GLIBC libmvec status

[GT]

‐‐‐‐‐‐‐ Original Message ‐‐‐‐‐‐‐
On Sunday, February 23, 2020 11:45 AM, Bill Schmidt <wschmidt@linux.ibm.com> wrote:

> On 2/21/20 6:49 AM, Tulio Magno Quites Machado Filho wrote:
>
> > +Bill, +Segher
> >
> > GT <tnggil@protonmail.com> writes:
> >
> > > Can I have until tomorrow morning to figure out exactly where/how to link the Power Vector
> > > Function ABI page? My first quick attempt resulted in the html tags being rendered on the
> > > page verbatim.
> >
> > Sure!
> > Let me know when you update the wiki and I'll send the patches to libc-alpha.
> >
> > Meanwhile, let me clarify another point...
> >
> > Bert, Bill, Segher,
> >
> > In the GCC discussion, Jakub pointed out [1] the new vector ABI targets ELFv2,
> > but there is nothing preventing it from being used on powerpc64-linux or
> > powerpc-linux.
> > On the other hand, the glibc patches enable libmvec on powerpc64le and
> > powerpc64.
> >
> > IMHO, regardless of the decision, GCC and glibc should be in sync.
> >
> > Bert, did you get a chance to test the GCC patches on powerpc64-linux?
> > I've been testing the glibc patches and they work fine, but they require
> > POWER8 (the vector ABI also requires P8).
> >
> > Bill, Segher,
> > What do you think is the best solution from the GCC point of view?
>
> As I just wrote on gcc-patches, we should disable libmvec for powerpc64.
> The vector ABI as written isn't compatible with ELFv1.  We would need
> a modified ABI that doesn't allow homogeneous aggregates of vectors to
> be returned in registers in order to support ELFv1.  I do not believe
> that is worth pursuing until and unless there is demand for it (which
> I do not expect).
>

Are we all agreed that the POWER Vector Function ABI will be implemented only
for powerpc64le?

If so, here are a few more questions:

1. The GLIBC implementation has files Makefile, Versions, configure, configure.ac among others
in directory sysdeps/powerpc/powerpc64/fpu. Do we need to create a new directory as
sysdeps/powerpc/powerpc64/powerpc64le/fpu and into it move the aforementioned files?

2. In GCC making SIMD clones available only for powerpc64le should be sufficient to guarantee that
the Vector Function ABI is applied only for systems implementing the ELFv2 ABI. Right?
Then, which macro is to be tested for in rs6000_simd_clone_usable? I expect that TARGET_VSX,
TARGET_P8_VECTOR or TARGET_P9_VECTOR are not specific enough.

Bert.