Function multiversioning question

[Martin Reinecke <martin@xxxxxxxxxxxxxxxxxxx>]

Hi,

I'm trying to use gcc's "target_clones" attribute for some functions in
a performance critical library. These functions use gcc builtins and
choose between different sets (standard code, SSE2, AVX) depending on
the predefined macros __SSE2__ and __AVX__.
Unfortunately these macros apparently are not set by the compiler when
it compiles for the individual targets.

Consider the code below:

#include <stdio.h>

__attribute__((target_clones("avx","sse2","default")))
void foo(void)
  {
#if defined(__AVX__)
  printf("AVX\n");
#elif defined(__SSE2__)
  printf("SSE2\n");
#else
  printf("nothing special\n");
#endif
  }

int main(void)
  {
  foo();
  return 0;
  }

Compiling and running this in an AVX-capable CPU prints "SSE2", where I
would have hoped to see "AVX".
Is there a way to achieve what I have in mind?

Thanks,
  Martin