https://gcc.gnu.org/bugzilla/show_bug.cgi?id=91652
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|UNCONFIRMED |RESOLVED
Resolution|--- |INVALID
--- Comment #3 from Jakub Jelinek <jakub at gcc dot gnu.org> ---
I don't believe this is a bug.
If you look up the Intel CPU manuals, the FMA CPUID Feature Flag guards the VEX
encoded VF{,N}M{ADD,SUB,ADDSUB}{132,213,231}{S,P}{S,D} instructions, but not
the EVEX encoded ones, those are guarded just by AVX512F or AVX512F and
AVX512VL CPUID Feature Flags. Thus, -mno-fma shouldn't affect them,
-mno-avx512f should.
And you can use -ffp-contract= to decide if code that isn't already using
explicit fma should be converted to FMA or not if the instructions are
available.
