SPRU514Z July   2001  – October 2023 SM320F28335-EP

 

  1.   1
  2.   Read This First
    1.     About This Manual
    2.     Notational Conventions
    3.     Related Documentation
    4.     Related Documentation From Texas Instruments
    5.     Trademarks
  3. 1 Introduction to the Software Development Tools
    1. 1.1 Software Development Tools Overview
    2. 1.2 Compiler Interface
    3. 1.3 ANSI/ISO Standard
    4. 1.4 Output Files
    5. 1.5 Utilities
  4. 2 Using the C/C++ Compiler
    1. 2.1  About the Compiler
    2. 2.2  Invoking the C/C++ Compiler
    3. 2.3  Changing the Compiler's Behavior with Options
      1. 2.3.1  Linker Options
      2. 2.3.2  Frequently Used Options
      3. 2.3.3  Miscellaneous Useful Options
      4. 2.3.4  Run-Time Model Options
      5. 2.3.5  Symbolic Debugging and Profiling Options
      6. 2.3.6  Specifying Filenames
      7. 2.3.7  Changing How the Compiler Interprets Filenames
      8. 2.3.8  Changing How the Compiler Processes C Files
      9. 2.3.9  Changing How the Compiler Interprets and Names Extensions
      10. 2.3.10 Specifying Directories
      11. 2.3.11 Assembler Options
      12. 2.3.12 Deprecated Options
    4. 2.4  Controlling the Compiler Through Environment Variables
      1. 2.4.1 Setting Default Compiler Options (C2000_C_OPTION)
      2. 2.4.2 Naming One or More Alternate Directories (C2000_C_DIR)
    5. 2.5  Controlling the Preprocessor
      1. 2.5.1  Predefined Macro Names
      2. 2.5.2  The Search Path for #include Files
        1. 2.5.2.1 Adding a Directory to the #include File Search Path (--include_path Option)
      3. 2.5.3  Support for the #warning and #warn Directives
      4. 2.5.4  Generating a Preprocessed Listing File (--preproc_only Option)
      5. 2.5.5  Continuing Compilation After Preprocessing (--preproc_with_compile Option)
      6. 2.5.6  Generating a Preprocessed Listing File with Comments (--preproc_with_comment Option)
      7. 2.5.7  Generating Preprocessed Listing with Line-Control Details (--preproc_with_line Option)
      8. 2.5.8  Generating Preprocessed Output for a Make Utility (--preproc_dependency Option)
      9. 2.5.9  Generating a List of Files Included with #include (--preproc_includes Option)
      10. 2.5.10 Generating a List of Macros in a File (--preproc_macros Option)
    6. 2.6  Passing Arguments to main()
    7. 2.7  Understanding Diagnostic Messages
      1. 2.7.1 Controlling Diagnostic Messages
      2. 2.7.2 How You Can Use Diagnostic Suppression Options
    8. 2.8  Other Messages
    9. 2.9  Generating Cross-Reference Listing Information (--gen_cross_reference_listing Option)
    10. 2.10 Generating a Raw Listing File (--gen_preprocessor_listing Option)
    11. 2.11 Using Inline Function Expansion
      1. 2.11.1 Inlining Intrinsic Operators
      2. 2.11.2 Inlining Restrictions
      3. 2.11.3 Unguarded Definition-Controlled Inlining
        1. 2.11.3.1 Using the Inline Keyword
      4. 2.11.4 Guarded Inlining and the _INLINE Preprocessor Symbol
        1. 2.11.4.1 Header File string.h
        2. 2.11.4.2 Library Definition File
    12. 2.12 Using Interlist
    13. 2.13 About the Application Binary Interface
    14. 2.14 Enabling Entry Hook and Exit Hook Functions
    15. 2.15 Live Firmware Update (LFU)
  5. 3 Optimizing Your Code
    1. 3.1  Invoking Optimization
    2. 3.2  Controlling Code Size Versus Speed
    3. 3.3  Performing File-Level Optimization (--opt_level=3 option)
      1. 3.3.1 Creating an Optimization Information File (--gen_opt_info Option)
    4. 3.4  Program-Level Optimization (--program_level_compile and --opt_level=3 options)
      1. 3.4.1 Controlling Program-Level Optimization (--call_assumptions Option)
      2. 3.4.2 Optimization Considerations When Mixing C/C++ and Assembly
    5. 3.5  Automatic Inline Expansion (--auto_inline Option)
    6. 3.6  Link-Time Optimization (--opt_level=4 Option)
      1. 3.6.1 Option Handling
      2. 3.6.2 Incompatible Types
    7. 3.7  Using Feedback Directed Optimization
      1. 3.7.1 Feedback Directed Optimization
        1. 3.7.1.1 Phase 1 -- Collect Program Profile Information
        2. 3.7.1.2 Phase 2 -- Use Application Profile Information for Optimization
        3. 3.7.1.3 Generating and Using Profile Information
        4. 3.7.1.4 Example Use of Feedback Directed Optimization
        5. 3.7.1.5 The .ppdata Section
        6. 3.7.1.6 Feedback Directed Optimization and Code Size Tune
        7. 3.7.1.7 Instrumented Program Execution Overhead
        8. 3.7.1.8 Invalid Profile Data
      2. 3.7.2 Profile Data Decoder
      3. 3.7.3 Feedback Directed Optimization API
      4. 3.7.4 Feedback Directed Optimization Summary
    8. 3.8  Using Profile Information to Analyze Code Coverage
      1. 3.8.1 Code Coverage
        1. 3.8.1.1 Phase1 -- Collect Program Profile Information
        2. 3.8.1.2 Phase 2 -- Generate Code Coverage Reports
      2. 3.8.2 Related Features and Capabilities
        1. 3.8.2.1 Path Profiler
        2. 3.8.2.2 Analysis Options
        3. 3.8.2.3 Environment Variables
    9. 3.9  Special Considerations When Using Optimization
      1. 3.9.1 Use Caution With asm Statements in Optimized Code
      2. 3.9.2 Use the Volatile Keyword for Necessary Memory Accesses
        1. 3.9.2.1 Use Caution When Accessing Aliased Variables
        2. 3.9.2.2 Use the --aliased_variables Option to Indicate That the Following Technique Is Used
        3. 3.9.2.3 On FPU Targets Only: Use restrict Keyword to Indicate That Pointers Are Not Aliased
          1. 3.9.2.3.1 Use of the restrict Type Qualifier With Pointers
          2. 3.9.2.3.2 Use of the restrict Type Qualifier With Pointers
    10. 3.10 Using the Interlist Feature With Optimization
    11. 3.11 Data Page (DP) Pointer Load Optimization
    12. 3.12 Debugging and Profiling Optimized Code
      1. 3.12.1 Profiling Optimized Code
    13. 3.13 Increasing Code-Size Optimizations (--opt_for_space Option)
    14. 3.14 Compiler Support for Re-Entrant VCU Code
    15. 3.15 Compiler Support for Generating DMAC Instructions
      1. 3.15.1 Automatic Generation of DMAC Instructions
      2. 3.15.2 Assertions to Specify Data Address Alignment
      3. 3.15.3 __dmac Intrinsic
    16. 3.16 What Kind of Optimization Is Being Performed?
      1. 3.16.1  Cost-Based Register Allocation
      2. 3.16.2  Alias Disambiguation
      3. 3.16.3  Branch Optimizations and Control-Flow Simplification
      4. 3.16.4  Data Flow Optimizations
      5. 3.16.5  Expression Simplification
      6. 3.16.6  Inline Expansion of Functions
      7. 3.16.7  Function Symbol Aliasing
      8. 3.16.8  Induction Variables and Strength Reduction
      9. 3.16.9  Loop-Invariant Code Motion
      10. 3.16.10 Loop Rotation
      11. 3.16.11 Instruction Scheduling
      12. 3.16.12 Register Variables
      13. 3.16.13 Register Tracking/Targeting
      14. 3.16.14 Tail Merging
      15. 3.16.15 Autoincrement Addressing
      16. 3.16.16 Removing Comparisons to Zero
      17. 3.16.17 RPTB Generation (for FPU Targets Only)
  6. 4 Linking C/C++ Code
    1. 4.1 Invoking the Linker Through the Compiler (-z Option)
      1. 4.1.1 Invoking the Linker Separately
      2. 4.1.2 Invoking the Linker as Part of the Compile Step
      3. 4.1.3 Disabling the Linker (--compile_only Compiler Option)
    2. 4.2 Linker Code Optimizations
      1. 4.2.1 Generating Function Subsections (--gen_func_subsections Compiler Option)
      2. 4.2.2 Generating Aggregate Data Subsections (--gen_data_subsections Compiler Option)
    3. 4.3 Controlling the Linking Process
      1. 4.3.1 Including the Run-Time-Support Library
        1. 4.3.1.1 Automatic Run-Time-Support Library Selection
          1. 4.3.1.1.1 Using the --issue_remarks Option
        2. 4.3.1.2 Manual Run-Time-Support Library Selection
        3. 4.3.1.3 Library Order for Searching for Symbols
      2. 4.3.2 Run-Time Initialization
      3. 4.3.3 Initialization by the Interrupt Vector
      4. 4.3.4 Global Object Constructors
      5. 4.3.5 Specifying the Type of Global Variable Initialization
      6. 4.3.6 Specifying Where to Allocate Sections in Memory
      7. 4.3.7 A Sample Linker Command File
    4. 4.4 Linking C28x and C2XLP Code
  7. 5 Post-Link Optimizer
    1. 5.1 The Post-Link Optimizer’s Role in the Software Development Flow
    2. 5.2 Removing Redundant DP Loads
    3. 5.3 Tracking DP Values Across Branches
    4. 5.4 Tracking DP Values Across Function Calls
    5. 5.5 Other Post-Link Optimizations
    6. 5.6 Controlling Post-Link Optimizations
      1. 5.6.1 Excluding Files (-ex Option)
      2. 5.6.2 Controlling Post-Link Optimization Within an Assembly File
      3. 5.6.3 Retaining Post-Link Optimizer Output (--keep_asm Option)
      4. 5.6.4 Disable Optimization Across Function Calls (-nf Option )
      5. 5.6.5 Annotating Assembly with Advice (--plink_advice_only option)
    7. 5.7 Restrictions on Using the Post-Link Optimizer
    8. 5.8 Naming the Outfile (--output_file Option)
  8. 6 C/C++ Language Implementation
    1. 6.1  Characteristics of TMS320C28x C
      1. 6.1.1 Implementation-Defined Behavior
    2. 6.2  Characteristics of TMS320C28x C++
    3. 6.3  Data Types
      1. 6.3.1 Size of Enum Types
      2. 6.3.2 Support for 64-Bit Integers
      3. 6.3.3 C28x double and long double Floating-Point Types
    4. 6.4  File Encodings and Character Sets
    5. 6.5  Keywords
      1. 6.5.1 The const Keyword
      2. 6.5.2 The __cregister Keyword
      3. 6.5.3 The __interrupt Keyword
      4. 6.5.4 The restrict Keyword
      5. 6.5.5 The volatile Keyword
    6. 6.6  C++ Exception Handling
    7. 6.7  Register Variables and Parameters
    8. 6.8  The __asm Statement
    9. 6.9  Pragma Directives
      1. 6.9.1  The CALLS Pragma
      2. 6.9.2  The CLINK Pragma
      3. 6.9.3  The CODE_ALIGN Pragma
      4. 6.9.4  The CODE_SECTION Pragma
      5. 6.9.5  The DATA_ALIGN Pragma
      6. 6.9.6  The DATA_SECTION Pragma
        1. 6.9.6.1 Using the DATA_SECTION Pragma C Source File
        2. 6.9.6.2 Using the DATA_SECTION Pragma C++ Source File
        3. 6.9.6.3 Using the DATA_SECTION Pragma Assembly Source File
      7. 6.9.7  The Diagnostic Message Pragmas
      8. 6.9.8  The FAST_FUNC_CALL Pragma
      9. 6.9.9  The FORCEINLINE Pragma
      10. 6.9.10 The FORCEINLINE_RECURSIVE Pragma
      11. 6.9.11 The FUNC_ALWAYS_INLINE Pragma
      12. 6.9.12 The FUNC_CANNOT_INLINE Pragma
      13. 6.9.13 The FUNC_EXT_CALLED Pragma
      14. 6.9.14 The FUNCTION_OPTIONS Pragma
      15. 6.9.15 The INTERRUPT Pragma
      16. 6.9.16 The LOCATION Pragma
      17. 6.9.17 The MUST_ITERATE Pragma
        1. 6.9.17.1 The MUST_ITERATE Pragma Syntax
        2. 6.9.17.2 Using MUST_ITERATE to Expand Compiler Knowledge of Loops
      18. 6.9.18 The NOINIT and PERSISTENT Pragmas
      19. 6.9.19 The NOINLINE Pragma
      20. 6.9.20 The NO_HOOKS Pragma
      21. 6.9.21 The once Pragma
      22. 6.9.22 The RETAIN Pragma
      23. 6.9.23 The SET_CODE_SECTION and SET_DATA_SECTION Pragmas
      24. 6.9.24 The UNROLL Pragma
      25. 6.9.25 The WEAK Pragma
    10. 6.10 The _Pragma Operator
    11. 6.11 Application Binary Interface
    12. 6.12 Object File Symbol Naming Conventions (Linknames)
    13. 6.13 Initializing Static and Global Variables in COFF ABI Mode
      1. 6.13.1 Initializing Static and Global Variables With the Linker
      2. 6.13.2 Initializing Static and Global Variables With the const Type Qualifier
    14. 6.14 Changing the ANSI/ISO C/C++ Language Mode
      1. 6.14.1 C99 Support (--c99)
      2. 6.14.2 C11 Support (--c11)
      3. 6.14.3 Strict ANSI Mode and Relaxed ANSI Mode (--strict_ansi and --relaxed_ansi)
    15. 6.15 GNU and Clang Language Extensions
      1. 6.15.1 Extensions
      2. 6.15.2 Function Attributes
      3. 6.15.3 For Loop Attributes
      4. 6.15.4 Variable Attributes
      5. 6.15.5 Type Attributes
      6. 6.15.6 Built-In Functions
      7. 6.15.7 Using the Byte Peripheral Type Attribute
    16. 6.16 Compiler Limits
  9. 7 Run-Time Environment
    1. 7.1  Memory Model
      1. 7.1.1 Sections
      2. 7.1.2 C/C++ System Stack
      3. 7.1.3 Allocating .econst to Program Memory
      4. 7.1.4 Dynamic Memory Allocation
      5. 7.1.5 Initialization of Variables
      6. 7.1.6 Allocating Memory for Static and Global Variables
      7. 7.1.7 Field/Structure Alignment
      8. 7.1.8 Character String Constants
    2. 7.2  Register Conventions
      1. 7.2.1 TMS320C28x Register Use and Preservation
      2. 7.2.2 Status Registers
    3. 7.3  Function Structure and Calling Conventions
      1. 7.3.1 How a Function Makes a Call
      2. 7.3.2 How a Called Function Responds
      3. 7.3.3 Special Case for a Called Function (Large Frames)
      4. 7.3.4 Accessing Arguments and Local Variables
      5. 7.3.5 Allocating the Frame and Accessing 32-Bit Values in Memory
    4. 7.4  Accessing Linker Symbols in C and C++
    5. 7.5  Interfacing C and C++ With Assembly Language
      1. 7.5.1 Using Assembly Language Modules With C/C++ Code
      2. 7.5.2 Accessing Assembly Language Functions From C/C++
        1. 7.5.2.1 Calling an Assembly Language Function From a C/C++ Program
        2. 7.5.2.2 Assembly Language Program Called by
        3.       261
      3. 7.5.3 Accessing Assembly Language Variables From C/C++
        1. 7.5.3.1 Accessing Assembly Language Global Variables
          1. 7.5.3.1.1 Assembly Language Variable Program
          2. 7.5.3.1.2 C Program to Access Assembly Language From
        2.       266
        3. 7.5.3.2 Accessing Assembly Language Constants
          1. 7.5.3.2.1 Accessing an Assembly Language Constant From C
          2. 7.5.3.2.2 Assembly Language Program for
          3.        270
      4. 7.5.4 Sharing C/C++ Header Files With Assembly Source
      5. 7.5.5 Using Inline Assembly Language
    6. 7.6  Using Intrinsics to Access Assembly Language Statements
      1. 7.6.1 Floating Point Conversion Intrinsics
      2. 7.6.2 Floating Point Unit (FPU) Intrinsics
      3. 7.6.3 Trigonometric Math Unit (TMU) Intrinsics
      4. 7.6.4 Fast Integer Division Intrinsics
    7. 7.7  Interrupt Handling
      1. 7.7.1 General Points About Interrupts
      2. 7.7.2 Using C/C++ Interrupt Routines
    8. 7.8  Integer Expression Analysis
      1. 7.8.1 Operations Evaluated With Run-Time-Support Calls
      2. 7.8.2 Division Operations with Fast Integer Division Support
      3. 7.8.3 C/C++ Code Access to the Upper 16 Bits of 16-Bit Multiply
    9. 7.9  Floating-Point Expression Analysis
    10. 7.10 System Initialization
      1. 7.10.1 Boot Hook Functions for System Pre-Initialization
      2. 7.10.2 Run-Time Stack
      3. 7.10.3 Automatic Initialization of Variables for COFF
        1. 7.10.3.1 Initialization Tables
        2.       291
        3. 7.10.3.2 Autoinitialization of Variables at Run Time for COFF
        4. 7.10.3.3 Initialization of Variables at Load Time for COFF
        5. 7.10.3.4 Global Constructors
      4. 7.10.4 Automatic Initialization of Variables for EABI
        1. 7.10.4.1 Zero Initializing Variables
        2. 7.10.4.2 Direct Initialization for EABI
        3. 7.10.4.3 Autoinitialization of Variables at Run Time for EABI
        4. 7.10.4.4 Autoinitialization Tables for EABI
          1. 7.10.4.4.1 Length Followed by Data Format
          2. 7.10.4.4.2 Zero Initialization Format
          3. 7.10.4.4.3 Run Length Encoded (RLE) Format
          4. 7.10.4.4.4 Lempel-Ziv-Storer-Szymanski Compression (LZSS) Format
        5. 7.10.4.5 Initialization of Variables at Load Time
        6. 7.10.4.6 Global Constructors
  10. 8 Using Run-Time-Support Functions and Building Libraries
    1. 8.1 C and C++ Run-Time Support Libraries
      1. 8.1.1 Linking Code With the Object Library
      2. 8.1.2 Header Files
      3. 8.1.3 Modifying a Library Function
      4. 8.1.4 Support for String Handling
      5. 8.1.5 Minimal Support for Internationalization
      6. 8.1.6 Support for Time and Clock Functions
      7. 8.1.7 Allowable Number of Open Files
      8. 8.1.8 Library Naming Conventions
    2. 8.2 The C I/O Functions
      1. 8.2.1 High-Level I/O Functions
        1. 8.2.1.1 Formatting and the Format Conversion Buffer
      2. 8.2.2 Overview of Low-Level I/O Implementation
        1.       open
        2.       close
        3.       read
        4.       write
        5.       lseek
        6.       unlink
        7.       rename
      3. 8.2.3 Device-Driver Level I/O Functions
        1.       DEV_open
        2.       DEV_close
        3.       DEV_read
        4.       DEV_write
        5.       DEV_lseek
        6.       DEV_unlink
        7.       DEV_rename
      4. 8.2.4 Adding a User-Defined Device Driver for C I/O
        1. 8.2.4.1 Mapping Default Streams to Device
      5. 8.2.5 The device Prefix
        1.       add_device
        2.       339
        3. 8.2.5.1 Program for C I/O Device
    3. 8.3 Handling Reentrancy (_register_lock() and _register_unlock() Functions)
    4. 8.4 Reinitializing Variables During a Warm Start
    5. 8.5 Library-Build Process
      1. 8.5.1 Required Non-Texas Instruments Software
      2. 8.5.2 Using the Library-Build Process
        1. 8.5.2.1 Automatic Standard Library Rebuilding by the Linker
        2. 8.5.2.2 Invoking mklib Manually
          1. 8.5.2.2.1 Building Standard Libraries
          2. 8.5.2.2.2 Shared or Read-Only Library Directory
          3. 8.5.2.2.3 Building Libraries With Custom Options
          4. 8.5.2.2.4 The mklib Program Option Summary
      3. 8.5.3 Extending mklib
        1. 8.5.3.1 Underlying Mechanism
        2. 8.5.3.2 Libraries From Other Vendors
  11. 9 C++ Name Demangler
    1. 9.1 Invoking the C++ Name Demangler
    2. 9.2 Sample Usage of the C++ Name Demangler
  12. 10CLA Compiler
    1. 10.1 How to Invoke the CLA Compiler
      1. 10.1.1 CLA-Specific Options
    2. 10.2 CLA C Language Implementation
      1. 10.2.1 Variables and Data Types
      2. 10.2.2 Pragmas, Keywords, and Intrinsics
      3. 10.2.3 Optimizations with the CLA Compiler
      4. 10.2.4 C Language Restrictions
      5. 10.2.5 Memory Model - Sections
      6. 10.2.6 Function Structure and Calling Conventions
  13.   A Glossary
    1.     369
  14.   B Revision History
  15.   B Earlier Revisions

7.1.1 Sections

The compiler produces relocatable blocks of code and data called sections, which are allocated in memory in a variety of ways to conform to various system configurations. For information about sections and allocating them, see the introductory object file information in the TMS320C28x Assembly Language Tools User's Guide.

There are two basic types of sections:

  • Uninitialized sections reserve space in memory (usually RAM). A program can use this space at run time to create and store variables. The compiler creates the following uninitialized sections:
    • The .bss section reserves space for uninitialized global and static variables. Uninitialized variables that are also unused are usually created as common symbols instead of being placed in .bss so that they can be excluded from the resulting application. (EABI only for compiler; EABI and COFF for assembler)
    • The .ebss section reserves space for all static variables (initialized or uninitialized; global or local). At program startup time, the C/C++ boot routine copies data out of the .cinit section (which can be in ROM) and uses it to initialize variables in the .ebss section. (COFF only)
    • The .stack section reserves memory for the C/C++ software stack. This memory is used to pass arguments to functions and to allocate space for local variables.
    • The .esysmem section reserves space for dynamic memory allocation. This space is used by dynamic memory allocation routines, such as malloc, calloc, realloc, or new. If a C/C++ program does not use these functions, the compiler does not create the .esysmem section. (COFF only)
    • The .sysmem section reserves space for dynamic memory allocation. The reserved space is used by dynamic memory allocation routines, such as malloc(), calloc(), realloc(), or new(). If a C/C++ program does not use these functions, the compiler does not create the .sysmem section. (EABI only)
  • Initialized sections contain data or executable code. Initialized sections are usually read-only; exceptions are noted below. The C/C++ compiler creates the following initialized sections:
    • The .args section contains space for the command-line arguments. See the --arg_size option.
    • The .binit section contains boot time copy tables. For details on BINIT, see the TMS320C28x Assembly Language Tools User's Guide.
    • The .cinit section contains tables for initializing variables and constants. The C28x .cinit record is limited to 16 bits. This limits initialized objects to 64K. (For EABI, the linker creates the .cinit section. For COFF, the compiler creates .cinit sections.)
    • The .ovly section contains copy tables for unions in which different sections have the same run address.
    • The .init_array section contains global constructor tables. (EABI only)
    • The .pinit section contains global constructor tables. (COFF only)
    • The .c28xabi.exidx section contains the index table for exception handling. The .c28xabi.extab section contains stack unwinding instructions for exception handling. See the --exceptions option for details. (EABI only)
    • The .ppdata section contains data tables for compiler-based profiling. See the --gen_profile_info option for details. This section is writable.
    • The .ppinfo section contains correlation tables for compiler-based profiling. See the --gen_profile_info option for details.
    • The .const section contains string literals and variables defined with the C/C++ qualifier const (even if the constant is defined as volatile, but not if the constant is one of the exceptions described in Section 6.5.1). String literals are placed in the .const:.string subsection to enable greater link-time placement control. (EABI only)
    • The .econst section contains string literals and global variables that are defined with the C/C++ qualifier const (even if the constant is defined as volatile, but not if the constant is one of the exceptions described in Section 6.5.1). String literals are placed in the .econst:.string subsection to enable greater link-time placement control. (COFF only)
    • The .data section reserves space for non-const, initialized static variables, whether they are global or local. (For EABI, the compiler generates this section and it is used for initialized global and static variables. For COFF, this section may be used by assembly code, but is not used otherwise.) This section is writable.
    • The .switch section contains tables for switch statements. This section is placed in data memory by default. If the --unified_memory option is used, this section is placed in program memory.
    • The .text section contains all the executable code and compiler-generated constants. This section is usually read-only.
    • The .TI.crctab section contains CRC checking tables.
    • The .TI.bound section is used to associate a symbol to a specific memory address. When either the LOCATION pragma (see Section 6.9.16) or the "location" or "preserve" variable attribute (see Section 6.15.4) is used to associate a symbol with a specific memory address, a .TI.bound section is created for the symbol. In the case of "preserve" symbols, when .TI.bound sections are contiguous in memory, the linker can coalesce them into a single output section, which reduces the number of CINIT records required to initialize them. This section may be writable or read-only.
    • The .TI.update section contains symbols that need to be reinitialized when a warm start occurs. Reinitialization is performed by the __TI_auto_init_warm() RTS function. It is recommended that you add an entry to the linker command file to place the .TI.update section in an appropriate memory range. This section is writable.

The following table shows the placement of various types of initialized variables:

EABI COFF
global local global local
const .const * .econst *
static .data .data .ebss .ebss
string constants, literals .const:.string .const:.string .econst:.string .econst:.string

* Initialized const (non-static) local variables are not placed in output sections; they are initialized in memory (usually RAM) at run-time as needed.

The assembler creates the default sections .text, .ebss or .bss (depending on the ABI), and .data. You can instruct the compiler to create additional sections by using the CODE_SECTION and DATA_SECTION pragmas (see Section 6.9.4 and Section 6.9.6).

The linker takes the individual sections from different object files and combines sections that have the same name. The resulting output sections and the appropriate placement in memory for each section are listed in Table 7-1. You can place these output sections anywhere in the address space as needed to meet system requirements.

The linker also creates some additional sections not referenced by the compiler. For example, the .common section contains common-block symbols allocated by the linker.

For EABI, it is encouraged that you use a unified memory scheme that places all sections on page 0. However, the default linker command file specifies page 0 or 1 for sections as indicated in the following table. In general, uninitialized and constant value sections are placed on page 1 by the linker command file; all other sections are generally placed on page 0.

Table 7-1 Summary of Sections and Memory Placement
Section Type of Memory Default Page
.binit expected to be in FLASH/ROM 1
.bss (EABI only) must be in RAM 1
.ebss (COFF only) must be in RAM 1
.c28xabi.exidx (EABI only) expected to be in FLASH/ROM 1
.c28xabi.extab (EABI only) expected to be in FLASH/ROM 1
.cinit (1) expected to be in FLASH/ROM 0
.const (EABI only) expected to be in FLASH/ROM 1
.econst (COFF only) expected to be in FLASH/ROM 1
.data (used mainly by EABI) must be in RAM 0
.init_array (EABI only) expected to be in FLASH/ROM 0
.pinit (COFF only) expected to be in FLASH/ROM 0
.ppdata must be in RAM 1
.stack must be in RAM 1
.switch depends on the --unified_memory option setting 0, 1
.sysmem (EABI only) must be in RAM 1
.esysmem (COFF only) must be in RAM 1
.text expected to be in FLASH/ROM 0
(1) The .cinit section is created by the compiler for COFF and by the linker for EABI.

You can use the SECTIONS directive in the linker command file to customize the section-allocation process. For more information about allocating sections into memory, see the linker description chapter in the TMS320C28x Assembly Language Tools User's Guide.