http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56068
--- Comment #13 from Uros Bizjak <ubizjak at gmail dot com> 2013-01-21 19:31:47 UTC --- (In reply to comment #12) > (In reply to comment #11) > > I will try 4.6 to prove that. Off to build 4.6... > > Thanks for checking. See http://gcc.gnu.org/wiki/InstallingGCC for the > foolproof way to do build it. > > You could also try this with any GCC version on the KVM guest: > > #include <stdio.h> > #include "cpuid.h" > > int main() > { > unsigned bit_osxsave = bit_AVX >> 1; > > unsigned int eax, ebx, ecx, edx; > > __cpuid (1, eax, ebx, ecx, edx); > > printf("bit_OSXSAVE (%u) = %u\n", bit_osxsave, ecx & bit_osxsave); > printf("bit_AVX (%u) = %u\n", bit_AVX, ecx & bit_AVX); > } > > If that prints 0 for OSXSAVE and non-zero for AVX then it's the same problem I > had. > > Maybe GCC could work around it by checking both flags in the AVX detection > logic. Recent 4.6+ does. Please see driver-i386.c around line 470: --snip-- /* Get XCR_XFEATURE_ENABLED_MASK register with xgetbv. */ #define XCR_XFEATURE_ENABLED_MASK 0x0 #define XSTATE_FP 0x1 #define XSTATE_SSE 0x2 #define XSTATE_YMM 0x4 if (has_osxsave) asm (".byte 0x0f; .byte 0x01; .byte 0xd0" : "=a" (eax), "=d" (edx) : "c" (XCR_XFEATURE_ENABLED_MASK)); /* Check if SSE and YMM states are supported. */ if (!has_osxsave || (eax & (XSTATE_SSE | XSTATE_YMM)) != (XSTATE_SSE | XSTATE_YMM)) { has_avx = 0; has_fma = 0; has_fma4 = 0; has_xop = 0; } --snip--
