[Bug c/56507] GCC -march=native for Core2Duo

[pinskia at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56507



Andrew Pinski <pinskia at gcc dot gnu.org> changed:



           What    |Removed                     |Added

----------------------------------------------------------------------------

             Status|UNCONFIRMED                 |RESOLVED

         Resolution|                            |INVALID



--- Comment #1 from Andrew Pinski <pinskia at gcc dot gnu.org> 2013-03-02 
07:23:26 UTC ---

(In reply to comment #0)

> GCC -march=native includes only flags: -mmmx -msse -msse2 -msse3 -mssse3

> but some Core2Duo processors have -msse4 -msse4.1.



But yours must not.  GCC's -march=native uses cpuid's flags field to see if

sse4/sse4.1 is supported.



>From driver-i386.c:

  __cpuid (1, eax, ebx, ecx, edx);

...  

  has_sse4_1 = ecx & bit_SSE4_1;

  has_sse4_2 = ecx & bit_SSE4_2;

...

      const char *sse4_2 = has_sse4_2 ? " -msse4.2" : " -mno-sse4.2";

      const char *sse4_1 = has_sse4_1 ? " -msse4.1" : " -mno-sse4.1";