From: Hongtao Liu <crazylht@gmail.com>
To: Jakub Jelinek <jakub@redhat.com>, Uros Bizjak <ubizjak@gmail.com>,
Hongtao Liu <crazylht@gmail.com>,
GCC Patches <gcc-patches@gcc.gnu.org>,
"H. J. Lu" <hjl.tools@gmail.com>,
Richard Sandiford <richard.sandiford@arm.com>
Subject: Re: [PATCH] [i386] Fix _mm256_zeroupper to notify LRA that vzeroupper will kill sse registers. [PR target/82735]
Date: Fri, 14 May 2021 10:27:04 +0800 [thread overview]
Message-ID: <CAMZc-bweYecznWAmDk5kZrHOgr2zxQqAf=9jVSizF+AFQRqL2A@mail.gmail.com> (raw)
In-Reply-To: <mpth7j6zw8x.fsf@arm.com>
On Thu, May 13, 2021 at 7:52 PM Richard Sandiford
<richard.sandiford@arm.com> wrote:
>
> Jakub Jelinek <jakub@redhat.com> writes:
> > On Thu, May 13, 2021 at 12:32:26PM +0100, Richard Sandiford wrote:
> >> Jakub Jelinek <jakub@redhat.com> writes:
> >> > On Thu, May 13, 2021 at 11:43:19AM +0200, Uros Bizjak wrote:
> >> >> > > Bootstrapped and regtested on X86_64-linux-gnu{-m32,}
> >> >> > > Ok for trunk?
> >> >> >
> >> >> > Some time ago a support for CLOBBER_HIGH RTX was added (and later
> >> >> > removed for some reason). Perhaps we could resurrect the patch for the
> >> >> > purpose of ferrying 128bit modes via vzeroupper RTX?
> >> >>
> >> >> https://gcc.gnu.org/legacy-ml/gcc-patches/2017-11/msg01325.html
> >> >
> >> > https://gcc.gnu.org/legacy-ml/gcc-patches/2019-09/msg01468.html
> >> > is where it got removed, CCing Richard.
> >>
> >> Yeah. Initially clobber_high seemed like the best appraoch for
> >> handling the tlsdesc thing, but in practice it was too difficult
> >> to shoe-horn the concept in after the fact, when so much rtl
> >> infrastructure wasn't prepared to deal with it. The old support
> >> didn't handle all cases and passes correctly, and handled others
> >> suboptimally.
> >>
> >> I think it would be worth using the same approach as
> >> https://gcc.gnu.org/legacy-ml/gcc-patches/2019-09/msg01466.html for
> >> vzeroupper: represent the instructions as call_insns in which the
> >> call has a special vzeroupper ABI. I think that's likely to lead
> >> to better code than clobber_high would (or at least, it did for tlsdesc).
From an implementation perspective， I guess you're meaning we should
implement TARGET_INSN_CALLEE_ABI and TARGET_FNTYPE_ABI in the i386
backend.
> >
> > Perhaps a magic call_insn that is split post-reload into a normal insn
> > with the sets then?
>
> I'd be tempted to treat it is a call_insn throughout. The unspec_volatile
> means that we can't move the instruction, so converting a call_insn to an
> insn isn't likely to help from that point of view. The sets are also
> likely to be handled suboptimally compared to the more accurate register
> information attached to the call: all code that handles calls has to be
> prepared to deal with partial clobbers, whereas most code dealing with
> sets will assume that the set does useful work, and that the rhs of the
> set is live.
>
> Thanks,
> Richard
>
--
BR,
Hongtao
next prev parent reply other threads:[~2021-05-14 2:22 UTC|newest]
Thread overview: 45+ messages / expand[flat|nested] mbox.gz Atom feed top
2021-05-13 9:23 Hongtao Liu
2021-05-13 9:40 ` Uros Bizjak
2021-05-13 9:43 ` Uros Bizjak
2021-05-13 9:54 ` Jakub Jelinek
2021-05-13 11:32 ` Richard Sandiford
2021-05-13 11:37 ` Jakub Jelinek
2021-05-13 11:52 ` Richard Sandiford
2021-05-14 2:27 ` Hongtao Liu [this message]
2021-05-17 8:44 ` Hongtao Liu
2021-05-17 9:56 ` Richard Sandiford
2021-05-18 13:12 ` Hongtao Liu
2021-05-18 15:18 ` Richard Sandiford
2021-05-25 6:04 ` Hongtao Liu
2021-05-25 6:30 ` Hongtao Liu
2021-05-27 5:07 ` Hongtao Liu
2021-05-27 7:05 ` Uros Bizjak
2021-06-01 2:24 ` Hongtao Liu
2021-06-03 6:54 ` [PATCH 1/2] CALL_INSN may not be a real function call liuhongt
2021-06-03 6:54 ` [PATCH 2/2] Fix _mm256_zeroupper by representing the instructions as call_insns in which the call has a special vzeroupper ABI liuhongt
2021-06-04 2:56 ` Hongtao Liu
2021-06-04 6:26 ` Uros Bizjak
2021-06-04 6:34 ` Hongtao Liu
2021-06-07 19:04 ` [PATCH] x86: Don't compile pr82735-[345].c for x32 H.J. Lu
2021-06-04 2:55 ` [PATCH 1/2] CALL_INSN may not be a real function call Hongtao Liu
2021-06-04 7:50 ` Jakub Jelinek
2021-07-05 23:30 ` Segher Boessenkool
2021-07-06 0:03 ` Jeff Law
2021-07-06 1:49 ` Hongtao Liu
2021-07-07 14:55 ` Segher Boessenkool
2021-07-07 17:56 ` Jeff Law
2021-07-06 1:37 ` Hongtao Liu
2021-07-07 2:44 ` Hongtao Liu
2021-07-07 8:15 ` Richard Biener
2021-07-07 14:52 ` Segher Boessenkool
2021-07-07 15:23 ` Hongtao Liu
2021-07-07 23:42 ` Segher Boessenkool
2021-07-08 4:14 ` Hongtao Liu
2021-07-07 15:32 ` Hongtao Liu
2021-07-07 23:54 ` Segher Boessenkool
2021-07-09 7:20 ` Hongtao Liu
2021-07-07 15:52 ` Hongtao Liu
2021-05-27 7:20 ` [PATCH] [i386] Fix _mm256_zeroupper to notify LRA that vzeroupper will kill sse registers. [PR target/82735] Jakub Jelinek
2021-05-27 10:50 ` Richard Sandiford
2021-06-01 2:22 ` Hongtao Liu
2021-06-01 2:25 ` Hongtao Liu
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