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

[sgk at troutmask dot apl.washington.edu]

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

--- Comment #39 from Steve Kargl <sgk at troutmask dot apl.washington.edu> ---
On Wed, Mar 04, 2020 at 12:07:18PM +0000, thenlich at gcc dot gnu.org wrote:
> https://gcc.gnu.org/bugzilla/show_bug.cgi?id=93871
> 
> On the other hand side, always folding sind(45...90) to cosd(45...0) and
> cosd(45...90) to sind(45...0) probably wouldn't be such a bad thing.
> 

It is not only a good thing, it is required to get small max ULP
near zero crossings.  Testing fma is as accurate and as fast as
the bit twiddling methods I devised.  I haven't verified, but it
seems gcc inlines fma, which likely is bit twiddling.