Texas Instruments TMS320C6000 Assembly Language Tools v 6.1 (Rev. Q) User's Guide
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TMS320C6000 Assembly Language Tools v7.4
User's Guide
Literature Number: SPRU186W
July 2012
Contents
Preface ......................................................................................................................................
1
2
3
Introduction to the Software Development Tools
1.1
Software Development Tools Overview
...................................................................
................................................................................
1.2
Tools Descriptions
.........................................................................................................
Introduction to Object Modules
2.1
Sections
...........................................................................................
.....................................................................................................................
2.2
How the Assembler Handles Sections
2.2.1
Uninitialized Sections
..................................................................................
............................................................................................
2.2.2
Initialized Sections
................................................................................................
2.2.3
Named Sections
2.2.4
Subsections
..................................................................................................
.......................................................................................................
2.2.5
Section Program Counters
2.2.6
Using Sections Directives
......................................................................................
.......................................................................................
2.3
2.4
2.5
2.6
2.7
2.8
How the Linker Handles Sections
.......................................................................................
2.3.1
Default Memory Allocation
......................................................................................
2.3.2
Placing Sections in the Memory Map
..........................................................................
Relocation
..................................................................................................................
2.4.1
Expressions With Multiple Relocatable Symbols (COFF Only)
............................................
2.4.2
Dynamic Relocation Entries (ELF Only)
.......................................................................
Run-Time Relocation
Loading a Program
......................................................................................................
........................................................................................................
Symbols in an Object File
2.7.1
External Symbols
................................................................................................
.................................................................................................
Object File Format Specifications
.......................................................................................
Assembler Description
3.1
Assembler Overview
.......................................................................................................
......................................................................................................
3.2
3.3
3.4
The Assembler's Role in the Software Development Flow
Invoking the Assembler
..........................................................
...................................................................................................
Controlling Application Binary Interface
................................................................................
3.5
3.6
3.7
Naming Alternate Directories for Assembler Input
3.5.1
Using the --include_path Assembler Option
....................................................................
..................................................................
3.5.2
Using the C6X_A_DIR Environment Variable
Source Statement Format
................................................................
................................................................................................
3.6.1
Label Field
.........................................................................................................
3.6.2
Mnemonic Field
...................................................................................................
3.6.3
Unit Specifier Field
...............................................................................................
3.6.4
Operand Field
3.6.5
Comment Field
.....................................................................................................
....................................................................................................
Constants
...................................................................................................................
3.7.1
Binary Integers
3.7.2
Octal Integers
....................................................................................................
.....................................................................................................
3.7.3
Decimal Integers
..................................................................................................
3.7.4
Hexadecimal Integers
............................................................................................
3.7.5
Character Constants
.............................................................................................
3.7.6
Assembly-Time Constants
......................................................................................
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4
5
3.8
3.9
Character Strings
..........................................................................................................
Symbols
.....................................................................................................................
3.9.1
Labels
..............................................................................................................
3.9.2
Local Labels
.......................................................................................................
3.9.3
Symbolic Constants
..............................................................................................
3.9.4
Defining Symbolic Constants (--asm_define Option)
........................................................
3.9.5
Predefined Symbolic Constants
3.9.6
Register Pairs
................................................................................
.....................................................................................................
3.9.7
Register Quads (C6600 Only)
3.9.8
Substitution Symbols
..................................................................................
.............................................................................................
3.10
Expressions
................................................................................................................
3.10.1
Operators
.........................................................................................................
3.10.2
Expression Overflow and Underflow
..........................................................................
3.10.3
Well-Defined Expressions
3.10.4
Conditional Expressions
......................................................................................
........................................................................................
3.10.5
Legal Expressions
...............................................................................................
3.10.6
Expression Examples
...........................................................................................
3.11
Built-in Functions and Operators
........................................................................................
3.11.1
Built-In Math and Trigonometric Functions
...................................................................
3.11.2
C6x Built-In ELF Relocation Generating Operators
.........................................................
3.12
Source Listings
............................................................................................................
3.13
Debugging Assembly Source
3.14
Cross-Reference Listings
............................................................................................
.................................................................................................
Assembler Directives
4.1
4.2
.........................................................................................................
Directives Summary
.......................................................................................................
Directives That Define Sections
.........................................................................................
4.3
4.4
4.5
Directives That Initialize Constants
.....................................................................................
Directives That Perform Alignment and Reserve Space
.............................................................
Directives That Format the Output Listings
............................................................................
4.6
4.7
4.8
4.9
Directives That Reference Other Files
..................................................................................
Directives That Enable Conditional Assembly
.........................................................................
Directives That Define Union or Structure Types
Directives That Define Enumerated Types
.....................................................................
.............................................................................
4.10
Directives That Define Symbols at Assembly Time
...................................................................
4.11
Miscellaneous Directives
4.12
Directives Reference
.................................................................................................
......................................................................................................
Macro Description
5.1
5.2
Using Macros
............................................................................................................
.............................................................................................................
Defining Macros
..........................................................................................................
5.3
Macro Parameters/Substitution Symbols
.............................................................................
5.3.1
Directives That Define Substitution Symbols
................................................................
5.3.2
Built-In Substitution Symbol Functions
5.3.3
Recursive Substitution Symbols
.......................................................................
..............................................................................
5.3.4
Forced Substitution
.............................................................................................
5.4
5.5
5.6
5.3.5
Accessing Individual Characters of Subscripted Substitution Symbols
5.3.6
Substitution Symbols as Local Variables in Macros
..................................
........................................................
Macro Libraries
...........................................................................................................
Using Conditional Assembly in Macros
...............................................................................
Using Labels in Macros
.................................................................................................
5.7
5.8
Producing Messages in Macros
........................................................................................
Using Directives to Format the Output Listing
.......................................................................
5.9
Using Recursive and Nested Macros
5.10
Macro Directives Summary
.................................................................................
.............................................................................................
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6
7
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Archiver Description
6.1
6.2
6.3
........................................................................................................
Archiver Overview
........................................................................................................
The Archiver's Role in the Software Development Flow
............................................................
Invoking the Archiver
....................................................................................................
6.4
6.5
Archiver Examples
.......................................................................................................
Library Information Archiver Description
..............................................................................
6.5.1
Invoking the Library Information Archiver
6.5.2
Library Information Archiver Example
....................................................................
........................................................................
6.5.3
Listing the Contents of an Index Library
6.5.4
Requirements
.....................................................................
....................................................................................................
Linker Description
7.1
7.2
7.3
...........................................................................................................
Linker Overview
..........................................................................................................
The Linker's Role in the Software Development Flow
..............................................................
Invoking the Linker
.......................................................................................................
7.4
Linker Options
............................................................................................................
7.4.1
Wild Cards in File, Section, and Symbol Patterns
..........................................................
7.4.2
Relocation Capabilities (--absolute_exe and --relocatable Options)
.....................................
7.4.3
Allocate Memory for Use by the Loader to Pass Arguments (--arg_size Option)
......................
7.4.4
Compression (--cinit_compression and --copy_compression Option)
...................................
7.4.5
Control Linker Diagnostics
.....................................................................................
7.4.6
Disable Automatic Library Selection (--disable_auto_rts Option)
.........................................
7.4.7
Controlling Unreferenced and Unused Sections
............................................................
7.4.8
Link Command File Preprocessing (--disable_pp, --define and --undefine Options)
...................
7.4.9
Define an Entry Point (--entry_point Option)
................................................................
7.4.10
Set Default Fill Value (--fill_value Option)
7.4.11
Define Heap Size (--heap_size Option)
..................................................................
.....................................................................
7.4.12
Hiding Symbols
.................................................................................................
7.5
7.4.13
Alter the Library Search Algorithm (--library Option, --search_path Option, and C6X_C_DIR
Environment Variable)
..........................................................................................
7.4.14
Change Symbol Localization
.................................................................................
7.4.15
Create a Map File (--map_file Option)
......................................................................
7.4.16
Managing Map File Contents (--mapfile_contents Option)
...............................................
7.4.17
Disable Name Demangling (--no_demangle)
..............................................................
7.4.18
Disable Merge of Symbolic Debugging Information (--no_sym_merge Option)
.......................
7.4.19
Strip Symbolic Information (--no_symtable Option)
.......................................................
7.4.20
Name an Output Module (--output_file Option)
............................................................
7.4.21
Prioritizing Function Placement (--preferred_order Option)
..............................................
7.4.22
C Language Options (--ram_model and --rom_model Options)
7.4.23
Retain Discarded Sections (--retain Option)
.........................................
................................................................
7.4.24
Create an Absolute Listing File (--run_abs Option)
........................................................
7.4.25
Scan All Libraries for Duplicate Symbol Definitions (--scan_libraries)
7.4.26
Define Stack Size (--stack_size Option)
..................................
....................................................................
7.4.27
Enforce Strict Compatibility (--strict_compatibility Option)
7.4.28
Mapping of Symbols (--symbol_map Option)
................................................
..............................................................
7.4.29
Generate Far Call Trampolines (--trampolines Option)
...................................................
7.4.30
Introduce an Unresolved Symbol (--undef_sym Option)
..................................................
7.4.31
Display a Message When an Undefined Output Section Is Created (--warn_sections Option)
.....
7.4.32
Generate XML Link Information File (--xml_link_info Option)
7.4.33
Zero Initialization (--zero_init Option)
............................................
........................................................................
Linker Command Files
..................................................................................................
7.5.1
Reserved Names in Linker Command Files
7.5.2
Constants in Linker Command Files
.................................................................
.........................................................................
7.5.3
The MEMORY Directive
........................................................................................
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8
9
7.6
7.7
7.8
7.5.4
The SECTIONS Directive
......................................................................................
7.5.5
Specifying a Section's Run-Time Address
...................................................................
7.5.6
Using UNION and GROUP Statements
......................................................................
7.5.7
Special Section Types (DSECT, COPY, NOLOAD, and NOINIT)
........................................
7.5.8
Assigning Symbols at Link Time
7.5.9
Creating and Filling Holes
..............................................................................
.....................................................................................
Object Libraries
...........................................................................................................
Default Allocation Algorithm
............................................................................................
7.7.1
How the Allocation Algorithm Creates Output Sections
...................................................
7.7.2
Reducing Memory Fragmentation
Linker-Generated Copy Tables
............................................................................
........................................................................................
7.8.1
A Current Boot-Loaded Application Development Process
...............................................
7.8.2
An Alternative Approach
.......................................................................................
7.8.3
Overlay Management Example
...............................................................................
7.8.4
Generating Copy Tables Automatically With the Linker
7.8.5
The table() Operator
...................................................
............................................................................................
7.8.6
Boot-Time Copy Tables
........................................................................................
7.8.7
Using the table() Operator to Manage Object Components
7.8.8
Compression Support
...............................................
..........................................................................................
7.8.9
Copy Table Contents
...........................................................................................
7.8.10
General Purpose Copy Routine
..............................................................................
7.8.11
Linker-Generated Copy Table Sections and Symbols
....................................................
7.9
7.8.12
Splitting Object Components and Overlay Management
Partial (Incremental) Linking
.................................................
............................................................................................
7.10
Linking C/C++ Code
.....................................................................................................
7.10.1
Run-Time Initialization
.........................................................................................
7.10.2
Object Libraries and Run-Time Support
....................................................................
7.10.3
Setting the Size of the Stack and Heap Sections
7.10.4
Autoinitialization of Variables at Run Time
.........................................................
.................................................................
7.10.5
Initialization of Variables at Load Time
......................................................................
7.10.6
The --rom_model and --ram_model Linker Options
.......................................................
7.11
Linker Example
...........................................................................................................
7.12
Dynamic Linking with the C6000 Code Generation Tools
7.12.1
Static vs Dynamic Linking
..........................................................
....................................................................................
7.12.2
Embedded Application Binary Interface (EABI) Required
7.12.3
Bare-Metal Dynamic Linking Model
................................................
.........................................................................
7.12.4
Building a Dynamic Executable
..............................................................................
7.12.5
Building a Dynamic Library
7.12.6
Symbol Import/Export
...................................................................................
.........................................................................................
Absolute Lister Description
8.1
8.2
8.3
Absolute Lister Example
...............................................................................................
Producing an Absolute Listing
Invoking the Absolute Lister
..........................................................................................
............................................................................................
................................................................................................
Cross-Reference Lister Description
9.1
Producing a Cross-Reference Listing
...................................................................................
.................................................................................
9.2
9.3
Invoking the Cross-Reference Lister
Cross-Reference Listing Example
..................................................................................
.....................................................................................
10 Object File Utilities ...........................................................................................................
10.1
Invoking the Object File Display Utility
10.2
Invoking the Disassembler
................................................................................
..............................................................................................
10.3
Invoking the Name Utility
10.4
Invoking the Strip Utility
...............................................................................................
.................................................................................................
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11 Hex Conversion Utility Description ....................................................................................
11.1
The Hex Conversion Utility's Role in the Software Development Flow
11.2
Invoking the Hex Conversion Utility
...........................................
...................................................................................
11.2.1
Invoking the Hex Conversion Utility From the Command Line
11.2.2
Invoking the Hex Conversion Utility With a Command File
..........................................
..............................................
11.3
Understanding Memory Widths
........................................................................................
11.3.1
Target Width
....................................................................................................
11.3.2
Specifying the Memory Width
................................................................................
11.3.3
Partitioning Data Into Output Files
...........................................................................
11.3.4
Specifying Word Order for Output Words
...................................................................
11.4
The ROMS Directive
.....................................................................................................
11.4.1
When to Use the ROMS Directive
11.4.2
An Example of the ROMS Directive
...........................................................................
.........................................................................
11.5
The SECTIONS Directive
...............................................................................................
11.6
The Load Image Format (--load_image Option)
.....................................................................
11.6.1
Load Image Section Formation
..............................................................................
11.6.2
Load Image Characteristics
11.7
Excluding a Specified Section
..................................................................................
..........................................................................................
11.8
Assigning Output Filenames
............................................................................................
11.9
Image Mode and the --fill Option
.......................................................................................
11.9.1
Generating a Memory Image
.................................................................................
11.9.2
Specifying a Fill Value
.........................................................................................
11.9.3
Steps to Follow in Using Image Mode
......................................................................
11.10
Building a Table for an On-Chip Boot Loader
11.10.1
Description of the Boot Table
.......................................................................
...............................................................................
11.10.2
The Boot Table Format
......................................................................................
11.10.3
How to Build the Boot Table
11.10.4
Using the C6000 Boot Loader
................................................................................
..............................................................................
11.11
Controlling the ROM Device Address
.................................................................................
11.12
Control Hex Conversion Utility Diagnostics
..........................................................................
11.13
Description of the Object Formats
.....................................................................................
11.13.1
ASCII-Hex Object Format (--ascii Option)
.................................................................
11.13.2
Intel MCS-86 Object Format (--intel Option)
..............................................................
11.13.3
Motorola Exorciser Object Format (--motorola Option)
11.13.4
Extended Tektronix Object Format (--tektronix Option)
..................................................
.................................................
11.13.5
Texas Instruments SDSMAC (TI-Tagged) Object Format (--ti_tagged Option)
11.13.6
TI-TXT Hex Format (--ti_txt Option)
......................
........................................................................
12 Sharing C/C++ Header Files With Assembly Source
12.2.1
Comments
.............................................................
12.1
Overview of the .cdecls Directive
12.2
Notes on C/C++ Conversions
......................................................................................
..........................................................................................
......................................................................................................
12.2.2
Conditional Compilation (#if/#else/#ifdef/etc.)
12.2.3
Pragmas
..............................................................
.........................................................................................................
12.2.4
The #error and #warning Directives
.........................................................................
12.2.5
Predefined symbol _ _ASM_HEADER_ _
..................................................................
12.2.6
Usage Within C/C++ asm( ) Statements
....................................................................
12.2.7
The #include Directive
.........................................................................................
12.2.8
Conversion of #define Macros
...............................................................................
12.2.9
The #undef Directive
12.2.10
Enumerations
..........................................................................................
.................................................................................................
12.2.11
C Strings
.......................................................................................................
12.2.12
C/C++ Built-In Functions
12.2.13
Structures and Unions
....................................................................................
.......................................................................................
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A
B
C
12.2.14
Function/Variable Prototypes
12.2.15
C Constant Suffixes
...............................................................................
..........................................................................................
12.2.16
Basic C/C++ Types
...........................................................................................
12.3
Notes on C++ Specific Conversions
...................................................................................
12.3.1
Name Mangling
12.3.2
Derived Classes
12.3.3
Templates
................................................................................................
................................................................................................
.......................................................................................................
12.3.4
Virtual Functions
12.4
Special Assembler Support
...............................................................................................
.............................................................................................
12.4.1
Enumerations (.enum/.emember/.endenum)
12.4.2
The .define Directive
...............................................................
...........................................................................................
12.4.3
The .undefine/.unasg Directives
.............................................................................
12.4.4
The $defined( ) Built-In Function
12.4.5
The $sizeof Built-In Function
.............................................................................
.................................................................................
12.4.6
Structure/Union Alignment and $alignof( )
12.4.7
The .cstring Directive
..................................................................
..........................................................................................
Symbolic Debugging Directives
A.1
A.2
A.3
Debug Directive Syntax
.........................................................................................
DWARF Debugging Format
COFF Debugging Format
............................................................................................
...............................................................................................
.................................................................................................
XML Link Information File Description
B.1
XML Information File Element Types
................................................................................
..................................................................................
B.2
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
....................................................................................................
Glossary .........................................................................................................................
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Contents 7
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List of Figures
1-1.
TMS320C6000 Software Development Flow
.........................................................................
2-1.
Partitioning Memory Into Logical Blocks
...............................................................................
2-2.
Using Sections Directives Example
.....................................................................................
2-3.
Object Code Generated by the File in
.................................................................................
2-4.
Combining Input Sections to Form an Executable Object Module
..................................................
3-1.
The Assembler in the TMS320C6000 Software Development Flow
................................................
3-2.
Example Assembler Listing
4-1.
The .field Directive
..............................................................................................
........................................................................................................
4-2.
Initialization Directives
....................................................................................................
4-3.
The .align Directive
........................................................................................................
4-4.
The .space and .bes Directives
..........................................................................................
4-5.
Double-Precision Floating-Point Format
................................................................................
4-6.
The .field Directive
.......................................................................................................
4-7.
Single-Precision Floating-Point Format
...............................................................................
4-8.
The .usect Directive
.....................................................................................................
6-1.
The Archiver in the TMS320C6000 Software Development Flow
.................................................
7-1.
The Linker in the TMS320C6000 Software Development Flow
....................................................
7-2.
Section Allocation Defined by
.........................................................................................
7-3.
Run-Time Execution of
.................................................................................................
7-4.
Memory Allocation Shown in and
.....................................................................................
7-5.
Compressed Copy Table
................................................................................................
7-6.
Handler Table
............................................................................................................
7-7.
Autoinitialization at Run Time
..........................................................................................
7-8.
Initialization at Load Time
...............................................................................................
7-9.
A Basic DSP Run-Time Model
.........................................................................................
7-10.
Dynamic Linking Model
.................................................................................................
7-11.
Base Image Executable
.................................................................................................
8-1.
Absolute Lister Development Flow
....................................................................................
9-1.
The Cross-Reference Lister Development Flow
.....................................................................
11-1.
The Hex Conversion Utility in the TMS320C6000 Software Development Flow
................................
11-2.
Hex Conversion Utility Process Flow
..................................................................................
11-3.
Object File Data and Memory Widths
.................................................................................
11-4.
Data, Memory, and ROM Widths
......................................................................................
11-5.
The infile.out File Partitioned Into Four Output Files
................................................................
11-6.
ASCII-Hex Object Format
...............................................................................................
11-7.
Intel Hexadecimal Object Format
......................................................................................
11-8.
Motorola-S Format
.......................................................................................................
11-9.
Extended Tektronix Object Format
....................................................................................
11-10. TI-Tagged Object Format
...............................................................................................
11-11. TI-TXT Object Format
...................................................................................................
8 List of Figures
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List of Tables
3-1.
TMS320C6000 Assembler Options
.....................................................................................
3-2.
CPU Control Registers
....................................................................................................
3-3.
Processor Symbols
........................................................................................................
3-4.
Operators Used in Expressions (Precedence)
3-5.
Built-In Mathematical Functions
........................................................................
.........................................................................................
3-6.
Symbol Attributes
..........................................................................................................
4-1.
Directives That Define Sections
.........................................................................................
4-2.
Directives That Initialize Values (Data and Memory)
.................................................................
4-3.
Directives That Perform Alignment and Reserve Space
.............................................................
4-4.
Directives That Format the Output Listing
.............................................................................
4-5.
Directives That Reference Other Files
..................................................................................
4-6.
Directives That Effect Symbol Linkage and Visibility
.................................................................
4-7.
Directives That Control Dynamic Symbol Visibility
....................................................................
4-8.
Directives That Enable Conditional Assembly
.........................................................................
4-9.
Directives That Define Union or Structure Types
4-10.
Directives That Define Symbols
.....................................................................
.........................................................................................
4-11.
Directives That Define Common Data Sections
.......................................................................
4-12.
Directives That Create or Effect Macros
...............................................................................
4-13.
Directives That Control Diagnostics
.....................................................................................
4-14.
Directives That Perform Assembly Source Debug
....................................................................
4-15.
Directives That Are Used by the Absolute Lister
......................................................................
4-16.
Directives That Perform Miscellaneous Functions
....................................................................
5-1.
Substitution Symbol Functions and Return Values
..................................................................
5-2.
Creating Macros
..........................................................................................................
5-3.
Manipulating Substitution Symbols
....................................................................................
5-4.
Conditional Assembly
...................................................................................................
5-5.
Producing Assembly-Time Messages
.................................................................................
5-6.
Formatting the Listing
...................................................................................................
7-1.
Basic Options Summary
................................................................................................
7-2.
File Search Path Options Summary
...................................................................................
7-3.
Command File Preprocessing Options Summary
...................................................................
7-4.
Diagnostic Options Summary
..........................................................................................
7-5.
Linker Output Options Summary
.......................................................................................
7-6.
Symbol Management Options Summary
7-7.
Run-Time Environment Options Summary
.............................................................................
...........................................................................
7-8.
Link-Time Optimization Options Summary
...........................................................................
7-9.
Dynamic Linking Options Summary
...................................................................................
7-10.
Miscellaneous Options Summary
......................................................................................
7-11.
Groups of Operators Used in Expressions (Precedence)
7-12.
Compiler Options For Dynamic Linking
..........................................................
...............................................................................
7-13.
Linker Options For Dynamic Linking
..................................................................................
9-1.
Symbol Attributes in Cross-Reference Listing
........................................................................
11-1.
Basic Hex Conversion Utility Options
.................................................................................
11-2.
Boot-Loader Options
.....................................................................................................
11-3.
Options for Specifying Hex Conversion Formats
....................................................................
A-1.
Symbolic Debugging Directives
........................................................................................
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List of Tables 9
Preface
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About This Manual
The TMS320C6000 Assembly Language Tools User's Guide explains how to use these assembly language tools:
• Assembler
• Archiver
• Linker
• Library information archiver
• Absolute lister
• Cross-reference lister
• 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 assembly language tools designed specifically for the TMS320C6000 ™ 32-bit devices. This book consists of four parts:
• Introductory information, consisting of
and
Chapter 2 , gives you an overview of the
assembly language development tools. It also discusses object modules, which helps you to use the
TMS320C6000 tools more effectively. Read
before using the assembler and linker.
• Assembler description, consisting of
through
, contains detailed information about using the assembler. This portion explains how to invoke the assembler and discusses source statement format, valid constants and expressions, assembler output, and assembler directives. It also describes the macro language.
• Additional assembly language tools description, consisting of
through
describes in detail each of the tools provided with the assembler to help you create executable object files. For example,
explains how to invoke the linker, how the linker operates, and how to use linker directives;
explains how to use the hex conversion utility.
• Reference material, consisting of
through
, provides supplementary information including symbolic debugging directives that the TMS320C6000 C/C++ compiler uses. It also provides a description of the XML link information file and a glossary.
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Notational Conventions
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, cruel 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, 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].
• The TMS320C6200 core is referred to as C6200. The TMS320C6400 core is referred to as C6400.
The TMS320C6700 core is referred to as C6700. TMS320C6000 and C6000 can refer to either C6200,
C6400, C6400+, C6700, C6700+, C6740, or C6600.
• Following are other symbols and abbreviations used throughout this document:
Symbol
B,b
H, h
LSB
MSB
0x
Q, q
Definition
Suffix — binary integer
Suffix — hexadecimal integer
Least significant bit
Most significant bit
Prefix — hexadecimal integer
Suffix — octal integer
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Related Documentation From Texas Instruments www.ti.com
Related Documentation From Texas Instruments
You can use the following books to supplement this user's guide:
SPRAAO8 — Common Object File Format Application Report. Provides supplementary information on the internal format of COFF object files. Much of this information pertains to the symbolic debugging information that is produced by the C compiler.
SPRAB89 — The C6000 Embedded Application Binary Interface Application Note. Provides a specification for the ELF-based 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.
SPRU187 — TMS320C6000 Optimizing Compiler v7.4 User's Guide. Describes the TMS320C6000 C compiler and the assembly optimizer. This C compiler accepts ANSI standard C source code and produces assembly language source code for the TMS320C6000 platform of devices (including the
C64x+ and C67x+ generations). The assembly optimizer helps you optimize your assembly code.
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).
SPRU198 — TMS320C6000 Programmer's Guide. Reference for programming the TMS320C6000 digital signal processors (DSPs). Before you use this manual, you should install your code generation and debugging tools. Includes a brief description of the C6000 DSP architecture and code development flow, includes C code examples and discusses optimization methods for the C code, describes the structure of assembly code and includes examples and discusses optimizations for the assembly code, and describes programming considerations for the C64x DSP.
SPRU731 — TMS320C62x DSP CPU and Instruction Set Reference Guide. Describes the CPU architecture, pipeline, instruction set, and interrupts for the TMS320C62x digital signal processors
(DSPs) of the TMS320C6000 DSP family. The C62x DSP generation comprises fixed-point devices in the C6000 DSP platform.
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.
SPRU733 — TMS320C67x/C67x+ DSP CPU and Instruction Set Reference Guide. Describes the CPU architecture, pipeline, instruction set, and interrupts for the TMS320C67x and TMS320C67x+ digital signal processors (DSPs) of the TMS320C6000 DSP platform. The C67x/C67x+ DSP generation comprises floating-point devices in the C6000 DSP platform. The C67x+ DSP is an enhancement of the C67x 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.
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
• Absolute lister
• Cross-reference lister
• 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
...........................................................................................................................
Page
1.1
Software Development Tools Overview
1.2
Tools Descriptions
................................................................
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1.1
Software Development Tools Overview
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
C/C++ source files
Macro source files
C/C++ compiler
Linear assembly
Archiver
Macro library
Archiver
Library of object files
Assembler source
Assembler
Object files
Linker
Assembly optimizer
Assembly optimized file
Library-build utility
Run-timesupport library
Debugging tools
Executable object file
Hex-conversion utility
EPROM programmer
Absolute lister
Cross-reference lister
Object file utilities
C6000
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Tools Descriptions
1.2
Tools Descriptions
The following list describes the tools that are shown in
• The C/C++ compiler accepts C/C++ source code and produces TMS320C6000 machine code object modules. A shell program, an optimizer, and an interlist utility are included in the compiler package:
– The shell program enables you to compile, assemble, and link source modules in one step.
– The optimizer modifies code to improve the efficiency of C/C++ programs.
– The interlist utility interlists C/C++ source statements with assembly language output to correlate code produced by the compiler with your source code.
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 various aspects of the assembly process, such as the source listing format, data alignment, and section content. See
through
Chapter 5 . See the TMS320C62x
DSP CPU and Instruction Set Reference Guide, TMS320C64x/C64x+ DSP CPU and Instruction Set
Reference Guide, TMS320C67x/C67x+ DSP CPU and Instruction Set Reference Guide, and
TMS320C66x CPU and Instruction Set Reference Guide for detailed information on the assembly language instruction set.
• The linker combines object files into a single static executable or object dynamic object module. As it creates a static executable module, it performs 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 or redefine global symbols. See
For more information about creating a dynamic object module, see http://processors.wiki.ti.com/index.php/C6000_Dynamic_Linking .
• The archiver allows you to collect a group of files into a single archive file, called a library. You can also use the archiver to collect a group of object files into an object library. 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. 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. See
• 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
.
• 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 an object file into TI-Tagged, ASCII-Hex, Intel, Motorola-S, or
Tektronix object format. The converted file can be downloaded to an EPROM programmer. See
• The absolute lister uses linked object files to create .abs files. These files can be assembled to produce a listing of the absolute addresses of object code. See
.
• The cross-reference lister uses object files to produce a cross-reference listing showing symbols, their definition, and their references in the linked source files. See
• The main product of this development process is a executable object file that can be executed in a
TMS320C6000 device. You can use one of several debugging tools to refine and correct your code.
Available products include:
– An instruction-accurate and clock-accurate software simulator
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– An XDS emulator www.ti.com
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Tools Descriptions
In addition, the following utilities are provided:
• The object file display utility prints the contents of object files, executable files, and archive libraries in either human readable or XML formats. See
• The disassembler decodes object modules to show the assembly instructions that it represents. See
.
• The name utility prints a list of linknames of objects and functions defined or referenced in a object or an executable file. See
.
• The strip utility removes symbol table and debugging information from object and executable files.
See
.
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17
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
...........................................................................................................................
Page
2.1
Sections ...........................................................................................................
2.2
How the Assembler Handles Sections .................................................................
2.3
How the Linker Handles Sections ........................................................................
2.4
Relocation ........................................................................................................
2.5
Run-Time Relocation .........................................................................................
2.6
Loading a Program ............................................................................................
2.7
Symbols in an Object File ...................................................................................
2.8
Object File Format Specifications ........................................................................
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Sections
2.1
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 with other sections. Each section of an object file is separate and distinct. Object files usually contain three default sections:
.text section
.data section
.bss section contains executable code (1) usually contains initialized data usually reserves space for uninitialized variables
(1) Some targets allow non-text in .text sections.
In addition, the assembler and linker allow you to create, name, and link named sections that are used like the .data, .text, and .bss sections.
There are two basic types of sections:
Initialized sections
Uninitialized sections contain data or code. The .text and .data sections are initialized; named sections created with the .sect assembler directive are also initialized.
reserve space in the memory map for uninitialized data. The .bss section is uninitialized; named sections created with the .usect assembler directive are also uninitialized.
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
.
One of the linker's functions is to relocate sections into the target system's memory map; this function is called allocation. 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 into a portion of the memory map that contains ROM.
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
EEPROM .data
.text
ROM
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Introduction to Object Modules 19
How the Assembler Handles Sections
2.2
How the Assembler Handles Sections
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The assembler identifies the portions of an assembly language program that belong in a given section.
The assembler has five directives that support this function:
• .bss
• .usect
• .text
• .data
• .sect
The .bss and .usect directives create uninitialized sections; the .text, .data, and .sect directives create
initialized sections.
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
Default Sections Directive
NOTE: If you do not use any of the sections directives, the assembler assembles everything into the
.text section.
2.2.1 Uninitialized Sections
Uninitialized sections reserve space in TMS320C6000 memory; they are usually allocated into 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 .bss and .usect assembler directives.
• The .bss directive reserves space in the .bss section.
• The .usect directive reserves space in a specific uninitialized named section.
Each time you invoke the .bss or .usect directive, the assembler reserves additional space in the .bss or the named section. The syntaxes for these directives are: symbol
.bss symbol, size in bytes[, alignment[, bank offset] ]
.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. 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. The value must be 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.
tells the assembler which named section to reserve space in. See
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How the Assembler Handles Sections
The initialized section directives (.text, .data, and .sect) tell the assembler to stop assembling into the current section and begin assembling into the indicated section. The .bss and .usect directives, however,
do not end the current section and begin a new one; they simply escape from the current section temporarily. The .bss and .usect directives can appear anywhere in an initialized section without affecting its contents. For an example, see
The .usect directive can also be used to create uninitialized subsections. See
information on creating subsections.
2.2.2 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 section-relative references.
Three directives tell the assembler to place code or data into a section. The syntaxes for these directives are:
.text
.data
.sect "section name"
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 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, 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 allof the code or data which was placed in that section.
Initialized subsections are created with the .sect directive. The .sect directive can also be used to create initialized subsections. See
, for more information on creating subsections.
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Introduction to Object Modules 21
How the Assembler Handles Sections www.ti.com
2.2.3 Named Sections
Named sections are sections that you create. You can use them like the default .text, .data, and .bss
sections, but they are assembled separately.
For example, repeated use of the .text directive builds up a single .text section in the object file. When linked, this .text section is allocated into memory as a single unit. Suppose there is a portion of executable code (perhaps an initialization routine) that you do not want allocated with .text. If you assemble this segment of code into a named section, it is assembled separately from .text, and you can 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.
Two directives let you create 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 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 section name parameter is the name of the section. For COFF, you can create up to 32 767 separate named sections. For ELF, the max number of sections is 2 32 -1 (4294967295). For the .usect and .sect
directives, a section name can refer to a subsection; see
for details.
Each time you invoke one of these directives with a new name, you create a new named section. Each time you invoke one of these directives with a name that was already used, the assembler assembles 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.
2.2.4 Subsections
Subsections are smaller sections within larger sections. Like sections, subsections can be manipulated by the linker. Placing each function and object in a uniquely-named subsection allows finer-grained memory placement, and also allows the linker finer-grained unused-function elimination. You can create subsections 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. 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. See
for an example using subsections.
You can create two types of subsections:
• Initialized subsections are created using the .sect directive. See
.
• Uninitialized subsections are created using the .usect directive. See
Subsections are allocated in the same manner as sections. See
for information on the
SECTIONS directive.
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How the Assembler Handles Sections
2.2.5 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 each section according to its final location in the memory map. See
for information on relocation.
2.2.6 Using Sections Directives
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
is a listing file.
shows how the SPCs are modified during assembly. A line in a listing file has four fields:
Field 1
Field 2
Field 3
Field 4 contains the source code line counter.
contains the section program counter.
contains the object code.
contains the original source statement.
See
for more information on interpreting the fields in a source listing.
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Introduction to Object Modules 23
How the Assembler Handles Sections
Figure 2-2. Using Sections Directives Example
4 00000000
5 00000000 00000011 coeff
00000004 00000022
.data
.word
011h,022h
9 00000000
10 00000004
.bss
.bss
var1,4 buffer,40
14 00000008 00001234 ptr .word
01234h
18 00000000
19 00000000 00800528 sum:
20 00000004 021085E0
21
.text
MVK
ZERO
22 00000008 01003664 aloop: LDW
23 0000000c 00004000 NOP
24 00000010 0087E1A0
25 00000014 021041E0
SUB
ADD
26 00000018 80000112 [A1]
27 0000001c 00008000
28
29 00000020 0200007C-
B
NOP
STW
10,A1
A4
*A0++,A2
3
A1,1,A1
A2,A4,A4 aloop
5
A4, *+B14(var1)
33 0000000c
34 0000000c 000000AA ivals
00000010 000000BB
00000014 000000CC
.data
.word
0aah, 0bbh, 0cch
38 00000000
39 00000004 var2 inbuf
.usect
”newvars”,4
.usect
”newvars”,4
43 00000024 .text
44 00000024 01003664 xmult: LDW
45 00000028 00006000
46 0000002c 020C4480
NOP
MPYHL
47 00000030 02800028-
48 00000034 02800068-
49 00000038 02140274
MVKL
MVKH
STW
*A0++,A2
4
A2,A3,A4 var2,A5 var2,A5
A4,*A5
53 00000000
54 00000000 00000012’
55 00000004 00008000
Field 1 Field 2 Field 3
.sect
B
NOP
”vectors” sum
5
Field 4 www.ti.com
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As
shows, the file in
creates five sections:
.text
.data
vectors
.bss
newvars
How the Assembler Handles Sections contains 15 32-bit words of object code.
contains six words of initialized data.
is a named section created with the .sect directive; it contains two words of object code.
reserves 44 bytes in memory.
is a 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
Line numbers Object code Section
.text
19
20
44
45
46
47
48
49
22
23
24
25
26
27
29
00800528
021085E0
01003664
00004000
0087E1A0
021041E0
80000112
00008000
0200007C-
01003664
00006000
020C4480
02800028-
02800068-
02140274
5
5
14
34
34
34
54
54
00000011
00000022
00001234
000000AA
000000BB
000000CC
00000000’
00000024’
.data
vectors
9
10
No data—
44 bytes reserved
.bss
38
39
No data—
8 bytes reserved newvars
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Introduction to Object Modules 25
How the Linker Handles Sections
2.3
How the Linker Handles Sections
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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 (when more than one file is being linked) 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 allow you to manipulate sections with greater precision. You can specify subsections with the linker's SECTIONS directive. If you do not specify a subsection explicitly, then the subsection is combined with the other sections with the same base section name.
It is not always necessary to use linker directives. If you do not use them, the linker uses the target processor's default allocation algorithm described in
. 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:
•
•
, The MEMORY Directive
•
, The SECTIONS Directive
•
, Default Allocation Algorithm
2.3.1 Default Memory Allocation
illustrates the process of linking two files together.
Figure 2-4. Combining Input Sections to Form an Executable Object Module
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Relocation
In
.text, .data, and .bss default sections; in addition, each contains a 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 named sections at the end. The memory map shows how the sections are put into memory.
By default, the linker begins at 0h and places the sections one after the other in the following order: .text,
.const, .data, .bss, .cinit, and then any named sections in the order they are encountered in the input files.
The C/C++ compiler uses the .const section to store string constants, and variables or arrays that are declared as far const. The C/C++ compiler produces tables of data for autoinitializing global variables; these variables are stored in a named section called .cinit (see
Example 7-8 ). For more information on the
.const and .cinit sections, see the TMS320C6000 Optimizing Compiler User's Guide .
2.3.2 Placing Sections in the Memory Map
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 named section placed where the .data section would normally be allocated. Most memory maps contain various types of memory (RAM, ROM, EPROM, 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
and
.
2.4
Relocation
The assembler treats each section as if it began at address 0. All relocatable symbols (labels) are relative to address 0 in their sections. Of course, all sections cannot actually begin at address 0 in memory, so the linker relocates 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.
contains a code segment for a
TMS320C6000 device that generates relocation entries.
Example 2 ‑‑ 1. Code That Generates Relocation Entries
1
2 00000000 00000012! Z:
3 00000004 0180082A'
4 00000008 0180006A'
5 0000000C 00004000
6
7 00000010 0001E000 Y:
8 00000014 00000212
9 00000018 00008000
.global X
B X
MVKL
; Uses an external relocation
Y,B3 ; Uses an internal relocation
MVKH
NOP
Y,B3
3
; Uses an internal relocation
IDLE
B
NOP
Y
5
In
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 (relative to address 0 in the .text
section). 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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Introduction to Object Modules 27
Relocation www.ti.com
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
Under the ELF EABI, the relocations are symbol-relative rather than section-relative. This means that in
COFF, the relocation generated for 'Y' will actually have a reference to the '.text' section symbol and will have an offset of 16. Under ELF, the relocation generated for 'Y' would actually refer to the symbol 'Y' and resolve the value for 'Y' in the opcode based on where the definition of 'Y' ends up.
2.4.1 Expressions With Multiple Relocatable Symbols (COFF Only)
Sometimes an expression contains more than one relocatable symbol, or cannot be evaluated at assembly time. In this case, the assembler encodes the entire expression in the object file. After determining the addresses of the symbols, the linker computes the value of the expression as shown in
Example 2-2. Simple Assembler Listing
1
2
3 00000000 00800028%
.global
sym1, sym2
MVKL sym2 - sym1, A1
The symbols sym1 and sym2 are both externally defined. Therefore, the assembler cannot evaluate the expression sym2 - sym1, so it encodes the expression in the object file. The '%' listing character indicates a relocation expression. Suppose the linker relocates sym2 to 300h and sym1 to 200h. Then the linker computes the value of the expression to be 300h - 200h = 100h. Thus the MVKL instruction is patched to:
00808028 MVKL 100h,A1
Expression Cannot Be Larger Than Space Reserved
NOTE: If the value of an expression is larger, in bits, than the space reserved for it, you will receive an error message from the linker.
Each section in an object module has a table of relocation entries. The table contains one relocation entry for each relocatable reference in the section. The linker usually removes relocation entries after it uses them. This prevents the output file from being relocated again (if it is relinked or when it is loaded). A file that contains no relocation entries is an absolute file (all its addresses are absolute addresses). If you want the linker to retain relocation entries, invoke the linker with the --relocatable option (see
).
2.4.2 Dynamic Relocation Entries (ELF Only)
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).
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Run-Time Relocation
2.5
Run-Time Relocation
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 an external-memory-based system. The code must be loaded into external memory, but it would run faster in internal memory.
The linker provides a simple 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.
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 an example that illustrates how to move a block of code at run time, see
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
2.6
Loading a Program
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, are combined and relocated into 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. Several methods can be used for loading a program, depending on the execution environment. Common situations are described below:
• Code Composer Studio can load an executable object module onto hardware. The Code Composer
Studio loader reads the executable file and copies the program into target memory.
• You can use the hex conversion utility (hex6x, which is shipped as part of the assembly language package) to convert the executable object module into one of several object file formats. You can then use the converted file with an EPROM programmer to burn the program into an EPROM.
• A standalone simulator can be invoked by the load6x command and the name of the executable object module. The standalone simulator reads the executable file, copies the program into the simulator and executes it, displaying any C I/O.
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Introduction to Object Modules 29
Symbols in an Object File www.ti.com
2.7
Symbols in an Object File
An object file contains a symbol table that stores information about symbols in the program. The linker uses this table when it performs relocation.
2.7.1 External Symbols
External symbols are symbols that are defined in one file and referenced in another file. You can use the
.def, .ref, or .global directive to identify symbols as external:
.def
.ref
.global
The symbol is defined in the current file and 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 following code segment illustrates these definitions.
.def
.ref
x y
.global z
.global q q: B
NOP
MVK x: MV
MVKL
MVKH
B
NOP
B3
4
1, B1
A0,A1 z
5 y,B3 y,B3
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.
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 must 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.
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Object File Format Specifications
2.8
Object File Format Specifications
The object files created by the assembler and linker conform to either the ELF (Executable and Linking
Format) or COFF (Common Object File Format) binary formats, depending on the ABI selected when building your program. When using the EABI mode, the ELF format is used. For the older COFF ABI mode, the legacy COFF format is used.
Some features of the assembler may apply only to the ELF or COFF object file format. In these cases, the proper object file format is stated in the feature description.
See the TMS320C6000 Optimizing Compiler User's Guide and The C6000 Embedded Application Binary
Interface Application Report for information on the different ABIs available.
See the Common Object File Format Application Note ( SPRAAO8 ) for information about the COFF object file format.
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) .
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Introduction to Object Modules 31
Chapter 3
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Assembler Description
The TMS320C6000 assembler translates assembly language source files into machine language object files. These files are in object modules, which are discussed in
. Source files can contain the following assembly language elements:
Assembler directives
Macro directives
Assembly language instructions described in described in
described in the TMS320C62x DSP CPU and Instruction Set
Reference Guide, TMS320C64x/C64x+ DSP CPU and
Instruction Set Reference Guide, TMS320C67x/C67x+ DSP
CPU and Instruction Set Reference Guide, and TMS320C66x
CPU and Instruction Set Reference Guide.
Topic
...........................................................................................................................
Page
3.1
Assembler Overview ..........................................................................................
3.2
The Assembler's Role in the Software Development Flow ......................................
3.3
Invoking the Assembler .....................................................................................
3.4
Controlling Application Binary Interface ...............................................................
3.5
Naming Alternate Directories for Assembler Input .................................................
3.6
Source Statement Format
3.7
Constants
...................................................................................
.........................................................................................................
3.8
Character Strings
3.9
Symbols
..............................................................................................
...........................................................................................................
3.10
Expressions ......................................................................................................
3.11
Built-in Functions and Operators
3.12
Source Listings
........................................................................
.................................................................................................
3.13
Debugging Assembly Source ..............................................................................
3.14
Cross-Reference Listings ...................................................................................
32 Assembler Description
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Assembler Overview
3.1
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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Assembler Description 33
The Assembler's Role in the Software Development Flow www.ti.com
3.2
The Assembler's Role in the Software Development Flow
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 3-1. The Assembler in the TMS320C6000 Software Development Flow
C/C++ source files
Macro source files
C/C++ compiler
Linear assembly
Archiver
Macro library
Archiver
Library of object files
Assembler source
Assembler
Object files
Linker
Assembly optimizer
Assembly optimized file
Library-build utility
Run-timesupport library
Debugging tools
Executable object file
Hex-conversion utility
EPROM programmer
Absolute lister
Cross-reference lister
Object file utilities
C6000
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3.3
Invoking the Assembler
To invoke the assembler, enter the following:
cl6x input file [options]
Invoking the Assembler 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 calls 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
Some runtime model options such as --abi=coffabi or --abi=eabi, --big_endian or little_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.
Option
--absolute_listing
-ar=num
--asm_define=name[=def]
--asm_dependency
--asm_includes
--asm_listing
--asm_undefine=name
--cmd_file=filename
--copy_file=filename
--cross_reference
--include_file=filename
--include_path=pathname
--output_all_syms
--quiet
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Alias
-aa
-ad
-apd
-api
-al
-au
-@
-ahc
-ax
-ahi
-I
-as
-q
Table 3-1. TMS320C6000 Assembler Options
Description
Creates an absolute listing. When you use --absolute_listing, the assembler does not produce an object file. The --absolute_listing option is used in conjunction with the absolute lister.
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.
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
.
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.
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.
Produces a listing file with the same name as the input file with a .lst extension.
Undefines the predefined constant name, which overrides any --asm_define options for the specified constant.
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"
Copies the specified file for the assembly module. The file is inserted before source file statements. The copied file appears in the assembly listing files.
Produces a cross-reference table and appends it to the end of the listing file; it also adds cross-reference information to the object file for use by the cross-reference utility. If you do not request a listing file but use the --cross_reference option, the assembler creates a listing file automatically, naming it with the same name as the input file with a .lst extension.
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.
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
Puts all defined symbols in the object file's symbol table. The assembler usually puts only global symbols into the symbol table. When you use --output_all_syms, symbols defined as labels or as assembly-time constants are also placed in the table.
Suppresses the banner and progress information (assembler runs in quiet mode).
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Assembler Description 35
Controlling Application Binary Interface
Option
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Table 3-1. TMS320C6000 Assembler Options (continued)
Alias
-g
-ac
Description
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 the --symdebug:dwarf option on assembly code that contains .line directives. See
Makes case insignificant in the assembly language files. For example, --syms_ignore_case makes the symbols ABC and abc equivalent. If you do not use this option, case is significant
(default). Case significance is enforced primarily with symbol names, not with mnemonics and register names.
3.4
Controlling Application Binary Interface
An Application Binary Interface (ABI) defines the low level interface between object files, and between an executable and its execution environment. An ABI allows 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
Object modules conforming to different ABIs cannot be linked together. The linker detects this situation and generates an error.
The C6000 compiler supports two ABIs. The ABI is chosen through the --abi option as follows:
• COFF ABI (--abi=coffabi)
The COFF ABI is the original, legacy ABI format. There is no COFF to ELF conversion possible; recompile or reassemble assembly code.
• C6000 EABI (--abi=eabi)
Use this option to select the C6000 Embedded Application Binary Interface (EABI).
All code in an EABI application must be built for EABI. Make sure all your libraries are available in
EABI mode before migrating your existing COFF ABI systems to C6000 EABI. For full details, see http://tiexpressdsp.com/index.php/EABI_Support_in_C6000_Compiler and The C6000 Embedded
Application Binary Interface Application Report ( SPRAB89 ).
3.5
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.
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
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Naming Alternate Directories for Assembler Input
Because of this search hierarchy, you can augment the assembler's directory search algorithm by using the --include_path option (described in
) or the C6X_A_DIR environment variable (described
in
). The C6X_C_DIR environment variable is discussed in the TMS320C6000 Optimizing
Compiler User's Guide.
3.5.1 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]
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
UNIX (Bourne shell)
Windows
Enter cl6x --include_path=/tools/files source.asm
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.
3.5.2 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:
Operating System
UNIX (Bourne Shell)
Windows
Enter
C6X_A_DIR=" pathname
1
; pathname
2
; . . . "; export C6X_A_DIR
set C6X_A_DIR= pathname
1
; pathname
2
; . . .
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Assembler Description 37
Naming Alternate Directories for Assembler Input www.ti.com
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
UNIX (Bourne shell)
Windows
Enter
C6X_A_DIR="/dsys"; export C6X_A_DIR cl6x --include_path=/tools/files source.asm
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
UNIX (Bourne shell)
Windows
Enter unset C6X_A_DIR set C6X_A_DIR=
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Source Statement Format
3.6
Source Statement Format
TMS320C6000 assembly language source programs consist of source statements that can contain assembler directives, assembly language instructions, macro directives, and comments. A source statement 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 .set
2 ; Symbol Two = 2
Label: MVK two,A2 ; Move 2 into register A2
.word 016h ; Initialize a word with 016h
There is no limit on characters per source statement. 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; 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.
• A mnemonic cannot begin in column 1 or it will be interpreted as a label. The assembler does not check to make sure you do not have a mnemonic in the label field.
The following sections describe each of the fields.
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3.6.1 Label Field
Labels are optional for all assembly language instructions and for most (but not all) assembler directives.
When used, a label must begin in column 1 of a source statement. A label can contain up to 400 alphanumeric characters (A-Z, a-z, 0-9, _, and $). Labels are case sensitive (except when the -syms_ignore_case option is used), and the first character cannot be a number. 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, its value is the current value of the SPC. The label points to the statement it is associated with. For example, if you use the .word directive to initialize several words, a label points to the first word. In the following example, the label Start has the value 40h.
.
.
.
.
.
.
9 * Assume some code was assembled
10 00000040 0000000A Start: .word 0Ah,3,7
00000044 00000003
00000048 00000007
The label assigns the current value of the section program counter to the label; this is equivalent to the following directive statement: label .equ
$ ; $ provides the current value of the SPC
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
If you do not use a label, the character in column 1 must be a blank, an asterisk, or a semicolon.
3.6.2 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 can begin with 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 for C64xx only, 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".
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Source Statement Format
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]" contructs are not legal in combination with an assembler directive.
• Macro call
3.6.3 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
.L1 and .L2
.M1 and .M2
.S1 and .S2
Data/addition/subtraction
ALU/compares/long data arithmetic
Multiply
Shift/ALU/branch/bit field
ALU refers to an arithmetic logic unit.
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 TMS320C62x DSP CPU and Instruction Set Reference Guide, TMS320C64x/C64x+ DSP
CPU and Instruction Set Reference Guide, or TMS320C67x/C67x+ DSP CPU and Instruction Set
Reference Guide.
3.6.4 Operand Field
The operand field follows the mnemonic field and contains one or more operands. The operand field is not required for all instructions or directives. An operand consists of the following items:
• Constants (see
• Character strings (see
• Symbols (see
• Expressions (combination of constants and symbols; see
)
You must separate operands with commas.
3.6.5 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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3.7
Constants
The assembler supports several types of constants:
• Binary integer
• Octal integer
• Decimal integer
• Hexadecimal integer
• Character
• Assembly time
The assembler maintains each constant internally as a 32-bit quantity. Constants are not sign extended.
For example, the constant 00FFh is equal to 00FF (base 16) or 255 (base 10); it does not equal -1.
However, when used with the .byte directive, -1 is equivalent to 00FFh.
3.7.1 Binary Integers
A binary integer constant is a string of up to 32 binary digits (0s and 1s) followed by the suffix B (or b). 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 constants:
00000000B Constant equal to 0
10 or 0
16
0100000b Constant equal to 32
10 or 20
16
01b Constant equal to 1
10 or 1
16
11111000B Constant equal to 248
10 or 0F8
16
3.7.2 Octal Integers
An octal integer constant is a string of up to 11 octal digits (0 through 7) followed by the suffix Q (or q).
These are examples of valid octal constants:
10Q
010
100000Q
226q
Constant equal to 8
10 or 8
16
Constant equal to 8
10 or 8
16
© format)
Constant equal to 32 768
10 or 8000
16
Constant equal to 150
10 or 96
16
3.7.3 Decimal Integers
A decimal integer constant is a string of decimal digits ranging from -2147 483 648 to 4 294 967 295.
These are examples of valid decimal constants:
1000
-32768
25
Constant equal to 1000
10 or 3E8
16
Constant equal to -32 768
10 or 8000
16
Constant equal to 25
10 or 19
16
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Constants
3.7.4 Hexadecimal Integers
A hexadecimal integer constant is a string of up to eight hexadecimal digits followed by the suffix H (or h) or preceded by 0x. Hexadecimal digits include the decimal values 0-9 and the letters A-F or a-f. A
hexadecimal constant must begin with a decimal value (0-9). If fewer than eight hexadecimal digits are specified, the assembler right justifies the bits. These are examples of valid hexadecimal constants:
78h
0x78
0Fh
37ACh
Constant equal to 120
10 or 0078
16
Constant equal to 120
10 or 0078
16
© format)
Constant equal to 15
10 or 000F
16
Constant equal to 14 252
10 or 37AC
16
3.7.5 Character Constants
A character constant 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 constant. A character constant consisting only of two single quotes is valid and is assigned the value 0. These are examples of valid character constants:
'a'
'C'
''''
Defines the character constant a and is represented internally as 61
16
Defines the character constant C and is represented internally as 43
16
Defines the character constant ' and is represented internally as 27
16
'' Defines a null character and is represented internally as 00
16
Notice the difference between character constants and character strings ( Section 3.8
discusses character strings). A character constant represents a single integer value; a string is a sequence of characters.
3.7.6 Assembly-Time Constants
If you use the .set directive to assign a value to a symbol (see
Define Assembly-Time Constant ), the
symbol becomes a constant. To use this constant in expressions, the value that is assigned to it must be absolute. For example: sym .set 3
MVK sym,B1
You can also use the .set directive to assign symbolic constants for register names. In this case, the symbol becomes a synonym for the register: sym .set B1
MVK 10,sym
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3.8
Character Strings
A character string is a string 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" defines the 14-character string sample program.
"PLAN ""C""" defines the 8-character string PLAN "C".
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
3.9
Symbols
Symbols are used as labels, constants, and substitution symbols. A symbol name is a string of alphanumeric characters, the dollar sign, and underscores (A-Z, a-z, 0-9, $, and _). The first character in a symbol cannot be a number, and symbols cannot contain embedded blanks. The symbols you define are case sensitive; for example, the assembler recognizes ABC, Abc, and abc as three unique symbols. You can override case sensitivity with the --syms_ignore_case assembler option (see
). A symbol is valid only during the assembly in which it is defined, unless you use the .global directive or the .def
directive to declare it as an external symbol (see
).
3.9.1 Labels
Symbols used as labels become symbolic addresses that are associated with locations in the program.
Labels used locally within a file must be unique. Mnemonic opcodes and assembler directive names without the . prefix are valid label names.
Labels can also be used as the operands of .global, .ref, .def, or .bss directives; for example:
.global label1 label2: MVKL
MVKH
B
NOP label2, B3 label2, B3 label1
5
3.9.2 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
• name?, where name is any legal symbol name 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. You cannot declare this label as global. See
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.
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A 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)
Example 3-1. Local Labels of the Form $n
This is an example of code that declares and uses a local label legally:
$1:
SUB A1,1,A1
[A1] B $1
SUBC A3,A0,A3
NOP 4
.newblock
; undefine $1 to use it again
$1 SUB A2,1,A2
[A2] B $1
MPY A3,A3,A3
NOP 4
The following code uses a local label illegally:
$1:
SUB A1,1,A1
[A1] B $1
SUBC A3,A0,A3
NOP 4
$1 SUB A2,1,A2 ; WRONG - $1 is multiply defined
[A2] B $1
MPY A3,A3,A3
NOP 4
The $1 label is not undefined before being reused by the second branch instruction. Therefore, $1 is redefined, which is illegal.
Symbols
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.
Because local labels are intended to be used only locally, branches to local labels are not expanded in case the branch's offset is out of range.
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Symbols
Example 3-2. 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
.
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Symbols
3.9.3 Symbolic Constants
Symbols can be set to constant values. By using constants, you can equate meaningful names with constant values. The .set and .struct/.tag/.endstruct directives enable you to set constants to symbolic names. Symbolic constants cannot be redefined. The following example shows how these directives can be used:
K .set
1024 maxbuf .set
2*K
; constant definitions item .struct
value .int
delta .int
i_len .endstruct
; item structure definition
; value offset = 0
; delta offset = 4
; item size = 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 several predefined symbolic constants; these are discussed in
.
3.9.4 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 in place of a constant value, a well-defined expression, or an otherwise undefined symbol used with assembly directives and instructions. 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.
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 the following directives:
Type of Test
Existence
Nonexistence
Equal to value
Not equal to value
Directive Usage
.if $isdefed(" name ")
.if $isdefed(" name ") = 0
.if name = 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.
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Symbols
Example 3 ‑‑ 3. Using Symbolic Constants Defined on Command Line
IF_4: .if
.byte
.else
.byte
.endif
IF_5: .if
.byte
.else
.byte
.endif
SYM4 = SYM2 * SYM2
SYM4
SYM2 * SYM2
SYM1 <= 10
10
SYM1
; Equal values
; Unequal values
; Less than / equal
; Greater than
IF_6: .if
.byte
.else
.byte
.endif
SYM3 * SYM2 != SYM4 + SYM2
SYM3 * SYM2
SYM4 + SYM4
; Unequal value
; Equal values
IF_7: .if
.byte
.elseif
SYM2 + SYM3 = 5
.byte
SYM2 + SYM3
.endif
SYM1 = SYM2
SYM1 www.ti.com
3.9.5 Predefined Symbolic Constants
The assembler has several predefined symbols, including the following types:
• $, the dollar-sign character, represents the current value of the section program counter (SPC). $ is a relocatable symbol.
• Register symbols, including A0-A15 and B0-B15; and A16-31 and B16-31 for C6400, C6400+,
C6700+, C6740, and C6600.
• CPU control registers, including those listed in
. Control registers can be entered as all upper-case or all lower-case characters; for example, CSR can also be entered as csr.
• Processor symbols, including those listed in
Register
AMR
CSR
DESR
DETR
DNUM
ECR
EFR
FADCR
FAUCR
FMCR
GFPGFR
GPLYA
GPLYB
ICR
Table 3-2. CPU Control Registers
Description
Addressing mode register
Control status register
(C6700+ only) dMAX event status register
(C6700+ only) dMAX event trigger register
(C6400+, C6740, C6600 only) DSP core number register
(C6400+, C6740, C6600 only) Exception clear register
(C6400+, C6740, C6600 only) Exception flag register
(C6700, C6700+, C6740, C6600 only) Floating-point adder configuration register
(C6700, C6700+, C6740, C6600 only) Floating-point auxiliary configuration register
(C6700, C6700+, C6740, C6600 only) Floating-point multiplier configuration register
(C6400 only) Galois field polynomial generator function register
(C6400+, C6740, C6600 only) GMPY A-side polynomial register
(C6400+, C6740, C6600 only) GMPY B-side polynomial register
Interrupt clear register
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REP
RILC
SSR
TSCH
TSCL
TSR
Register
IER
IERR
IFR
ILC
NRP
IRP
ISR
ITSR
ISTP
NTSR
PCE1
Table 3-2. CPU Control Registers (continued)
Description
Interrupt enable register
(C6400+, C6740, C6600 only) Interrupt exception report register
Interrupt flag register
(C6400+, C6740, C6600 only) Inner loop count register
Nonmaskable interrupt return pointer
Interrupt return pointer
Interrupt set register
(C6400+, C6740, C6600 only) Interrupt task state register
Interrupt service table pointer
(C6400+, C6740, C6600 only) NMI/Exception task state register
Program counter
(C6400+, C6740, C6600 only) Restricted entry point address register
(C6400+, C6740, C6600 only) Reload inner loop count register
(C6400+, C6740, C6600 only) Saturation status register
(C6400+, C6740, C6600 only) Time-stamp counter (high 32) register
(C6400+, C6740, C6600 only) Time-stamp counter (low 32) register
(C6400+, C6740, C6600 only) Task status register
Table 3-3. Processor Symbols
Symbol name
_ _TI_EABI_ _
.TMS320C6X
.TMS320C6200
.TMS320C6400
.TMS320C6400_PLUS
.TMS320C6600
Description
Set to 1 if EABI is enabled (see
Always set to 1
Set to 1 if target is C6200, otherwise 0
Set to 1 if target is C6400, C6400+, C6740, or C6600; otherwise 0
Set to 1 if target is C6400+, C6740, or C6600; otherwise 0
Set to 1 if target is C6600, otherwise 0
.TMS320C6700
.TMS320C6700_PLUS
.TMS320C6740
.LITTLE_ENDIAN
Set to 1 if target is C6700, C6700+, C6740, or C6600; otherwise 0
Set to 1 if target is C6700+, C6740, or C6600; otherwise 0
Set to 1 if target is C6740 or C6600, otherwise 0
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
.LARGE_MODEL
Set to 1 if --memory_model:code=near and --memory_model:data=near, otherwise 0.
Set to 1 if .SMALL_MODEL is 0, otherwise 0.
Symbols
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3.9.6 Register Pairs
Many instructions in the C6000 instruction set across the various available target processors (C6200,
C6400, C6400+, etc.) support a 64-bit register operand which 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
B1:B0
B3:B2
B5:B4
B7:B6
B9:B8
B11:B10
B13:B12
B15:B14
In addition, these register pairs are available on C6400, C6400+, C6600 (not C62xx or C67xx):
A17:A16
A19:A18
A21:A20
A23:A22
A25:A24
A27:A26
A29:A30
A31:A32
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 TMS320C62x DSP CPU and Instruction Set Reference Guide, TMS320C64x/C64x+ DSP
CPU and Instruction Set Reference Guide, TMS320C67x/C67x+ DSP CPU and Instruction Set Reference
Guide, or TMS320C66x CPU and Instruction Set Reference Guide.
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Symbols
3.9.7 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
A3:A2:A1:A0
A7:A6:A5:A4
A11:A10:A9:A8
A15:A14:A13:A12
A19:A18:A17:A16
A23:A22:A21:A20
A27:A26:A25:A24
A31:A30:A29:A28
Short Form
A3::A0
A7::A4
A11::A8
A15::A12
A19::A16
A23::A20
A27::A24
A31::A28
B Register Quads
B3:B2:B1:B0
B7:B6:B5:B4
B11:B10:B9:B8
B15:B14:B13:B12
B19:B18:B17:B16
B23:B22:B21:B20
B27:B26:B25:B24
B31:B30:B29:B28
Short Form
B3::B0
B7::B4
B11::B8
B15::B12
B19::B16
B23::B20
B27::B24
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.
3.9.8 Substitution Symbols
Symbols can be assigned a string value (variable). This enables you to alias 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 _table
.asg
"B14", PAGEPTR
.asg
.asg
"*+B15(4)", LOCAL1
"*+B15(8)", LOCAL2
LDW
NOP
STW
*+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
for more information about macros.
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3.10 Expressions
An expression is a constant, a symbol, or a series of constants and symbols separated by arithmetic operators. The 32-bit ranges of valid expression values are -2147 483 648 to 2147 483 647 for signed values, and 0 to 4 294 967 295 for unsigned values. 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
, 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
3.10.1 Operators
lists the operators that can be used in expressions, according to precedence group.
Table 3-4. Operators Used in Expressions (Precedence)
(1)
(2)
Group
1
2
3
4
5
6
7
8
9
(1) Operator
*
/
%
+
-
~
!
+
-
<<
>>
<
<=
>
>=
=[=]
!=
&
|
^
Description
Unary plus
Unary minus
1s complement
Logical NOT
Multiplication
Division
Modulo
Addition
Subtraction
Shift left
Shift right
Less than
Less than or equal to
Greater than
Greater than or equal to
Equal to
Not equal to
Bitwise AND
Bitwise exclusive OR (XOR)
Bitwise OR
(2)
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.
3.10.2 Expression Overflow and Underflow
The assembler checks for overflow and underflow conditions when arithmetic operations are performed at assembly time. It issues a warning (the message Value Truncated) whenever an overflow or underflow occurs. The assembler does not check for overflow or underflow in multiplication.
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Expressions
3.10.3 Well-Defined Expressions
Some assembler directives require well-defined expressions as operands. Well-defined expressions contain only symbols or assembly-time constants that are defined before they are encountered in the expression. The evaluation of a well-defined expression must be absolute.
This is an example of a well-defined expression:
1000h+X where X was previously defined as an absolute symbol.
3.10.4 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.
3.10.5 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 an expression contains more than one relocatable symbol or cannot be evaluated at assembly time, the assembler encodes a relocation expression in the object file that is later evaluated by the linker. If the final value of the expression is larger in bits than the space reserved for it, you receive an error message from the linker. See
for more information on relocation expressions.
• When using the register relative addressing mode, the expression in brackets or parenthesis must be a well-defined expression, as described in
. 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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3.10.6 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 intern_2
; current module
; Relocatable, defined in intern_3
; current module
; Relocatable, defined in
; current module
• Example 1
In these contexts, there are no limitations on how expressions can be formed.
.word
extern_1 * intern_2 - 13 ; Legal
MVKL (intern_1 - extern_1),A1 ; Legal
• Example 2
The first statement in the following example is valid; the statements that follow it are invalid.
B (extern_1 - 10)
B (10-extern_1)
; Legal
; Can't negate reloc. symbol
LDW *+B14 (-(intern_1)), A1 ; Can't negate reloc. symbol
LDW *+B14 (extern_1/10), A1 ; / not an additive operator
B (intern_1 + extern_1) ; 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) ; Illegal
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Built-in Functions and Operators
3.11 Built-in Functions and Operators
The assembler supports built-in mathematical functions and built-in addressing operators.
Function
$acos(expr)
$asin(expr)
$atan(expr)
$atan2(expr, y)
$ceil(expr)
$cos(expr)
$cosh(expr)
$cvf(expr)
$cvi(expr)
$exp(expr)
$fabs(expr)
$floor(expr)
$fmod(expr, y)
$int(expr)
$ldexp(expr, expr2)
$log(expr)
$log10(expr)
$max(expr1, expr2)
$min(expr1, expr2)
$pow(expr1, expr2)
$round(expr)
$sgn(expr)
$sin(expr)
$sinh(expr)
$sqrt(expr)
$strtod(str)
3.11.1 Built-In Math and Trigonometric Functions
The assembler supports built-in functions for conversions and various math computations.
describes the built-in functions. The expr must be a constant value.
The built-in substitution symbol functions are discussed in
.
$tan(expr)
$tanh(expr)
$trunc(expr)
Table 3-5. Built-In Mathematical Functions
Description
Returns the arc cosine of expr as a floating-point value
Returns the arc sin of expr as a floating-point value
Returns the arc tangent of expr as a floating-point value
Returns the arc tangent of expr as a floating-point value in range [π , π ]
Returns the smallest integer not less than expr
Returns the cosine of expr as a floating-point value
Returns the hyperbolic cosine of expr as a floating-point value
Converts expr to a floating-point value converts expr to integer value
Returns the exponential function e expr
Returns the absolute value of expr as a floating-point value
Returns the largest integer not greater than expr
Returns the remainder of expr1 ÷ expr2
Returns 1 if expr has an integer value; else returns 0. Returns an integer.
Multiplies expr by an integer power of 2. That is, expr1 × 2 expr2
Returns the natural logarithm of expr, where expr>0
Returns the base 10 logarithm of expr, where expr>0
Returns the maximum of two values
Returns the minimum of two values
Returns expr1raised to the power of expr2
Returns expr rounded to the nearest integer
Returns the sign of expr.
Returns the sine of expr
Returns the hyperbolic sine of expr as a floating-point value
Returns the square root of expr, expr ≥ 0, as a floating-point value
Converts a character string to a double precision floating-point value. The string contains a properlyformatted C99-style floating-point constant. C99-style constants are otherwise not accepted anywhere in the tools.
Returns the tangent of expr as a floating-point value
Returns the hyperbolic tangent of expr as a floating-point value
Returns expr rounded toward 0
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3.11.2 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 ).
3.11.2.1 $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.
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:
; load (xyz - $bss)/4 into A0 MVKL $DPR_WORD(xyz),A0
MVKH $DPR_WORD(xyz),A0
LDW *+DP[A0],A1 ; 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:
; load (xyz - $bss) into A0 MVKL $DPR_BYTE(xyz),A0
MVKH $DPR_BYTE(xyz),A0
LDB *+DP[A0],A1 ; load *xyz into A1
The $DPR_HWORD(sym) operator is provided to facilitate far DP-relative addressing of 16-bit data objects:
; load (xyz - $bss)/2 into A0 MVKL $DPR_HWORD(xyz),A0
MVKH $DPR_HWORD(xyz),A0
LDH *+DP[A0],A1 ; load *xyz into A1
For code on processors that are not compatible with C64x+, the compiler also uses these operators when it needs to take the address of an object that is within signed 16-bit range of the DP. For example, the compiler can compute the address of an 8-bit data object in the .bss section:
MVK $DPR_BYTE(_char_X),A4 ; load (_char_X - $bss) into A4
ADD DP,A4,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 $DPR_HWORD(_short_X),A4 ; load (_short_X - $bss)/2 into A4
ADD 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 $DPR_WORD(_int_X),A4
ADD DP,A4,A4
; load (_int_X - $bss)/4 into A4
; compute address of _int_X
These operators were added to the assembler to assist in migrating existing COFF code, which used expressions like 'xyz - $bss' to indicate DP-relative access to the address of a data object, to ELF code which is able to resolve the DP-relative offset calculation with a single relocation.
In summary:
$DPR_BYTE(sym) is equivalent to 'sym - $bss'
$DPR_HWORD(sym) is equivalent to '(sym - $bss) / 2'
$DPR_WORD(sym) is equivalent to '(sym - $bss) / 4'
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3.11.2.2 $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 the external wiki
( http://processors.wiki.ti.com/index.php/C6000_Dynamic_Linking ) 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 Dynamic Linking wiki site or 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 $DPR_GOT(xyz),A0
MVKH $DPR_GOT(xyz),A0
LDW *+DP[A0],A1
LDW *A1,A2
; load DP-relative offset of
; GOT entry for xyz into A0
; get address of xyz via GOT entry
; load xyz into A2
3.11.2.3 $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.
3.11.2.4 $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
a switch table is generated which contains the PC-relative offsets of the switch case labels:
Example 3-4. Generating a Switch Table With Offset Switch Case Labels
.asg A15, FP
.asg B14, DP
.asg B15, SP
.global $bss
.sect ".text"
.clink
.global myfunc
;******************************************************************************
;* FUNCTION NAME: myfunc *
;****************************************************************************** myfunc:
;** --------------------------------------------------------------------------*
||
||
B .S1
SUB .L2X
$C$L10
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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Built-in Functions and Operators
Example 3-4. 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
BNOP .S2
B5,B4,B4
B4,5
; BRANCH OCCURS {B4} ;
; Combine to get case label into B5
; Branch to case label
; Switch table definition
.align 32
.clink
$C$SW1: .nocmp
.word $LABEL_DIFF($C$L1,$C$SW1) ; 10
.word $LABEL_DIFF($C$L2,$C$SW1) ; 11
.word $LABEL_DIFF($C$L3,$C$SW1) ; 12
.word $LABEL_DIFF($C$L4,$C$SW1) ; 13
.word $LABEL_DIFF($C$L5,$C$SW1) ; 14
.word $LABEL_DIFF($C$L6,$C$SW1) ; 15
.word $LABEL_DIFF($C$L7,$C$SW1) ; 16
.word $LABEL_DIFF($C$L8,$C$SW1) ; 17
.align 32
.sect ".text"
...
mixes data into the code section. For C64+ compatible processors, compression will be disabled for the code section that contains the $LABEL_DIFF() operator since the label difference must resolve to a constant value at assembly time.
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Source Listings www.ti.com
3.12 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
).
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. and show these in actual listing files.
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.
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.
shows an assembler listing with each of the four fields identified.
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Figure 3-2. Example Assembler Listing
Include file letter Nesting level number
Line number
A
A
10
1
2
2
4 00000000
5 00000004
6
8
A
A
A
A
A
9
11
5
7
13
11
** Global variables
.bss
.bss
var1, 4 var2, 4
** Include multiply macro mpy32
.copy
mpy32.inc
.macro
A,B
.endm
15 00000000
16 00000000
17 00000000 0200006C-
18 00000004 0000016E-
19 00000008 00006000
20 0000000c
_func
.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
B
NOP
* end _func
Field 1 Field 2 Field 3
B3
5
Field 4
Source Listings
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Debugging Assembly Source www.ti.com
3.13 Debugging Assembly Source
When you invoke cl6x with --symdebug:dwarf (or -g) when compiling 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 .asmfunc and .endasmfunc (see
Mark Function Boundaries ) 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
).
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
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=rts6200.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 3 ‑‑ 5. Viewing Assembly Variables as C Types C Program typedef struct
{ int m1; int m2;
} X;
X svar = { 1, 2 };
Example 3 ‑‑ 6. Assembly Program for
;--------------------------------------------------------------------------------------
; 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
RET
NOP
.D2T2
.S2
*+B14(_svar+4),B4 ; load svar.m2 into B4
B3 ; return from function
ADD
STW
.D2
3
5,B4,B4
; delay slots 1-3
; add 5 to B4 (delay slot 4)
.D2T2
B4,*+B14(_svar+4) ; store B4 back into svar.m2 (delay slot 5)
.endasmfunc
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Cross-Reference Listings
3.14 Cross-Reference Listings
A cross-reference listing shows symbols and their definitions. To obtain a cross-reference listing, invoke the assembler with the --cross_reference option (see
) 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.
shows the four fields contained in the cross-reference listing.
Example 3 ‑‑ 7. An Assembler Cross-Reference Listing
LABEL
.BIG_ENDIAN
.LITTLE_ENDIAN
.TMS320C6200
.TMS320C6700
.TMS320C6X
_func var1 var2
VALUE
00000000
00000001
00000001
00000000
00000001
00000000'
00000000-
00000004-
DEFN REF
0
18
4
5
0
0
0
0
17
18
Label
Value
Definition
Reference 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.
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 3-6. 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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Assembler Description 63
Chapter 4
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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 4.1
through
directives according to function, and the second part (
) is an alphabetical reference.
Topic
...........................................................................................................................
Page
4.1
Directives Summary ..........................................................................................
4.2
Directives That Define Sections ..........................................................................
4.3
Directives That Initialize Constants ......................................................................
4.4
Directives That Perform Alignment and Reserve Space
4.5
Directives That Format the Output Listings
.........................................
..........................................................
4.6
Directives That Reference Other Files ..................................................................
4.7
Directives That Enable Conditional Assembly .......................................................
4.8
Directives That Define Union or Structure Types ...................................................
4.9
Directives That Define Enumerated Types ............................................................
4.10
Directives That Define Symbols at Assembly Time ................................................
4.11
Miscellaneous Directives ....................................................................................
4.12
Directives Reference ..........................................................................................
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4.1
Directives Summary
Directives Summary
through
summarize the assembler directives.
Besides the assembler directives documented here, the TMS320C6000 software tools support the following directives:
• The assembler uses several directives for macros. Macro directives are discussed in
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.
discusses these directives; they are not discussed in this chapter.
Labels and Comments Are Not Shown in Syntaxes
NOTE: Any source statement that contains 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.
Mnemonic and Syntax
.bss symbol, size in bytes[, alignment
[, bank offset]]
.clink
.data
.retain
.sect "section name"
.text
symbol .usect "section name", size in bytes
[, alignment[, bank offset]]
Table 4-1. Directives That Define Sections
Description
Reserves size bytes in the .bss (uninitialized data) section
See
Enables conditional linking for the current or specified section
Assembles into the .data (initialized data) section
Instructs the linker to include the current or specified section in the
linked output file, regardless of whether the section is referenced or not
Assembles into a named (initialized) section
Assembles into the .text (executable code) section
Reserves size bytes in a named (uninitialized) section
.field value[, size]
.float value
1
[, ... , value n
]
.half value
1
[, ... , value n
]
.int value
1
[, ... , value n
]
.long value
1
[, ... , value n
]
.short value
1
[, ... , value n
]
.string {expr
1
|"string
1
"}[,... , {expr n
|"string n
"}]
.ubyte value
1
[, ... , value n
]
.uhalf value
1
[, ... , value n
]
Table 4-2. Directives That Initialize Values (Data and Memory)
Mnemonic and Syntax
.byte value
1
[, ... , value n
]
.char value
1
[, ... , value n
]
.cstring {expr
1
|"string
1
"}[,... , {expr n
|"string n
"}]
.double value
1
[, ... , value n
]
Description
Initializes one or more successive bytes in the current section
See
Initializes one or more successive bytes in the current section
Initializes one or more text strings
Initializes one or more 64-bit, IEEE double-precision, floating-point
constants
Initializes a field of size bits (1-32) with value
Initializes one or more 32-bit, IEEE single-precision, floating-point
constants
Initializes one or more 16-bit integers (halfword)
Initializes one or more 32-bit integers
Initializes one or more 32-bit integers
Initializes one or more 16-bit integers (halfword)
Initializes one or more text strings
Initializes one or more successive unsigned bytes in the current section
Initializes one or more unsigned 16-bit integers (halfword)
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65
Directives Summary www.ti.com
Table 4-2. Directives That Initialize Values (Data and Memory) (continued)
Mnemonic and Syntax
.uint value
1
[, ... , value n
]
.ushort value
1
[, ... , value n
]
.uword value
1
[, ... , value n
]
.word value
1
[, ... , value n
]
Description
Initializes one or more unsigned 32-bit integers
Initializes one or more unsigned 16-bit integers (halfword)
Initializes one or more unsigned 32-bit integers
Initializes one or more 32-bit integers
See
Mnemonic and Syntax
.align [size in bytes]
.bes size
.space size
Table 4-3. Directives That Perform Alignment and Reserve Space
Description
Aligns the SPC on a boundary specified by size in bytes, which must be a power of 2; defaults to byte boundary
See
Reserves size bytes in the current section; a label points to the end
of the reserved space
Reserves size bytes in the current section; a label points to the beginning of the reserved space
Mnemonic and Syntax
.drlist
.drnolist
.fclist
.fcnolist
.length [page length]
.list
.mlist
.mnolist
.nolist
.option option
1
[, option
2
, . . .]
.page
.sslist
.ssnolist
.tab size
.title "string"
.width [page width]
Table 4-4. Directives That Format the Output Listing
Description
Enables listing of all directive lines (default)
Suppresses listing of certain directive lines
Allows false conditional code block listing (default)
Suppresses false conditional code block listing
Sets the page length of the source listing
Restarts the source listing
Allows macro listings and loop blocks (default)
Suppresses macro listings and loop blocks
Stops the source listing
Selects output listing options; available options are A, B, D, H, L,
M, N, O, R, T, W, and X
Ejects a page in the source listing
Allows expanded substitution symbol listing
Suppresses expanded substitution symbol listing (default)
Sets tab to size characters
Prints a title in the listing page heading
Sets the page width of the source listing
See
Mnemonic and Syntax
.copy ["]filename["]
.include ["]filename["]
.mlib ["]filename["]
Table 4-5. Directives That Reference Other Files
Description
Includes source statements from another file
Includes source statements from another file
Specifies a macro library from which to retrieve macro definitions
See
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Directives Summary
Table 4-6. Directives That Effect Symbol Linkage and Visibility
Mnemonic and Syntax
.def symbol
1
[, ... , symbol n
]
.global symbol
.ref symbol
1
1
[, ... , symbol
[, ... , symbol n
] n
]
Description
Identifies one or more symbols that are defined in the current module and that can be used in other modules
Identifies one or more global (external) symbols
See
Identifies one or more symbols used in the current module that are
defined in another module
.symdepend dst symbol name[, src symbol name] Creates an artificial reference from a section to a symbol
.weak symbol name Identifies a symbol used in the current module that is defined in another module
Mnemonic and Syntax
.export "symbolname"
.hidden"symbolname"
.import "symbolname"
.protected "symbolname"
Mnemonic and Syntax
.cstruct
.cunion
.emember
.endenum
.endstruct
.endunion
.enum
.union
.struct
.tag
Table 4-7. Directives That Control Dynamic Symbol Visibility
Description
Sets visibility of symbolname to STV_EXPORT
Sets visibility of symbolname to STV_HIDDEN
Sets visibility of symbolname to STV_IMPORT
Sets visibility of symbolname to STV_PROTECTED
See
Mnemonic and Syntax
.break [well-defined expression]
.else
.elseif well-defined expression
.endif
.endloop
.if well-defined expression
.loop [well-defined expression]
Table 4-8. Directives That Enable Conditional Assembly
Description
Assembles code block if the .if well-defined expression is false.
When using the .if construct, the .else construct is optional.
See
Ends .loop assembly if well-defined expression is true. When using
the .loop construct, the .break construct is optional.
Assembles code block if the .if well-defined expression is false and
the .elseif condition is true. When using the .if construct, the .elseif
construct is optional.
Ends .if code block
Ends .loop code block
Assembles code block if the well-defined expression is true
Begins repeatable assembly of a code block; the loop count is determined by the well-defined expression.
Table 4-9. Directives That Define Union or Structure Types
Description See
Acts like .struct, but adds padding and alignment like that which is
done to C structures
Acts like .union, but adds padding and alignment like that which is
done to C unions
Sets up C-like enumerated types in assembly code
Sets up C-like enumerated types in assembly code
Ends a structure definition
,
Ends a union definition
Sets up C-like enumerated types in assembly code
Begins a union definition
Begins structure definition
Assigns structure attributes to a label
,
,
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Directives Summary
symbol .equ value
.elfsym name, SYM_SIZE(size)
.eval well-defined expression , substitution symbol
.label symbol
.mapsymbol/register
Table 4-10. Directives That Define Symbols
Mnemonic and Syntax
.asg ["]character string["], substitution symbol
.clearmap
Description
Assigns a character string to substitution symbol
Cancels all .map assignments. Used by compiler for linear assembly source.
Equates value with symbol
Provides ELF symbol information
Performs arithmetic on a numeric substitution symbol
.newblock
symbol .set value
.unasg symbol
.undefine symbol
Defines a load-time relocatable label in a section
Assigns symbol toregister. Used by compiler for linear assembly source.
Undefines local labels
Equates value with symbol
Turns off assignment of symbol as a substitution symbol
Turns off assignment of symbol as a substitution symbol www.ti.com
See
Table 4-11. Directives That Define Common Data Sections
Mnemonic and Syntax
.endgroup
.gmember section name
.group group section name group type :
Description
Ends the group declaration
Designates section name as a member of the group
Begins a group declaration
See
Mnemonic and Syntax
.emsg string
.mmsg string
.noremark[num]
.remark [num]
.wmsg string
Table 4-12. Directives That Create or Effect Macros
Mnemonic and Syntax
.endm
.loop[well-defined expression]
Description
End macro definition
Begins repeatable assembly of a code block; the loop count is determined by the well-defined expression.
macname .macro [parameter
1
][,... , parameter n
] Define macro by macname
.mexit
.mlib filename
Go to .endm
Identify library containing macro definitions
.var
Adds a local substitution symbol to a macro's parameter list
See
Table 4-13. Directives That Control Diagnostics
Description
Sends user-defined error messages to the output device; produces no .obj file
See
Sends user-defined messages to the output device
Identifies the beginning of a block of code in which the assembler
suppresses the num remark
Resumes the default behavior of generating the remark(s) previously suppressed by .noremark
Sends user-defined warning messages to the output device
Mnemonic and Syntax
.asmfunc
.endasmfunc
Table 4-14. Directives That Perform Assembly Source Debug
Description See
Identifies the beginning of a block of code that contains a function
Identifies the end of a block of code that contains a function
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Mnemonic and Syntax
.setsect
.setsym
Directives That Define Sections
Table 4-15. Directives That Are Used by the Absolute Lister
Description
Produced by absolute lister; sets a section
Produced by the absolute lister; sets a symbol
See
Table 4-16. Directives That Perform Miscellaneous Functions
Mnemonic and Syntax
.cdecls [options ,]"filename"[, "filename2"[, ...]
.end
.nocmp
Description
Share C headers between C and assembly code
Ends program
Instructs tools to not utilize 16-bit instructions for section
See
In addition to the assembly directives that you can use in your code, the 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
• COFF/STABS directives listed in
• 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 .template directive is used for early template instantiation. It encodes information about a template that has yet to be instantiated. This is a COFF C++ directive.
• The .compiler_opts directive indicates that the assembly code was produced by the compiler, and which build model options were used for this file.
4.2
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 .clink directive can be used in the COFF ABI model to indicate that a section is eligible for removal at link-time via conditional linking. Thus if no other sections included in the link reference the current or specified section, then the section is not included in the link. The .clink directive can be applied to initialized or uninitialized sections.
• The .data directive identifies portions of code in the .data section. The .data section usually contains initialized data.
• The .retain directive can be used in the EABI model 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 .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.
discusses these sections in detail.
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
perform the following tasks:
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Directives That Define Sections www.ti.com
.text
.data
var_defs
.bss
xy 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.
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 4 ‑‑ 1. Sections Directives
9
10
7
8
00000004 00000002
6 00000008 00000003
0000000c 00000004
14
15
16
17
11 00000000
12 00000000 00000009
00000004 0000000A
13 00000008 0000000B
0000000c 0000000C
21
22
23
24
18
19 00000000
20 00000000 00000011
00000004 00000012
25 00000010
26 00000010 0000000D
00000014 0000000E
27 00000000
28 00000018 0000000F
0000001c 00000010
29
30
31
32
33 00000010
34 00000010 00000005
00000014 00000006
35 00000000
36 00000018 00000007
0000001c 00000008 usym
.word
**************************************************
* Start assembling into the .data section *
**************************************************
.data
.word
9, 10
.word
11, 12
**************************************************
* Start assembling into a named, *
* initialized section, var_defs *
**************************************************
.sect
"var_defs"
.word
17, 18
**************************************************
* Resume assembling into the .data section *
**************************************************
.data
.word
13, 14
.bss
.word
**************************************************
* Resume assembling into the .text section *
**************************************************
.text
.word
5, 6
.usect
.word
3,4 sym, 19
15, 16
"xy", 20
7, 8
; Reserve space in .bss
; Still in .data
; Reserve space in xy
; Still in .text
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Directives That Initialize Constants
4.3
Directives That Initialize Constants
Several directives assemble values for the current section:
• The .byte and .char directives place one or more 8-bit values into consecutive bytes of the current section. These directives are similar to .long and .word, except that the width of each value is restricted to eight 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.
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
3,4
.field
8,5
.field
16,7
Figure 4-1. 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, .uhalf, .short, and .ushort directives place one or more 16-bit values into consecutive 16-bit fields (halfwords) in the current section. The .half and .short directives automatically align to a short (2byte) boundary.
• The .int, .uint, .long, .word, .uword directives place one or more 32-bit values into consecutive 32-bit fields (words) in the current section. The .int, .long, and .word 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.
Directives That Initialize Constants When Used in a .struct/.endstruct Sequence
NOTE: The .byte, .char, .int, .long, .word, .double, .half, .short, .string, .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
.
compares the .byte, .half, .word, and .string directives. Using the following assembled code:
1 00000000 000000AB
2
3 00000004 0000CDEF
4 00000008 89ABCDEF
5 0000000c 00000068
0000000d 00000065
0000000e 0000006C
0000000f 00000070
.byte
0ABh
.align 4
.half
0CDEFh
.word
089ABCDEFh
.string "help"
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Directives That Perform Alignment and Reserve Space
Figure 4-2. Initialization Directives www.ti.com
4.4
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.
demonstrates the .align directive. Using the following assembled code:
1
2 00000000 00AABBCC
3
4 00000000 0BAABBCC
5 00000004 000000DE
.field
0AABBCCh,24
.align
2
.field
0Bh,5
.field
0DEh,10
Figure 4-3. The .align Directive
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Directives That Format the Output Listings
• 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.
shows how the .space and .bes directives work for the following assembled code:
1
2 00000000 00000100
00000004 00000200
3 00000008
4 0000001c 0000000F
5 00000033
6 00000034 000000BA
.word
Res_1: .space
.word
Res_2: .bes
.byte
100h, 200h
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 4-4. The .space and .bes Directives
Res_1 = 08h
17 bytes reserved
20 bytes reserved
Res_2 = 33h
4.5
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
.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.
• The .option directive controls certain features in the listing file. This directive has the following operands:
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Directives That Reference Other Files www.ti.com
L
M
N
O
A
B
D
H
R
T
W
X 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 --cross_reference option (see
• 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.
4.6
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
). 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
4.7
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 well-defined expression marks the beginning of a conditional block and assembles code if the .if well-defined expression is true.
[.elseif well-defined expression]
.else
.endif
marks a block of code to be assembled if the .if well-defined
expression is false and the .elseif condition is true.
marks a block of code to be assembled if the .if well-defined
expression is false and any .elseif conditions are false.
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 [well-defined expression] marks the beginning of a repeatable block of code. The optional expression evaluates to the loop count.
.break [well-defined expression] tells the assembler to assemble repeatedly when the .break
well-defined expression 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
4.8
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 .struct
X .byte
Y .byte
T_LEN .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 12 . 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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Assembler Directives 75
Directives That Define Enumerated Types www.ti.com
4.9
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
.
See
for an example of using .enum.
4.10 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 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 .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 = 1
; Begin conditional loop.
x*10h ; Store value into current section.
x = 4 ; Break loop if x = 4.
x+1, x ; Increment x by 1.
; End conditional loop.
• 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 .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
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
4.11 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 a common data section for member of an
ELF group section.
• The .import, .export, .hidden, and .protected directives set the dynamic visibility of a global symbol for ELF only. See
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
for information on local labels.
• The .nocmp directive for C6400+, C6740, and C6600 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
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Directives Reference www.ti.com
4.12 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
Syntax
Description
Example
Align SPC on the Next Boundary
.align [size in bytes]
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 assembler assembles words containing null values (0) up to the next size in bytes boundary:
1 aligns SPC to byte boundary
2
4 aligns SPC to halfword boundary aligns SPC to word boundary
8
128 aligns SPC to doubleword boundary aligns SPC to page 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.
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
Assign a Substitution Symbol
Syntax
Description
.asg "character string",substitution symbol
.define "character string",substitution symbol
.eval well-defined expression,substitution symbol
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
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 well-defined 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 well-defined expression is an alphanumeric expression in which all symbols have been previously defined in the current source module, so that the result is an absolute.
• 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
for information on turning off a substitution symbol.
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Directives Reference
Example www.ti.com
1
#
1
#
1
#
1
#
1
#
1
#
1
#
1
#
1
#
1
#
This example shows how .asg and .eval can be used.
.sslist ; show expanded substitution symbols
3
4
1
2
5
6 00000000 003B22E4
.asg
.asg
*+B14(100), GLOB100
*+B15(4), ARG0
#
#
7 00000004 00BC22E4
LDW
LDW
LDW
LDW
NOP
ADD
GLOB100,A0
*+B14(100),A0
ARG0,A1
*+B15(4),A1
4
A0,A1,A2
12
13
14
15
10
11
8 00000008 00006000
9 0000000c 010401E0
00000010 00000000
00000014 00000064
00000018 000000C8
0000001c 0000012C
00000020 00000190
.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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Directives Reference
.asmfunc/.endasmfunc
Mark Function Boundaries
Syntax
Description
Example symbol .asmfunc [stack_usage(num)]
.endasmfunc
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
accomplish assembly debugging; those directives should be used only by the compiler to generate symbolic debugging information for C/C++ source files.
The .asmfunc and .endasmfunc directives cannot be used when invoking the compiler with the backwards-compatibility --symdebug:coff option. This option instructs the compiler to use the obsolete COFF symbolic debugging format, which does not support these directives.
The symbol is a label that must appear in the label field.
The .asmfunc directive has an optional parameter, stack_usage, which sets the stack 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 $
In this example the assembly source generates debug information for the user_func section.
3
4
1 00000000
2
5
6 00000000 00000010!
7 00000004 01BC94F6
8 00000008 01800E2A'
17 00000024 00004000
18 00000028 000C0362
19 0000002c 00008000
20
.sect
".text"
.global userfunc
.global _printf userfunc: .asmfunc stack_usage(16)
CALL .S1
_printf
STW
MVKL
.D2T2
.S2
B3,*B15--(16)
RL0,B3
MVKL
MVKH
.S1
.S1
SL1+0,A3
SL1+0,A3
9 0000000c 01800028+
10 00000010 01800068+
11
12 00000014 01BC22F5
13 00000018 0180006A' ||
14
15 0000001c 01BC92E6 RL0:
16 00000020 020008C0
STW
MVKH
.D2T1
.S2
A3,*+B15(4)
RL0,B3
LDW
ZERO
NOP
RET
NOP
.D2T2
*++B15(16),B3
.D1
A4
.S2
3
B3
5
.endasmfunc
21
22 00000000
23 00000000 00000048 SL1:
00000001 00000065
00000002 0000006C
00000003 0000006C
00000004 0000006F
00000005 00000020
.sect
".const"
.string "Hello World!",10,0
00000006 00000057
00000007 0000006F
00000008 00000072
00000009 0000006C
0000000a 00000064
0000000b 00000021
0000000c 0000000A
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Directives Reference
0000000d 00000000 www.ti.com
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.bss
Syntax
Description
Example
Directives Reference
Reserve Space in the .bss Section
.bss symbol,size in bytes[, alignment[, bank offset]]
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 label 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 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 boundary indicates the size of the slot in bytes and must be set to a power of 2. If the SPC is 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
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.
17
18
19
20
1
2
3
4 00000000
7
8
5 00000000 008001A0
6
9
10 00000000
11
12
13
14
15 00000004 010401A0
16
*******************************************
** Start assembling into .text section. **
*******************************************
.text
MV A0,A1
*******************************************
** Allocate 100 bytes in .bss.
**
*******************************************
.bss
array,100
*******************************************
** Still in .text
**
*******************************************
MV A1,A2
*******************************************
** Declare external .bss symbol **
*******************************************
.global array
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Directives Reference
.byte/.char
Syntax
Description
Example www.ti.com
Initialize Byte
.byte value
1
[, ... , value n
]
.char value
1
[, ... , value n
]
The .byte and .char 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.
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
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.
.byte
10,-1,"abc",'a' 1 00000000 0000000A STRX
00000001 000000FF
00000002 00000061
00000003 00000062
00000004 00000063
00000005 00000061
2 00000006 00000008 STRY .char
8,-3,"def",'b'
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.cdecls
Syntax
Syntax
Description
Directives Reference
Share C Headers Between C and Assembly Code
Single Line:
.cdecls [options ,] " filename "[, " filename2 "[,...]]
Multiple Lines:
.cdecls [options]
%{
/*---------------------------------------------------------------------------------*/
/* C/C++ code - Typically a list of #includes and a few defines */
/*---------------------------------------------------------------------------------*/
%}
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 #define's.
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A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
A
Directives Reference
Example
86 www.ti.com
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
for more information on setting up and using the .cdecls directive with C header files.
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: .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
Listing File:
.cdecls C,LIST,"myheader.h"
; ------------------------------------------
; Assembly Generated from C/C++ Source Code
; ------------------------------------------
12
13
14
15
10
11
8
9
6
7
4
5
2
3
1
1
16
17
18
19
20
21
; =========== MACRO DEFINITIONS ===========
.define "10",WANT_ID
.define """John\n""",NAME
; =========== TYPE DEFINITIONS =========== status_enum
00000001 OK
00000100 FAILED
00000000 RUNNING
.enum
.emember 1
.emember 256
.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)
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A
A
A
A
A
A www.ti.com
A 22
23
24
25
00000008 .endstruct
; final size=(8 bytes|64 bits)
26
27
28
29
; =========== EXTERNAL FUNCTIONS ===========
.global _cvt_integer
; =========== EXTERNAL VARIABLES ===========
.global _a_variable
2 00000000 00000008 size: .int $sizeof(myCstruct)
3 00000004 00000000 aoffset: .int myCstruct.member_a
4 00000008 00000004 boffset: .int myCstruct.member_b
5 0000000c 00000001 okvalue: .int status_enum.OK
6 00000010 00000100 failval: .int status_enum.FAILED
7 .if $defined(WANT_ID)
8 00000014 0000004A id
00000015 0000006F
.cstring NAME
00000016 00000068
00000017 0000006E
00000018 0000000A
00000019 00000000
9 .endif
Directives Reference
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Directives Reference
.clink/.retain
Syntax
Description www.ti.com
Control Whether to Conditionally Leave Section Out of Object Module Output
.clink["section name"]
.retain["section name"]
The .clink directive enables conditional linking by telling the linker to leave a section out of the final object module output of the linker if there are no references found to any symbol in that section. The .clink directive can be applied to initialized or uninitialized sections.
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 .clink directive is useful only with the COFF object file format. Under the COFF ABI model, the linker assumes that all sections are ineligible for removal via conditional linking by default. If you want to make a section eligible for removal, you must apply a
.clink directive to it. In contrast, under the ELF EABI model, the linker assumes that all sections are eligible for removal via conditional linking. Therefore, the .clink directive has no effect under EABI.
A section in which the entry point of a C program is defined cannot be marked as a conditionally linked section.
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.
Since under the ELF EABI model the linker assumes that all sections are eligible for removal via conditional linking by default, the .retain directive becomes useful for overriding the default conditional linking behavior for those 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.
Under the COFF ABI model, the linker assumes that all sections are not eligible for removal via conditional linking by default. So under the COFF ABI mode, the .retain
directive does not have any real effect on the section.
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Example 1
Example 2
Directives Reference
Here's an 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
STW
STW
STW
.D2
.D2
.D2
.D2
FP,*SP++(-88)
B3,*SP(80)
A4,*SP(24)
B2,*SP(84)
; [B_D] |31|
; [B_D] |31|
; [B_D] |31|
; [B_D] |31|
STW
STW
STW
STW
STW
STW
STW
STW
STW
STW
STW
.D2
.D2
.D2
.D2
.D2
.D2
.D2
.D2
.D2
.D2
.D2
B9,*SP(76)
B8,*SP(72)
B7,*SP(68)
B6,*SP(64)
B5,*SP(60)
B4,*SP(56)
B1,*SP(52)
B0,*SP(48)
A7,*SP(36)
A6,*SP(32)
A5,*SP(28)
; [B_D] |31|
; [B_D] |31|
; [B_D] |31|
; [B_D] |31|
; [B_D] |31|
; [B_D] |31|
; [B_D] |31|
; [B_D] |31|
; [B_D] |31|
; [B_D] |31|
; [B_D] |31|
||
CALL
STW
.S1
.D2
_foo
A8,*SP(40)
; [A_S] |32|
; [B_D] |31|
||
...
STW
RET
LDW
.D2
.S2
.D2
B4,*+DP(_a_i)
IRP
*SP(56),B4
; [B_D] |33|
; [B_Sb] |34|
; [B_D] |34|
LDW
NOP
.D2
*++SP(88),FP
4
; [B_D] |34|
; [A_L]
In this example, the Vars and Counts sections are set for conditional linking.
3
4
1 00000000
2
5 00000000 0000001A X:
6 00000004 0000001A Y:
7 00000008 0000001A Z:
8 00000000
.sect "Vars"
.clink
; Vars section is conditionally linked
.word 01Ah
.word 01Ah
.word 01Ah
.sect "Counts"
9
10
.clink
; Counts section is conditionally linked
11
12 00000000 0000001A XCount: .word 01Ah
13 00000004 0000001A YCount: .word 01Ah
14 00000008 0000001A ZCount: .word 01Ah
15 00000000
16
.text
; By default, .text is unconditionally linked
17
18 00000000 00B802C4
19 00000004 00000028+
20 00000008 00000068+
21
22
23 0000000c 00040AF8
LDH
MVKL
MVKH
; These references to symbol X cause the Vars
; section to be linked into the object output
CMPLT
*B14,A1
X,A0
X,A0
A0,A1,A0
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Assembler Directives 89
Directives Reference
.copy/.include
Syntax
Description
Example 1 www.ti.com
Copy Source File
.copy "filename"
.include "filename"
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
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.
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 byte.asm
(first copy file)
** In byte.asm
.byte 32,1+ 'A' word.asm
(second copy file)
** In word.asm
.word 0ABCDh, 56q
.copy "word.asm"
.string "done"
** Back in byte.asm
.byte 67h + 3q
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Example 2
Directives Reference
Listing file:
A
B
B
A
A
A
A
1 00000000
2
1
2 0000001d 00000020
0000001e 00000042
3
1
2 00000020 0000ABCD
00000024 0000002E
3
4
4
5 00000028 0000006A
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) byte2.asm
(first copy file) word2.asm
(second copy file)
.space 29
.include "byte2.asm"
** In byte2.asm
.byte 32,1+ 'A'
** In word2.asm
.word 0ABCDh, 56q
** Back in original file
.string "done"
.include
"word2.asm"
** Back in byte2.asm
.byte 67h + 3q
Listing file:
3
4
1 00000000
2
5 00000029 00000064
0000002a 0000006F
0000002b 0000006E
0000002c 00000065
.space 29
.include "byte2.asm"
** Back in original file
.string "done"
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Assembler Directives 91
Directives Reference www.ti.com
.cstruct/.cunion/.endstruct/.endunion/.tag
Declare C Structure Type
Syntax
Description
Example
[stag] .cstruct|.cunion [expr]
[mem
0
] element
[mem
1
] element
.
.
.
.
.
.
.
.
.
[expr
0
]
[expr
1
]
[mem n
] .tag stag
[mem
N
] element
[size]
[expr
[expr
.endstruct|.endunion n
N
]
] label .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. A .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 expr n/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 mem n/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.
This example illustrates a structure in C that will be accessed in assembly code.
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Directives Reference typedef struct STRUCT1
; { int i0; /* offset 0 */
; short s0;
; } struct1;
;
/* offset 4 */
/* size 8, alignment 4 */
; typedef struct STRUCT2
; { struct1 st1; /* offset 0 */
; short s1;
; } struct2;
/* offset 8 */
/* 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
.struct
.int
s0 .short
struct1len .endstruct
struct2 st1
.struct
.tag struct1 s1 .short
endstruct2 .endstruct
; bytes 0-3
; bytes 4-5
; size 6, alignment 4
; bytes 0-5
; bytes 6-7
; size 8, alignment 4
.sect "data1"
.word struct1.i0
.word struct1.s0
.word struct1len cstruct1 i0
.cstruct
.int
s0 .short
cstruct1len .endstruct
; 0
; 4
; 6
.sect "data2"
.word struct2.st1
.word struct2.s1
.word endstruct2
; 0
; 6
; 8
;
; The .cstruct/.cunion directives calculate the 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.
; bytes 0-3
; bytes 4-5
; size 8, alignment 4 cstruct2 st1
.cstruct
.tag cstruct1 s1 .short
cendstruct2 .endstruct
; bytes 0-7
; bytes 8-9
; size 12, alignment 4
.sect "data3"
.word cstruct1.i0, struct1.i0
; 0
.word cstruct1.s0, struct1.s0
; 4
.word cstruct1len, struct1len ; 8
.sect "data4"
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93
Directives Reference
.word cstruct2.st1, struct2.st1 ; 0
.word cstruct2.s1, struct2.s1
; 8
.word cendstruct2, endstruct2 ; 12
.data
Syntax
Description
Example www.ti.com
Assemble Into the .data Section
.data
The .data directive tells the assembler to begin assembling source code into the .data
section; .data becomes the current section. The .data section is normally used to contain tables of data or preinitialized variables.
For more information about sections, see
In this example, code is assembled into the .data and .text sections.
1
2
3
4 00000000
7
8
5 00000000
6
***********************************************
** Reserve space in .data
**
***********************************************
.data
.space
0CCh
9
10 00000000
11 00000000 00800358
12
13
14
15
16 000000cc
***********************************************
** Assemble into .text
**
***********************************************
.text
ABS A0,A1
***********************************************
** Assemble into .data
**
*********************************************** table: .data
.word
-1
.byte
0FFh
17 000000cc FFFFFFFF
18 000000d0 000000FF
19
20
21
22
23 00000004
24 00000004 008001A0
***********************************************
** Assemble into .text
**
***********************************************
.text
MV A0,A1
25
26
27
28
29 000000d1
***********************************************
** Resume assembling into the .data section **
***********************************************
.data
30 000000d4 00000000 coeff .word
00h,0ah,0bh
000000d8 0000000A
000000dc 0000000B
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.double
Syntax
Description
Example
Directives Reference
Initialize Double-Precision Floating-Point Value
.double value
1
[, ... , value n
]
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 a floatingpoint constant or a symbol that has been equated to a floating-point constant. Each constant is converted to a floating-point value in IEEE double-precision 64-bit format.
Double-precision floating point constants are aligned to a double word boundary.
The 64-bit value is stored in the format shown in
.
Figure 4-5. Double-Precision Floating-Point Format
S E E E E E E E E E E E M M M M M M M M M M M M M M M M M M M M
31 20 0
M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M M
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 .
This example shows the .double directive.
.double -2.0e25
1 00000000 2C280291
00000004 C5308B2A
2 00000008 00000000
0000000c 40180000
3 00000010 00000000
00000014 407C8000
.double 6
.double 456
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Assembler Directives 95
Directives Reference
.drlist/.drnolist
Syntax
Description
Example www.ti.com
Control Listing of Directives
.drlist
.drnolist
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.
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
1
1
Listing file:
5
6
3
4
12
13
7
8
14
.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
Syntax
Description
Example
Directives Reference
ELF Symbol Information
.elfsym name, SYM_SIZE(size)
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.
This example shows the use of the ELF symbol information directive.
.ex_sym:
.sect
".examp"
.alignment 4
.elfsym
ex_sym, SYM_SIZE(4)
.emsg/.mmsg/.wmsg
Define Messages
Syntax
Description
Example
.emsg string
.mmsg string
.wmsg string
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.
In this example, the message ERROR -- MISSING PARAMETER is sent to the standard output device.
Source file:
.global PARAM
MSG_EX .macro
parm1
.if
$symlen(parm1) = 0
.emsg
"ERROR -- MISSING PARAMETER"
.else
MVK
.endif
.endm
parm1, A1
MSG_EX PARAM
MSG_EX
Listing file:
3
4
1
2
5
6
.global PARAM
MSG_EX .macro
parm1
.if
$symlen(parm1) = 0
.emsg
"ERROR -- MISSING PARAMETER"
.else
MVK parm1, A1
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Directives Reference
1
1
1
1
1
1
1
1
1
1
7
8
9
10 00000000
.endif
.endm
00000000 00800028!
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
.else
MVK parm1, A1
.endif
1 Error, No Warnings www.ti.com
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
Syntax
Description
Example
Directives Reference
End Assembly
.end
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.
This example shows how the .end directive terminates assembly. If any source statements follow the .end directive, the assembler ignores them.
Source file: start: .text
ZERO
ZERO
ZERO
.end
ZERO
A0
A1
A3
A4
Listing file:
1 00000000
2 00000000 000005E0
3 00000004 008425E0
4 00000008 018C65E0
5 start: .text
ZERO
ZERO
ZERO
.end
A0
A1
A3
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Assembler Directives 99
Directives Reference
.fclist/.fcnolist
Syntax
Description
Example www.ti.com
Control Listing of False Conditional Blocks
.fclist
.fcnolist
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.
This example shows the assembly language and listing files for code with and without the conditional blocks listed.
Source file: a b
.set
.set
MVK
.else
0
1
.fclist
; list false conditional blocks
.if
a
5,A0
MVK
.endif
MVK
.else
0,A0
.fcnolist ; do not list false conditional blocks
.if
a
5,A0
MVK
.endif
0,A0
Listing file:
3
4
1
2
00000000
00000001
5
6
7 00000000 00000028
8
9
13 00000004 00000028 a b
.set
.set
MVK
.else
0
1
.fclist
; list false conditional blocks
.if
a
5,A0
MVK
.endif
0,A0
.fcnolist ; do not list false conditional blocks
MVK 0,A0
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.field
Syntax
Description
Example
Directives Reference
Initialize Field
.field value[, size in bits]
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. If you do not specify a size, the assembler assumes the 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 slot. 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.
You can use the .align directive to force the next .field directive to begin packing into 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 .
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.
shows how the directives in this example affect memory.
7
8
5
6
1
2
3
4 00000000 00BBCCDD
9 00000000 0ABBCCDD
10
11
12
13
14
15 00000004 0000000C
16
************************************
**
**
Initialize a 24-bit field.
************************************
Initialize a 5-bit field
***********************************
**
**
Initialize a 4-bit field in a new word.
**
**
************************************
.field
0Ch, 4
**
************************************
.field
0Ah, 5
**
************************************
.field
0BBCCDDh, 24
21
22
23
24
17
18
************************************
** Initialize a 3-bit field **
19 ************************************
20 00000004 0000001C x: .field
01h, 3
************************************
** Initialize a 32-bit field
** relocatable field in the
** next word
**
**
** 25
26
27 00000008 00000004'
************************************
.field
x
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Figure 4-6. The .field Directive www.ti.com
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.float
Syntax
Description
Example
Directives Reference
Initialize Single-Precision Floating-Point Value
.float value[, ... , value n
]
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 a floating-point constant or a symbol that has been equated to a floating-point constant.
Each constant is converted to a floating-point value in IEEE single-precision 32-bit format.
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 4-7. Single-Precision Floating-Point Format
S E E E E E E E E M M M M M M M M M M M M M M M M M M M M M M M
31 23 0 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 .
Following are examples of the .float directive:
1 00000000 E9045951
2 00000004 40400000
3 00000008 42F60000
.float
-1.0e25
.float
3
.float
123
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Directives Reference
.global/.def/.ref
Syntax
Description
Example www.ti.com
Identify Global Symbols
.global symbol
1
[, ... , symbol n
]
.def symbol
1
[, ... , symbol n
]
.ref symbol
1
[, ... , symbol n
]
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. As with all symbols, if a global symbol is defined more than once, the linker issues a multiple-definition error. 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.
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
9
10
11
3
4
1
2
5 00000000
6 00000000 00902058
7 00000004 00000000!
8 ;
;
;
; 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
9
10
11
12
3
4
1
2
5
6
00000001 X:
00000002 Y:
7 00000003 Z:
8 00000000 00000000!
; Global symbols defined in this file
.global X, Y, Z
; Global symbol defined in file1.lst
.global INIT
.set
.set
.set
.word
1
2
3
INIT
;
;
;
.
.
.
.end
file3.lst
9
10
11
3
4
1
2
5 00000000
6 00000000 00902058
7 00000004 00000000!
8 ;
;
;
; 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
9
10
11
12
3
4
1
2
5
6
00000001 X:
00000002 Y:
7 00000003 Z:
8 00000000 00000000!
; Global symbols defined in this file
.def
X, Y, Z
; Global symbol defined in file3.lst
.ref
INIT
.set
.set
.set
.word
1
2
3
INIT
;
;
;
.
.
.
.end
Directives Reference
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.group/.gmember/.endgroup
Define Common Data Section
Syntax
Description
.group group section name group type
.gmember section name
.endgroup
Three directives instruct the assembler to make certain sections members of an ELF group section (see 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
The .gmember directive designates section name as a member of the group.
The .endgroup directive ends the group declaration.
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Directives Reference
.half/.short/.uhalf/.ushort
Initialize 16-Bit Integers
Syntax
Description
Example
.half value
1
[, ... , value n
]
.short value
1
[, ... , value n
]
.uhalf value
1
[, ... , value n
]
.ushort value
1
[, ... , value n
]
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 slot 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
.
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.
.space
100h * 16
.half
10, -1, "abc", 'a'
1 00000000
2 00001000 0000000A
00001002 0000FFFF
00001004 00000061
00001006 00000062
00001008 00000063
0000100a 00000061
3 0000100c 00000008 STRN
0000100e 0000FFFD
00001010 00000064
00001012 00000065
00001014 00000066
00001016 00000062
.short
8, -3, "def", 'b'
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.if/.elseif/.else/.endif
Assemble Conditional Blocks
Syntax
Description
Example
.if well-defined expression
[.elseif well-defined expression]
[.else]
.endif
Four directives provide conditional assembly:
The .if directive marks the beginning of a conditional block. The well-defined expression 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 directive is optional in the conditional block, and more than one .elseif can be used. If an expression is false and there is no .elseif
statement, 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 .endif directive terminates a conditional block.
The .elseif and .else directives can be used in the same conditional assembly block, and the .elseif directive can be used more than once within a conditional assembly block.
See
for information about relational operators.
This example shows conditional assembly:
9
10
11
12
3
4
1
2
00000001 SYM1
00000002 SYM2
00000003 SYM3
00000004 SYM4
5
6
7 00000000 00000004
8
If_4:
.set
.set
.set
.set
.if
1
2
3
4
SYM4 = SYM2 * SYM2
.byte
SYM4
.else
.byte
SYM2 * SYM2
.endif
; Equal values
; Unequal values
13 00000001 0000000A
14
15
16
If_5: .if
SYM1 <;= 10
.byte
10
.else
.byte
SYM1
.endif
; Less than / equal
; Greater than
17
18
19
20
21 00000002 00000008
22
23
24
25
If_6: .if
If_7:
.else
.endif
.if
.byte
SYM3 * SYM2 != SYM4 + SYM2
.byte
SYM3 * SYM2
.byte
SYM4 + SYM4
SYM1 = SYM2
SYM1
; Unequal value
; Equal values
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26
27 00000003 00000005
28
.elseif SYM2 + SYM3 = 5
.byte
SYM2 + SYM3
.endif
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.import/.export/.hidden/.protected
Set Dynamic Visibility of Global Symbol
Syntax
Description
.import "symbolname"
.export "symbolname"
.hidden "symbolname"
.protected "symbolname"
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
for an explanation of symbol visibility.
Theses directives are commonly used in the context of dynamic linking, for more detail see the Dynamic Linking wiki site
( http://processors.wiki.ti.com/index.php/C6000_Dynamic_Linking ).
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Directives Reference
.int/.long/.word/.uint/.uword
Initialize 32-Bit Integers
Syntax
Description
Example 1
Example 2
Example 3
.int value
1
[, ... , value n
]
.long value
1
[, ... , value n
]
.word value
1
[, ... , value n
]
.uint value
1
[, ... , value n
]
.uword value
1
[, ... , value n
]
The .int, .uint, .long, .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
.
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 00000000
2 00000000
5 00000078 0000000A
0000007c 00000080-
.space 73h
.bss
PAGE, 128
3 00000080 .bss
SYMPTR, 3
4 00000074 003C12E4 INST: LDW.D2 *++B15[0],A0
.int
10, SYMPTR, -1, 35 + 'a', INST
00000080 FFFFFFFF
00000084 00000084
00000088 00000074'
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 DAT1: .long
0FFFFABCDh,'A'+100h
00000004 00000141
This example initializes five words. The symbol WordX points to the first word.
1 00000000 00000C80 ;WordX .word
3200,1+'AB',-'AF',0F410h,'A'
00000004 00004242
00000008 FFFFB9BF
0000000c 0000F410
00000010 00000041
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Directives Reference
.label
Syntax
Description
Example www.ti.com
Create a Load-Time Address Label
.label symbol
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.
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.
This example shows the use of a load-time address label.
sect ".examp"
.label examp_load ; load address of section start: ; run address of section finish:
<code>
; run address of section end
.label examp_end ; load address of section end
See
for more information about assigning run-time and load-time addresses in the linker.
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.length/.width
Syntax
Description
Example
Directives Reference
Set Listing Page Size
.length [page length]
.width [page width]
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.
The following example shows how to change the page length and width.
********************************************
** Page length = 65 lines **
** Page width = 85 characters **
********************************************
.length
.width
65
85
********************************************
** Page length = 55 lines **
** Page width = 100 characters **
********************************************
.length
.width
55
100
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Directives Reference
.list/.nolist
Syntax
Description
Example www.ti.com
Start/Stop Source Listing
.list
.nolist
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
), the assembler ignores the .list directive.
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
0CCh
.text
ABS A0,A1
.nolist
table: .data
.word
-1
.byte
0FFh
.list
.text
MV A0,A1
.data
coeff .word
00h,0ah,0bh
Listing file:
1 00000000
2 00000000
3 00000000
4 00000000 00800358
5
13
14 00000004
15 00000004 008001A0
.text
MV A0,A1
16 000000d1 .data
17 000000d4 00000000 coeff .word
00h,0ah,0bh
000000d8 0000000A
000000dc 0000000B
.data
.space
0CCh
.text
ABS A0,A1
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Directives Reference
.loop/.endloop/.break
Assemble Code Block Repeatedly
Syntax
Description
Example
.loop [well-defined expression]
.break [well-defined expression]
.endloop
Three directives allow you to repeatedly assemble a block of code:
The .loop directive begins a repeatable block of code. The optional expression evaluates to the loop count (the number of loops to be performed). If there is no well-
defined expression, the loop count defaults to 1024, unless the assembler first encounters a .break directive with an expression that is true (nonzero) or omitted.
The .break directive, along with its expression, is optional. This means that when you use the .loop construct, you do not have to use the .break construct. The .break directive terminates a repeatable block of code only if the well-defined expression is true
(nonzero) or omitted, and the assembler breaks the loop and assembles the code after the .endloop directive. If the expression is false (evaluates to 0), the loop continues.
The .endloop directive terminates a repeatable block of code; it executes when the
.break directive is true (nonzero) or when the number of loops performed equals the loop count given by .loop.
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
1
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.
0,x
3
4
1
2
5
6
00000000 00000000
00000004 00000064
00000008 000000C8
0000000c 0000012C
00000010 00000190
00000014 000001F4
.eval
COEF .loop
.word
.eval
.break
.endloop
.word
.eval
.break
.word
.eval
.break
.word
.eval
.break
.word
.eval
.break
.word
.eval
.break
.word
.eval
.break
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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Assembler Directives 115
Directives Reference
.macro/.endm
Syntax
Description www.ti.com
Define Macro
macname .macro [parameter
1
[, ... , parameter n
]] model statements or macro directives
.endm
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
.
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.map/.clearmap
Syntax
Description
Example
Directives Reference
Assign a Variable to a Register
.map symbol
1
/ register
1
[, symbol
2
/ register
2
, ...]
.clearmap
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.
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 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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Directives Reference
.mlib
Syntax
Description
Example www.ti.com
Define Macro Library
.mlib "filename"
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
for more information about the --include_path option.
When the assembler encounters a .mlib directive, it opens the library specified by the
filename and creates a table of the library's contents. The assembler enters the names of the individual library members into the opcode table 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 in the same way it expands other macros, but it does not place the source code into the listing. Only macros that are actually called from the library are extracted, and they are extracted only once.
See
for more information on macros and macro libraries.
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:
.mlib
"mac.lib"
1
1
1
2
3
4 00000000
00000000 000021A0
5
6
7 00000004
00000004 0003E1A2
* Macro Call inc1
ADD
* Macro Call dec1
SUB
A0
A0,1,A0
B0
B0,1,B0
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.mlist/.mnolist
Syntax
Description
Example
Directives Reference
Start/Stop Macro Expansion Listing
.mlist
.mnolist
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
for more information on macros and macro libraries. See the
for information on conditional blocks.
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
3
4
1
2
5 00000000
00000000 0000003A
00000001 00000070
00000002 00000031
00000003 0000003A
00000004 0000003A
00000005 00000070
00000006 00000032
00000007 0000003A
00000008 0000003A
00000009 00000070
0000000a 00000033
0000000b 0000003A
6
7 0000000c
8
9 00000018
00000018 0000003A
00000019 00000070
0000001a 00000031
0000001b 0000003A
0000001c 0000003A
0000001d 00000070
0000001e 00000032
0000001f 0000003A
00000020 0000003A
00000021 00000070
00000022 00000033
00000023 0000003A
STR_3 .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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Assembler Directives 119
Directives Reference
.newblock
Syntax
Description
Example www.ti.com
Terminate Local Symbol Block
.newblock
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, cannot be used in expressions, and do not qualify for branch expansion if used with a branch. 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
for more information on the use of local labels.
This example shows how the local label $1 is declared, reset, and then declared again.
1
2
3 00000000 00000028!
4 00000004 00000068!
.global table1, table2
MVKL
5 00000008 008031A9
6 0000000c 010848C0 ||
MVK
ZERO
7
8 00000010 80000212 $1:[A1] B table1,A0
MVKH
99, A1
A2 table1,A0
9 00000014 01003674
10 00000018 0087E1A0
11 0000001c 00004000
12
STW
SUB
NOP
$1
A2, *A0++
A1,1,A1
3
13
14
15 00000020 00000028!
16 00000024 00000068!
.newblock ; undefine $1
17 00000028 008031A9
18 0000002c 010829C0 ||
19
20 00000030 80000212 $1:[A1] B
21 00000034 01003674
22 00000038 0087E1A0
23 0000003c 00004000
MVKL
MVKH
MVK
SUB
STW
SUB
NOP table2,A0 table2,A0
99, A1
A2,1,A2
$1
A2, *A0++
A1,1,A1
3
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.nocmp
Syntax
Description
Example
Directives Reference
Do Not Utilize 16-Bit Instructions in Section
.nocmp
The C6400+, C6740, and C6600 .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.
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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Assembler Directives 121
Directives Reference www.ti.com
.noremark/.remark
Control Remarks
Syntax
Description
Example
.noremark num
.remark [num]
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.
This example shows how to suppress the R5002 remark:
Partial source file:
;;; cl6x -mv6700+ usenoremark.asm
.noremark 5002
ADDSP A4, A4, A4
Resulting listing file:
"usenoremark.asm", REMARK at line 4: [R5002] An ADDSP/SUBSP, ADDDP/SUBDP instruction has no unit specifier, but the assembler can place it on the .L or .S unit on C6700+. On C6700+, the lack of unit specifier may cause an unintended functional unit conflict in 4/7th cycle on the
.L or .S unit. Please check and add unit specifiers to these instructions to avoid this hazard. Details can be found in section "Constrains on
Floating-Point Instructions" and
"Functional Unit Constraints" in document SPRU733
ADDSP A4, A4, A4
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Directives Reference
.option
Syntax
Description
M
N
O
R
B
D
H
L
T
W
X
Select Listing Options
.option option
1
[, option
2
,. . .]
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 --cross_reference option
(see
).
Example
Options are not case sensitive.
This example shows how to limit the listings of the .byte, .char, .int, long, .word, and
.string directives to one line each.
3
4
1
2
5
6
7 00000000 000000BD
8 00000003 000000BC
13
14
15
16
9 00000008 0000000A
10 0000001c AABBCCDD
11 00000024 000015AA
12 0000002c 00000052
17
18 00000035 000000BD
00000036 000000B0
00000037 00000005
19 00000038 000000BC
00000039 000000C0
0000003a 00000006
20 0000003c 0000000A
00000040 00000084
00000044 00000061
00000048 00000062
0000004c 00000063
21 00000050 AABBCCDD
00000054 00000259
22 00000058 000015AA
0000005c 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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123
Directives Reference
.page
Syntax
Description
Example www.ti.com
23 00000060 00000052
00000061 00000065
00000062 00000067
00000063 00000069
00000064 00000073
00000065 00000074
00000066 00000065
00000067 00000072
00000068 00000073
.string "Registers"
Eject Page in Listing
.page
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.
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 ****
Year
PAGE 1
2
3
;
;
4
TMS320C6000 Assembler
;
Version x.xx
.
Day Time
Copyright (c) 1996-2011 Texas Instruments Incorporated
**** Page Directive Example ****
.
.
Year
PAGE 2
No Errors, No Warnings
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.sect
Syntax
Description
Example
Directives Reference
Assemble Into Named Section
.sect " section name "
.sect " section name " [,{RO|RW}] [,{ALLOC|NOALLOC}]
The .sect directive defines a named section that can be used like the default .text and
.data sections. The .sect directive tells the assembler to begin assembling source code into the named 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.
In ELF mode 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
The extra operands are allowed only in ELF mode. They are ignored but generate a warning in COFF mode. For example:
"t.asm", WARNING!
at line 1:[W0000] Trailing operands ignored
.sect "cosnt_sect",RO
See
for more information about sections.
This example defines two special-purpose sections, Sym_Defs and Vars, and assembles code into them.
1
2
3
4 00000000
**********************************************
** Begin assembling into .text section.
**
**********************************************
.text
5 00000000 000005E0
6 00000004 008425E0
ZERO
ZERO
A0
A1
7
8
9
10
**********************************************
** Begin assembling into vars section.
**
**********************************************
11 00000000
12 00000000 4048F5C3 pi
.sect
"vars"
.float
3.14
13 00000004 000007D0 max
14 00000008 00000001 min
15
16
17
18
19 00000008
20 00000008 010000A8
21 0000000c 018000A8
22
.int
.int
2000
1
**********************************************
** Resume assembling into .text section.
**
**********************************************
.text
MVK
MVK
1,A2
1,A3
23
24
25
26 0000000c
**********************************************
** Resume assembling into vars section.
**********************************************
.sect
"vars"
27 0000000c 00000019 count .short
25
**
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Assembler Directives 125
Directives Reference
.set/.equ
Syntax
Description
Example www.ti.com
Define Assembly-Time Constant
symbol .set value
symbol .equ value
The .set and .equ directives equate a constant value to a 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.
This example shows how symbols can be assigned with .set and .equ.
3
4
1
2
**********************************************
** Equate symbol AUX_R1 to register A1 **
** and use it instead of the register.
**
**********************************************
5 00000001 AUX_R1 .set
6 00000000 00B802D4 STH
A1
AUX_R1,*+B14
7
8
9
10
11
12
13 00000004 01001AD0
**********************************************
**
**
Set symbol index to an integer expr.
00000035 INDEX .equ
** and use it as an immediate operand.
**
**********************************************
ADDK
100/2 +3
INDEX, A2
22
23
24
25
14
15
16
17
18
**********************************************
** Set symbol SYMTAB to a relocatable expr. **
** and use it as a relocatable operand.
**
**********************************************
19 00000008 0000000A LABEL .word
10
20
21
00000009' SYMTAB .set
LABEL + 1
**********************************************
**
**
Set symbol NSYMS equal to the symbol
INDEX and use it as you would INDEX.
**
**
**********************************************
26 00000035 NSYMS .set
27 0000000c 00000035 .word
INDEX
NSYMS
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.space/.bes
Syntax
Description
Example
Directives Reference
Reserve Space
[label] .space size in bytes
[label] .bes 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.
This example shows how memory is reserved with the .space and .bes directives.
1
2
3
4 00000000
5
6
7
8 00000000
10
11
9 000000f0 00000100
000000f4 00000200
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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Assembler Directives 127
Directives Reference
.sslist/.ssnolist
Syntax
Description
Example www.ti.com
Control Listing of Substitution Symbols
.sslist
.ssnolist
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.
1
#
1
1
1
#
1
#
1
1
1
1
1
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.
7
8
5
6
1 00000000
2 00000004
3 00000008
4
9
10
11
12
13 00000000
00000000 0000006C-
00000004 0080016C-
00000008 00006000
0000000c 000401E0
00000010 0000027C-
14
15
16 00000014
00000014 0000006Caddm
.bss
.bss
.bss
.macro
src1,src2,dst
LDW *+B14(:src1:), A0
LDW
NOP
*+B14(:src2:), A1
4
ADD
STW
.endm
A0,A1,A0
A0,*+B14(:dst:) addm
LDW
LDW
NOP
ADD
STW x,4 y,4 z,4 x,y,z
*+B14(x), A0
*+B14(y), A1
4
A0,A1,A0
A0,*+B14(z)
00000018 0080016C-
0000001c 00006000
00000020 000401E0
00000024 0000027C-
.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
Syntax
Description
Example
Directives Reference
Initialize Text
.string {expr
1
| "string
1
"} [, ... , {expr n
| "string n
"} ]
.cstring {expr
1
| "string
1
"} [, ... , {expr n
| "string n
"} ]
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
.
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 00000041 Str_Ptr: .string
"ABCD"
00000001 00000042
00000002 00000043
00000003 00000044
.string
41h, 42h, 43h, 44h 2 00000004 00000041
00000005 00000042
00000006 00000043
00000007 00000044
.string
"Austin", "Houston" 3 00000008 00000041
00000009 00000075
0000000a 00000073
0000000b 00000074
0000000c 00000069
0000000d 0000006E
0000000e 00000048
0000000f 0000006F
00000010 00000075
00000011 00000073
00000012 00000074
00000013 0000006F
00000014 0000006E
4 00000015 00000030 .string
36 + 12
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Assembler Directives 129
Directives Reference www.ti.com
.struct/.endstruct/.tag
Declare Structure Type
Syntax
Description
[stag] .struct
[expr]
[mem
0
]
[mem
1
]
.
.
.
element element
.
.
.
[mem n
] .tag stag
.
.
.
.
.
.
[mem
N
[size] label
]
[expr
0
]
[expr
1
]
.
.
[expr n
]
.
.
.
.
element [expr
N
]
.endstruct
.tag
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. A .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 mem n/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 expr n/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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Example 1
Example 2
Example 3
Example 4
Directives Reference
The following examples show various uses of the .struct, .tag, and .endstruct directives.
3
4
1
2 real_rec .struct
00000000 nom .int
00000004 den .int
00000008 real_len .endstruct
7
8
5
6 00000000 0080016C-
9 00000000
10
LDW
; stag
; member1 = 0
; member2 = 1
; real_len = 2
*+B14(real+real_rec.den), A1
.bss real, real_len
; access structure
; allocate mem rec
7
8
5
6
3
4
1
2
11
12
13
14
15
16
17
18 00000008
00000008
19
20 00000004 0100046C-
21
22 00000008 0100036C-
23
24 0000000c 018C4A78 cplx_rec .struct
00000000 reali imagi complex
.tag real_rec
.tag real_rec
00000010 cplx_len .endstruct
.tag cplx_rec
.bss complex, cplx_len ; allocate mem rec
LDW
LDW
; stag
; member1
; member2
; cplx_len = 4
; assign structure
; attribute
*+B14(complex.imagi.nom), A2
CMPEQ A2, A3, A3
= 0
= 2
; access structure
*+B14(complex.reali.den), A2
; access structure
00000000
00000001
00000002
00000003
X
Y
Z
.struct
.byte
.byte
.byte
.endstruct
; no stag puts
; mems into global
; symbol table
; create 3 dim
; templates
7
8
5
6
3
4
1
2 00000000
00000040
00000040
00000042
00000044
00000045 bit_len .endstruct
9
10 00000000
11
12 00000000 0100106C-
13
14 00000004 0109E7A0 bit_rec .struct
stream bit7 bit1 bit5 x_int bits
.string 64
.field
.field
.field
.byte
.tag bit_rec
.bss bits, bit_len
LDW
AND
7
9
10
; stag
; bit7 = 64
; bit9 = 64
; bit5 = 64
; x_int = 68
; length = 72
*+B14(bits.bit7), A2
0Fh, A2, A2
; load field
; mask off garbage
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Directives Reference www.ti.com
.symdepend/.weak
Effect Symbol Linkage and Visibility
Syntax
Description
.symdepend dst symbol name[, src symbol name]
.weak symbol name
These directives are used to effect symbol linkage and visibility. The .weak directive is only valid when ELF mode is used.
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. 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. As with all symbols, if a global symbol is defined more than once, the linker issues a multiple-definition error. 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 for either of two reasons:
• If the symbol is not defined in the current module (which includes macro, copy, and include files), the .weak 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 .symdepend directive declares that the symbol and its definition can be used externally by other modules. These types of references are resolved at link time.
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.tab
Syntax
Description
Example
Directives Reference
Define Tab Size
.tab size
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.
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 00000000 00000000
3 00000004 00000000
4 00000008 00000000
5
7 0000000c 00000000
8 00000010 00000000
9 00000014 00000000
10
12 00000018 00000000
13 0000001c 00000000
14 00000020 00000000
; default tab size
NOP
NOP
NOP
.tab4
NOP
NOP
NOP
.tab 16
NOP
NOP
NOP
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Assembler Directives 133
Directives Reference
.text
Syntax
Description
Example www.ti.com
Assemble Into the .text Section
.text
The .text directive tells the assembler to begin assembling 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
This example assembles code into the .text and .data sections.
1
2
3
4 00000000
6
7
5 00000000 00000005
00000001 00000006
8
9
10 00000000
11 00000000 00000001
12 00000001 00000002
00000002 00000003
13
14
19
20
21
22
15
16
17 00000002
18 00000002 00000007
00000003 00000008
23 00000003
24 00000003 00000004
******************************************
** 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
4
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.title
Syntax
Description
Example
Directives Reference
Define Page Title
.title "string"
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.
In this example, one title is printed on the first page and a different title is printed on succeeding pages.
;
;
;
Source file:
.title
"**** Fast Fourier Transforms ****"
.
.
.
.title
"**** Floating-Point Routines ****"
.page
Listing file:
TMS320C6000 Assembler Version x.xx
Day Time
Copyright (c) 1996-2011 Texas Instruments Incorporated
**** Fast Fourier Transforms ****
Year
PAGE 1
2
3
;
;
4
TMS320C6000 Assembler
;
Version x.xx
.
Day Time
Copyright (c) 1996-2011 Texas Instruments Incorporated
**** Floating-Point Routines ****
.
.
Year
PAGE 2
No Errors, No Warnings
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Assembler Directives 135
Directives Reference www.ti.com
.union/.endunion/.tag
Declare Union Type
Syntax
Description
[stag] .union
[expr]
[mem
0
[mem
1
.
.
.
] element [expr
0
] element [expr
1
.
.
.
.
.
.
]
]
[mem n
.
.
.
] .tag stag [expr n
.
.
.
.
.
.
]
[mem
N
] element [expr
N
]
[size] .endunion
label .tag
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 mem n/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 expr n/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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Example 1
Example 2
Directives Reference
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.
3
4
1
2
5
6
7
8 000000
0000
0000
9
10
11 000000 0000xample ival
0000 fval sval
.global employid
.union
.word
.float
.string
0002 real_len .endunion
employid
.bss
.tag
ADD employid, real_len xample employid.fval, A
; utag
; member1 = int
; member2 = float
; member3 = string
; real_len = 2
;allocate memory
; name an instance
; access union element
5
6
7
3
4
1
2
0000 x
0000 y
0000 z
0002 size_u
.long
.float
.word
.endunion
; utag
; member1 = long
; member2 = float
; member3 = word
; real_len = 2
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Assembler Directives 137
Directives Reference
.usect
Syntax
Description
Example www.ti.com
Reserve Uninitialized Space
symbol .usect "section name", size in bytes[, alignment[, bank offset] ]
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 indicates the size of the slot in bytes and 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) end the current section and tell the assembler to 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
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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Directives Reference
shows how this example reserves space in two uninitialized sections, var1 and var2.
1
2
3
4 00000000
7
8
5 00000000 008001A0
6
9
10 00000000
11 00000004 0100004C-
12
13
14
15
16 00000002
17 00000008 01800128-
18 0000000c 01800068-
19
20
21
22
23 00000066
24 00000010 02003328-
25 00000014 02000068-
26
27
28
29
30 00000000
31 00000018 0000002A-
32 0000001c 0000006A-
***************************************************
** Assemble into .text section **
***************************************************
.text
MV A0,A1
***************************************************
** Reserve 2 bytes in var1.
**
*************************************************** ptr .usect
"var1",2
LDH *+B14(ptr),A2 ; still in .text
***************************************************
** Reserve 100 bytes in var1 **
*************************************************** array .usect
"var1",100
MVK
MVKH array,A3 array,A3
; still in .text
***************************************************
** Reserve 50 bytes in var1 **
*************************************************** dflag .usect
"var1",50
MVK
MVKH dflag,A4 dflag,A4
***************************************************
** Reserve 100 bytes in var1 **
*************************************************** vec .usect
"var2",100
MVK
MVKH vec,B0 vec,B0
; still in .text
ptr array
Figure 4-8. The .usect Directive
Section var1 Section var2
2 bytes ptr
100 bytes
100 bytes
100 bytes reserved in var2 dflag
50 bytes
152 bytes reserved in var1
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Directives Reference www.ti.com
.unasg/.undefine
Turn Off Substitution Symbol
Syntax
Description
.unasg symbol
.undefine symbol
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
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
for more information about using
C/C++ headers in assembly source.
.var
Syntax
Description
Use Substitution Symbols as Local Variables
.var sym
1
[, sym
2
, ... , sym n
]
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
for more information on substitution symbols .See
for information on macros.
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Chapter 5
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Macro 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
...........................................................................................................................
Page
5.1
Using Macros ..................................................................................................
5.2
Defining Macros ..............................................................................................
5.3
Macro Parameters/Substitution Symbols
5.4
Macro Libraries
............................................................
...............................................................................................
5.5
Using Conditional Assembly in Macros
5.6
Using Labels in Macros
..............................................................
....................................................................................
5.7
Producing Messages in Macros .........................................................................
5.8
Using Directives to Format the Output Listing
5.9
Using Recursive and Nested Macros
....................................................
..................................................................
5.10
Macro Directives Summary ...............................................................................
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Macro Description 141
Using Macros www.ti.com
5.1
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
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
, 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
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
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.
5.2
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
); they can also be defined in a macro library. For more information about macro libraries, see
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
A macro definition is a series of source statements in the following format: macname .macro
[parameter
1
] [, ... , parameter n
] model statements or macro directives
[.mexit]
.endm
macname
.macro
parameter parameter n
1
, 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
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Defining Macros model statements are instructions or assembler directives that are executed each time the macro is called.
macro directives
.mexit
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.
.endm
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
for more information about macro comments.
shows the definition, call, and expansion of a macro.
Example 5 ‑‑ 1. Macro Definition, Call, and Expansion
Macro definition: The following code defines a macro, sadd4, with four parameters:
7
8
5
6
9
3
4
1
2 sadd4 .macro
r1,r2,r3,r4
!
!
sadd4 r1, r2 ,r3, r4
!
r1 = r1 + r2 + r3 + r4 (saturated)
!
SADD
SADD
SADD
.endm
r1,r2,r1 r1,r3,r1 r1,r4,r1
Macro call: The following code calls the sadd4 macro with four arguments:
10
11 00000000 sadd4 A0,A1,A2,A3
1
1
1
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.
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
5.3
Macro Parameters/Substitution Symbols
www.ti.com
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
).
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
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.
shows the expansion of a macro with varying numbers of arguments.
Example 5-2. Calling a Macro With Varying Numbers of Arguments
;
;
;
;
;
;
Macro definition:
.macro
;
;
Parms
;
.endm
a,b,c a = :a: b = :b: c = :c:
;
;
;
Calling the macro:
Parms 100,label a = 100 b = label c = " "
Parms 100, , x a = 100 b = " " c = x
Parms """string""",x,y a = "string" b = x c = y
Parms 100,label,x,y
; a = 100
; b = label
; c = x,y
Parms "100,200,300",x,y
; a = 100,200,300
; b = x
; c = y
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Macro Parameters/Substitution Symbols
5.3.1 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
shows character strings being assigned to substitution symbols.
Example 5-3. 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
shows arithmetic being performed on substitution symbols.
Example 5-4. The .eval Directive
.asg
1,counter
.loop
100
.word
counter
.eval
counter + 1,counter
.endloop
In
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
for more information about the .asg and .eval assembler directives.
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5.3.2 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 5-1 , 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 5-1. Substitution Symbol Functions and Return Values
(1)
Function
$symlen (a)
$symcmp (a,b)
$firstch (a,ch)
$lastch (a,ch)
$isdefed (a)
$ismember (a,b)
$iscons (a)
$isname (a)
$isreg (a) (1)
Return Value
Length of string a
< 0 if a < b; 0 if a = b; > 0 if a > b
Index of the first occurrence of character constant ch in string a
Index of the last occurrence of character constant ch in string a
1 if string a is defined in the symbol table
0 if string a is not defined in the symbol table
Top member of list b is assigned to string a
0 if b is a null string
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
1 if string a is a valid symbol name
0 if string a is not a valid symbol name
1 if string a is a valid predefined register name
0 if string a is not a valid predefined register name
For more information about predefined register names, see
shows built-in substitution symbol functions.
Example 5 ‑‑ 5. Using Built-In Substitution Symbol Functions pushx .macro list
!
! Push more than one item
! $ismember removes the first item in the list
.var
.loop
.break
STW
.endloop
.endm
item
($ismember(item, list) = 0) item,*B15--[1] pushx A0,A1,A2,A3
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Macro Parameters/Substitution Symbols
5.3.3 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
recognizes this as infinite recursion and ceases substitution.
Example 5 ‑‑ 6. Recursive Substitution
.asg
"x",z ; declare z and assign z = "x"
.asg
"z",y ; declare y and assign y = "z"
.asg
"y",x ; declare x and assign x = "y"
MVKL x, A1
MVKH x, A1
* MVKL x, A1 ; recursive expansion
* MVKH x, A1 ; recursive expansion
5.3.4 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.
shows how the forced substitution operator is used.
Example 5-7. Using the Forced Substitution Operator force .macro
x
.loop
8
PORT:x: .set
.eval
x*4 x+1, x
.endloop
.endm
.global
portbase force
PORT0 .set
PORT1 .set
.
.
.
PORT7 .set
0
4
28
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5.3.5 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, expression
1 represents the substring's starting position, and expression
2 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.
and
show built-in substitution symbol functions used with subscripted substitution symbols.
In
Example 5-8 , subscripted substitution symbols redefine the STW instruction so that it handles
immediates. In
Example 5-9 , 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 5 ‑‑ 8. Using Subscripted Substitution Symbols to Redefine an Instruction storex .macro
.var
.asg
.if
STW x,*A15--(4)
.elseif
$symcmp(tmp,"B") == 0
STW x,*A15--(4)
.elseif
$iscons(x)
MVK
STW
.else
.emsg
x tmp
:x(1):, tmp
$symcmp(tmp,"A") == 0 x,A0
A0,*A15--(4)
"Bad Macro Parameter"
.endif
.endm
storex storex
10h
A15
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Example 5 ‑‑ 9. Using Subscripted Substitution Symbols to Find Substrings substr .macro
start,strg1,strg2,pos
.var
len1,len2,i,tmp
.if
.eval
$symlen(start) = 0
1,start
.endif
.eval
.eval
.eval
0,pos start,i
$symlen(strg1),len1
$symlen(strg2),len2 .eval
.loop
.break
I = (len2 - len1 + 1)
.asg
":strg2(i,len1):",tmp
.if
.eval
.break
.else
$symcmp(strg1,tmp) = 0 i,pos
.eval
.endif
.endloop
.endm
I + 1,i
.asg
.asg
0,pos
"ar1 ar2 ar3 ar4",regs substr 1,"ar2",regs,pos
.word
pos
Macro Libraries
5.3.6 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
sym
1
[,sym
2
, ... ,sym n
]
The .var directive is used in
and
5.4
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 simple add3
Filename in Macro Library simple.asm
add3.asm
You can access the macro library by using the .mlib assembler directive (described in
.mlib filename
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Using Conditional Assembly in Macros www.ti.com
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 in the same way it expands other macros. See
for how the assembler expands macros. You can control the listing of library entry expansions with the .mlist
directive. For more information about the .mlist directive, see
and
. 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
.
5.5
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
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
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
, and
show the .loop/.break/ .endloop directives, properly nested conditional assembly directives, and built-in substitution symbol functions used in a conditional assembly code block.
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Example 5 ‑‑ 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
Using Conditional Assembly in Macros
Example 5 ‑‑ 11. Nested Conditional Assembly Directives
.asg
.loop
1,x
.if
(x == 10) ; if x == 10, quit loop
.break
(x == 10) ; force break
.endif
.eval
x+1,x
.endloop
Example 5 ‑‑ 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 A0,A1,A3,0
MACK3 A0,A1,A3,100
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Using Labels in Macros www.ti.com
5.6
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. The syntax for a unique label is:
label ?
1
1
1
1
1
1
1
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
Example 5 ‑‑ 13. Unique Labels in a Macro
7
8
5
6
3
4
1
2
9
10
11
12 00000000 min
||
[y] l?
00000000 010401A1
00000004 00840AF8 ||
00000008 80000292 [A1]
0000000c 00008000
00000010 010001A0
00000014 l?
.macro
x,y,z
MV y,z
CMPLT x,y,y
B
NOP
MV l?
5 x,z
.endm
MIN A0,A1,A2
MV A1,A2
CMPLT A0,A1,A1
B
NOP
MV l?
5
A0,A2
LABEL
.TMS320C60
.tms320C60
l$1$
VALUE
00000001
00000001
00000014'
DEFN
0
0
12
REF
12
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Producing Messages in Macros
5.7
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.
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
Example 5 ‑‑ 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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5.8
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.
.mnolist
suppresses the listing of macro expansions and .loop/ .endloop blocks.
For macro and loop expansion listing, .mlist is the default.
• 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
5.9
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.
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 5 ‑‑ 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
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 5 ‑‑ 16. Using Recursive Macros
.fcnolist
fact1 .macro n
.if n == 1
MVK globcnt, A1 fact1 temp
.endif
; 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.
; Recursive call.
.endm
fact .macro n
.if ! $iscons(n)
.emsg "Parm not a constant"
; Test that input is a constant.
.elseif n < 1
MVK 0, A1
.else
.var temp
.asg n, globcnt fact1 n
.endif
.endm
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; Type check input.
; Perform recursive procedure
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Macro Directives Summary
5.10 Macro Directives Summary
The directives listed in
through
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 5-2. Creating Macros
Mnemonic and Syntax
.endm
macname .macro [parameter
1
][,... , parameter n
]
.mexit
.mlib filename
Description
End macro definition
Define macro by macname
Go to .endm
Identify library containing macro definitions
Macro Use
See
Directive
Table 5-3. Manipulating Substitution Symbols
Mnemonic and Syntax
.asg ["]character string["], substitution symbol
.eval well-defined expression, substitution symbol
.var
sym
1
[, sym
2
, ..., sym n
]
See
Description
Assign character string to substitution symbol
Macro Use
Directive
Perform arithmetic on numeric substitution symbols
Define local macro symbols
Table 5-4. Conditional Assembly
Mnemonic and Syntax
.break [well-defined expression]
.endif
.endloop
.else
.elseif well-defined expression
.if well-defined expression
.loop [well-defined expression]
Description
Optional repeatable block assembly
End conditional assembly
End repeatable block assembly
Optional conditional assembly block
Optional conditional assembly block
Begin conditional assembly
Begin repeatable block assembly
Macro Use
See
Directive
Mnemonic and Syntax
.emsg
.mmsg
.wmsg
Mnemonic and Syntax
.fclist
.fcnolist
.mlist
.mnolist
.sslist
.ssnolist
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Table 5-5. Producing Assembly-Time Messages
Description
Send error message to standard output
Send assembly-time message to standard output
Send warning message to standard output
Macro Use
See
Directive
Table 5-6. Formatting the Listing
Description
Allow false conditional code block listing (default)
Suppress false conditional code block listing
Allow macro listings (default)
Macro Use
Suppress macro listings
Allow expanded substitution symbol listing
Suppress expanded substitution symbol listing (default)
See
Directive
Macro Description 157
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Chapter 6
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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
...........................................................................................................................
Page
6.1
Archiver Overview ...........................................................................................
6.2
The Archiver's Role in the Software Development Flow ........................................
6.3
Invoking the Archiver
6.4
Archiver Examples
.......................................................................................
...........................................................................................
6.5
Library Information Archiver Description ............................................................
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Archiver Overview
6.1
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.
discusses macros and macro libraries in detail, while this chapter explains how to use the archiver to build libraries.
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6.2
The Archiver's Role in the Software Development Flow
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 6-1. The Archiver in the TMS320C6000 Software Development Flow
C/C++ source files
Macro source files
C/C++ compiler
Linear assembly
Archiver
Macro library
Archiver
Library of object files
Assembler source
Assembler
Object files
Linker
Assembly optimizer
Assembly optimized file
Library-build utility
Run-timesupport library
Debugging tools
Executable object file
Hex-conversion utility
EPROM programmer
Absolute lister
Cross-reference lister
Object file utilities
C6000
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6.3
Invoking the Archiver
To invoke the archiver, enter:
ar6x [-]command [options] libname [filename
1
... filename n
]
Invoking the Archiver 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
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: 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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6.4
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 SIZE DATE
------------------------------------------sine.obj
cos.obj
flt.obj
300
300
300
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 [email protected]
The archiver responds as follows:
==> building archive 'modules.lib'
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.
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Example 6 ‑‑ 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
Library Information Archiver Description
6.5
Library Information Archiver Description
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. Unfortunately, if there are several different versions of your library it can become 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.
6.5.1 Invoking the Library Information Archiver
To invoke the library information archiver, enter:
libinfo6x [options] -o=libname libname
1
[libname
2
... libname n
] libinfo6x options libnames 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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6.5.2 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 mylib_6200_be.lib
mylib_6200_le.lib
mylib_64plus_be.lib
mylib_64plus_le.lib
Build Options
-mv6200 --endian=big
-mv6200 --endian=little
-mv64plus --endian=big
-mv64plus --endian=little
Using the library information archiver, you can create an index library called mylib.lib from the above libraries: libinfo62 -o mylib.lib mylib_6200_be.lib mylib_6200_le.lib
mylib_64plus_be.lib mylib_64plus_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 6700, big endian): cl6x -mv6700 --endian=big --issue_remarks main.c -z -l lnk.cmd ./mylib.lib
<Linking> remark: linking in "mylib_6200_be.lib" in place of "mylib.lib"
In Example 2, there was no version of the library for C6700, but a C6200 library was available and is compatible, so it was used.
6.5.3 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 FILE NAME
-----------------------------------------------
119 Wed Feb 03 12:45:22 2010 mylib_6200_be.lib
119 Wed Feb 03 12:45:22 2010 mylib_6200_le.lib
119 Wed Feb 03 12:45:22 2010 mylib_64plus_be.lib
119 Wed Feb 03 12:45:22 2010 mylib_64plus_le.lib
0 Wed Sep 30 12:45:22 2009 __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.
6.5.4 Requirements
You must follow these requirements to use library index files:
• At least one of the application’s object files 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.
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Library Information Archiver Description
• The linker expects the index library and all of the libraries it indexes to be in a single directory.
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Chapter 7
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Linker Description
The TMS320C6000 linker can be used to create 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;
discusses the object module sections in detail.
Topic
...........................................................................................................................
Page
7.1
Linker Overview ..............................................................................................
7.2
The Linker's Role in the Software Development Flow ...........................................
7.3
Invoking the Linker
7.4
Linker Options
..........................................................................................
................................................................................................
7.5
Linker Command Files
7.6
Object Libraries
.....................................................................................
...............................................................................................
7.7
Default Allocation Algorithm .............................................................................
7.8
Linker-Generated Copy Tables ..........................................................................
7.9
Partial (Incremental) Linking
7.10
Linking C/C++ Code
.............................................................................
.........................................................................................
7.11
Linker Example ...............................................................................................
7.12
Dynamic Linking with the C6000 Code Generation Tools ......................................
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Linker Overview
7.1
Linker Overview
The TMS320C6000 linker allows you to configure system memory by allocating output sections efficiently into 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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7.2
The Linker's Role in the Software Development Flow
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 7-1. The Linker in the TMS320C6000 Software Development Flow
C/C++ source files
Macro source files
C/C++ compiler
Linear assembly
Archiver
Macro library
Archiver
Library of object files
Assembler source
Assembler
Object files
Linker
Assembly optimizer
Assembly optimized file
Library-build utility
Run-timesupport library
Debugging tools
Executable object file
Hex-conversion utility
EPROM programmer
Absolute lister
Cross-reference lister
Object file utilities
C6000
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7.3
Invoking the Linker
The general syntax for invoking the linker is:
cl6x --run_linker [options] filename
1
.... filename n
Invoking the Linker 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 link command file. (Options are discussed in
can be object files, link 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 link command file. Filenames that are specified inside a link 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
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7.4
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.
summarizes the linker options.
Option
--output_file
--map_file
--stack_size
--heap_size
Alias
-o
-m
-stack
-heap
Table 7-1. Basic Options Summary
Description Section
Names the executable output module. The default filename is a.out.
Produces a map or listing of the input and output sections, including holes, and
places the listing in filename
Sets C system stack size to size bytes and defines a global symbol that specifies the stack size. Default = 1K bytes
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
Option
--library
--search_path
--priority
--reread_libs
--disable_auto_rts
Alias
-l
-i
-priority
-x
Table 7-2. File Search Path Options Summary
Description
Names an archive library or link command filename as linker input
Section
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.
Satisfies unresolved references by the first library that contains a definition for
that symbol
Forces rereading of libraries, which resolves back references
Disables the automatic selection of a run-time-support library
Option
--define
--undefine
--disable_pp
Table 7-3. Command File Preprocessing Options Summary
Alias Description
Predefines name as a preprocessor macro.
Removes the preprocessor macro name.
Disables preprocessing for command files
Section
Option
--diag_error
--diag_remark
--diag_suppress
Alias
--diag_warning
--display_error_number
--emit_warnings_as_errors -pdew
--issue_remarks
--no_demangle
--no_warnings
--set_error_limit
--verbose_diagnostics
--warn_sections -w
Table 7-4. Diagnostic Options Summary
Description
Categorizes the diagnostic identified by num as an error
Categorizes the diagnostic identified by num as a remark
Suppresses the diagnostic identified by num
Categorizes the diagnostic identified by num as a warning
Displays a diagnostic's identifiers along with its text
Treats warnings as errors
Issues remarks (nonserious warnings)
Disables demangling of symbol names in diagnostics
Suppresses warning diagnostics (errors are still issued)
Sets the error limit to num. The linker abandons linking after this number of errors. (The default is 100.)
Provides verbose diagnostics that display the original source with line-wrap
Displays a message when an undefined output section is created
Section
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Option
--absolute_exe
--mapfile_contents
--relocatable
--rom
--run_abs
--xml_link_info
Option
--entry_point
--globalize
--hide
--localize
--make_global
--make_static
--no_sym_merge
--no_symtable
--retain
--scan_libraries
--symbol_map
--undef_sym
--unhide
Option
--arg_size
--fill_value
--ram_model
--rom_model
--trampolines
Alias
-a
-r
-r
-abs
Linker Options
Table 7-5. Linker Output Options Summary
Description
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.
Controls the information that appears in the map file.
Produces a nonexecutable, relocatable output module
Create a ROM object
Produces an absolute listing file
Generates a well-formed XML file containing detailed information about the result of a link
Section
Table 7-6. Symbol Management Options Summary
Alias
-e
-u
Description
Defines a global symbol that specifies the primary entry point for the output module
Changes the symbol linkage to global for symbols that match pattern
Hides global symbols that match pattern
-g
-h
-b
-s
Changes the symbol linkage to local for symbols that match pattern
Makes symbol global (overrides -h)
Makes all global symbols static
Disables merge of symbolic debugging information in COFF object files
Strips symbol table information and line number entries from the output module
Retains a list of sections that otherwise would be discarded
-scanlibs Scans all libraries for duplicate symbol definitions
Maps symbol references to a symbol definition of a different name
Places an unresolved external symbol into the output module's symbol table
Reveals (un-hides) global symbols that match pattern
Section
Alias
--args
-f
-cr
-c
Table 7-7. Run-Time Environment Options Summary
Description
Allocates memory to be used by the loader to pass arguments
Sets default fill values for holes within output sections; fill_value is a 32-bit constant
Initializes variables at load time
Autoinitializes variables at run time
Generates far call trampolines; on by default
Section
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Option
--dsbt_index
--dsbt_size
--dynamic
--export
--fini
--import
--init
--linux
--pic
--rpath
--runpath
--shared
--soname
--sysv
Linker Options
Option
--cinit_compression
--compress_dwarf
--copy_compression
--unused_section_elimination
Alias
Table 7-8. Link-Time Optimization Options Summary
Description
Specifies the type of compression to apply to the c auto initialization data
(default is rle)
Aggressively reduces the size of DWARF information from input object files
Compresses data copied by linker copy tables
Eliminates sections that are not needed in the executable module; on by default www.ti.com
Section
Alias
Table 7-9. Dynamic Linking Options Summary
Description Section
Specifies the Data Segment Base Table (DSBT) index to be assumed for the
dynamic shared object or dynamic library being linked
Specifies the number of entries to be reserved for the Data Segment Base
Table (DSBT)
Generates a bare-metal dynamic executable or library (argument is optional; if
no argument is specified, then a dynamic executable (exe) is generated)
Exports the specified function symbol (sym)
Specifies function symbol (sym) of the termination code
Imports the specified symbol
Specifies the function symbol (sym) of the initialization code
Generates code for Linux
Generates position independent addressing for a shared object. Default is near.
Adds specified directory to the beginning of the dynamic library search path
Adds specified directory to the end of the dynamic library search path
Generates an ELF dynamically shared object (DSO)
Specifies the name to be associated with this linked dynamic output; this name
is stored in the file's dynamic table
Generates SysV ELF output file
Option
--disable_clink
--linker_help
--minimize_trampolines
--preferred_order
--strict_compatibility
--trampoline_min_spacing
--zero_init
Alias
-j
-help
Table 7-10. Miscellaneous Options Summary
Description
Disables conditional linking of COFF object modules
Section
Displays information about syntax and available options –
Selects the trampoline minimization algorithm (argument is optional; algoriithm
is postorder by default)
Prioritizes placement of functions
Performs more conservative and rigorous compatibility checking of input object
files
When trampoline reservations are spaced more closely than the specified limit,
tries to make them adjacent
Controls preinitialization of uninitialized variables. Default is on.
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Linker Options
7.4.1 Wild Cards in File, Section, and Symbol Patterns
The linker allows file, section, and symbol names to be specified using the asterisk (*) and question mark
(?) wild cards. Using * matches any number of characters and using ? matches a single character. Using wild cards 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
}
7.4.2 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. 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).
7.4.2.1
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
)
• An optional 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.
7.4.2.2
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.
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
.)
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7.4.2.3
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 and creates an executable, relocatable output module called xr.out: cl6x --run_linker -ar file1.obj file2.obj --output_file=xr.out
7.4.3 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 a number representing 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.
7.4.4 Compression (--cinit_compression and --copy_compression Option)
By default, the linker does not compress data. There are two options that specify compression through the linker.
The ELF mode --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.
• lzss. Compress data using Lempel-Ziv Storer and Symanski compression.
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Linker Options
7.4.5 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
Categorizes the diagnostic identified by num 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=num to recategorize the diagnostic as an error. You can only alter the severity of discretionary diagnostics.
Categorizes the diagnostic identified by num 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=num to recategorize the diagnostic as a remark. You can only alter the severity of discretionary diagnostics.
Suppresses the diagnostic identified by num. To determine 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.
Categorizes the diagnostic identified by num 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=num to recategorize the diagnostic as a warning. You can only alter the severity of discretionary diagnostics.
--display_error_number 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.
--emit_warnings_as_ errors
Treats 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
--no_warnings
Issues remarks (nonserious warnings), which are suppressed by default.
Suppresses warning diagnostics (errors are still issued).
--set_error_limit=num Sets the error limit to num, which can be any decimal value. The linker abandons linking after this number of errors. (The default is 100.)
--verbose_diagnostics Provides verbose diagnostics that display the original source with line-wrap and indicate the position of the error in the source line
7.4.6 Disable Automatic Library Selection (--disable_auto_rts Option)
The --disable_auto_rts option disables the automatic selection of a run-time-support library. See the
TMS320C6000 Optimizing Compiler User's Guide for details on the automatic selection process.
7.4.7 Controlling Unreferenced and Unused Sections
7.4.7.1
Disable Conditional Linking (--disable_clink Option)
The --disable_clink option disables removal of unreferenced sections in COFF object modules. Only sections marked as candidates for removal with the .clink assembler directive are affected by conditional linking. See
Conditionally Leave Section Out of Object Module Output
for details on setting up conditional linking using the .clink directive, which is available under ELF as well as COFF.
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7.4.7.2
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.
7.4.8 Link Command File Preprocessing (--disable_pp, --define and --undefine Options)
The linker preprocesses link 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 /* expands to --undefine 123 (!) */
--undefine "MYSYM" /* ahh, that's better */
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
)
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 has the standard built-in definitions for the macros __FILE__, __DATE__, and __TIME__. It does not, however, have the compiler-specific options for the target (__.TMS320C6000__), version
(__TI_COMPILER_VERSION__), run-time model, and so on.
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7.4.9 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
7.4.10 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
7.4.11 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 __SYSMEM_SIZE and assigns it a value equal to the size of the heap. The default size is 1K bytes.
For more information about C/C++ linking, see
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7.4.12 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 which have a linkname matching the pattern. It hides the symbols matching the pattern by changing the name to an empty string. A global symbol which 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 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 Hidden Symbols heading.
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7.4.13 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.
Assume that 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 link 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
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.
7.4.13.1 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:
Operating System Enter cl6x --run_linker f1.obj f2.obj --search_path=/ld --search_path=/ld2
UNIX (Bourne shell) --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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7.4.13.2 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=" pathname
1
; pathname
2
; . . . "; export C6X_C_DIR
Windows set C6X_C_DIR= pathname
1
; pathname
2
; . . .
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 link 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
UNIX (Bourne shell)
Windows
Invocation Command
C6X_C_DIR="/ld ;/ld2"; export C6X_C_DIR; cl6x --run linker f1.obj f2.obj --library=r.lib --library=lib2.lib
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
UNIX (Bourne shell)
Windows
Enter unset C6X_C_DIR 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
.
For more information about object libraries, see
.
7.4.13.3 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 references A lib1 defines B lib2 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 rts6200.lib without providing a full replacement for rts6200.lib. Using --priority and linking your new library before rts6200.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.
7.4.14 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 wild cards ? 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.
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Specifying C/C++ Symbols with --localize and --globalize
NOTE: For COFF ABI, the compiler prepends an underscore _ to the beginning of all C/C++ identifiers. That is, for a function named foo2(), foo2() is prefixed with _ and _foo2 becomes the link-time symbol. The --localize and --globalize options accept the link-time symbols.
Thus, you specify --localize='_foo2' to localize the C function _foo2(). For more information on linknames see the C/C++ Language Implementation chapter in the TMS320C6000
Optimizing Compiler User's Guide.
For EABI, the link-time symbol is the same as the C/C++ identifier name.
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
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.
7.4.14.1 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
7.4.14.2 Make a Symbol Global (--make_global Option)
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
7.4.15 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
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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 link 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:
I
X
R specifies that the memory can be read.
W specifies that the memory can be written to.
specifies that the memory can contain executable code.
specifies that the memory can be initialized.
For more information about the MEMORY directive, see
.
• A table showing the linked addresses of each output section and the input sections that make up the output sections (section allocation map). This table has the following columns; this information is generated on the basis of the information in the SECTIONS directive in the link 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
• 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
shows an example of a map file.
7.4.16 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 new --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:
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Attribute copytables entry load_addr memory sections sym_defs sym_name sym_runaddr all none
Description
Copy tables
Entry point
Display load addresses
Memory ranges
Sections
Defined symbols per file
Symbols sorted by name
Symbols sorted by run address
Enables all attributes
Disables all attributes
On
Off
On
On
Default State
On
On
Off
On www.ti.com
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.
There are two new filters included with the --mapfile_contents option, load_addr and sym_defs. These 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).
The sym_defs filter can be used to include information about all static and global symbols defined in an application on a file by file basis. You may find it useful to replace the sym_name 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_runaddr,sym_defs
7.4.17 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
7.4.18 Disable Merge of Symbolic Debugging Information (--no_sym_merge Option)
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.
Use the COFF only --no_sym_merge option if you want the linker to keep such duplicate entries in COFF object files. Using the --no_sym_merge option has the effect of the linker running faster and using less host memory during linking, but the resulting executable file may be very large due to duplicated debug information.
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7.4.19 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
.
7.4.20 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
7.4.21 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 most by --preferred_option.
7.4.22 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
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7.4.23 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 .initvec sections from all input files:
--retain='init*'
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 '*<*>(*)'.
7.4.24 Create an Absolute Listing File (--run_abs Option)
The --run_abs option produces an output file for each file that was linked. These files are named with the input filenames and an extension of .abs. Header files, however, do not generate a corresponding .abs
file.
7.4.25 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.
7.4.26 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.
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When the linker defines the .stack section, it also defines a global symbol, __STACK_SIZE, and assigns it a value equal to the size of the section. The default software stack size is 1K bytes.
7.4.27 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.
7.4.28 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'
7.4.29 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:
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--trampolines[=on|off]
The default setting is on. For C6000, trampolines are turned on by default.
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.
7.4.29.1 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.
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
These operators allow you to define symbols to represent the load-time start address and size inside the link 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 : { -l=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.
7.4.29.2 Disadvantages of Using Trampolines
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.
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.
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7.4.29.3 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.
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. 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.
7.4.29.4 Making Trampoline Reservations Adjacent (--trampoline_min_spacing Option)
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.
7.4.30 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 rts6200.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 rts6200.lib for the member that defines symtab and to link in the member.
cl6x --run_linker --undef_sym=symtab file1.obj file2.obj rts6200.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.
7.4.31 Display a Message When an Undefined Output Section Is Created (--warn_sections
Option)
In a link 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
. For more information about the
default actions of the linker, see
.
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Linker Options
7.4.32 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
for specifics on the contents of the generated XML file.
7.4.33 Zero Initialization (--zero_init Option)
In ANSI C, global and static variables that are not explicitly initialized must be set to 0 before program execution. The C/C++ EABI compiler supports preinitialization of uninitialized variables by default. This can be turned off by specifying the linker option --zero_init=off. COFF ABI does not support zero initialization.
The syntax for the --zero_init option is:
--zero_init[={on|off}]
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7.5
Linker Command Files
Linker command files allow you to put linking information in a file; this is useful when you invoke the linker often with the same information. 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
). The SECTIONS directive controls how sections are built and allocated (see
• 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.
shows a sample link command file called link.cmd.
Example 7 ‑‑ 1. Linker Command File a.obj
b.obj
/* First input filename
/* Second input filename
*/
*/
--output_file=prog.out
/* Option to specify output file */
--map_file=prog.map
/* Option to specify map file */
The sample file in
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.
shows a sample command file that contains linker directives.
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Example 7 ‑‑ 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: origin = 0x0100
SLOW_MEM: origin = 0x7000
/* MEMORY directive length = 0x0100 length = 0x1000
}
/* SECTIONS directive SECTIONS
{
.text: > SLOW_MEM
.data: > SLOW_MEM
.bss: > FAST_MEM
}
*/
*/
*/
*/
Linker Command Files
For more information, see
for the MEMORY directive, and
for the SECTIONS directive.
7.5.1 Reserved Names in Linker Command Files
The following names (in lowercase also) are reserved as keywords for linker directives. Do not use them as symbol or section names in a command file.
ALIGN
ATTR
FILL
GROUP
BLOCK HIGH
COMPRESSION l (lowercase L)
COPY
DSECT f
END len
LENGTH
LOAD
LOAD_END
LOAD_SIZE
LOAD_START
MEMORY
NOINIT
NOLOAD o org
ORIGIN
PAGE
PALIGN
RUN
RUN_END
RUN_SIZE
RUN_START
SECTIONS
SIZE
START
TABLE
TYPE
UNION
UNORDERED
7.5.2 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 used in the assembler (see
) or the scheme used for integer
constants in C syntax.
Examples:
Format
Assembler format
C format
Decimal
32
32
Octal
40q
040
Hexadecimal
020h
0x20
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7.5.3 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
and
7.5.3.1
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 (2 32 locations) is present in the system and available for use. For more information about the default memory model, see
.
7.5.3.2
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 loading code. 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
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
).
Example 7-3. The MEMORY Directive
/********************************************************/
/* Sample command file with MEMORY directive */
/********************************************************/ file1.obj file2.obj
/* Input files */
--output_file=prog.out
#define BUFFER 0
/* Options */
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 attr origin length fill
Linker Command Files 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:
I
X
R specifies that the memory can be read.
W specifies that the memory can be written to.
specifies that the memory can contain executable code.
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 an expression of 32-bit constants, 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 an expression of 32-bit constants, 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 a 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.
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 allocation of output sections. After you use MEMORY to specify the target system's memory model, you can use
SECTIONS to allocate 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.
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7.5.3.3
Expressions and Address Operators
Memory range origin and length can now use expressions of integer constants with below 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 new address operators have been added for referencing 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 7-4. Origin and Length as Expressions
/********************************************************/
/* Sample command file with MEMORY directive */
/********************************************************/ file1.obj file2.obj
/* Input files */
--output_file=prog.out
#define ORIGIN 0x00000000
/* Options */
#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
7.5.4 The SECTIONS Directive
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
• Specifies where output sections are placed in memory (in relation to each other and to the entire memory space)
• Permits renaming of output sections
For more information, see
, and
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.
describes this algorithm in detail.
7.5.4.1
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.
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The general syntax for the SECTIONS directive is:
SECTIONS
{
name : [property [, property] [, property] . . . ]
name : [property [, property] [, property] . . . ]
name : [property [, property] [, property] . . . ]
}
Linker Command Files
Each section specification, beginning with name, defines an output section. (An output section is a section in the output file.) A section name can be a subsection specification. (See
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.
Syntax: load = allocation or allocation
> allocation or
• 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.
Syntax: { input_sections }
• Section type defines flags for special section types. See
Syntax: type = COPY or type = DSECT type = NOLOAD or
• Fill value defines the value used to fill uninitialized holes. See
Syntax: fill = value or
name : [properties = value]
shows a SECTIONS directive in a sample link command file.
Example 7-5. The SECTIONS Directive
/**************************************************/
/* Sample command file with SECTIONS directive */
/**************************************************/ file1.obj
file2.obj
/* Input files */
--output_file=prog.out
/* Options */
SECTIONS
{
.text:
.const:
.bss:
.vectors:
{ load = EXT_MEM, run = 0x00000800 load = FAST_MEM load = SLOW_MEM load = 0x00000000 t1.obj(.intvec1) t2.obj(.intvec2) endvec = .;
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Linker Command Files
Example 7-5. The SECTIONS Directive (continued)
}
.data:alpha: align = 16
.data:beta: align = 16
} www.ti.com
shows the six output sections defined by the SECTIONS directive in
(.vectors,
.text, .const, .bss, .data:alpha, and .data:beta) and shows how these sections are allocated in memory using the MEMORY directive given in
.
0x00000000
FAST_MEM
.vectors
.const
Figure 7-2. Section Allocation Defined by
- Bound at 0x00000000
- Allocated in FAST_MEM
The .vectors
section is composed of the .intvec1
section from t1.obj and the .intvec2 section from t2.obj.
The .const
section combines the .const sections from file1.obj and file2.obj.
0x00001000
SLOW_MEM
.bss
0x00001800
.data:alpha
.data:beta
0x10000000
EXT_MEM
.text
- Allocated in SLOW_MEM The .bss
section combines the .bss sections from file1.obj and file2.obj.
- Aligned on 16-byte boundary
- 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.
- Empty range of memory as defined in above
- 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
7.5.4.2
Allocation
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 allocation. For more information about using separate load and run allocation, see
If you do not tell the linker how a section is to be allocated, it uses a default algorithm to allocate the section. Generally, the linker puts sections wherever they fit into configured memory. You can override this default allocation for a section by defining it within a SECTIONS directive and providing instructions on how to allocate it.
You control allocation 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 allocation are separate, all parameters following the keyword LOAD apply to load allocation, and those following the keyword RUN apply to run allocation. The allocation parameters are:
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Linker Command Files
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
Blocking uses the align or palign keyword to specify that the section must start on an address boundary.
.text: align = 0x100 uses the block keyword to specify that the section must fit between two address boundaries: if the section is too big, it starts on an address boundary.
.text: block(0x100)
For the load (usually the only) allocation, you can simply 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
7.5.4.2.1 Binding
You can supply a specific 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.
7.5.4.2.2 Named Memory
You can allocate a section into a memory range that is defined by the MEMORY directive (see
). This example names ranges and links sections into them:
MEMORY
{
SLOW_MEM (RIX) : origin = 0x00000000, length = 0x00001000
FAST_MEM (RWIX) : origin = 0x03000000, length = 0x00000300
}
SECTIONS
{
.text
: > SLOW_MEM
.data
: > FAST_MEM ALIGN(128)
.bss
: > FAST_MEM
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}
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) /* .text --> executable memory
.data: > (RI) /* .data --> read or init memory
.bss : > (RW) /* .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.
7.5.4.2.3 Controlling Allocation 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.
For example, given this MEMORY directive:
MEMORY
{
RAM
FLASH
VECTORS
RESET
}
: origin = 0x0200, length = 0x0800
: origin = 0x1100, length = 0xEEE0
: origin = 0xFFE0, length = 0x001E
: origin = 0xFFFE, length = 0x0002 and an accompanying SECTIONS directive:
SECTIONS
{
.bss
: {} > RAM
.sysmem
: {} > RAM
.stack
: {} > RAM (HIGH)
}
The HIGH specifier used on the .stack section allocation 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.
illustrates a portion of a map file that shows where the given sections are allocated within RAM for a typical program.
Example 7-6. Linker Allocation With the HIGH Specifier
.bss
200
0 00000200
00000200
0000031a
000003a2
0000041a
00000460
00000468
0000046c
0000046e
00000270
0000011a
00000088
00000078
00000046
00000008
00000004
00000002
00000002
Linker Description
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)
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Example 7-6. Linker Allocation With the HIGH Specifier (continued)
.sysmem
.stack
0
0
00000470
00000470
00000120
00000004
000008c0
000008c0
00000140
00000002
UNINITIALIZED rtsxxx .lib : memory.obj (.sysmem)
UNINITIALIZED rtsxxx .lib : boot.obj (.stack)
Linker Command Files
As shown in
, 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
The HIGH specifier is ignored if it is used with specific address binding or automatic section splitting (>> operator).
Example 7-7. Linker Allocation Without HIGH Specifier
.bss
0
.stack
.sysmem
0
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)
00000470
00000470
00000140
00000002
000005b0
000005b0
00000120
00000004
UNINITIALIZED rtsxxx.lib
: boot.obj (.stack)
UNINITIALIZED rtsxxx.lib
: memory.obj (.sysmem)
7.5.4.2.4 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)
You can specify the same alignment with the palign keyword. In addition, palign ensures the section's size is a multiple of its placement alignment restrictions, padding the section size up to such a boundary, as needed.
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 page 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.
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7.5.4.2.5 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
202
.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 content
---- -------
0000 0x1234
0002 0x1234
0004 0x1234
After the palign operator is applied, the length of .mytext is 8 bytes, and its contents are as follows: addr content
---- -------
0000 0x1234
0002 0x1234
0004 0x1234
0006 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.
The fill value specified in the linker command file is interpreted as a 16-bit constant, so 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 content
---- -------
0000 0x1234
0002 0x1234
0004 0x1234
0006 0xffff
0008 0x00ff
000a 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 addr size align
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-------
.mytext
----------
0x00010080
-----
0x80
-----
128
Linker Command Files
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7.5.4.3
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.
shows the most common type of section specification; note that no input sections are listed.
Example 7-8. The Most Common Method of Specifying Section Contents
SECTIONS
{
.text:
.data:
.bss:
}
In
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) f2.obj(sec1)
/* Link .text section from f1.obj
/* 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
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 the input files. This format is useful when:
• 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.
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• 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.
7.5.4.4
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 link 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 be used to 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 the 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:north:finland europe:north:iceland europe:central:germany europe:central:denmark 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)} /* malta, iceland */ europe:north:finland : {} /* finland */ europe:north europe:central
: {}
: {} europe:central:france: {}
/* norway, sweden
/* france
*/
/* germany, denmark */
*/
}
/* (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 link 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 new rules for multiple levels to see if it affects a particular system link.
7.5.4.5
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 7-9. Archive Members to Output Sections
SECTIONS
{ boot
{
> BOOT1
-l=rtsXX.lib<boot.obj> (.text)
-l=rtsXX.lib<exit.obj strcpy.obj> (.text)
}
.rts
{
}
.text
{
}
> BOOT2
-l=rtsXX.lib (.text)
>
* (.text)
RAM
}
In
support 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
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 rts6200.lib into the
.rtstest section:
SECTIONS
{
.rtstest { -l=rts6200.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.
7.5.4.6
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 : origin = 0x02000, length = 0x01000
P_MEM2 : origin = 0x04000, length = 0x01000
P_MEM3 : origin = 0x06000, length = 0x01000
P_MEM4 : origin = 0x08000, length = 0x01000
}
SECTIONS
{
.text
: { } > 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 link command file, you can let the linker move the section into one of the other areas.
7.5.4.7
Automatic Splitting of Output Sections Among Non-Contiguous Memory Ranges
The linker can split output sections among multiple memory ranges to achieve an efficient allocation. Use the >> operator to indicate that an output section can be split, if necessary, into the specified memory ranges. For example:
MEMORY
{
P_MEM1 : origin = 0x2000, length = 0x1000
P_MEM2 : origin = 0x4000, length = 0x1000
P_MEM3 : origin = 0x6000, length = 0x1000
P_MEM4 : origin = 0x8000, length = 0x1000
}
SECTIONS
{
.text: { *(.text) } >> 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.
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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, length = 0x2000
P_MEM2 (RWI) : origin = 0x4000, 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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7.5.5 Specifying a Section's Run-Time Address
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
for an overview on run-time relocation.
7.5.5.1
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. 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
.
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
.)
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 below specify load and run addresses:
.data: load = SLOW_MEM, align = 32, run = FAST_MEM
(align applies only to load)
.data: load = (SLOW_MEM align 32), run = FAST_MEM
(identical to previous example)
.data: run = FAST_MEM, align 32, load = align 16
(align 32 in FAST_MEM for run; align 16 anywhere for load)
For more information on run-time relocation see
7.5.5.2
Uninitialized Sections
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.
.bss: load = FAST_MEM
.bss: run = FAST_MEM
.bss: > FAST_MEM
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7.5.5.3
Referring to the Load Address by Using the .label Directive
Normally, any reference to a symbol in a section 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
for more information on the .label directive.
and
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.
illustrates the run-time execution of
The table operator and cpy_in can also be used to refer to a load address; see
Example 7-10. Copying Section Assembly Language File fir
.sect
".fir"
.align 4
.label fir_src
; insert code here
.label fir_end
.text
MVKL fir_src, A4
MVKH fir_src, A4
MVKL fir_end, A5
MVKH fir_end, A5
MVKL fir, A6
MVKH fir, A6
SUB A5, A4, A1 loop:
[!A1] B
LDW
NOP done
*A4+ +, B3
4
; branch occurs
STW
SUB
B3, *A6+ +
A1, 4, A1
B
NOP loop
5
; branch occurs done:
B
NOP fir
5
; call occurs
Example 7-11. Linker Command File for
/******************************************************/
/* PARTIAL LINKER COMMAND FILE FOR FIR EXAMPLE */
/******************************************************/
MEMORY
{
FAST_MEM : origin = 0x00001000, length = 0x00001000
SLOW_MEM : origin = 0x10000000, length = 0x00001000
}
SECTIONS
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Example 7-11. Linker Command File for
(continued)
{
.text: load = FAST_MEM
.fir: load = SLOW_MEM, run FAST_MEM
}
Figure 7-3. Run-Time Execution of
0x00000000
FAST_MEM
.text
fir (relocated to run here)
0x00001000
Linker Command Files
0x10000000
SLOW_MEM fir (loads here)
0x10001000
0xFFFFFFFF
7.5.6 Using UNION and GROUP Statements
Two SECTIONS statements allow you to conserve memory: GROUP and UNION. Unioning sections causes the linker to allocate them to the same run address. Grouping sections causes the linker to allocate them contiguously in memory. Section names can refer to sections, subsections, or archive library members.
7.5.6.1
Overlaying Sections With the UNION Statement
For some applications, you may want to allocate more than one section to occupy the same address during run time. For example, you may have several routines you want in fast external memory at various 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 7-12 , 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 7-12. 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) }
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Example 7-12. The UNION Statement (continued)
} www.ti.com
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 7-13. 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) }
}
Figure 7-4. Memory Allocation Shown in
and
FAST_MEM
.bss:part2
.bss:part1
Sections can run as a union. This is run-time allocation only.
FAST_MEM
.text 2 (run)
.text 1 (run)
Copies at run time
.bss:part3 .bss:part3
SLOW_MEM
.text
Sections cannot load as a union
SLOW_MEM
.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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7.5.6.2
Grouping Output Sections Together
The SECTIONS directive's GROUP option forces several output sections to be allocated contiguously. 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 7-14. Allocate Sections Together
SECTIONS
{
.text
.bss
/* Normal output section
/* Normal output section
GROUP 0x00001000 : /* Specify a group of sections
{
.data
term_rec
*/
*/
*/
/* 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.
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.
7.5.6.3
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.
shows how two overlays can be grouped together.
Example 7-15. Nesting GROUP and UNION Statements
SECTIONS
{
GROUP 0x1000 : run = FAST_MEM
{
UNION:
{ mysect1: load = SLOW_MEM mysect2: load = SLOW_MEM
}
UNION:
{ mysect3: load = SLOW_MEM mysect4: 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.
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• 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
In this notation, 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.
7.5.6.4
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.
• 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.
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7.5.6.5
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
7.5.7 Special Section Types (DSECT, COPY, NOLOAD, and NOINIT)
You can assign three special types to output sections: DSECT, COPY, and NOLOAD. 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: load = 0x00002000, type = DSECT {f1.obj} sec2: load = 0x00004000, type = COPY {f2.obj} sec3: load = 0x00006000, type = NOLOAD {f3.obj} sec4: load = 0x00008000, type = NOINIT {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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7.5.8 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.
7.5.8.1
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
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
/* Input file */ cur_tab = Table1; /* Assign cur_tab to one of the tables */
7.5.8.2
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
.)
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
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7.5.8.3
Assignment Expressions
These rules apply to linker expressions:
• Expressions can contain global symbols, constants, and the C language operators listed in
.
• 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
in order of precedence. Operators in the same group have the same precedence. Besides the operators listed in
, 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 7-11. Groups of Operators Used in Expressions (Precedence)
Group 6 Group 1 (Highest Precedence)
Logical NOT
Bitwise NOT
Negation
Group 2
Multiplication
Division
Modulus
Group 3
Addition
Subtraction
Group 4
Arithmetic right shift
Arithmetic left shift
Group 5
Equal to
Not equal to
Greater than
Less than
Less than or equal to
Greater than or equal to
&
|
&&
||
=
+ =
- =
* =
/ =
Group 7
Group 8
Group 9
Group 10 (Lowest Precedence)
Assignment
A + = B
A - = B
A * = B
A / = B
Bitwise AND
Bitwise OR
Logical AND
Logical OR is equivalent to A = A + B is equivalent to A = A - B is equivalent to A = A * B is equivalent to A = A / B
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7.5.8.4
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
__STACK_END
__STACK_SIZE
__SYSMEM_SIZE
__TI_SYSMEM_SIZE is assigned the end of the .stack size for ELF.
is assigned the size of the .stack section for ELF.
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 end of the .stack size for COFF.
is assigned the size of the .stack section for COFF.
is assigned the size of the .sysmem section for COFF.
is assigned the size of the .sysmem section for ELF.
7.5.8.5
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 link command file. Then execute a sequence of instructions (the copying code in
Example 7-10 ) 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
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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7.5.8.6
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 that is 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 due to the fact that 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; }
}
7.5.8.7
Address and Dimension Operators
Six new operators have been added to the link command file syntax:
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.
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The new 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.
7.5.8.7.1 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.
7.5.8.7.2 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.
7.5.8.7.3 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.
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7.5.8.7.4 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.
7.5.9 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.
7.5.9.1
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
) 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.
7.5.9.2
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
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
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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.
/* Hole at the beginning */ .text: { .+= 0x0100; }
.data: { *(.data)
. += 0x0100; } /* 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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7.5.9.3
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
). 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.
7.5.9.4
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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7.6
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.
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
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.
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
.) 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
describes methods for specifying directories that contain object libraries.
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Default Allocation Algorithm
7.7
Default Allocation Algorithm
The MEMORY and SECTIONS directives provide flexible methods for building, combining, and allocating sections. However, any memory locations or sections that you choose not to specify must still be handled by the linker. The linker uses default algorithms to build and allocate sections within the specifications you supply.
If you do not use the MEMORY and SECTIONS directives, the linker allocates output sections as though the definitions in
were specified.
Example 7 ‑‑ 16. Default Allocation for TMS320C6000 Devices
MEMORY
{
RAM
}
: origin = 0x00000001, length = 0xFFFFFFFE
SECTIONS
{
.text
: ALIGN(32) {} > RAM
.const : ALIGN(8) {} > RAM
.data
: ALIGN(8) {} > RAM
.bss
: ALIGN(8) {} > RAM
.cinit : ALIGN(4) {} > RAM
.pinit : ALIGN(4) {} > RAM
.stack : ALIGN(8) {} > RAM
.far
: ALIGN(8) {} > RAM
.sysmem: ALIGN(8) {} > RAM
.switch: ALIGN(4) {} > RAM
.cio
: ALIGN(4) {} > RAM
}
; cflag option only
; cflag option only
; cflag option only
; cflag option only
; cflag option only
; cflag option only
; cflag option only
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 the default allocation. Allocation is performed according to the rules specified by the SECTIONS directive and the general algorithm described next in
.
7.7.1 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
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
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
for more information on configuring memory.)
7.7.2 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 have supplied 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.
7.8
Linker-Generated Copy Tables
The linker supports extensions to the link 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
7.8.1 A Current Boot-Loaded Application Development Process
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 you can develop an application like this 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 into 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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7.8.2 An Alternative Approach
You can avoid some of this maintenance burden by using the LOAD_START(), RUN_START(), and
SIZE() operators that are already part of the link command file syntax . For example, instead of building the application to generate a .map file, the link 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
_flash_code_ld_start
_flash_code_rn_start
_flash_code_size
Description
Load address of .flashcode section
Run address of .flashcode section
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
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 link 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
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7.8.3 Overlay Management Example
Consider an application which contains a memory overlay that must be managed at run time. The memory overlay is defined using a UNION in the link command file as illustrated in
:
Example 7-17. 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.
7.8.4 Generating Copy Tables Automatically With the Linker
The linker supports extensions to the link 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,
can be written as shown in
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Example 7-18. 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
...
Linker-Generated Copy Tables
Using the SECTIONS directive from
in the link 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 do not have to 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.
7.8.5 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
. The table operator can be used with
compression; see
.
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7.8.6 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. For example, the link command file for the boot-loaded application described in
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 link 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.
7.8.7 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 link command file excerpt in
Example 7-19. 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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7.8.8 Compression Support
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.
7.8.8.1
Compressed Copy Table Format
The copy table format is the same irrespective of the compression. The size field of the copy record is overloaded to support compression.
illustrates the compressed copy table layout.
Figure 7-5. Compressed Copy Table
Rec size Rec cnt
Load address Run address Size (0 if load data is compressed)
In
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.
7.8.8.2
Compressed Section Representation in the Object File
When the load data is not compressed, the object file can have only one section with a different load and run address.
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 a 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.
7.8.8.3
Compressed Data Layout
The compressed load data has the following layout:
8-bit index Compressed data
The first eight 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 7-6. 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().
7.8.8.4
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 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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7.8.8.5
Compression Algorithms
Run Length Encoding (RLE):
8-bit index Initialization data compressed using run length encoding
Linker-Generated Copy Tables
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, a 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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7.8.9 Copy Table Contents
In order to use a copy table that is generated by the linker, you must be aware of the contents of the copy table. This information is included in a new run-time-support library header file, cpy_tbl.h, which contains a
C source representation of the copy table data structure that is automatically generated by the linker.
shows the TMS320C6000 copy table header file.
Example 7-20. 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
} COPY_TABLE; recs[1];
/****************************************************************************/
/* 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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Linker-Generated Copy Tables
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
, 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> } };
7.8.10 General Purpose Copy Routine
The cpy_tbl.h file in
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 7-21. 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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7.8.11 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.
illustrates how you can control the placement of the linker-generated copy table sections using the input section names in the link command file.
Example 7-22. 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 link command file in
, 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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7.8.12 Splitting Object Components and Overlay Management
In previous versions of the linker, splitting sections that have separate load and run placement instructions was not permitted. This restriction was because there was no effective mechanism for you, the developer, to gain access to the load address or run address of each one of the pieces of the split object component.
Therefore, there was no effective way to write a copy routine that could move the split section from its load location to its run location.
However, 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
illustrates a possible driver for such an application.
Example 7-23. 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: { *(.task4) }
.task5: { *(.task5) }
.task6: { *(.task6) }
.task7: { *(.task7) }
}
} load >> LMEM1 | LMEM3 | LMEM4, table(_task47_ctbl)
} run = PMEM
...
.ovly: > LMEM4
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Linker-Generated Copy Tables
Example 7-24. 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();
...
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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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Partial (Incremental) Linking
7.9
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
• 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
• 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.
When 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
).
• 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
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
}
}
Step 2: 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
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Linking C/C++ Code www.ti.com
7.10 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 ... rts6200.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.
7.10.1 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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7.10.2 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.
7.10.3 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
for setting heap sizes and
for setting stack sizes.
7.10.4 Autoinitialization of 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.
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 external memory and copied to fast external memory each time the program starts.
illustrates autoinitialization at run time. Use this method in any system where your application runs from code burned into slow external memory.
Figure 7-7. Autoinitialization at Run Time
Object file Memory
.cinit
section
Loader cint Initialization tables
(EXT_MEM)
Boot routine
.bss
section
(D_MEM)
7.10.5 Initialization of Variables at Load Time
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.
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Linking C/C++ Code www.ti.com
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.
illustrates the initialization of variables at load time.
Figure 7-8. Initialization at Load Time
Object file Memory
.cinit
Loader
.bss
7.10.6 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 designate to the boot routine
(autoinitialize at run time) or the loader (initialize at load time) when to stop reading the 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.
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Linker Example
7.11 Linker Example
This example links three object files named demo.obj, ctrl.obj, and tables.obj and creates a program called demo.out.
Assume that target memory has the following program memory configuration:
Address Range
0x00000000 to 0x00001000
0x00001000 to 0x00002000
0x08000000 to 0x08000400
Contents
SLOW_MEM
FAST_MEM
EEPROM
The output sections are constructed in the following manner:
• Executable code, contained in the .text sections of demo.obj, fft.obj, and tables.obj, is linked into program memory ROM.
• Variables, contained in the var_defs section of demo.obj, are linked into data memory in block
FAST_MEM_2.
• Tables of coefficients in the .data sections of demo.obj, tables.obj, and fft.obj are linked into
FAST_MEM_1. A hole is created with a length of 100 and a fill value of 0x07A1C.
• The xy section form demo.obj, which contains buffers and variables, is linked by default into page 1 of the block STACK, since it is not explicitly linked.
• Executable code, contained in the .text sections of demo.obj, ctrl.obj, and tables.obj, must be linked into FAST_MEM.
• A set of interrupt vectors, contained in the .intvecs section of tables.obj, must be linked at address
0x00000000.
• A table of coefficients, contained in the .data section of tables.obj, must be linked into EEPROM. The remainder of block EEPROM must be initialized to the value 0xFF00FF00.
• A set of variables, contained in the .bss section of ctrl.obj, must be linked into SLOW_MEM and preinitialized to 0x00000100.
• The .bss sections of demo.obj and tables.obj must be linked into SLOW_MEM.
shows the link command file for this example.
shows the map file.
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Linker Example
Example 7 ‑‑ 25. Linker Command File, demo.cmd
/**********************************************************************/
/*** Specify Linker Options ***/
/**********************************************************************/
--entry_point SETUP /* Define the program entry point */
--output_file=demo.out
--map_file=demo.map
/* Name the output file
/* Create an output map file
*/
*/
/**********************************************************************/
/*** Specify the Input Files ***/
/**********************************************************************/ demo.obj
ctrl.obj
tables.obj
/**********************************************************************/
/*** Specify the Memory Configurations ***/
/**********************************************************************/
MEMORY
{
FAST_MEM : org = 0x00000000 len = 0x00001000
SLOW_MEM : org = 0x00001000 len = 0x00001000
EEPROM : org = 0x08000000 len = 0x00000400
}
/**********************************************************************/
/* Specify the Output Sections ***/
/**********************************************************************/
SECTIONS
{
.text
: {} > FAST_MEM /* Link all .text sections into ROM
.intvecs : {} > 0x0 /* Link interrupt vectors at 0x0
.data
{
: /* Link .data sections tables.obj(.data)
. = 0x400; /* Create hole at end of block
} = 0xFF00FF00 > EEPROM /* Fill and link into EEPROM ctrl_vars:
{
/* Create new ctrl variables section
*/
*/
*/
*/
*/
*/ ctrl.obj(.bss)
} = 0x00000100 > SLOW_MEM /* Fill with 0x100 and link into RAM
.bss
*/
: {} > SLOW_MEM /* Link remaining .bss sections into RAM */
}
/**********************************************************************/
/*** End of Command File ***/
/**********************************************************************/ www.ti.com
Invoke the linker by entering the following command: cl6x --run_linker demo.cmd
This creates the map file shown in
and an output file called demo.out that can be run on a
TMS320C6000.
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Example 7 ‑‑ 26. Output Map File, demo.map
OUTPUT FILE NAME: <demo.out>
ENTRY POINT SYMBOL: 0
MEMORY CONFIGURATION name origin length used attributes fill
----------------------------------------------
FAST_MEM 00000000 000001000 00000078 RWIX
SLOW_MEM 00001000 000001000 00000502
EEPROM 08000000 000000400 00000400
RWIX
RWIX
SECTION ALLOCATION MAP output section page origin length attributes/ input sections
--------------------------------------------
.text
.intvecs
0
0
00000000
00000000
00000030
00000030
00000040
00000000
00000064
00000030
00000000
00000010
00000024
00000014 demo.obj (.text) tables.obj (.text)
--HOLE-- [fill = 00000000] ctrl.obj (.text) tables.obj (.intvecs)
.data
ctrl_vars
0
0
00000000
08000000
08000000
08000004
08000400
08000400
00001000
00001000
00000014
00000400
00000004
000003fc
00000000
00000000
00000500
00000500 tables.obj (.data)
--HOLE-- [fill = ff00ff00] ctrl.obj (.data) demo.obj (.data)
.bss
0 00001500
00001500
00001502
00000002
00000002
00000000 ctrl.obj (.bss) [fill = 00000100]
UNINITIALIZED demo.obj (.bss) tables.obj (.bss)
GLOBAL SYMBOLS address name
-------- ----
00001500 $bss
00001500 .bss
08000000 .data
00000000 .text
00000018 _SETUP
00000040 _fill_tab
00000000 _x42
08000400 edata
00001502 end
00000064 etext
08000000 gvar
[11 symbols] address name
-------- ----
00000000 .text
00000000 _x42
00000018 _SETUP
00000040 _fill_tab
00000064 etext
00001500 $bss
00001500 .bss
00001502 end
08000000 gvar
08000000 .data
08000400 edata
Linker Example
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7.12 Dynamic Linking with the C6000 Code Generation Tools
The C6000 v7.2 Code Generation Tools (CGT) support dynamic linking provided you build with EABI. If you are not already familiar with the limitations of EABI support in the C6000 compiler, please see http://processors.wiki.ti.com/index.php/EABI_Support_in_C6000_Compiler and The C6000 Embedded
Application Binary Interface Application Report ( SPRAB89 ).
7.12.1 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.
7.12.1.1 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.
7.12.1.2 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.
7.12.1.3 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.
7.12.1.4 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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7.12.2 Embedded Application Binary Interface (EABI) Required
All software components in a system that uses the Dynamic Linking Model must use the EABI Run-time model. The EABI Run-Time Model can be specified using the --abi=eabi option.
The compiler generates object files in ELF object file format when EABI is specified. The C6000 CGT makes use of the industry-standard dynamic linking mechanisms that are detailed in the ELF Specification
(Tool Interface Standard).
Specifically, for OMAP developers that are using devices with ROMed code, you must be sure that the
ROMed code has been built using the EABI model. Similarly, if your application uses BIOS, you need to ensure that the BIOS version that you are using has been built using the EABI model. Finally, for developers that are relying on Code Composer Studio (CCS) to run and/or debug their application, you must use CCS version 4 or later (CCS ELF support begins in CCS version 4).
7.12.3 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.
7.12.3.1 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 7-9. 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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7.12.3.2 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 7-10. Dynamic Linking Model
DSP Memory
DSP Dynamic Lib
Dynamically
Loaded Task
DSP Dynamic Exe
DSP Dynamic Lib
DSP Dynamic Exe
GPP File
System
Loader
Application Tasks
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 7-10 , 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 7-11. Base Image Executable
DSP Memory
DSP Dynamic Lib
I/O
DSP Dynamic Lib
Dynamically
Loaded Task
DSP Dynamic Exe
Application Tasks
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 .
7.12.3.3 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
7.12.4 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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7.12.4.1 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 --abi=elfabi ... -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_EABI:Dynamic_Loader as an example of how to build a dynamic executable or base image: cl6x --abi=elfabi ... -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.
7.12.5 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.
7.12.5.1 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 --abi=elfabi ... -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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7.12.5.2 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+ --abi=elfabi 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 site
( http://processors.wiki.ti.com/index.php/C6000_Dynamic_Loader) )
7.12.5.3 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. For more details, see the C6000 EABI wiki article
( http://processors.wiki.ti.com/index.php/EABI_Support_in_C6000_Compiler ).
Option
--abi=eabi
--dsbt
--export_all_cpp_vtbl
--import_undef[=off|on]
--import_helper_functions
--inline_plt[=off|on]
--linux
--pic[=off|on]
--visibility={hidden| default|protected}
–wchar_t
Table 7-12. Compiler Options For Dynamic Linking
Description
Specifies that EABI run-time model is to be used.
Generates addressing via Dynamic Segment Base Table
Exports C++ virtual tables by default
Specifies that all global symbol references that are not defined in a module are imported. Default is on.
Specifies that all compiler generated calls to run-time-support functions are treated as calls to imported functions. See
.
Inlines the import function call stub. Default is on.
Generates code for Linux.
Generates position independent addressing for a shared object. Default is near.
Specifies a default visibility to be assumed for global symbols. See
.
Generates 32-bit wchar_t type when --abi=eabi is specified. By default the compiler generates 16bit wchar_t.
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Dynamic Linking with the C6000 Code Generation Tools
Option
--dsbt_index=int
--dsbt_size=int
--dynamic[=exe]
--dynamic=lib
--export=symbol
--fini=symbol
--import=symbol
--init=symbol
--rpath=dir
--runpath=dir
--shared
--soname=string
--sysv www.ti.com
Table 7-13. Linker Options For Dynamic Linking
Description
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.
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).
Specifies that the result of a link will be a dynamic executable. See
Specifies that the result of a link will be a dynamic library. See
Specifies that symbol is exported by the ELF object that is generated for this link.
Specifies the symbol name of the termination code for the output file currently being linked.
Specifies that symbol is imported by the ELF object that is generated for this link.
Specifies the symbol name of the initialization code for the output file currently being linked.
Adds a directory to the beginning of the dynamic library search path.
Adds a directory to the end of the dynamic library search path.
Generates a dynamically shared object.
Specifies shared object name to be used to identify this ELF object to the any downstream ELF object consumers.
Generates SysV ELF output file.
7.12.6 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.
7.12.6.1 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).
7.12.6.1.1 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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7.12.6.1.2 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.
7.12.6.2 Controlling Import/Export of Symbols
Symbols can be imported/exported by using:
• Source Code Annotations
• ELF Linkage Macros
• Compiler Options
• Linker Options
7.12.6.2.1 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();
__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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7.12.6.2.2 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.
7.12.6.2.3 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 effected 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.
7.12.6.2.4 Import/Export Using Linker Options
To import or export a symbol when the source code can not 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 symbolto 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 8
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Absolute Lister Description
The TMS320C6000 absolute lister is a debugging tool that accepts linked object files as input and creates
.abs files as output. These .abs files can be assembled to produce a listing that shows the absolute addresses of object code. Manually, this could be a tedious process requiring many operations; however, the absolute lister utility performs these operations automatically.
Absolute Listing Is Not Supported for C6400+, C6740, and C6600
NOTE: The absolute listing capability is not supported for C6400+, C6740, and C6600. You can use the disassembler (dis6x) or the --map_file linker option instead.
Topic
...........................................................................................................................
Page
8.1
Producing an Absolute Listing
8.2
Invoking the Absolute Lister
..........................................................................
.............................................................................
8.3
Absolute Lister Example ...................................................................................
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8.1
Producing an Absolute Listing
illustrates the steps required to produce an absolute listing.
Figure 8-1. Absolute Lister Development Flow
Step 1: Assembler source file
First, assemble a source file.
Producing an Absolute Listing
Step 2:
Assembler
Object file
Linker
Link the resulting object file.
Step 3:
Linked object file
Absolute lister
Invoke the absolute lister; use the linked object file as input. This creates a file with an .abs extension.
Step 4:
.abs
file
Assembler
Finally, assemble the .abs file; you must invoke the assembler with the compiler
--absolute_listing option.
This produces a listing file that contains absolute addresses.
Absolute listing
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Absolute Lister Description 259
Invoking the Absolute Lister
8.2
Invoking the Absolute Lister
The syntax for invoking the absolute lister is:
abs6x [-options] input file www.ti.com
abs6x options input file is the command that invokes the absolute lister.
identifies the absolute lister 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 (-). The absolute lister options are as follows:
-e enables you to change the default naming conventions for filename extensions on assembly files, C source files, and C header files. The valid options are:
• ea [.]asmext for assembly files (default is .asm)
• ec [.]cext for C source files (default is .c)
• eh [.]hext for C header files (default is .h)
• ep [.]pext for CPP source files (default is cpp)
The . in the extensions and the space between the option and the extension are optional.
-q (quiet) suppresses the banner and all progress information.
names the linked object file. If you do not supply an extension, the absolute lister assumes that the input file has the default extension .out. If you do not supply an input filename when you invoke the absolute lister, the absolute lister prompts you for one.
The absolute lister produces an output file for each file that was linked. These files are named with the input filenames and an extension of .abs. Header files, however, do not generate a corresponding .abs
file.
Assemble these files with the --absolute_listing assembler option as follows to create the absolute listing:
cl6x --absolute_listing filename .abs
The -e options affect both the interpretation of filenames on the command line and the names of the output files. They should always precede any filename on the command line.
The -e options are useful when the linked object file was created from C files compiled with the debugging option (--symdebug:dwarf compiler option). When the debugging option is set, the resulting linked object file contains the name of the source files used to build it. In this case, the absolute lister does not generate a corresponding .abs file for the C header files. Also, the .abs file corresponding to a C source file uses the assembly file generated from the C source file rather than the C source file itself.
For example, suppose the C source file hello.csr is compiled with the debugging option set; the debugging option generates the assembly file hello.s. The hello.csr file includes hello.hsr. Assuming the executable file created is called hello.out, the following command generates the proper .abs file: abs6x -ea s -ec csr -eh hsr hello.out
An .abs file is not created for hello.hsr (the header file), and hello.abs includes the assembly file hello.s, not the C source file hello.csr.
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Absolute Lister Example
8.3
Absolute Lister Example
This example uses three source files. The files module1.asm and module2.asm both include the file globals.def.
module1.asm
.text
.align
4
.bss
.bss
array, 100 dflag, 4
.copy
globals.def
MVKL
MVKH
LDW nop offset, A0 offset, A0
*+b14(dflag), A2
4 module2.asm
.bss
offset,2
.copy
globals.def
mvkl mvkh mvkl mvkh offset,a0 offset,a0 array,a3 array,a3 globals.def
.global dflag
.global array
.global offset
The following steps create absolute listings for the files module1.asm and module2.asm:
Step 1:
Step 2:
First, assemble module1.asm and module2.asm: cl6x module1 cl6x module2
This creates two object files called module1.obj and module2.obj.
Next, link module1.obj and module2.obj using the following linker command file, called bttest.cmd:
--output_file=bttest.out
--map_file=bttest.map
module1.obj
module2.obj
MEMORY
{
}
SECTIONS
{
PMEM: origin=00000000h
DMEM: origin=80000000h
.data: >DMEM
.text: >PMEM
.bss: >DMEM
} length=00010000h length=00010000h
Invoke the linker: cl6x --run_linker bttest.cmd
This command creates an executable object file called bttest.out; use this new file as input for the absolute lister.
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Absolute Lister Description 261
Absolute Lister Example
Step 3: Now, invoke the absolute lister: abs6x bttest.out
This command creates two files called module1.abs and module2.abs: module1.abs: array dflag offset
.data
.nolist
.setsym
.setsym
.setsym
.setsym
___data__ .setsym
edata .setsym
___edata__ .setsym
.text
.setsym
___text__ .setsym
etext .setsym
___etext__ .setsym
.bss
.setsym
___bss__ .setsym
end .setsym
___end__ .setsym
$bss .setsym
.setsect
.setsect
.setsect
.list
.text
.copy
080000000h
080000064h
080000068h
080000000h
080000000h
080000000h
080000000h
000000000h
000000000h
000000040h
000000040h
080000000h
080000000h
08000006ah
08000006ah
080000000h
".text",000000020h
".data",080000000h
".bss",080000000h
"module1.asm" module2.abs: array dflag offset
.data
.nolist
.setsym
.setsym
.setsym
.setsym
___data__ .setsym
edata .setsym
___edata__ .setsym
.text
.setsym
___text__ .setsym
etext .setsym
___etext__ .setsym
.bss
.setsym
___bss__ .setsym
end .setsym
___end__ .setsym
$bss .setsym
.setsect
.setsect
.setsect
.list
.text
.copy
080000000h
080000064h
080000068h
080000000h
080000000h
080000000h
080000000h
000000000h
000000000h
000000040h
000000040h
080000000h
080000000h
08000006ah
08000006ah
080000000h
".text",000000000h
".data",080000000h
".bss",080000068h
"module2.asm" www.ti.com
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Absolute Lister Example
Step 4:
These files contain the following information that the assembler needs for Step 4:
• They contain .setsym directives, which equate values to global symbols. Both files contain global equates for the symbol dflag. The symbol dflag was defined in the file globals.def, which was included in module1.asm and module2.asm.
• They contain .setsect directives, which define the absolute addresses for sections.
• They contain .copy directives, which defines the assembly language source file to include.
The .setsym and .setsect directives are useful only for creating absolute listings, not normal assembly.
Finally, assemble the .abs files created by the absolute lister (remember that you must use the --absolute_listing option when you invoke the assembler): cl6x --absolute_listing module1.abs
cl6x --absolute_listing module2.abs
This command sequence creates two listing files called module1.lst and module2.lst; no object code is produced. These listing files are similar to normal listing files; however, the addresses shown are absolute addresses.
The absolute listing files created are module1.lst (see
) and module2.lst (see
).
Example 8 ‑‑ 1. module1.lst
module1.abs
22 00000020
A
A
23
1 00000020
A
A
2
3 80000000
A
B
4 80000064
5
B
B
1
2
A
A
3
6
A
A
7 00000020 00003428!
8 00000024 00400068!
A
9 00000028 0100196C-
10 0000002c 00006000
No Errors, No Warnings
.text
.copy
.text
.align
4
"module1.asm"
.bss
.bss
array, 100 dflag, 4
.copy
globals.def
.global dflag
.global array
.global offset
MVKL
MVKH
LDW nop offset, A0 offset, A0
*+b14(dflag), A2
4
PAGE 1
Example 8 ‑‑ 2. module2.lst
module2.abs
22 00000000
A
A
23
1 80000068
B
B
2
1
B
A
2
3
A
A
3
4 00000000 00003428-
A
A
5 00000004 00400068-
6 00000008 01800028!
7 0000000c 01C00068!
No Errors, No Warnings
.text
.copy
"module2.asm"
.bss offset,2
.copy globals.def
.global dflag
.global array
.global offset mvkl mvkh mvkl mvkh offset,a0 offset,a0 array,a3 array,a3
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Chapter 9
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Cross-Reference Lister Description
The TMS320C6000 cross-reference lister is a debugging tool. This utility accepts linked object files as input and produces a cross-reference listing as output. This listing shows symbols, their definitions, and their references in the linked source files.
Cross-Reference Listing Not Supported for C6400+, C6740, and C6600
NOTE: The cross-reference listing capability is not supported for C6400+, C6740, and C6600. You can use the disassembler, the -m linker option or the object file utility (ofd6x) to obtain similar information.
Topic
...........................................................................................................................
Page
9.1
Producing a Cross-Reference Listing .................................................................
9.2
Invoking the Cross-Reference Lister
9.3
Cross-Reference Listing Example
..................................................................
......................................................................
264 Cross-Reference Lister Description
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Producing a Cross-Reference Listing
9.1
Producing a Cross-Reference Listing
illustrates the steps required to produce a cross-reference listing.
Figure 9-1. The Cross-Reference Lister Development Flow
Step 1:
Assembler source file
Assembler
First, invoke the assembler with the compiler
--cross_reference option. This produces a cross-reference table in the listing file and adds to the object file cross-reference information. By default, only global symbols are cross-referenced. If you use the compiler
--output_all_syms option, local symbols are cross-referenced as well.
Object file
Step 2: Link the object file (.obj) to obtain an executable object file (.out).
Linker
Step 3:
Linked object file
Cross-reference lister
Invoke the cross-reference lister. The following section provides the command syntax for invoking the cross-reference lister utility.
Cross-reference listing
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Invoking the Cross-Reference Lister www.ti.com
9.2
Invoking the Cross-Reference Lister
To use the cross-reference utility, the file must be assembled with the correct options and then linked into an executable file. Assemble the assembly language files with the --cross_reference option. This option creates a cross-reference listing and adds cross-reference information to the object file. By default, the assembler cross-references only global symbols, but if the assembler is invoked with the -output_all_syms option, local symbols are also added. Link the object files to obtain an executable file.
To invoke the cross-reference lister, enter the following:
xref6x [options] [input filename [output filename]] xref6x options is the command that invokes the cross-reference utility.
identifies the cross-reference lister options you want to use. Options are not case sensitive and can appear anywhere on the command line following the command.
-l (lowercase L) specifies the number of lines per page for the output file. The format of the -l option is -lnum, where num is a decimal constant. For example, -l30 sets the number of lines per page in the output file to 30. The space between the option and the decimal constant is optional. The default is 60 lines per page.
-q suppresses the banner and all progress information (run quiet).
input filename is a linked object file. If you omit the input filename, the utility prompts for a filename.
output filename is the name of the cross-reference listing file. If you omit the output filename, the default filename is the input filename with an .xrf extension.
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9.3
Cross-Reference Listing Example
is an example of cross-reference listing.
Cross-Reference Listing Example
Example 9 ‑‑ 1. Cross-Reference Listing
================================================================================
Symbol: _SETUP
Filename
________
RTYP
____
AsmVal
________
LnkVal
________
DefLn
______
RefLn
_______
RefLn
_______
RefLn
_______ demo.asm
EDEF '00000018 00000018 18 13 20
================================================================================
Symbol: _fill_tab
Filename
________
RTYP AsmVal LnkVal
____ ________ ________
DefLn
______
RefLn
_______
RefLn
_______
RefLn
_______ ctrl.asm
EDEF '00000000 00000040 10 5
================================================================================
Symbol: _x42
Filename
________ demo.asm
RTYP
____
AsmVal
________
LnkVal
________
EDEF '00000000 00000000
DefLn
______
7
RefLn
_______
4
RefLn
_______
18
RefLn
_______
================================================================================
Symbol: gvar
Filename
________ tables.asm
RTYP
____
AsmVal
________
LnkVal
________
EDEF "00000000 08000000
DefLn
______
11
RefLn
_______
10
RefLn
_______
RefLn
_______
================================================================================
The terms defined below appear in the preceding cross-reference listing:
Symbol
Filename
RTYP
AsmVal
LnkVal
DefLn
RefLn
Name of the symbol listed
Name of the file where the symbol appears
The symbol's reference type in this file. The possible reference types are:
STAT The symbol is defined in this file and is not declared as global.
EDEF The symbol is defined in this file and is declared as global.
EREF The symbol is not defined in this file but is referenced as global.
UNDF The symbol is not defined in this file and is not declared as global.
This hexadecimal number is the value assigned to the symbol at assembly time. A value may also be preceded by a character that describes the symbol's attributes.
lists these characters and names.
This hexadecimal number is the value assigned to the symbol after linking.
The statement number where the symbol is defined.
The line number where the symbol is referenced. If the line number is followed by an asterisk (*), then that reference can modify the contents of the object. A blank in this column indicates that the symbol was never used.
Table 9-1. Symbol Attributes in Cross-Reference
Listing
Character
'
"
+
-
Meaning
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 10
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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
...........................................................................................................................
Page
10.1
Invoking the Object File Display Utility ...............................................................
10.2
Invoking the Disassembler ................................................................................
10.3
Invoking the Name Utility ..................................................................................
10.4
Invoking the Strip Utility ...................................................................................
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Invoking the Object File Display Utility
10.1 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 is the command that invokes the object file display utility.
input filename names the object file (.obj), executable file (.out), or archive library (.lib) source file.
The filename must contain an extension.
options 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.
--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
-g
-h
-o=filename
--obj_display attributes
-v
-x
--xml_indent=num
The ordering of attributes is important (see --obj_display).
The list of available display attributes can be obtained by invoking ofd6x --dwarf_display=help.
appends DWARF debug information to program output.
displays help sends program output to filename rather than to the screen.
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.
prints verbose text output.
displays output in XML format.
sets the number of spaces to indent nested XML tags.
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.
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Invoking the Disassembler
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.
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10.2 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]
-a
-b
-c
-d 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: disables the printing of branch destination addresses along with labels.
displays data as bytes instead of words.
dumps the object file information.
disables display of data sections.
-h
-i
-l
-n shows the current help screen.
disassembles .data sections as instructions.
disassembles data sections as text.
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.
-s
(super quiet mode) suppresses all headers.
suppresses printing of address and data words.
-t
-v suppresses the display of text sections in the listing.
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 output filename 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.
10.3 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]
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Invoking the Strip Utility nm6x input filename options
-a
-c
-d
-f 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: prints all symbols.
also prints C_NULL symbols for a COFF object module.
also prints debug symbols for a COFF object module.
prepends file name to each symbol.
-g
-h
-l
-n prints only global symbols.
shows the current help screen.
produces a detailed listing of the symbol information.
sorts symbols numerically rather than alphabetically.
-o file outputs to the given file.
-p causes the name utility to not sort any symbols.
-q
-r
(quiet mode) suppresses the banner and all progress information.
sorts symbols in reverse order.
-t
-u also prints tag information symbols for a COFF object module.
only prints undefined symbols.
10.4 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 is the command that invokes the strip utility.
input filename is an object file (.obj) or an executable file (.out).
options 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 11
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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
...........................................................................................................................
Page
11.1
The Hex Conversion Utility's Role in the Software Development Flow ....................
11.2
Invoking the Hex Conversion Utility ...................................................................
11.3
Understanding Memory Widths
11.4
The ROMS Directive
.........................................................................
.........................................................................................
11.5
The SECTIONS Directive ...................................................................................
11.6
The Load Image Format (--load_image Option) ....................................................
11.7
Excluding a Specified Section
11.8
Assigning Output Filenames
...........................................................................
.............................................................................
11.9
Image Mode and the --fill Option ........................................................................
11.10 Building a Table for an On-Chip Boot Loader
11.11 Controlling the ROM Device Address
....................................................
................................................................
11.12 Control Hex Conversion Utility Diagnostics
11.13 Description of the Object Formats
.......................................................
....................................................................
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The Hex Conversion Utility's Role in the Software Development Flow
11.1 The Hex Conversion Utility's Role in the Software Development Flow
highlights the role of the hex conversion utility in the software development process.
Figure 11-1. The Hex Conversion Utility in the TMS320C6000 Software Development Flow
C/C++ source files
Macro source files
C/C++ compiler
Linear assembly
Archiver
Macro library
Archiver
Library of object files
Assembler source
Assembler
Object files
Linker
Assembly optimizer
Assembly optimized file
Library-build process
Run-timesupport library
Debugging tools
Executable object file
Hex-conversion utility
EPROM programmer
Absolute lister
Cross-reference lister
Object file utilities
C6000
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Hex Conversion Utility Description 273
Invoking the Hex Conversion Utility
11.2 Invoking the Hex Conversion Utility
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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.
11.2.1 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.
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
Option
--byte
--entry_point=addr
--exclude={fname(sname) |
sname}
--fill=value
--help
--image
--linkerfill
--map=filename
--memwidth=value
--olength=value
Table 11-1. Basic Hex Conversion Utility Options
Alias
-byte
-e
-exclude
-fill
-options, -h
-image
-linkerfill
-map
-memwidth
-olength
Description
General Options
Number output locations by bytes rather than by target addressing
Specify the entry point address or global symbol at which to begin execution after boot loading
If the filename (fname) is omitted, all sections matching
sname will be excluded.
See
--
Fill holes with value
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.
For example, to see information about options associated with generating a boot table, use --help boot.
Select image mode
Include linker fill sections in images
--
Generate a map file
Define the system memory word width (default 32 bits)
Specify maximum number of data items per line of output
--
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Invoking the Hex Conversion Utility
Option
--order={L|M}
--outfile=filename
--quiet
--romwidth=value
--zero
--diag_error=id
--diag_remark=id
--diag_suppress=id
--diag_warning=id
--display_error_number
--issue_remarks
--no_warnings
--set_error_limit=count
--boot
--bootorg=addr
--bootsection=section
--ascii
--intel
--motorola=1
--motorola=2
--motorola=3
--tektronix
--ti_tagged
--ti_txt
Table 11-1. Basic Hex Conversion Utility Options (continued)
--load_image
--section_name_prefix=string
-a
-i
-m1
-m2
-m3
Alias
-order
-o
-q
-romwidth
-zero, -z
-boot
-bootorg
-bootsection
-x
-t
Description
Specify data ordering (endianness)
See
Specify an output filename
Run quietly (when used, it must appear before other options)
Specify the ROM device width (default depends on format used)
Reset the address origin to 0 in image mode
Diagnostic Options
Categorizes the diagnostic identified by id as an error
Categorizes the diagnostic identified by id as a remark
Suppresses the diagnostic identified by id
Categorizes the diagnostic identified by id as a warning
Displays a diagnostic's identifiers along with its text
Issues remarks (nonserious warnings)
Suppresses warning diagnostics (errors are still issued)
Sets the error limit to count. The linker abandons linking after this number of errors. (The default is 100.)
Boot Table Options
Convert all initialized sections into bootable form (use instead of a SECTIONS directive)
Specify origin address of the boot loader table
Specify which section contains the boot routine and where it should be placed
Output Options
Select ASCII-Hex
Select Intel
Select Motorola-S1
Select Motorola-S2
Select Motorola-S3 (default -m option)
Select Tektronix (default format when no output option is specified)
Select TI-Tagged
Select TI-Txt
Load Image Options
Select load image
Specify the section name prefix for load image object files
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Invoking the Hex Conversion Utility www.ti.com
11.2.2 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
• SECTIONS directive. The hex conversion utility SECTIONS directive specifies which sections from the object file are selected. (See
.)
• 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
/* input file */
/* TI-Tagged */
--outfile=firm.lsb
/* output file */
--outfile=firm.msb
/* 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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11.3 Understanding Memory Widths
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.
illustrates the separate and distinct phases of the hex conversion utility's process flow.
Figure 11-2. Hex Conversion Utility Process Flow
Input file
Raw data in object files is represented in the target’s addressable units. For the
C6000, this is 32 bits.
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.).
Output file(s)
11.3.1 Target Width
Target width is the unit size (in bits) of the target processor's word. The unit size corresponds to the data bus size on the target processor. The width is fixed for each target and cannot be changed. The
TMS320C6000 targets have a width of 32 bits.
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Understanding Memory Widths www.ti.com
11.3.2 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
.
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.
demonstrates how the memory width is related to object file data.
Figure 11-3. Object File Data and Memory Widths
Source file
.word
.word
0
0
A A B B CCDD
1 1 2 2 3 3 4 4 h h
Object file data (assumed to be in little-endian format)
A A B B C C DD
1 1 2 2 3 3 4 4
Data after phase I of hex6x
Memory widths (variable)
--memwidth=32 (default)
A A B B CCDD
1 1 2 2 3 3 4 4
--memwidth=16
CCDD
A A B B
3 3 4 4
1 1 2 2
--memwidth=8
DD
CC
B B
A A
4 4
3 3
2 2
1 1
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Understanding Memory Widths
11.3.3 Partitioning 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). The ROM width determines how the hex conversion utility partitions the data into output files. 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
.
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 (16 bits for TI-Tagged or
8 bits for all others), the utility simply writes multibyte fields into the file.
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 0
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Understanding Memory Widths
Figure 11-4. Data, Memory, and ROM Widths
Source file
.word
.word
0
0
A A B B CCDD
1 1 2 2 3 3 4 4 h h
Object file data (assumed to be in little-endian format)
A A B B C C DD
1 1 2 2 3 3 4 4
Data after phase I of hex6x
Memory widths (variable)
--memwidth=32
A A B B CCDD
1 1 2 2 3 3 4 4
--memwidth=16
CCDD
A A B B
3 3 4 4
1 1 2 2
--memwidth=8
DD
CC
B B
A A
4 4
3 3
2 2
1 1
Data after phase II of hex6x
Output files
--romwidth=8
--outfile=file.b0
--outfile=file.b1
--outfile=file.b2
DD 4 4
CC 3 3
B B 2 2
--outfile=file.b3
A A 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 2 2
--outfile=file.b1
CC A A 3 3 1 1
--romwidth=8
--outfile=file.byt
DDCC B B A A 4 4 3 3 2 2 1 1 www.ti.com
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The ROMS Directive
11.3.4 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.
NOTE:
When the -order Option Applies
• 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.
11.4 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 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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The ROMS Directive
Constant
Hexadecimal
Octal
Decimal
Notation
0x prefix or h suffix
0 prefix
No prefix or suffix
Example
0x77 or 077h
077
77 www.ti.com
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 value, it defaults to the length of the entire address space.
specifies the physical ROM width of the range in bits (see
). 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
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
.) 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
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
. 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.
11.4.1 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.
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The ROMS Directive
• Use image mode. When you use the --image option, you must use a ROMS directive. Each range is 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.
11.4.2 An Example of the ROMS Directive
The ROMS directive in
shows how 16K bytes of 16-bit memory could be partitioned for two
8K-byte 8-bit EPROMs.
illustrates the input and output files.
Example 11-1. 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 11-5. The infile.out File Partitioned Into Four Output Files
0x00004000
0x0000487F
0x00005B80
0x0000633F
0x00006700
COFF file: infile.out
.text
.data
0x00004000
(org)
Output files:
EPROM1 rom4000.b0
rom4000.b1
.text
.text
0x00004880
0h 0h
0x00005B80
.data
.data
0x00005FFF
.table
0x00007C7F
Width = 8 bits len = 2000h (8K)
0x00006000
0x00006340
0x00006700
EPROM2 rom6000.b0
rom6000.b1
.data
FFh
.data
00h
.table
.table
0x00007C80
0x00007FFF
FFh 00h
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.
is a segment of the map file resulting from the example in
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The ROMS Directive
Example 11-2. Map File Output From
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 www.ti.com
EPROM1 defines the address range from 0x00004000 through 0x00005FFF with the following sections:
This section ...
.text
.data
Has this range ...
0x00004000 through 0x0000487F
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 ...
.data
.table
Has this range ...
0x00006000 through 0x0000633F
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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The SECTIONS Directive
11.5 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
SECTIONS directive 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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The Load Image Format (--load_image Option)
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
and
.
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11.6 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.
11.6.1 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.
11.6.2 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.
11.7 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.
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Assigning Output Filenames
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, enter 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, then the quotes should not be specified.
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.
11.8 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
i a t m x for ASCII-Hex for Intel for Motorola-S for TI-Tagged for Tektronix
(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.
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Image Mode and the --fill Option www.ti.com
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 ...
a.i00, a.i01, a.i02, a.i03
a.i10, a.i11, a.i12, a.i13
Contain data in these locations ...
0x00001000 through 0x00001FFF
0x00002000 through 0x00002FFF
11.9 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.
11.9.1 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.
11.9.2 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.
11.9.3 Steps to Follow in Using Image Mode
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Building a Table for an On-Chip Boot Loader
Step 1: Define the ranges of target memory with a ROMS directive. See
Step 2: 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.
11.10 Building a Table for an On-Chip Boot Loader
On the C621x, C671x, and C64x devices, a ROM boot process is supported where the EDMA copies 1K bytes from the beginning of CE1 (EMIFB CE1 on C64x) to address 0, using default ROM timings. After the transfer, the CPU begins executing from address 0. In this mode a second level boot load typically occurs, due to the limited amount of memory copied at boot.
The hex conversion utility supports the second level boot loader by automatically building the boot table.
11.10.1 Description of the Boot Table
The input for a boot loader is the boot table. The boot table contains records that instruct the boot loader to copy blocks of data contained in the table to specified destination addresses. The hex conversion utility automatically builds the boot table for the boot loader. Using the utility, you specify the sections you want the boot loader to initialize through the boot table, the table location, and the name of the section containing the boot loader and where it should be located. The hex conversion utility builds a complete image of the table and converts it into hexadecimal in the output files. Then, you can burn the table into
ROM.
11.10.2 The Boot Table Format
The boot table format is simple. There is a header record containing a 4-byte field that indicates where the boot loader should branch after it has completed copying data. After the header, each section that is to be included in the boot table will have the following:
1. 4-byte field containing the size of the section
2. 4-byte field containing the destination address for the copy
3. The actual data to be copied
Multiple sections can be entered; a termination block containing a 4-byte field of zeros follows the last section.
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Building a Table for an On-Chip Boot Loader
Section 1 Size
Section 1 Dest
Section 1 Data
Section 2 Size
Section 2 Dest
Section 2 Data
Section N Size
Section N Dest
Section N Data
0x00000000 www.ti.com
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Building a Table for an On-Chip Boot Loader
11.10.3 How to Build the Boot Table
summarizes the hex conversion utility options available for the boot loader.
Option
--boot
--bootorg=value
--bootsection=section value
--entry_point=value
Table 11-2. Boot-Loader Options
Description
Convert all sections into bootable form (use instead of a SECTIONS directive).
Specify the source address of the boot loader table.
Specify the section name containing the boot loader routine. The value argument tells the hex utility where to place the boot loader routine.
Specify the entry point at which to begin execution after boot loading. The value can be an address or a global symbol.
11.10.3.1 Building the Boot Table
To build the boot table, follow these steps:
Step 1: Link the file. Each block of the boot table data corresponds to an initialized section in the object file. Uninitialized sections are not converted by the hex conversion utility (see
). You must link into your application a boot loader routine that will read the boot table and perform the copy operations. It should be linked to its eventual run-time address.
When you select a section for placement in a boot-loader table, the hex conversion utility places the section's load address in the destination address field for the block in the boot table. The section content is then treated as raw data for that block. The hex conversion utility does not use
the section run address. When linking, you need not worry about the ROM address or the construction of the boot table; the hex conversion utility handles this.
Step 2: Identify the bootable sections. You can use the --boot option to tell the hex conversion utility to configure all sections for boot loading. Or, you can use a SECTIONS directive to select specific sections to be configured (see
). If you use a SECTIONS directive, the -boot option is ignored.
Step 3: Set the ROM address of the boot table. Use the --bootorg option to set the source address of the complete table. For example, if you are using the C6711 and booting from memory location
0x90000400, specify --bootorg=0x90000400. The address field for the boot table in the hex conversion utility output file will then start at 0x90000400.
If you do not use the --bootorg option at all, the utility places the table at the origin of the first memory range in a ROMS directive. If you do not use a ROMS directive, the table will start at the first section load address.
Step 4: Set boot-loader-specific options. Set entry point. If --entry_point is not used to set the entry point, then it will default to the entry point indicated in the object file.
Step 5: Describe the boot routine. If the boot option is used, then you should use the --bootsection option to indicate to the hex utility which section contains the boot routine. This option will prevent the boot routine from being in the boot table. The --bootsection option also indicates to the hex utility where the routine should be placed in ROM. For the C621x, C671x, and C64x devices, this address would typically be the beginning of CE1 (EMIFB CE1 on C64x). This option is ignored if --boot is not used.
When the SECTIONS directive is used to explicitly identify which sections should exits in the boot table, use the PADDR section option to indicate where the boot routine section will exist.
Step 6: Describe your system memory configuration. See
and
.
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Building a Table for an On-Chip Boot Loader www.ti.com
11.10.3.2 Leaving Room for the Boot Table
The complete boot table is similar to a single section containing all of the header records and data for the boot loader. The address of this section is the boot table origin. As part of the normal conversion process, the hex conversion utility converts the boot table to hexadecimal format and maps it into the output files like any other section.
Be sure to leave room in your system memory for the boot table, especially when you are using the
ROMS directive. The boot table cannot overlap other nonboot sections or unconfigured memory. Usually, this is not a problem; typically, a portion of memory in your system is reserved for the boot table. Simply configure this memory as one or more ranges in the ROMS directive, and use the --bootorg option to specify the starting address.
11.10.3.3 Setting the Entry Point for the Boot Table
After the boot routine finishes copying data, it branches to the entry point defined the object file. By using the --entry_point option with the hex conversion utility, you can set the entry point to a different address.
For example, if you want your program to start running at address 0x0123 after loading, specify -entry_point=0x0123 on the command line or in a command file. You can determine the --entry_point address by looking at the map file that the linker generates.
Valid Entry Points
NOTE: The value can be a constant, or it can be a symbol that is externally defined (for example, with a .global) in the assembly source.
11.10.4 Using the C6000 Boot Loader
This subsection explains how to use the hex conversion utility with the boot loader for C6000 devices through sample hex utility command files.
uses the SECTIONS directive to specify exactly which sections will be placed in the boot table.
Example 11-3. Sample Command File for Booting From a C6000 EPROM abc.out
--ascii
--image
--zero
--memwidth 8
--map=abchex.map
--bootorg=0x90000400
/* input file
/* ascii format
*/
*/
/* create complete ROM image */
/* reset address origin to 0 */
/* 8-bit memory
/* create a hex map file
/* external memory boot
*/
*/
*/
ROMS
{
FLASH: org=0x90000000, len=0x20000, romwidth=8, files={abc.hex}
}
SECTIONS
{
.boot_load: PADDR=0x90000000
.text: BOOT
.cinit:
.const:
BOOT
BOOT
}
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Building a Table for an On-Chip Boot Loader
does not explicitly name the boot sections with the SECTIONS directive. Instead, it uses the
--boot option to indicate that all initialized sections should be placed in the boot table. It also uses the -bootsection option to distinguish the section containing the boot routine.
Example 11-4. Alternative Sample Command File for Booting From a C6000 EPROM abc.out
--ascii
--image
--zero
/* input file
/* ascii format
*/
*/
/* create complete Rom image */
/* reset address origin to 0 */
--memwidth=8
--map=abchex.map
--boot
--bootorg=0x90000400
/* 8-bit memory
/* create a hex map file
/* create boot table
/* external memory boot
*/
*/
*/
*/
--bootsection=.boot_load 0x90000000 /* give boot section & addr */
ROMS
{
FLASH: org=0x90000000, len=0x20000, romwidth=8, files={abc.hex}
}
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11.11 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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Control Hex Conversion Utility Diagnostics
11.12 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
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.
--display_error_number 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.
--issue_remarks
--no_warnings
Issues remarks (nonserious warnings), which are suppressed by default.
Suppresses warning diagnostics (errors are still issued).
--set_error_limit=count 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.)
--verbose_diagnostics 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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11.13 Description of the Object Formats
The hex conversion utility has options that identify each format.
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).
Option
--ascii
--intel
--motorola=1
--motorola=2
--motorola=3
--ti-tagged
--ti_txt
--tektronix
Table 11-3. Options for Specifying Hex Conversion Formats
Alias
-a
-i
-m1
-m2
-m3
-t
-x
Format
ASCII-Hex
Intel
Motorola-S1
Motorola-S2
Motorola-S3
TI-Tagged
TI_TXT
Tektronix
Address Bits
16
32
16
24
32
16
8
32
Default Width
8
8
8
8
8
16
8
8
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.
11.13.1 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.
illustrates the ASCII-Hex format.
Figure 11-6. 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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Description of the Object Formats
11.13.2 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
00
01
04
Description
Data record
End-of-file record
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.
illustrates the Intel hexadecimal object format.
Figure 11-7. Intel Hexadecimal Object Format
Start character
Address
Most significant 16 bits
Extended linear address record
Data records
:00000001FF
Byte count
Record type
Checksum
End-of-file record
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11.13.3 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
S0
S1
S2
S3
S7
S8
S9
Description
Header record
Code/data record for 16-bit addresses (S1 format)
Code/data record for 24-bit addresses (S2 format)
Code/data record for 32-bit addresses (S3 format)
Termination record for 32-bit addresses (S3 format)
Termination record for 24-bit addresses (S2 format)
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.
illustrates the Motorola-S object format.
Figure 11-8. Motorola-S Format
Record type
Address Checksum
S00600004844521B
S31A0001FFEB000000000000000000000000000000000000000000FA
S70500000000FA
Checksum
Byte count
Address for S3 records
Header record
Data records
Termination record
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11.13.4 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:
Item
%
Block length
Block type
Checksum
Number of ASCII
Characters
1
2
1
2
Description
Data type is Tektronix format
Number of characters in the record, minus the %
6 = data record
8 = termination record
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.
illustrates the Tektronix object format.
Figure 11-9. Extended Tektronix Object Format
Checksum: 21h =
0+
1+5+6+8+1+0+0+0+0+0+0+
Block length
1ah = 26
0
2+0+2+0+2+0+2+0+2+0+2+
Object code: 6 bytes
%15621810000000202020202020
Header character
Block type: 6
(data)
Length of load address
Load address: 10000000h
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11.13.5 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
K
7
8
9
B
F
*
Description
Followed by the program identifier
Followed by a checksum
Followed by a dummy checksum (ignored)
Followed by a 16-bit load address
Followed by a data word (four characters)
Identifies the end of a data record
Followed by a data byte (two characters)
illustrates the tag characters and fields in TI-Tagged object format.
Figure 11-10. TI-Tagged Object Format
Start-of-file record
Program identifier
Load address Tag characters
Data records
BFFFFBFFFFBFFFFBFFFFBFFFFBFFFFBFFFFBFFFFBFFFFBFFFF7F245F
:
End-of-file record
Data words 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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11.13.6 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
@ADDR
DATAn q
Description
Hexadecimal start address of a section
Hexadecimal data byte
End-of-file termination character
Figure 11-11. 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 11-5. 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 12
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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
...........................................................................................................................
Page
12.1
Overview of the .cdecls Directive .......................................................................
12.2
Notes on C/C++ Conversions ............................................................................
12.3
Notes on C++ Specific Conversions ...................................................................
12.4
Special Assembler Support ...............................................................................
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12.1 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
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!" /* will be issued */
#endif
%}
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.
12.2 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.
12.2.1 Comments
Comments are consumed entirely at the C level, and do not appear in the resulting converted assembly file.
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12.2.2 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.
12.2.3 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
for the WARN and
NOWARN parameter discussion for where these warnings are created.
12.2.4 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.
12.2.5 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.
12.2.6 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.
12.2.7 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.
12.2.8 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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Notes on C/C++ Conversions
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
for suggestions on how to use C/C++ macro strings.
Macros are converted using the new .define directive (see
), 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
).
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.
12.2.9 The #undef Directive
Symbols undefined using the #undef directive before the end of the .cdecls are not converted to assembly.
12.2.10 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
.enum
.emember 16
SLEEPING .emember 1
NTERRUPT .emember 256
POWEROFF .emember 257
LAST .emember 258
.endenum
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.
12.2.11 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
for the .cstring directive syntax.)
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12.2.12 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.
12.2.13 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
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.
12.2.14 Function/Variable Prototypes
Non-static function and variable prototypes (not definitions) will result in a .global directive being generated for each symbol found.
See
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
for information on variables names which are of a structure/union type.
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12.2.15 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.
12.2.16 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.
12.3 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.
12.3.1 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);
...
}
12.3.2 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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Special Assembler Support
12.3.3 Templates
No support exists for templates.
12.3.4 Virtual Functions
No support exists for virtual functions, as they have no assembly representation.
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12.4 Special Assembler Support
12.4.1 Enumerations (.enum/.emember/.endenum)
New directives have been created to support a pseudo-scoping for enumerations.
The format of these new directives is:
ENUM_NAME .enum
MEMBER1 .emember [value]
MEMBER2
...
.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.
12.4.2 The .define Directive
The new .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.
12.4.3 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.
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Also see
, which covers the .define directive.
Special Assembler Support
12.4.4 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
and
for the use of .define and .undef in assembly.
12.4.5 The $sizeof Built-In Function
The new 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
, which notes that this conversion does not happen automatically if the C/C++
sizeof( ) built-in function is used within a macro.
12.4.6 Structure/Union Alignment and $alignof( )
The assembly .struct and .union directives now 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.
12.4.7 The .cstring Directive
You can use the new .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
for more information on the new .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 differ for the two debugging formats, DWARF and COFF.
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
...........................................................................................................................
Page
A.1
DWARF Debugging Format
A.2
COFF Debugging Format
...............................................................................
..................................................................................
A.3
Debug Directive Syntax ....................................................................................
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DWARF Debugging Format
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
COFF Debugging Format
COFF symbolic debug is now obsolete. These directives are supported for backwards-compatibility only.
The decision to switch to DWARF as the symbolic debug format was made to overcome many limitations of COFF symbolic debug, including the absence of C++ support.
The COFF debugging format consists of the following directives:
• The .sym directive defines a global variable, a local variable, or a function. Several parameters allow you to associate various debugging information with the variable or function.
• The .stag, .etag, and .utag directives define structures, enumerations, and unions, respectively. The
.member directive specifies a member of a structure, enumeration, or union. The .eos directive ends a structure, enumeration, or union definition.
• The .func and .endfunc directives specify the beginning and ending lines of a C/C++ function.
• The .block and .endblock directives specify the bounds of C/C++ blocks.
• The .file directive defines a symbol in the symbol table that identifies the current source filename.
• The .line directive identifies the line number of a C/C++ source statement.
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A.3
Debug Directive Syntax
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.
Label
CIE label
DIE label
Directive
.block
.dwattr
.dwcfi
.dwcie
.dwendentry
.dwendtag
.dwfde
.dwpsn
.dwtag
Table A-1. Symbolic Debugging Directives
Arguments
[beginning line number]
DIE label , DIE attribute name ( DIE attribute value )[, DIE attribute name ( attribute value ) [, ...]
call frame instruction opcode[, operand[, operand]]
version , return address register
CIE label
" filename ", line number , column number
DIE tag name , DIE attribute name ( DIE attribute value )[, DIE attribute name ( attribute value )
[, ...]
[ending line number]
[ending line number[, register mask[, frame size]]]
.endblock
.endfunc
.eos
.etag
.file
.func
.line
.member
.stag
.sym
.utag
name[, size]
" filename "
[beginning line number]
line number[, address]
name , value[, type , storage class , size , tag , dims]
name[, size]
name , value[, type , storage class , size , tag , dims]
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
...........................................................................................................................
Page
B.1
XML Information File Element Types ..................................................................
B.2
Document Elements .........................................................................................
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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
, 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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Document Elements
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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Document Elements
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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Document Elements
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> www.ti.com
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Document Elements
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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Document Elements
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
ABI— Application binary interface.
absolute address— An address that is permanently assigned to a TMS320C6000 memory location.
absolute lister— A debugging tool that allows you to create assembler listings that contain absolute addresses.
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.
COFF— Common object file format; a system of object files configured according to a standard developed by AT&T. These files are relocatable in memory space.
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.
cross-reference lister— A utility that produces an output file that lists the symbols that were defined, what file they were defined in, what reference type they are, what line they were defined on, which lines referenced them, and their assembler and linker final values. The cross-reference lister uses linked object files as input.
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).
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.
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.
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hole— An area between the input sections that compose an output section that contains no code.
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).
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.
mnemonic— An instruction name that the assembler translates into machine code.
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.
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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.
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.
simulator— A software development system that simulates TMS320C6000 operation.
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.
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 string of alphanumeric characters that represents an address or a value.
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symbolic debugging— The ability of a software tool to retain symbolic information that can be used by a debugging tool such as a simulator or 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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