On Mon, Oct 09, 2017 at 09:28:58PM +0200, Uros Bizjak wrote:
> On Mon, Oct 9, 2017 at 9:16 PM, Jakub Jelinek <ja...@redhat.com> wrote:
> > Hi!
> >
> > The following builtins have {SSE,SSE2,SSSE3} CPUID, yet they have
> > MMX register operands (either input or output or both).
> > As -mno-mmx doesn't imply -mno-sse, we get ICEs on these though, because
> > with MMX disabled it is not possible to emit them.
> >
> > The following patch cheats and declares these builtins to require
> > both the MMX and {SSE,SSE2,SSSE3} ISA, making them unavailable in -mno-mmx
> > code, but I think it is the right thing to do, when somebody uses -mno-mmx,
> > the intent is usually not to have any instructions touching the MMX register
> > file and thus needing EMMS etc.
> >
> > Bootstrapped/regtested on x86_64-linux and i686-linux, ok for trunk?
>
> Hm, I remember there was similar patch for PR79565 [1], which seems
> related. Does your patch also fix all builtins that HJ's patch touch?
Ah, I wasn't aware of that patch. Will look in detail tomorrow.
> [1] https://gcc.gnu.org/ml/gcc-patches/2017-08/msg00751.html
Just quick analysis, while -mno-mmx doesn't imply -mno-sse (that is
right), it implies -mno-3dnow and -mno-3dnow implies -mno-3dnowa.
So all the spots that were changed from OPTION_MASK_ISA_3DNOW
to OPTION_MASK_ISA_3DNOW | OPTION_MASK_ISA_MMX or from
OPTION_MASK_ISA_3DNOW_A to OPTION_MASK_ISA_3DNOW_A | OPTION_MASK_ISA_MMX
were useless, we can do what we did before.
It is just OPTION_MASK_ISA_SSE or higher with OPTION_MASK_ISA_MMX that
is needed.
I have no idea why __builtin_ia32_sfence or __builtin_ia32_movntq were
changed.
Nor I understand why any sse.md changes are needed, then the builtins
aren't available, those insns shouldn't be synthetized out of thin air.
And the i386.c def_builtin change IMNSHO isn't needed either, it is
a compile time speed/memory optimization not to declare everything
unconditionally, and the way it works right now is that any of the enabled
ISAs enables the builtin, meaning that MMX enabled will mean those
35 will be declared, even when perhaps SSE isn't enabled, or for
SSE when MMX isn't enabled, but that isn't that big deal.
Jakub
