avx512 support

[Johann Koenig]

Is there compile support for avx512? I tried to add some files but the jobs are failing with:

clang: error: unknown argument: '-mavx512'

I've seen some mentions of avx512 but nothing in any of the build files. 

For Visual Studio and avx2, we added /arch:AVX2. The VS 2017 documentation doesn't appear to have a similar flag for avx512.

https://logs.chromium.org/v/?s=chromium%2Fbb%2Ftryserver.chromium.mac%2Fmac_chromium_rel_ng%2F584298%2F%2B%2Frecipes%2Fsteps%2Fcompile__with_patch_%2F0%2Fstdout

[Dale Curtis]

Seems you need -march=knl?

http://lists.llvm.org/pipermail/cfe-commits/Week-of-Mon-20130819/086319.html

- dale

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[Johann Koenig]

On Wed, Nov 8, 2017 at 10:14 AM Dale Curtis <dalec...@chromium.org> wrote:

Seems you need -march=knl?

Sadly no, the problem is instead of -mavx512 I need -mavx512f -mavx512cd -mavx512bw -mavx512dq -mavx512vl 

 

Why?

A question for the ages.

[mtk...@chromium.org]

Skylake Xeon and Xeon Phi already support different subsets of AVX-512.  :/

As an alternative to your slew of -mavx512foo, you might want to just -march=skylake-avx512 ?  I believe that'll enable {F,CD,BW,DQ,VL} just like you do manually.