[PATCH] D70453: [Support] Don't require the XCR0 OSXSAVE bits when detecting skylake-avx512.

Tue Nov 19 15:00:52 PST 2019

craig.topper added a comment.

In D70453#1752570 <https://reviews.llvm.org/D70453#1752570>, @fhahn wrote:

> In D70453#1752392 <https://reviews.llvm.org/D70453#1752392>, @craig.topper wrote:
>
> > Can we check sysctl for apple?
>
>
> sysctl would return AVX512 as optional, but I am not sure if that adds any value? As mentioned in the comment, Darwin will save the AXV512 context on AVX512 hardware on-demand. More details can be found here: https://github.com/apple/darwin-xnu/blob/master/osfmk/i386/fpu.c#L174

How long has that support been in Darwin. Is it possible someone might be using an old version of darwin that completely lacks avx512 support and tries to run -march=native on a recent CPU? I guess that can only happen in a hackintosh setup since any Apple system that supports avx512 would have proper kernel support.

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https://reviews.llvm.org/D70453