Michael Matz via Gcc-patches writes:
> Hello,
>
> the ELF psABI for x86-64 doesn't have any callee-saved SSE
> registers (there were actual reasons for that, but those don't
> matter anymore). This starts to hurt some uses, as it means that
> as soon as you have a call (say to memmove/memcpy, eve
On Tue, 11 Jul 2023, Michael Matz wrote:
> Hey,
>
> On Tue, 11 Jul 2023, Alexander Monakov via Gcc-patches wrote:
>
> > > > > * nosseclobber: claims (and ensures) that xmm8-15 aren't clobbered
> > > >
> > > > This is the weak/active form; I'd suggest "preserve_high_sse".
> > >
> > > But it
Hey,
On Tue, 11 Jul 2023, Alexander Monakov via Gcc-patches wrote:
> > > > * nosseclobber: claims (and ensures) that xmm8-15 aren't clobbered
> > >
> > > This is the weak/active form; I'd suggest "preserve_high_sse".
> >
> > But it preserves only the low parts :-) You swapped the two in your
On Tue, 11 Jul 2023, Michael Matz wrote:
> > > To that end I introduce actually two related attributes (for naming
> > > see below):
> > > * nosseclobber: claims (and ensures) that xmm8-15 aren't clobbered
> >
> > This is the weak/active form; I'd suggest "preserve_high_sse".
>
> But it preser
Hello,
On Mon, 10 Jul 2023, Alexander Monakov wrote:
> I think the main question is why you're going with this (weak) form
> instead of the (strong) form "may only clobber the low XMM regs":
I want to provide both. One of them allows more arbitrary function
definitions, the other allows more r
Hello,
On Tue, 11 Jul 2023, Jan Hubicka wrote:
> > > > When a function doesn't contain calls to
> > > > unknown functions we can be a bit more lenient: we can make it so that
> > > > GCC simply doesn't touch xmm8-15 at all, then no save/restore is
> > > > necessary.
>
> One may also take into ac
On Tue, 11 Jul 2023, Richard Biener wrote:
> > > If a function contains calls then GCC can't know which
> > > parts of the XMM regset is clobbered by that, it may be parts
> > > which don't even exist yet (say until avx2048 comes out), so we must
> > > restrict ourself to only save/restore the S
> > > When a function doesn't contain calls to
> > > unknown functions we can be a bit more lenient: we can make it so that
> > > GCC simply doesn't touch xmm8-15 at all, then no save/restore is
> > > necessary.
One may also take into account that first 8 registers are cheaper to
encode than the l
On Mon, Jul 10, 2023 at 9:08 PM Alexander Monakov via Gcc-patches
wrote:
>
>
> On Mon, 10 Jul 2023, Michael Matz via Gcc-patches wrote:
>
> > Hello,
> >
> > the ELF psABI for x86-64 doesn't have any callee-saved SSE
> > registers (there were actual reasons for that, but those don't
> > matter anym
On Tue, Jul 11, 2023 at 10:53 AM Jan Hubicka wrote:
>
> > > > FWIW, this particular patch was regstrapped on x86-64-linux
> > > > with trunk from a week ago (and sniff-tested on current trunk).
> > >
> > > This looks really cool.
> >
> > The biggest benefit might be from IPA with LTO where we'd ca
> > > FWIW, this particular patch was regstrapped on x86-64-linux
> > > with trunk from a week ago (and sniff-tested on current trunk).
> >
> > This looks really cool.
>
> The biggest benefit might be from IPA with LTO where we'd carefully place
> those
> attributes at WPA time (at that time tiei
On Mon, Jul 10, 2023 at 9:08 PM Alexander Monakov via Gcc-patches
wrote:
>
>
> On Mon, 10 Jul 2023, Michael Matz via Gcc-patches wrote:
>
> > Hello,
> >
> > the ELF psABI for x86-64 doesn't have any callee-saved SSE
> > registers (there were actual reasons for that, but those don't
> > matter anym
On Mon, 10 Jul 2023, Alexander Monakov wrote:
> > I chose to make it possible to write function definitions with that
> > attribute with GCC adding the necessary callee save/restore code in
> > the xlogue itself.
>
> But you can't trivially restore if the callee is sibcalling — what
> happens the
On Mon, 10 Jul 2023, Michael Matz via Gcc-patches wrote:
> Hello,
>
> the ELF psABI for x86-64 doesn't have any callee-saved SSE
> registers (there were actual reasons for that, but those don't
> matter anymore). This starts to hurt some uses, as it means that
> as soon as you have a call (say
> Am 10.07.2023 um 17:56 schrieb Michael Matz via Gcc-patches
> :
>
> Hello,
>
> the ELF psABI for x86-64 doesn't have any callee-saved SSE
> registers (there were actual reasons for that, but those don't
> matter anymore). This starts to hurt some uses, as it means that
> as soon as you ha
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