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RealView Compiler User's Guide
Preface Introduction Getting started with the ARM Compiler Compiler Features Coding Practices Optimizing code
Optimizing for size versus speed Optimization levels and the debug view Selecting the target device Optimizing loops Using volatile Code metrics Measuring code and data sizes Measuring stack use Reducing debug information in objects and librarie Functions Minimizing parameter passing overhead __value_in_regs __pure Placing ARM function qualifiers Inlining How the compiler decides to inline When is it practical for the compiler to inline? Managing inlining Inlining functions across multiple files Debugging data and the --[no]_inline keyword Marking functions as static Setting breakpoints on inlined functions in ROM im Aligning data About data alignment The __packed qualifier and unaligned accesses to d __packed structures versus individually __packed f Using floating-point arithmetic Support for floating-point operations VFP architectures The --fpu option Floating-point linkage The --fpmode option Using the --fpu option VFP support Trapping and identifying division-by-zero errors Integer division (Software) Floating point division Support for ARM architecture v6 Instruction generation Alignment support Endian support Diagnostic Messages Using the Inline and Embedded Assemblers SemihostingOptimizing for size versus speed
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| Home > Coding Practices > Optimizing code > Optimizing for size versus speed | |||
The compiler provides two options for optimizing code size and performance:
-OspaceThis option causes the compiler to optimize mainly for code size. This is the default option.
-OtimeThis option causes the compiler to optimize mainly for speed.
For best results, you must build your application using the most appropriate command-line option.
Note
For small functions, it is not guaranteed that -Otime always generates faster code, or that -Ospace always generates smaller code. The exact outcome of a particular optimization cannot be determined until all optimizations have been applied, at which point it is too late to undo any optimizations.
For more information see:
| Copyright © 2007 ARM Limited. All rights reserved. | ARM DUI 0375A |
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