[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";