https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79722
--- Comment #2 from Marc Glisse <glisse at gcc dot gnu.org> --- -mavx2 does not enable fma. Did you try with -mfma, or with a suitable -march flag?
https://gcc.gnu.org/bugzilla/show_bug.cgi?id=79722
--- Comment #2 from Marc Glisse <glisse at gcc dot gnu.org> --- -mavx2 does not enable fma. Did you try with -mfma, or with a suitable -march flag?