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Check if xsave is enabled by OS before calling xgetbv in XmmYmmStateSupport #8939

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Jan 14, 2017
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Check if xsave is enabled by OS before calling xgetbv in XmmYmmStateSupport #8939

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0c92960
Check if xsave is enabled by OS before calling xgetbv in XmmYmmStateS…
Jan 13, 2017
6258eb1
Add ebx to clobbered registers.
Jan 13, 2017
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16 changes: 12 additions & 4 deletions src/pal/src/arch/amd64/processor.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -54,10 +54,18 @@ Return value:
extern "C" unsigned int XmmYmmStateSupport()
{
unsigned int eax;
__asm(" xgetbv\n" \
: "=a"(eax) /*output in eax*/\
: "c"(0) /*inputs - 0 in ecx*/\
: "eax", "edx" /* registers that are clobbered*/
__asm(" mov $1, %%eax\n" \
" cpuid\n" \
" xor %%eax, %%eax\n" \
" and $0x18000000, %%ecx\n" /* check for xsave feature set and that it is enabled by the OS */ \
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A nit - if you do xor %%eax, %%eax right after the cpuid and at line 61 do jne end, you can get rid of the jmp and xor after xgetbv.

" cmp $0x18000000, %%ecx\n" \
" jne end\n" \
" xor %%ecx, %%ecx\n" \
" xgetbv\n" \
"end:\n" \
: "=a"(eax) /* output in eax */ \
: /* no inputs */ \
: "eax", "ebx", "ecx", "edx" /* registers that are clobbered */
);
// Check OS has enabled both XMM and YMM state support
return ((eax & 0x06) == 0x06) ? 1 : 0;
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