion process to
pass the specific alignment from C/C++ to assembly.
The assembly built-in function $alignof( ) can be used to report the alignment of these structures. This can
be used even on assembly structures, and the function will return the minimum alignment calculated by
the assembler.
11.4.7 The .cstring Directive
You can use the .cstring directive to cause the escape sequences and NULL termination to be properly
handled as they would in C/C++.
.cstring "String with C escapes.\nWill be NULL terminated.\012"
See Section 11.2.11 for more information on the .cstring directive.
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Appendix A
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Symbolic Debugging Directives
The assembler supports several directives that the TMS320C6000 C/C++ compiler uses for symbolic
debugging.
These directives are not meant for use by assembly-language programmers. They require arguments that
can be difficult to calculate manually, and their usage must conform to a predetermined agreement
between the compiler, the assembler, and the debugger. This appendix documents these directives for
informational purposes only.
Topic
A.1
A.2
312
...........................................................................................................................
Page
DWARF Debugging Format ................................................................................ 313
Debug Directive Syntax ..................................................................................... 313
Symbolic Debugging Directives
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A.1
DWARF Debugging Format
A subset of the DWARF symbolic debugging directives are always listed in the assembly language file that
the compiler creates for program analysis purposes. To list the complete set used for full symbolic debug,
invoke the compiler with the --symdebug:dwarf option, as shown below:
cl6x --symdebug:dwarf --keep_asm input_file
The --keep_asm option instructs the compiler to retain the generated assembly file.
To disable the generation of all symbolic debug directives, invoke the compiler with the -symdebug:none
option:
cl6x --symdebug:none --keep_asm input_file
The DWARF debugging format consists of the following directives:
• The .dwtag and .dwendtag directives define a Debug Information Entry (DIE) in the .debug_info
section.
• The .dwattr directive adds an attribute to an existing DIE.
• The .dwpsn directive identifies the source position of a C/C++ statement.
• The .dwcie and .dwendentry directives define a Common Information Entry (CIE) in the .debug_frame
section.
• The .dwfde and .dwendentry directives define a Frame Description Entry (FDE) in the .debug_frame
section.
• The .dwcfi directive defines a call frame instruction for a CIE or FDE.
A.2
Debug Directive Syntax
Table A-1 is an alphabetical listing of the symbolic debugging directives. For information on the C/C++
compiler, refer to the TMS320C6000 Optimizing Compiler User's Guide.
Table A-1. Symbolic Debugging Directives
Label
CIE label
Directive
Arguments
.block
[beginning line number]
.dwattr
DIE label , DIE attribute name ( DIE attribute value )[, DIE attribute name ( attribute value ) [, ...]
.dwcfi
call frame instruction opcode[, operand[, operand]]
.dwcie
version , return address register
.dwendentry
.dwendtag
DIE label
.dwfde
CIE label
.dwpsn
" filename ", line number , column number
.dwtag
DIE tag name , DIE attribute name ( DIE attribute value )[, DIE attribute name ( attribute value )
[, ...]
.endblock
[ending line number]
.endfunc
[ending line number[, register mask[, frame size]]]
.eos
.etag
name[, size]
.file
" filename "
.func
[beginning line number]
.line
line number[, address]
.member
name , value[, type , storage class , size , tag , dims]
.stag
name[, size]
.sym
name , value[, type , storage class , size , tag , dims]
.utag
name[, size]
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Appendix B
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XML Link Information File Description
The TMS320C6000 linker supports the generation of an XML link information file via the --xml_link_info
file option. This option causes the linker to generate a well-formed XML file containing detailed information
about the result of a link. The information included in this file includes all of the information that is currently
produced in a linker-generated map file.
As the linker evolves, the XML link information file may be extended to include additional information that
could be useful for static analysis of linker results.
This appendix enumerates all of the elements that are generated by the linker into the XML link
information file.
Topic
B.1
B.2
314
...........................................................................................................................
Page
XML Information File Element Types ................................................................... 315
Document Elements .......................................................................................... 315
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B.1
XML Information File Element Types
These element types will be generated by the linker:
• Container elements represent an object that contains other elements that describe the object.
Container elements have an id attribute that makes them accessible from other elements.
• String elements contain a string representation of their value.
• Constant elements contain a 32-bit unsigned long representation of their value (with a 0x prefix).
• Reference elements are empty elements that contain an idref attribute that specifies a link to another
container element.
In Section B.2, the element type is specified for each element in parentheses following the element
description. For instance, the <link_time> element lists the time of the link execution (string).
B.2
Document Elements
The root element, or the document element, is <link_info>. All other elements contained in the XML link
information file are children of the <link_info> element. The following sections describe the elements that
an XML information file can contain.
B.2.1 Header Elements
The first elements in the XML link information file provide general information about the linker and the link
session:
• The <banner> element lists the name of the executable and the version information (string).
• The <copyright> element lists the TI copyright information (string).
• The <link_time> is a timestamp representation of the link time (unsigned 32-bit int).
• The <output_file> element lists the name of the linked output file generated (string).
• The <entry_point> element specifies the program entry point, as determined by the linker (container)
with two entries:
– The <name> is the entry point symbol name, if any (string).
– The <address> is the entry point address (constant).
Example B-1. Header Element for the hi.out Output File
<banner>TMS320Cxx Linker
Version x.xx (Jan 6 2008)</banner>
<copyright>Copyright (c) 1996-2008 Texas Instruments Incorporated</copyright>
<link_time>0x43dfd8a4</link_time>
<output_file>hi.out</output_file>
<entry_point>
<name>_c_int00</name>
<address>0xaf80</address>
</entry_point>
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B.2.2 Input File List
The next section of the XML link information file is the input file list, which is delimited with a
<input_file_list> container element. The <input_file_list> can contain any number of <input_file>
elements.
Each <input_file> instance specifies the input file involved in the link. Each <input_file> has an id attribute
that can be referenced by other elements, such as an <object_component>. An <input_file> is a container
element enclosing the following elements:
• The <path> element names a directory path, if applicable (string).
• The <kind> element specifies a file type, either archive or object (string).
• The <file> element specifies an archive name or filename (string).
• The <name> element specifies an object file name, or archive member name (string).
Example B-2. Input File List for the hi.out Output File
<input_file_list>
<input_file id="fl-1">
<kind>object</kind>
<file>hi.obj</file>
<name>hi.obj</name>
</input_file>
<input_file id="fl-2">
<path>/tools/lib/</path>
<kind>archive</kind>
<file>rtsxxx.lib</file>
<name>boot.obj</name>
</input_file>
<input_file id="fl-3">
<path>/tools/lib/</path>
<kind>archive</kind>
<file>rtsxxx.lib</file>
<name>exit.obj</name>
</input_file>
<input_file id="fl-4">
<path>/tools/lib/</path>
<kind>archive</kind>
<file>rtsxxx.lib</file>
<name>printf.obj</name>
</input_file>
...
</input_file_list>
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B.2.3 Object Component List
The next section of the XML link information file contains a specification of all of the object components
that are involved in the link. An example of an object component is an input section. In general, an object
component is the smallest piece of object that can be manipulated by the linker.
The <object_component_list> is a container element enclosing any number of <object_component>
elements.
Each <object_component> specifies a single object component. Each <object_component> has an id
attribute so that it can be referenced directly from other elements, such as a <logical_group>. An
<object_component> is a container element enclosing the following elements:
• The <name> element names the object component (string).
• The <load_address> element specifies the load-time address of the object component (constant).
• The <run_address> element specifies the run-time address of the object component (constant).
• The <size> element specifies the size of the object component (constant).
• The <input_file_ref> element specifies the source file where the object component originated
(reference).
Example B-3. Object Component List for the fl-4 Input File
<object_component id="oc-20">
<name>.text</name>
<load_address>0xac00</load_address>
<run_address>0xac00</run_address>
<size>0xc0</size>
<input_file_ref idref="fl-4"/>
</object_component>
<object_component id="oc-21">
<name>.data</name>
<load_address>0x80000000</load_address>
<run_address>0x80000000</run_address>
<size>0x0</size>
<input_file_ref idref="fl-4"/>
</object_component>
<object_component id="oc-22">
<name>.bss</name>
<load_address>0x80000000</load_address>
<run_address>0x80000000</run_address>
<size>0x0</size>
<input_file_ref idref="fl-4"/>
</object_component>
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B.2.4 Logical Group List
The <logical_group_list> section of the XML link information file is similar to the output section listing in a
linker-generated map file. However, the XML link information file contains a specification of GROUP and
UNION output sections, which are not represented in a map file. There are three kinds of list items that
can occur in a <logical_group_list>:
• The <logical_group> is the specification of a section or GROUP that contains a list of object
components or logical group members. Each <logical_group> element is given an id so that it may be
referenced from other elements. Each <logical_group> is a container element enclosing the following
elements:
– The <name> element names the logical group (string).
– The <load_address> element specifies the load-time address of the logical group (constant).
– The <run_address> element specifies the run-time address of the logical group (constant).
– The <size> element specifies the size of the logical group (constant).
– The <contents> element lists elements contained in this logical group (container). These elements
refer to each of the member objects contained in this logical group:
• The <object_component_ref> is an object component that is contained in this logical group
(reference).
• The <logical_group_ref> is a logical group that is contained in this logical group (reference).
• The <overlay> is a special kind of logical group that represents a UNION, or a set of objects that
share the same memory space (container). Each <overlay> element is given an id so that it may be
referenced from other elements (like from an <allocated_space> element in the placement map). Each
<overlay> contains the following elements:
– The <name> element names the overlay (string).
– The <run_address> element specifies the run-time address of overlay (constant).
– The <size> element specifies the size of logical group (constant).
– The <contents> container element lists elements contained in this overlay. These elements refer to
each of the member objects contained in this logical group:
• The <object_component_ref> is an object component that is contained in this logical group
(reference).
• The <logical_group_ref> is a logical group that is contained in this logical group (reference).
• The <split_section> is another special kind of logical group that represents a collection of logical
groups that is split among multiple memory areas. Each <split_section> element is given an id so that
it may be referenced from other elements. The id consists of the following elements.
– The <name> element names the split section (string).
– The <contents> container element lists elements contained in this split section. The
<logical_group_ref> elements refer to each of the member objects contained in this split section,
and each element referenced is a logical group that is contained in this split section (reference).
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Example B-4. Logical Group List for the fl-4 Input File
<logical_group_list>
...
<logical_group id="lg-7">
<name>.text</name>
<load_address>0x20</load_address>
<run_address>0x20</run_address>
<size>0xb240</size>
<contents>
<object_component_ref idref="oc-34"/>
<object_component_ref idref="oc-108"/>
<object_component_ref idref="oc-e2"/>
...
</contents>
</logical_group>
...
<overlay id="lg-b">
<name>UNION_1</name>
<run_address>0xb600</run_address>
<size>0xc0</size>
<contents>
<object_component_ref idref="oc-45"/>
<logical_group_ref idref="lg-8"/>
</contents>
</overlay>
...
<split_section id="lg-12">
<name>.task_scn</name>
<size>0x120</size>
<contents>
<logical_group_ref idref="lg-10"/>
<logical_group_ref idref="lg-11"/>
</contents>
...
</logical_group_list>
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B.2.5 Placement Map
The <placement_map> element describes the memory placement details of all named memory areas in
the application, including unused spaces between logical groups that have been placed in a particular
memory area.
The <memory_area> is a description of the placement details within a named memory area (container).
The description consists of these items:
• The <name> names the memory area (string).
• The <page_id> gives the id of the memory page in which this memory area is defined (constant).
• The <origin> specifies the beginning address of the memory area (constant).
• The <length> specifies the length of the memory area (constant).
• The <used_space> specifies the amount of allocated space in this area (constant).
• The <unused_space> specifies the amount of available space in this area (constant).
• The <attributes> lists the RWXI attributes that are associated with this area, if any (string).
• The <fill_value> specifies the fill value that is to be placed in unused space, if the fill directive is
specified with the memory area (constant).
• The <usage_details> lists details of each allocated or available fragment in this memory area. If the
fragment is allocated to a logical group, then a <logical_group_ref> element is provided to facilitate
access to the details of that logical group. All fragment specifications include <start_address> and
<size> elements.
– The <allocated_space> element provides details of an allocated fragment within this memory area
(container):
• The <start_address> specifies the address of the fragment (constant).
• The <size> specifies the size of the fragment (constant).
• The <logical_group_ref> provides a reference to the logical group that is allocated to this
fragment (reference).
– The <available_space element provides details of an available fragment within this memory area
(container):
• The <start_address> specifies the address of the fragment (constant).
• The <size> specifies the size of the fragment (constant).
Example B-5. Placement Map for the fl-4 Input File
<placement_map>
<memory_area>
<name>PMEM</name>
<page_id>0x0</page_id>
<origin>0x20</origin>
<length>0x100000</length>
<used_space>0xb240</used_space>
<unused_space>0xf4dc0</unused_space>
<attributes>RWXI</attributes>
<usage_details>
<allocated_space>
<start_address>0x20</start_address>
<size>0xb240</size>
<logical_group_ref idref="lg-7"/>
</allocated_space>
<available_space>
<start_address>0xb260</start_address>
<size>0xf4dc0</size>
</available_space>
</usage_details>
</memory_area>
...
</placement_map>
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B.2.6 Far Call Trampoline List
The <far_call_trampoline_list> is a list of <far_call_trampoline> elements. The linker supports the
generation of far call trampolines to help a call site reach a destination that is out of range. A far call
trampoline function is guaranteed to reach the called function (callee) as it may utilize an indirect call to
the called function.
The <far_call_trampoline_list> enumerates all of the far call trampolines that are generated by the linker
for a particular link. The <far_call_trampoline_list> can contain any number of <far_call_trampoline>
elements. Each <far_call_trampoline> is a container enclosing the following elements:
• The <callee_name> element names the destination function (string).
• The <callee_address> is the address of the called function (constant).
• The <trampoline_object_component_ref> is a reference to an object component that contains the
definition of the trampoline function (reference).
• The <trampoline_address> is the address of the trampoline function (constant).
• The <caller_list> enumerates all call sites that utilize this trampoline to reach the called function
(container).
• The <trampoline_call_site> provides the details of a trampoline call site (container) and consists of
these items:
– The <caller_address> specifies the call site address (constant).
– The <caller_object_component_ref> is the object component where the call site resides
(reference).
Example B-6. Fall Call Trampoline List for the fl-4 Input File
<far_call_trampoline_list>
...
<far_call_trampoline>
<callee_name>_foo</callee_name>
<callee_address>0x08000030</callee_address>
<trampoline_object_component_ref idref="oc-123"/>
<trampoline_address>0x2020</trampoline_address>
<caller_list>
<call_site>
<caller_address>0x1800</caller_address>
<caller_object_component_ref idref="oc-23"/>
</call_site>
<call_site>
<caller_address>0x1810</caller_address>
<caller_object_component_ref idref="oc-23"/>
</call_site>
</caller_list>
</far_call_trampoline>
...
</far_call_trampoline_list>
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B.2.7 Symbol Table
The <symbol_table> contains a list of all of the global symbols that are included in the link. The list
provides information about a symbol's name and value. In the future, the symbol_table list may provide
type information, the object component in which the symbol is defined, storage class, etc.
The <symbol> is a container element that specifies the name and value of a symbol with these elements:
• The <name> element specifies the symbol name (string).
• The <value> element specifies the symbol value (constant).
Example B-7. Symbol Table for the fl-4 Input File
<symbol_table>
<symbol>
<name>_c_int00</name>
<value>0xaf80</value>
</symbol>
<symbol>
<name>_main</name>
<value>0xb1e0</value>
</symbol>
<symbol>
<name>_printf</name>
<value>0xac00</value>
</symbol>
...
</symbol_table>
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Appendix C
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Glossary
C.1
Terminology
ABI — Application binary interface.
absolute address — An address that is permanently assigned to a TMS320C6000 memory location.
absolute constant expression — An expression that does not refer to any external symbols or any
registers or memory reference. The value of the expression must be knowable at assembly time.
address constant expression — A symbol with a value that is an address plus an addend that is an
absolute constant expression with an integer value.
alignment — A process in which the linker places an output section at an address that falls on an n-byte
boundary, where n is a power of 2. You can specify alignment with the SECTIONS linker directive.
allocation — A process in which the linker calculates the final memory addresses of output sections.
ANSI — American National Standards Institute; an organization that establishes standards voluntarily
followed by industries.
archive library — A collection of individual files grouped into a single file by the archiver.
archiver — A software program that collects several individual files into a single file called an archive
library. With the archiver, you can add, delete, extract, or replace members of the archive library.
ASCII — American Standard Code for Information Interchange; a standard computer code for
representing and exchanging alphanumeric information.
assembler — A software program that creates a machine-language program from a source file that
contains assembly language instructions, directives, and macro definitions. The assembler
substitutes absolute operation codes for symbolic operation codes and absolute or relocatable
addresses for symbolic addresses.
assembly-time constant — A symbol that is assigned a constant value with the .set directive.
big endian — An addressing protocol in which bytes are numbered from left to right within a word. More
significant bytes in a word have lower numbered addresses. Endian ordering is hardware-specific
and is determined at reset. See also little endian
binding — A process in which you specify a distinct address for an output section or a symbol.
block — A set of statements that are grouped together within braces and treated as an entity.
.bss section — One of the default object file sections. You use the assembler .bss directive to reserve a
specified amount of space in the memory map that you can use later for storing data. The .bss
section is uninitialized.
byte — Per ANSI/ISO C, the smallest addressable unit that can hold a character.
C/C++ compiler — A software program that translates C source statements into assembly language
source statements.
command file — A file that contains options, filenames, directives, or commands for the linker or hex
conversion utility.
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comment — A source statement (or portion of a source statement) that documents or improves
readability of a source file. Comments are not compiled, assembled, or linked; they have no effect
on the object file.
compiler program — A utility that lets you compile, assemble, and optionally link in one step. The
compiler runs one or more source modules through the compiler (including the parser, optimizer,
and code generator), the assembler, and the linker.
conditional processing — A method of processing one block of source code or an alternate block of
source code, according to the evaluation of a specified expression.
configured memory — Memory that the linker has specified for allocation.
constant — A type whose value cannot change.
constant expression — An expression that does not in any way refer to a register or memory reference.
cross-reference listing — An output file created by the assembler that lists the symbols that were
defined, what line they were defined on, which lines referenced them, and their final values.
.data section — One of the default object file sections. The .data section is an initialized section that
contains initialized data. You can use the .data directive to assemble code into the .data section.
directives — Special-purpose commands that control the actions and functions of a software tool (as
opposed to assembly language instructions, which control the actions of a device).
DWARF — A standardized debugging data format that was originally designed along with ELF, although it
is independent of the object file format.
EABI — An embedded application binary interface (ABI) that provides standards for file formats, data
types, and more.
ELF — Executable and linking format; a system of object files configured according to the System V
Application Binary Interface specification.
emulator — A hardware development system that duplicates the TMS320C6000 operation.
entry point — A point in target memory where execution starts.
environment variable — A system symbol that you define and assign to a string. Environmental
variables are often included in Windows batch files or UNIX shell scripts such as .cshrc or .profile.
epilog — The portion of code in a function that restores the stack and returns. See also pipelined-loop
epilog.
executable module — A linked object file that can be executed in a target system.
expression — A constant, a symbol, or a series of constants and symbols separated by arithmetic
operators.
external symbol — A symbol that is used in the current program module but defined or declared in a
different program module.
field — For the TMS320C6000, a software-configurable data type whose length can be programmed to
be any value in the range of 1-32 bits.
global symbol — A symbol that is either defined in the current module and accessed in another, or
accessed in the current module but defined in another.
GROUP — An option of the SECTIONS directive that forces specified output sections to be allocated
contiguously (as a group).
hex conversion utility — A utility that converts object files into one of several standard ASCII
hexadecimal formats, suitable for loading into an EPROM programmer.
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high-level language debugging — The ability of a compiler to retain symbolic and high-level language
information (such as type and function definitions) so that a debugging tool can use this
information.
hole — An area between the input sections that compose an output section that contains no code.
identifier— Names used as labels, registers, and symbols.
immediate operand — An operand whose value must be a constant expression.
incremental linking — Linking files in several passes. Incremental linking is useful for large applications,
because you can partition the application, link the parts separately, and then link all of the parts
together.
initialization at load time — An autoinitialization method used by the linker when linking C/C++ code.
The linker uses this method when you invoke it with the --ram_model link option. This method
initializes variables at load time instead of run time.
initialized section — A section from an object file that will be linked into an executable module.
input section — A section from an object file that will be linked into an executable module.
ISO — International Organization for Standardization; a worldwide federation of national standards
bodies, which establishes international standards voluntarily followed by industries.
label — A symbol that begins in column 1 of an assembler source statement and corresponds to the
address of that statement. A label is the only assembler statement that can begin in column 1.
linker — A software program that combines object files to form an object module that can be allocated
into system memory and executed by the device.
listing file — An output file, created by the assembler, that lists source statements, their line numbers,
and their effects on the section program counter (SPC).
literal constant — A value that represents itself. It may also be called a literal or an immediate value.
little endian — An addressing protocol in which bytes are numbered from right to left within a word. More
significant bytes in a word have higher numbered addresses. Endian ordering is hardware-specific
and is determined at reset. See also big endian
loader — A device that places an executable module into system memory.
macro — A user-defined routine that can be used as an instruction.
macro call — The process of invoking a macro.
macro definition — A block of source statements that define the name and the code that make up a
macro.
macro expansion — The process of inserting source statements into your code in place of a macro call.
macro library — An archive library composed of macros. Each file in the library must contain one macro;
its name must be the same as the macro name it defines, and it must have an extension of .asm.
map file — An output file, created by the linker, that shows the memory configuration, section
composition, section allocation, symbol definitions and the addresses at which the symbols were
defined for your program.
member — The elements or variables of a structure, union, archive, or enumeration.
memory map — A map of target system memory space that is partitioned into functional blocks.
memory reference operand — An operand that refers to a location in memory using a target-specific
syntax.
mnemonic — An instruction name that the assembler translates into machine code.
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model statement — Instructions or assembler directives in a macro definition that are assembled each
time a macro is invoked.
named section — An initialized section that is defined with a .sect directive.
object file — An assembled or linked file that contains machine-language object code.
object library — An archive library made up of individual object files.
object module — A linked, executable object file that can be downloaded and executed on a target
system.
operand — An argument of an assembly language instruction, assembler directive, or macro directive
that supplies information to the operation performed by the instruction or directive.
optimizer — A software tool that improves the execution speed and reduces the size of C programs. See
also assembly optimizer.
options — Command-line parameters that allow you to request additional or specific functions when you
invoke a software tool.
output module — A linked, executable object file that is downloaded and executed on a target system.
output section — A final, allocated section in a linked, executable module.
partial linking — Linking files in several passes. Incremental linking is useful for large applications
because you can partition the application, link the parts separately, and then link all of the parts
together.
quiet run — An option that suppresses the normal banner and the progress information.
raw data — Executable code or initialized data in an output section.
register operand — A special pre-defined symbol that represents a CPU register.
relocatable constant expression— An expression that refers to at least one external symbol, register, or
memory location. The value of the expression is not known until link time.
relocation — A process in which the linker adjusts all the references to a symbol when the symbol's
address changes.
ROM width — The width (in bits) of each output file, or, more specifically, the width of a single data value
in the hex conversion utility file. The ROM width determines how the utility partitions the data into
output files. After the target words are mapped to memory words, the memory words are broken
into one or more output files. The number of output files is determined by the ROM width.
run address — The address where a section runs.
run-time-support library — A library file, rts.src, that contains the source for the run time-support
functions.
section — A relocatable block of code or data that ultimately will be contiguous with other sections in the
memory map.
section program counter (SPC) — An element that keeps track of the current location within a section;
each section has its own SPC.
sign extend — A process that fills the unused MSBs of a value with the value's sign bit.
source file — A file that contains C/C++ code or assembly language code that is compiled or assembled
to form an object file.
static variable — A variable whose scope is confined to a function or a program. The values of static
variables are not discarded when the function or program is exited; their previous value is resumed
when the function or program is reentered.
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storage class — An entry in the symbol table that indicates how to access a symbol.
string table — A table that stores symbol names that are longer than eight characters (symbol names of
eight characters or longer cannot be stored in the symbol table; instead they are stored in the string
table). The name portion of the symbol's entry points to the location of the string in the string table.
structure — A collection of one or more variables grouped together under a single name.
subsection — A relocatable block of code or data that ultimately will occupy continuous space in the
memory map. Subsections are smaller sections within larger sections. Subsections give you tighter
control of the memory map.
symbol — A name that represents an address or a value.
symbolic constant — A symbol with a value that is an absolute constant expression.
symbolic debugging — The ability of a software tool to retain symbolic information that can be used by a
debugging tool such as an emulator.
tag — An optional type name that can be assigned to a structure, union, or enumeration.
target memory — Physical memory in a system into which executable object code is loaded.
.text section — One of the default object file sections. The .text section is initialized and contains
executable code. You can use the .text directive to assemble code into the .text section.
unconfigured memory — Memory that is not defined as part of the memory map and cannot be loaded
with code or data.
uninitialized section — A object file section that reserves space in the memory map but that has no
actual contents. These sections are built with the .bss and .usect directives.
UNION — An option of the SECTIONS directive that causes the linker to allocate the same address to
multiple sections.
union — A variable that can hold objects of different types and sizes.
unsigned value — A value that is treated as a nonnegative number, regardless of its actual sign.
variable — A symbol representing a quantity that can assume any of a set of values.
well-defined expression — A term or group of terms that contains only symbols or assembly-time
constants that have been defined before they appear in the expression.
word — A 32-bit addressable location in target memory
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Appendix D
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Revision History
D.1
Recent Revisions
Table D-1 lists significant changes that have been made between the TMS320C6000 Assembly Language
Tools User's Guide for the v7.4 of the Code Generation Tools (SPRU186) and the current version of this
document.
Table D-1. Revision History
Version
Added
Chapter
Location
Additions / Modifications / Deletions
SPRUI03B
Linker
Description
Section 8.4
Several linker options have been deprecated, removed, or renamed. The linker
continues to accept some of the deprecated options, but they are not
recommended for use. See the Compiler Option Cleanup wiki page for a list of
deprecated and removed options, options that have been removed from CCS,
and options that have been renamed.
SPRUI03B
Linker
Description
Section 8.4.8
The --multithread linker option has been added.
SPRUI03B
Linker
Description
Section 8.5.9
Documented revised behavior of ECC directives.
Previous Revisions:
328
SPRUI03A
Linker
Description
Section 8.5.3
Information about accessing files and libraries from a linker command file has
been added.
SPRUI03A
Object File
Utilities
Section 9.1
A –cg option has been added to the Object File Display utility to display
function stack usage and callee information in XML format.
SPRUI03
Preface
--
The C6200, C6400, C6700, and C6700+ variants are not supported in v8.0 and
later versions of the TI Code Generation Tools. This document applies to the
C64x+, C6740, and C6600 variants of the TMS320C6000™ processor series.
Sections of this document that referred to the legacy variants have been
removed or simplified. If you are using a legacy device, please use v7.4 of the
Code Generation Tools and refer to SPRU186 for documentation.
SPRUI03
--
--
The software simulator for C6000 devices is no longer supported. It was
supported only for legacy devices.
SPRUI03
Introduction
Section 1.2
The Absolute Lister and Cross-Reference Lister are no longer supported. They
were supported only for legacy devices.
SPRUI03
Object
Modules
Section 2.1
The COFF object file format and the associated STABS debugging format are
no longer supported. The C6000 Code Generation Tools now support only the
Embedded Application Binary Interface (EABI) ABI, which works only with
object files that use the ELF object file format and the DWARF debug format.
Sections of this document that referred to the COFF format have been
removed or simplified. If you want COFF support, please use v7.4 of the Code
Generation Tools and refer to SPRU186 for documentation.
SPRUI03
Object
Modules
Section 2.6.2
You can now define weak symbols using assembly or the linker command file.
The linker can omit weak symbols if they are not needed to resolve references.
SPRUI03
Program
Loading and
Running
Section 3.1.2
Secondary bootloaders are no longer described. They were used with legacy
devices.
SPRUI03
Linker
Section 8.4.10
Added a list of the linker's predefined macros.
SPRUI03
Linker
Section 8.5.10.7
Information is provided about the _symval operator.
SPRUI03
Linker
Section 8.6.1
Added information about referencing linker symbols.
Revision History
SPRUI03B – May 2017
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