From: "H.J. Lu" <hjl.tools@gmail.com>
To: Jakub Jelinek <jakub@redhat.com>
Cc: Eric Botcazou <ebotcazou@adacore.com>, gcc-patches@gcc.gnu.org
Subject: Re: [PATCH v3] x86: Disable SSE on unwind-c.c and unwind-dw2.c
Date: Tue, 8 Mar 2022 07:37:17 -0800 [thread overview]
Message-ID: <CAMe9rOq=+e1fD7edAwF+XMARCePvbJ-SN1=4BdaX3P=uXYUtLQ@mail.gmail.com> (raw)
In-Reply-To: <YidMOvVHLWBwgBxz@tucnak>
On Tue, Mar 8, 2022 at 4:29 AM Jakub Jelinek <jakub@redhat.com> wrote:
>
> On Tue, Mar 08, 2022 at 12:15:15PM +0100, Jakub Jelinek via Gcc-patches wrote:
> > > --- gcc/config/i386/i386.h.jj 2022-02-25 12:06:45.535493490 +0100
> > > +++ gcc/config/i386/i386.h 2022-03-08 11:20:43.207043370 +0100
> > > @@ -2848,6 +2848,10 @@ extern enum attr_cpu ix86_schedule;
> > > #define NUM_X86_64_MS_CLOBBERED_REGS 12
> > > #endif
> > >
> > > +/* __builtin_eh_return can't handle stack realignment, so disable SSE in
> > > + libgcc functions that call it. */
> > > +#define LIBGCC2_UNWIND_ATTRIBUTE __attribute__((target ("no-sse")))
> > > +
> > > /*
> > > Local variables:
> > > version-control: t
> > >
> > >
> > > As mentioned in PR104838, this likely isn't specific to just Solaris and
> > > cygwin/mingw. Fedora uses -msse2 -mfpmath=sse -mstackrealign in its C{,XX}FLAGS
> > > among other things for i686.
> >
> > Now verified that with your full patch applied gcc on Fedora/i686 doesn't
> > build (gets those sorry messages when compiling unwind-dw2), while if I
> > replace those 2 libgcc hunks from your patch with the above one it seems to
> > get past the previous hanging point of gnat1 processes.
>
> Though, perhaps it should be
> #ifndef __x86_64__
> #define LIBGCC2_UNWIND_ATTRIBUTE __attribute__((target ("no-sse")))
> #endif
> or something similar, on x86-64 one at least normally doesn't use lower
> stack realignment unless avx or later. Maybe we want to use
> no-avx for the x86-64 case though.
I have verified that AVX and AVX512 have no issues on x86-64. In 32-bit,
-mstackrealign triggers the problem.
> Disabling sse/sse2 might be a problem especially on mingw where we need to
> restore SSE registers in the EH return, no?
No, it isn't needed.
> Even better would be to make __builtin_eh_return work even with DRAP,
> but I admit I haven't understood what exactly is the problem that prevents
> it from working.
The EH return is a very special case. Disable SSE in 32-bit is the simplest
way to make the EH return to work.
--
H.J.
next prev parent reply other threads:[~2022-03-08 15:37 UTC|newest]
Thread overview: 14+ messages / expand[flat|nested] mbox.gz Atom feed top
2022-03-07 15:06 H.J. Lu
2022-03-08 10:23 ` Jakub Jelinek
2022-03-08 11:15 ` Jakub Jelinek
2022-03-08 12:29 ` Jakub Jelinek
2022-03-08 12:49 ` Eric Botcazou
2022-03-08 15:37 ` H.J. Lu [this message]
2022-03-08 15:46 ` Jakub Jelinek
2022-03-08 16:09 ` H.J. Lu
2022-03-08 17:35 ` [PATCH] x86: Define LIBGCC2_UNWIND_ATTRIBUTE on ia32 [PR104781] Jakub Jelinek
2022-03-08 17:49 ` H.J. Lu
2022-03-09 7:18 ` Richard Biener
2022-03-09 9:59 ` [PATCH] x86, v2: " Jakub Jelinek
2022-03-09 11:30 ` Richard Biener
2022-03-08 17:50 ` [PATCH] x86: " H.J. Lu
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