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Re: altivec triplets: comments?


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.

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

-- 
Daniel Jacobowitz                           Carnegie Mellon University
MontaVista Software                         Debian GNU/Linux Developer


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