[Bug libfortran/93871] COTAN is slow for complex types

[thenlich at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93871

--- Comment #35 from Thomas Henlich <thenlich at gcc dot gnu.org> ---
(In reply to Steve Kargl from comment #34)
> Even this appears to have some irregularities as my exhaustive
> test in the interval [1.e-8,1) with direct call to sinf() yields
> 

This looks like a job for FMA: "Correctly rounded multiplication by arbitrary
precision constants"
(http://perso.ens-lyon.fr/jean-michel.muller/MultConstant.html) show that it
can be proven to always work.