Re: Patch for cacosh

[Szabolcs Nagy <nsz@port70.net>]

* Michael Morrell <mmorrell@tachyum.com> [2019-10-01 21:57:17 +0000]:
> Running the gcc validation suite, I noticed that gfortran.dg/complex_intrinsic_5.f90 was failing when using MUSL.
> 
> I tracked it down to the cacosh routines not getting the correct result when the imaginary part of the argument was negative.

yeah the complex functions are not expected to be correct:
i made no attempt to get all principal values right nor
to deal with fp format special cases (rounding, overflow,..)

i suspect that even with the sign check all sorts of
special cases are wrong (input with large real or imag part),
but if it helps somewhere then i think it's ok to add the
patch (it should just be clear that the implementation
is not expected to be correct, fixing up complex would
be a huge amount of work)

> 
> Attached is a patch to fix this.
> 
>   Michael