Profiling - GNU Compiler Collection (GCC) Internals
Description: GNU Compiler Collection (GCC) Internals

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#### 17.10.12 Generating Code for Profiling

These macros will help you generate code for profiling.

— Macro: FUNCTION_PROFILER (file, labelno)

> A C statement or compound statement to output to file some assembler code to call the profiling subroutine `mcount`.

> The details of how `mcount` expects to be called are determined by your operating system environment, not by GCC. To figure them out, compile a small program for profiling using the system's installed C compiler and look at the assembler code that results.

> Older implementations of `mcount` expect the address of a counter variable to be loaded into some register. The name of this variable is ‘`LP`’ followed by the number labelno, so you would generate the name using ‘`LP%d`’ in a `fprintf`.

— Macro: PROFILE_HOOK

> A C statement or compound statement to output to file some assembly code to call the profiling subroutine `mcount` even the target does not support profiling.

— Macro: NO_PROFILE_COUNTERS

> Define this macro to be an expression with a nonzero value if the `mcount` subroutine on your system does not need a counter variable allocated for each function. This is true for almost all modern implementations. If you define this macro, you must not use the labelno argument to `FUNCTION_PROFILER`.

— Macro: PROFILE_BEFORE_PROLOGUE

> Define this macro if the code for function profiling should come before the function prologue. Normally, the profiling code comes after.