[Bug libfortran/78379] Processor-specific versions for matmul

[tkoenig at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=78379

--- Comment #24 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
Could be a good idea to add a version with -mfma to the flags for AVX2.

I'll see what I can do. It might be too late for gcc 7, and I also
don't have an AVX2 machine to test on.

Might also be a good idea to include this for AVX512F (if it is
automatically included).