https://gcc.gnu.org/bugzilla/show_bug.cgi?id=112873
--- Comment #6 from anlauf at gcc dot gnu.org ---
(In reply to Steve Kargl from comment #5)
> On Wed, Dec 06, 2023 at 09:58:18PM +0000, anlauf at gcc dot gnu.org wrote:
> > In your experience, how good (or bad) is a naive inline version
> > like we do for the degree versions?
>
> It would be possible to use a naive version, but it will
> likely not approach the requirements placed on these functions
> by at least the IEEE 754 and C23 standards.
I see. The naive version would have done only range reduction and scaling,
maybe good enough for F2023 ("SINPI (X) is approximately equal to SIN (X×π)")
but not more.
Also, one needs mpfr-4.2.0 or higher for simple simplification, or do more
work.
> I think gfortran
> should test with configure for these functions in libm and
> use those if available (e.g., HAVE_COSPI, etc). In libgfortran,
> we'll need fallbacks if not available. To see the complexity
> of the implementation details see
>
> https://cgit.freebsd.org/src/tree/lib/msun/src/s_cospi.c
>
> Header files defining computation kernels and these use
> the computation kernels for sin() and cos() from fdlibm.
>
> https://cgit.freebsd.org/src/tree/lib/msun/src/k_cospi.h
> https://cgit.freebsd.org/src/tree/lib/msun/src/k_sinpi.h
>
> Note, AFAIK, glibc does not implement these functions.
Right.
Would you like to open a separate PR for dealing with the half-cycle
trigonometric functions?
