[x86-64 psABI]: Extend x86-64 psABI to support AVX-512

[Ondřej Bílka]

On Wed, Jul 24, 2013 at 07:36:31PM +0200, Richard Biener wrote:
> "H.J. Lu" <hjl.tools@gmail.com> wrote:
> 
> >On Wed, Jul 24, 2013 at 8:23 AM, Richard Biener
> ><richard.guenther@gmail.com> wrote:
> >> "H.J. Lu" <hjl.tools@gmail.com> wrote:
> >>
> >>>Hi,
> >>>
> >>>Here is a patch to extend x86-64 psABI to support AVX-512:
> >>
> >> Afaik avx 512 doubles the amount of xmm registers. Can we get them
> >callee saved please?
> >>
> >
> >Make them callee saved means we need to change ld.so to
> >preserve them and we need to change unwind library to
> >support them.  It is certainly doable.
> 
> IMHO it was a mistake to not have any callee saved xmm register in the original abi - we should fix this at this opportunity. Loops with function calls are not that uncommon.
>
I also noticed this problem and best solution that I came upon is analogue to
__attribute__((fastcall))

This would make possible for libraries to add versioned symbols that use
attribute and migrate to saner calling convention.

> Richard.
> 
> >--
> >H.J.
>