[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 #18 from Thomas Koenig <tkoenig at gcc dot gnu.org> ---
Created attachment 40119
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=40119&action=edit
Version that works (AVX only)

Here is a version that should only do AVX stuff on Intel processors.
Optimization for other processor types could come later.