[PATCH] Add simplification rule tanh (x) * cosh (x) -> sinh (x)

[Jakub Jelinek]

On Tue, Apr 30, 2019 at 07:57:20AM -0600, Jeff Law wrote:
> > Just curious, do we want to add math identities like above to match.pd ?
> I'd think so.
> 
> 
> > In practice, I am not sure how often we'd see  "tanh * cosh" instead
> > of sinh directly in source,
> We're often surprised when what ultimately shows up in sources :-)  And
> a transformation that allows us to turn two transcendentals and a
> multiplication into a single transcendental  is going to be a big win.

I guess an important question is if such transformations need to be guarded
by some -ffast-math suboptions, whether those transformations work properly
for signed zeros, NaNs, sNaNs, infinities, guarantee the same ulp, have the
same -ferrno-math behavior etc.

	Jakub