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add required test of OS support for AVX register use

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This commit is contained in:
Paul Davis 2015-08-11 17:23:11 -04:00
parent 4079855507
commit c0ad97c179
1 changed files with 35 additions and 2 deletions
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37
libs/pbd/fpu.cc
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@ -37,6 +37,22 @@
using namespace PBD;
using namespace std;
/* This function is provided by MSVC are part of the compiler instrinsics. We
* don't care about this on OS X (though perhaps we should), but we need to
* test AVX support on Linux also. It doesn't hurt that this works on OS X
* also.
*/
#if __GNUC__ > 4 || __GNUC__ == 4 && __GNUC_MINOR__ >= 4
static inline unsigned long long _xgetbv(unsigned int index){
unsigned int eax, edx;
__asm__ __volatile__("xgetbv" : "=a"(eax), "=d"(edx) : "c"(index));
return ((unsigned long long)edx << 32) | eax;
}
#else
#define _xgetbv() 0
#endif
FPU::FPU ()
{
unsigned long cpuflags = 0;
@ -96,8 +112,25 @@ FPU::FPU ()
#endif /* _LP64 */
#endif /* PLATFORM_WINDOWS */
if (cpuflags & ((1<<27)|(1<<28))) {
_flags = Flags (_flags | HasAVX);
if (cpuflags & ((1<<27) /* AVX */ |(1<<28) /* XGETBV */)) {
std::cerr << "Looks like AVX\n";
/* now check if YMM resters state is saved: which means OS does
* know about new YMM registers and saves them during context
* switches it's true for most cases, but we must be sure
*
* giving 0 as the argument to _xgetbv() fetches the
* XCR_XFEATURE_ENABLED_MASK, which we need to check for
* the 2nd and 3rd bits, indicating correct register save/restore.
*/
uint64_t xcrFeatureMask = _xgetbv (0);
if (xcrFeatureMask & 0x6) {
std::cerr << "Definitely AVX\n";
_flags = Flags (_flags | (HasAVX) );
}
}
if (cpuflags & (1<<25)) {