[Bug target/97142] __builtin_fmod not optimized on POWER

[segher at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=97142

--- Comment #8 from Segher Boessenkool <segher at gcc dot gnu.org> ---
I don't think we have an instruction for that?  But we can inline the
code we need instead of doing a library call, which is much faster.
(We probably can use FMAs here usefully, btw; maybe even without needing
-ffast-math.)