Re: altivec triplets: comments?

[Geoff Keating <geoffk at geoffk dot org>]

> Date: Thu, 8 Nov 2001 11:30:07 -0500
> From: Daniel Jacobowitz <drow@mvista.com>
> Cc: Geoff Keating <geoffk@redhat.com>, gcc@gcc.gnu.org
> Mail-Followup-To: Aldy Hernandez <aldyh@redhat.com>,
> 	Geoff Keating <geoffk@redhat.com>, gcc@gcc.gnu.org
> Content-Disposition: inline
> User-Agent: Mutt/1.3.23i
> 
> On Wed, Nov 07, 2001 at 09:36:43PM -0500, Aldy Hernandez wrote:
> > >>>>> "Geoff" == Geoff Keating <geoffk@geoffk.org> writes:
> > 
> >  > The other problems only happen if you have a call-saved altivec
> >  > register, or use them for argument passing.  There's nothing that
> >  > prevents you from making all the altivec registers call-clobbered, and
> >  > prohibiting passing arguments in altivec registers, and then
> >  > everything should Just Work, although perhaps a little less efficiently.
> > 
> > Vector registers are only used to hold arguments for -mabi=altivec,
> > otherwise they go in the stack.  Also, altivec registers are
> > call-saved only for altivec abi.  So theoretically it should just
> > work.
> 
> Oh, I see that we actually already have 128-bit alignment for our
> stack in SysV.  I didn't know that.
> 
> Just to clarify my understanding - do the ABI changes include
> anything that would disturb non-Altivec-aware assembly (such as the
> stubs in glibc)?  I suppose they could in the presence of
> __attribute__((aligned)) and hard-coded structure offsets, but
> hopefully we don't have that problem very often.

They change setjmp and similar code.  I think `most' routines won't
need changes.

> (Is -mabi=altivec orthogonal to -maltivec, or does it imply it?)

I'm not sure if it has to imply it, but I think the intent is that it will.

-- 
- Geoffrey Keating <geoffk@geoffk.org> <geoffk@redhat.com>