bug: codec_choose_x86 does not check for OS AVX512 support

[mayeut]

The check for OS support has not been updated & still only checks for AVX support.
AVX512 added masks, 512-bit register size & 16 new registers. There are 3 corresponding bits that need to be checked in XCR0.

[aklomp]

I don't have any hardware that supports AVX512, and CI also does not support it. The only way I can run the codec is under an emulator (Intel SDE). Otherwise I would have found this, and probably also added an optimized inline asm implementation.

Will fix.

[mayeut]

I use SDE as well (in CI also) to check for some "check SIMD capability" code. Having the hardware wouldn't have helped in this case.
I don't know of a tool that can help for this one. I had hoped SDE could clear some XCR0 bits on demand to emulate lack of OS support but it seems it can't.

[lucshi]

The check for OS support has not been updated & still only checks for AVX support. AVX512 added masks, 512-bit register size & 16 new registers. There are 3 corresponding bits that need to be checked in XCR0.

Hi Matthieu,
May I know which OS configuration may break this detection? I ever tested this code on HW (Icelake avx512 + ubuntu) and saw the detection was OK.