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simd-support: Hopefully correct AVX512 check #392

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45 changes: 22 additions & 23 deletions simd-support/avx512.c
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Original file line number Diff line number Diff line change
Expand Up @@ -31,37 +31,36 @@

#include "amd64-cpuid.h"

int X(have_simd_avx512)(void)
{
static int init = 0, res;
int X(have_simd_avx512) (void) {
static int init = 0, res = 0;
int max_stdfn, eax, ebx, ecx, edx;

/* NOTE: this code is a total guess. I don't have an avx512
machine available. The code contributed by Erik Lindahl would
crash on a machine without XGETBV, so I had to guess a fix. */
if (!init) {
cpuid_all(0,0,&eax,&ebx,&ecx,&edx);
max_stdfn = eax;
if (max_stdfn >= 0x1) {
/* have OSXSAVE? (implies XGETBV exists) */
cpuid_all(0x1, 0, &eax, &ebx, &ecx, &edx);
if ((ecx & 0x08000000) == 0x08000000) {
/* have AVX512? */
cpuid_all(7,0,&eax,&ebx,&ecx,&edx);
if (ebx & (1 << 16)) {
/* have OS support for XMM, YMM, ZMM */
int zmm_ymm_xmm = (7 << 5) | (1 << 2) | (1 << 1);
res = ((xgetbv_eax(0) & zmm_ymm_xmm) == zmm_ymm_xmm);
}
}
}
init = 1;
cpuid_all(0, 0, &eax, &ebx, &ecx, &edx);
max_stdfn = eax;

if (max_stdfn >= 0x7) {
cpuid_all(0x1, 0, &eax, &ebx, &ecx, &edx);

/* have OSXSAVE? (implies XGETBV exists) */
if ((ecx & 0x08000000) == 0x08000000) {
cpuid_all(7, 0, &eax, &ebx, &ecx, &edx);

/* have OS support for XMM, YMM, OPMASK/ZMM */
if ((xgetbv_eax(0) & 0xe6) == 0xe6) {
/* have AVX512 */
res = ((ebx & 0xd0030000) == 0xd0030000);
}
}
}

init = 1;
}

return res;
}

#else /* 32-bit code */
#else /* 32-bit code */

#error "Avx512 is 64 bits only"

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