Re: [PATCH newlib v1 0/4] Add FreeBSD long double functions

[Joel Sherrill <joel@rtems.org>]

On Wed, Aug 24, 2022 at 4:26 AM Corinna Vinschen <vinschen@redhat.com>
wrote:

> On Aug 22 17:50, Joel Sherrill wrote:
> > Hi
> >
> > To be clear, this is a V1 for review. It actually does **NOT**
> > add every long double math method from FreeBSD. That would add
> > unnecessary bulk to this patch set at this point.
> >
> > The FreeBSD long double code requires there to be an architecture
> > specific _fpmath.h file. This is only available for a handful of
> > architestures. Further, LDBL does EQ DBL on many architectures.
> > The FreeBSD long double code will **NOT** compile if there isn't
> > an _fpmath.h file. Thus, the overall approach is:
> >
> >   if architecture has _fpmath.h
> >      use FreeBSD long double code in libm/common/ldbl
> >   else
> >      use existing long double code
>
> Erm... Did you actually read my last reply?


Yes. If we do that, we end up with long double support on 8
architectures and lose it immediately on all others. On the
18 RTEMS target architectures,

+ Current: long double support on 12
+ Proposed: long double support on all
+ Delete ldbl=dbl implementation: 8 would have long double


We should really not add YA
> code path.  Merging the FreeBSD long double functions should work for
> basically all supported arches.  We only have to create our own
> _fpmath.h supporting all arches based on LDBL_MANT_DIG, isn't it?
>

It should if someone creates all the _fpmath.h headers. There are 61
directories under libc/machine. That leaves 53 _fpmath.h headers to
complete and most are likely ldbl==dbl. That is up to 53 target
architectures
which would lose the long double math APIs in libm.a.

Honestly, I don't mind long term planning to delete them but I was
thinking this approach improves the current situation a lot since it will
support the targets which really have long double support. It leaves
in place support for where ldbl==dbl with no change in available APIs.
It is a net win for users.

If there is a target with long double which doesn't have a FreeBSD
_fpmath.h file, then there is value in creating it.  Honestly, unless
someone
can script writing the missing 50+ _fpmath.h files, I am not comfortable
or eager to dive in. Ignoring the lack of time to so.

This approach works and doesn't abandon the targets which the
ldbl==dbl method works for.

--joel


>
>
> Corinna
>
>