TMS320C55x Optimizing C/C++ Compiler v 4.4 User's Guide Literature Number: SPRU281G December 2011 2 SPRU281G–December 2011 Submit Documentation Feedback Copyright © 2011, Texas Instruments Incorporated Contents Preface ...................................................................................................................................... 11 1 Introduction to the Software Development Tools ................................................................... 15 1.1 Software Development Tools Overview ................................................................................ 16 1.2 C/C++ Compiler Overview ................................................................................................ 17 1.2.1 ANSI/ISO Standard ............................................................................................... 17 1.2.2 Output Files ....................................................................................................... 18 1.2.3 Compiler Interface ................................................................................................ 18 1.2.4 Utilities ............................................................................................................. 18 2 Using the C/C++ Compiler .................................................................................................. 19 2.1 About the Compiler ........................................................................................................ 20 2.2 Invoking the C/C++ Compiler ............................................................................................ 20 2.3 Changing the Compiler's Behavior With Options ...................................................................... 21 2.3.1 Frequently Used Options ........................................................................................ 30 2.3.2 Miscellaneous Useful Options .................................................................................. 31 2.3.3 Run-Time Model Options ........................................................................................ 32 2.3.4 Selecting the Device Version (--silicon_version Option) .................................................... 34 2.3.5 Symbolic Debugging and Profiling Options ................................................................... 35 2.3.6 Specifying Filenames ............................................................................................ 36 2.3.7 Changing How the Compiler Interprets Filenames ........................................................... 36 2.3.8 Changing How the Compiler Processes C Files ............................................................. 36 2.3.9 Changing How the Compiler Interprets and Names Extensions ........................................... 37 2.3.10 Specifying Directories ........................................................................................... 37 2.3.11 Assembler Options .............................................................................................. 38 2.3.12 Deprecated Options ............................................................................................. 39 2.4 Controlling the Compiler Through Environment Variables ........................................................... 40 2.4.1 Setting Default Compiler Options (C55X_C_OPTION) ...................................................... 40 2.4.2 Naming an Alternate Directory (C55X_C_DIR) ............................................................... 41 2.5 Controlling the Preprocessor ............................................................................................. 41 2.5.1 Predefined Macro Names ....................................................................................... 41 2.5.2 The Search Path for #include Files ............................................................................ 42 2.5.3 Generating a Preprocessed Listing File (--preproc_only Option) .......................................... 43 2.5.4 Continuing Compilation After Preprocessing (--preproc_with_compile Option) .......................... 44 2.5.5 Generating a Preprocessed Listing File With Comments (--preproc_with_comment Option) .......... 44 2.5.6 Generating a Preprocessed Listing File With Line-Control Information (--preproc_with_line Option) ............................................................................................................. 44 2.5.7 Generating Preprocessed Output for a Make Utility (--preproc_dependency Option) ................... 44 2.5.8 Generating a List of Files Included With the #include Directive (--preproc_includes Option) .......... 44 2.5.9 Generating a List of Macros in a File (--preproc_macros Option) .......................................... 44 2.6 Understanding Diagnostic Messages ................................................................................... 44 2.6.1 Controlling Diagnostics .......................................................................................... 46 2.6.2 How You Can Use Diagnostic Suppression Options ........................................................ 46 2.7 Other Messages ........................................................................................................... 47 2.8 Generating Cross-Reference Listing Information (--gen_acp_xref Option) ........................................ 47 2.9 Generating a Raw Listing File (--gen_acp_raw Option) .............................................................. 48 2.10 Using Inline Function Expansion ........................................................................................ 49 SPRU281G–December 2011 Contents 3 Submit Documentation Feedback Copyright © 2011, Texas Instruments Incorporated www.ti.com 2.10.1 Inlining Intrinsic Operators ..................................................................................... 49 2.10.2 Unguarded Definition-Controlled Inlining ..................................................................... 49 2.10.3 Guarded Inlining and the _INLINE Preprocessor Symbol .................................................. 50 2.10.4 Inlining Restrictions ............................................................................................. 52 2.11 Using Interlist ............................................................................................................... 53 2.12 Enabling Entry Hook and Exit Hook Functions ........................................................................ 54 3 Optimizing Your Code ........................................................................................................ 55 3.1 Invoking Optimization ..................................................................................................... 56 3.2 Performing File-Level Optimization (--opt_level=3 option) ........................................................... 57 3.2.1 Controlling File-Level Optimization (--std_lib_func_def Options) ........................................... 57 3.2.2 Creating an Optimization Information File (--gen_opt_info Option) ........................................ 57 3.3 Performing Program-Level Optimization (--program_level_compile and --opt_level=3 options) ................ 58 3.3.1 Controlling Program-Level Optimization (--call_assumptions Option) ..................................... 58 3.3.2 Optimization Considerations When Mixing C/C++ and Assembly ......................................... 59 3.4 Indicating Whether Certain Aliasing Techniques Are Used .......................................................... 60 3.4.1 Use the --aliased_variables Option When Certain Aliases are Used ...................................... 60 3.4.2 Use the --no_bad_aliases Option to Indicate That These Techniques Are Not Used ................... 61 3.5 Use Caution With asm Statements in Optimized Code .............................................................. 62 3.6 Automatic Inline Expansion (--auto_inline Option) .................................................................... 62 3.7 Using the Interlist Feature With Optimization .......................................................................... 63 3.8 Debugging and Profiling Optimized Code .............................................................................. 64 3.8.1 Debugging Optimized Code (--symdebug:dwarf, --symdebug:coff, and --opt_level Options) .......... 64 3.8.2 Profiling Optimized Code ........................................................................................ 64 3.9 Controlling Code Size Versus Speed ................................................................................... 65 3.10 What Kind of Optimization Is Being Performed? ...................................................................... 66 3.10.1 Cost-Based Register Allocation ............................................................................... 66 3.10.2 Alias Disambiguation ............................................................................................ 66 3.10.3 Branch Optimizations and Control-Flow Simplification ..................................................... 67 3.10.4 Data Flow Optimizations ........................................................................................ 67 3.10.5 Expression Simplification ....................................................................................... 67 3.10.6 Inline Expansion of Functions ................................................................................. 67 3.10.7 Function Symbol Aliasing .....................................................................................