PRU Optimizing C/C++ Compiler v2.3 User's Guide Literature Number: SPRUHV7C July 2014–Revised July 2018 Contents Preface ........................................................................................................................................ 8 1 Introduction to the Software Development Tools.................................................................... 11 1.1 Software Development Tools Overview ................................................................................. 12 1.2 Compiler Interface.......................................................................................................... 13 1.3 ANSI/ISO Standard ........................................................................................................ 14 1.4 Output Files ................................................................................................................. 14 1.5 Utilities ....................................................................................................................... 14 2 Using the C/C++ Compiler ................................................................................................... 15 2.1 About the Compiler......................................................................................................... 16 2.2 Invoking the C/C++ Compiler ............................................................................................. 16 2.3 Changing the Compiler's Behavior with Options ....................................................................... 17 2.3.1 Linker Options ..................................................................................................... 23 2.3.2 Frequently Used Options......................................................................................... 25 2.3.3 Miscellaneous Useful Options ................................................................................... 26 2.3.4 Run-Time Model Options......................................................................................... 27 2.3.5 Symbolic Debugging Options .................................................................................... 28 2.3.6 Specifying Filenames ............................................................................................. 28 2.3.7 Changing How the Compiler Interprets Filenames ........................................................... 29 2.3.8 Changing How the Compiler Processes C Files .............................................................. 29 2.3.9 Changing How the Compiler Interprets and Names Extensions ............................................ 29 2.3.10 Specifying Directories............................................................................................ 30 2.3.11 Assembler Options............................................................................................... 30 2.4 Controlling the Compiler Through Environment Variables............................................................ 31 2.4.1 Setting Default Compiler Options (PRU_C_OPTION)........................................................ 31 2.4.2 Naming One or More Alternate Directories (PRU_C_OPTION)............................................. 31 2.5 Controlling the Preprocessor ............................................................................................. 32 2.5.1 Predefined Macro Names ........................................................................................ 32 2.5.2 The Search Path for #include Files ............................................................................. 33 2.5.3 Support for the #warning and #warn Directives ............................................................... 34 2.5.4 Generating a Preprocessed Listing File (--preproc_only Option) ........................................... 34 2.5.5 Continuing Compilation After Preprocessing (--preproc_with_compile Option) ........................... 34 2.5.6 Generating a Preprocessed Listing File with Comments (--preproc_with_comment Option) ........... 35 2.5.7 Generating Preprocessed Listing with Line-Control Details (--preproc_with_line Option) ............... 35 2.5.8 Generating Preprocessed Output for a Make Utility (--preproc_dependency Option) ................... 35 2.5.9 Generating a List of Files Included with #include (--preproc_includes Option) ........................... 35 2.5.10 Generating a List of Macros in a File (--preproc_macros Option) ......................................... 35 2.6 Passing Arguments to main()............................................................................................. 35 2.7 Understanding Diagnostic Messages.................................................................................... 36 2.7.1 Controlling Diagnostic Messages ............................................................................... 37 2.7.2 How You Can Use Diagnostic Suppression Options ......................................................... 38 2.8 Other Messages ............................................................................................................ 39 2.9 Generating Cross-Reference Listing Information (--gen_cross_reference Option)................................ 39 2.10 Generating a Raw Listing File (--gen_preprocessor_listing Option)................................................. 39 2.11 Using Inline Function Expansion ......................................................................................... 41 2.11.1 Inlining Intrinsic Operators ...................................................................................... 42 2 Contents SPRUHV7C–July 2014–Revised July 2018 Submit Documentation Feedback Copyright © 2014–2018, Texas Instruments Incorporated www.ti.com 2.11.2 Inlining Restrictions .............................................................................................. 42 2.12 Using Interlist ............................................................................................................... 43 2.13 Enabling Entry Hook and Exit Hook Functions......................................................................... 44 3 Optimizing Your Code......................................................................................................... 45 3.1 Invoking Optimization ...................................................................................................... 46 3.2 Controlling Code Size Versus Speed ................................................................................... 47 3.3 Performing File-Level Optimization (--opt_level=3 option)............................................................ 47 3.3.1 Creating an Optimization Information File (--gen_opt_info Option)......................................... 47 3.4 Program-Level Optimization (--program_level_compile and --opt_level=3 options)............................... 48 3.4.1 Controlling Program-Level Optimization (--call_assumptions Option)...................................... 49 3.4.2 Optimization Considerations When Mixing C/C++ and Assembly .......................................... 50 3.5 Automatic Inline Expansion (--auto_inline Option) ..................................................................... 51 3.6 Link-Time Optimization (--opt_level=4 Option) ......................................................................... 52 3.6.1 Option Handling ................................................................................................... 52 3.6.2 Incompatible Types ............................................................................................... 52 3.7 Accessing Aliased Variables in Optimized Code....................................................................... 53 3.8 Use Caution With asm Statements in Optimized Code ............................................................... 53 3.9 Using the Interlist Feature With Optimization........................................................................... 53 3.10 Debugging and Profiling Optimized Code............................................................................... 54 3.11 What Kind of Optimization Is Being Performed? ....................................................................... 54 3.11.1 Cost-Based Register Allocation ................................................................................ 55 3.11.2 Alias Disambiguation ............................................................................................ 55 3.11.3 Branch Optimizations and Control-Flow Simplification ...................................................... 55 3.11.4 Data Flow Optimizations ........................................................................................ 55 3.11.5 Expression Simplification........................................................................................ 56 3.11.6 Inline Expansion of Functions .................................................................................. 56 3.11.7 Function Symbol Aliasing ....................................................................................... 56 3.11.8 Induction Variables and Strength Reduction ................................................................. 56 3.11.9 Loop-Invariant Code Motion .................................................................................... 56 3.11.10 Loop Rotation ................................................................................................... 56 3.11.11 Instruction Scheduling.......................................................................................... 56 3.11.12