Re: [musl] PPC64(LE) support in musl requires ALTIVEC

[David Edelsohn <dje.gcc@gmail.com>]

On Mon, Feb 3, 2020 at 11:04 AM Jeffrey Walton <noloader@gmail.com> wrote:
>
> On Mon, Feb 3, 2020 at 10:43 AM Romain Naour <romain.naour@gmail.com> wrote:
> >
> > Le 03/02/2020 à 15:50, Rich Felker a écrit :
> > > On Mon, Feb 03, 2020 at 03:16:17PM +0100, Romain Naour wrote:
> > >> Hi,
> > >>
> > >> We noticed that musl toolchain doesn't work on PPC64 e5500 cpus due to
> > >> Altived instructions in src/setjmp/powerpc64/setjmp.s [1].
> > >>
> > >> A patch has been sent by Vincent Fazio to the Buildroot mailing list to disable
> > >> musl for such cpus [2].
> > >>
> > >> Maybe the supported-platforms list could be updated [3].
> > >>
> > >> [1] https://git.musl-libc.org/cgit/musl/tree/src/setjmp/powerpc64/setjmp.s#n74
> > >> [2] http://patchwork.ozlabs.org/patch/1231986/
> > >> [3] https://wiki.musl-libc.org/supported-platforms.html
> > >
> > > Is this like the 32-bit Freescale things with the weird alternate FPU?
> >
> > Indeed, it seems that the only one ppc64 cpu without Altivec support.
>
> I'm not sure if it matters or how it relates here, but I believe IBM
> compilers (XL C and XL C++) do not allow Altivec until Power5. I think
> the decision was more policies and procedures, though. Power5 was the
> first ABI specification from the OpenPower group.
>
> Other compilers supported Altivec earlier then Power5. For example,
> Apple's GCC supported Altivec at least as early as Power3. And I have
> a PowerMac that is Power4 and Altivec works fine.

The PPC64LE ELFv2 ABI specifies Power8 with VSX as the minimum ISA.
Musl is free to ignore that.

The rest of the discussion above about processor support for Altivec
is wrong, but correcting that is off topic.

Thanks, David