Low priority. Someone just added an avx512 function to libvpx. It is disabled in chromium for the time being.

What steps will reproduce the problem?
Attempt to build a file which contains avx512 instructions.
https://chromium.googlesource.com/webm/libvpx/+/master/vpx_dsp/x86/sad4d_avx512.c

https://chromium-review.googlesource.com/c/chromium/src/+/758802
plus
$ roll_dep.py third_party/libvpx/source/libvpx
$ cd third_party/libvpx
$ ./generate_gni --enable-avx512

cl.exe does not appear to require any arguments to build the file. libvpx builds (outside chromium) in VS 2017 and does not even set /arch:avx (as it does for avx/avx2 files)

What is the expected result?
Builds successfully.

What happens instead?
clang: error: argument unused during compilation: '/arch:AVX512' [-Werror,-Wunused-command-line-argument]

Unfortunately there is no documentation about /arch:AVX512, but cl.exe accepts it and defines __AVX512F__