From: Richard Biener <richard.guenther@gmail.com>
To: Alexandre Oliva <aoliva@redhat.com>
Cc: Szabolcs Nagy <szabolcs.nagy@arm.com>,
Alan Lawrence <Alan.Lawrence@arm.com>, Jeff Law <law@redhat.com>,
James Greenhalgh <James.Greenhalgh@arm.com>,
"H.J. Lu" <hjl.tools@gmail.com>,
Segher Boessenkool <segher@kernel.crashing.org>,
GCC Patches <gcc-patches@gcc.gnu.org>,
Christophe Lyon <christophe.lyon@linaro.org>,
David Edelsohn <dje.gcc@gmail.com>,
Eric Botcazou <ebotcazou@adacore.com>
Subject: Re: [PR64164] drop copyrename, integrate into expand
Date: Thu, 08 Oct 2015 10:00:00 -0000 [thread overview]
Message-ID: <CAFiYyc0pnU4B=NjD548QLEQa9jxC9xbRv_PSXivSMRrrOcCvbA@mail.gmail.com> (raw)
In-Reply-To: <orvbai8fwl.fsf@livre.home>
On Thu, Oct 8, 2015 at 12:36 AM, Alexandre Oliva <aoliva@redhat.com> wrote:
> On Sep 29, 2015, Szabolcs Nagy <szabolcs.nagy@arm.com> wrote:
>
>> this commit
>
>> commit 33cc9081157a8c90460e4c0bdda2ac461a3822cc
>> Author: aoliva <aoliva@138bc75d-0d04-0410-961f-82ee72b054a4>
>> Date: 2015-09-27 09:02:00 +0000
>
>> revert to assign_parms assignments using default defs
>> ...
>
>> introduced a test failure on arm-none-eabi (using newlib, compiling
>> with -mthumb -march=armv8-a -mfpu=crypto-neon-fp-armv8 -mfloat-abi=hard ):
>
>> FAIL: gcc.target/arm/pr43920-2.c scan-assembler-times pop 2
>
> Thanks for the report.
>
> The problem here is that we don't allocate the pseudo assigned to
> <retval> to r0. That's because we coalesce <retval> versions with
> another variable that crosses a function call. We do that because
> uncprop brings these unrelated variables, that happen to contain the
> same -1 value we want to return, into the PHI node with the final
> <retval> value.
>
> We can't coalesce both start and end with <retval>, because start and
> end conflict, but by chance we try start first, and that succeeds. If
> we tried end first (e.g., by giving it a higher coalesce priority,
> because fewer calls are crossed by its value in the path to the relevant
> edge), we could have got the coalesced variable assigned to r0, and that
> would enable us to optimize out the copy to r0 before return, and so
> merge the return-only basic block with other blocks. But ATM we don't
> take the definition point or path to the edge into account when
> computing coalesce costs, so we can't deterministically do better for
> this testcase, and I'm not sure using these additional information would
> make it better overall.
>
> Compiling with -fno-tree-dominator-opts skips uncprop so that we don't
> even try to coalesce other variables with <retval>, so we get the code
> expected by the testcase. But we obviously don't want to disable this
> optimization in general.
>
> Any other thoughts, anyone?
Bad luck? Add some heuristics that always help?
Ok, that wasn't really useful :/
Richard.
>
> --
> Alexandre Oliva, freedom fighter http://FSFLA.org/~lxoliva/
> You must be the change you wish to see in the world. -- Gandhi
> Be Free! -- http://FSFLA.org/ FSF Latin America board member
> Free Software Evangelist|Red Hat Brasil GNU Toolchain Engineer
next prev parent reply other threads:[~2015-10-08 10:00 UTC|newest]
Thread overview: 127+ messages / expand[flat|nested] mbox.gz Atom feed top
2015-03-27 18:04 Alexandre Oliva
2015-03-27 18:11 ` Alexandre Oliva
2015-03-28 19:22 ` Alexandre Oliva
2015-03-31 5:11 ` Jeff Law
2015-04-03 13:17 ` Alexandre Oliva
2015-04-06 16:08 ` Jeff Law
2015-04-24 1:56 ` Alexandre Oliva
2015-04-27 11:39 ` Richard Biener
2015-06-06 5:12 ` Alexandre Oliva
2015-06-08 8:16 ` Richard Biener
2015-06-09 8:58 ` Christophe Lyon
2015-06-10 0:28 ` Alexandre Oliva
2015-06-10 13:36 ` Richard Biener
2015-07-16 7:58 ` Alexandre Oliva
2015-07-16 8:50 ` Richard Biener
2015-07-16 21:33 ` Alexandre Oliva
2015-07-18 8:26 ` Alexandre Oliva
2015-07-21 13:25 ` Richard Biener
2015-07-22 17:13 ` Alexandre Oliva
2015-07-22 17:43 ` Alexandre Oliva
2015-07-23 11:04 ` Richard Biener
2015-07-23 15:42 ` Alexandre Oliva
2015-07-23 20:35 ` Segher Boessenkool
2015-07-23 21:24 ` H.J. Lu
2015-07-23 22:11 ` H.J. Lu
2015-07-24 1:31 ` David Edelsohn
2015-07-24 5:08 ` H.J. Lu
2015-07-24 9:26 ` Richard Biener
2015-07-24 12:50 ` H.J. Lu
2015-07-24 20:20 ` Alexandre Oliva
2015-07-25 2:37 ` David Edelsohn
2015-07-27 22:16 ` Alexandre Oliva
2015-07-27 22:31 ` H.J. Lu
2015-07-24 18:51 ` Alexandre Oliva
2015-07-24 19:12 ` H.J. Lu
2015-07-24 19:31 ` David Edelsohn
2015-07-24 20:43 ` Alexandre Oliva
2015-07-24 20:47 ` Alexandre Oliva
2015-07-24 21:53 ` H.J. Lu
2015-07-25 7:17 ` Richard Biener
2015-07-29 20:52 ` Alexandre Oliva
2015-07-29 21:06 ` H.J. Lu
2015-07-30 17:47 ` H.J. Lu
2015-08-03 23:46 ` Alexandre Oliva
2015-08-04 9:48 ` Richard Biener
2015-08-05 0:39 ` Alexandre Oliva
2015-08-05 9:14 ` Richard Biener
2015-08-05 23:03 ` Alexandre Oliva
2015-08-10 8:24 ` James Greenhalgh
2015-08-10 15:14 ` Jeff Law
2015-08-11 4:53 ` Patrick Marlier
2015-08-14 19:03 ` Alexandre Oliva
2015-08-15 8:57 ` Andreas Schwab
2015-08-16 13:00 ` Alexandre Oliva
[not found] ` <m2k2sv8s21.fsf@linux-m68k.org>
2015-08-17 5:05 ` Alexandre Oliva
2015-08-17 9:29 ` Kyrill Tkachov
2015-08-17 16:23 ` Andrew Pinski
2015-08-18 16:18 ` Kyrill Tkachov
2015-08-16 16:42 ` Andreas Schwab
2015-08-17 2:57 ` Alexandre Oliva
2015-08-17 8:23 ` Andreas Schwab
2015-08-17 9:21 ` Andreas Schwab
2015-08-17 11:58 ` Alexandre Oliva
2015-08-17 7:48 ` Christophe Lyon
2015-08-17 12:43 ` Alexandre Oliva
2015-08-17 13:39 ` Christophe Lyon
2015-08-18 6:53 ` Alexandre Oliva
2015-08-19 6:50 ` Alexandre Oliva
2015-08-19 10:17 ` Richard Biener
2015-08-19 13:35 ` Andreas Schwab
2015-08-19 13:45 ` Andreas Schwab
2015-08-19 17:48 ` Alexandre Oliva
2015-08-20 1:44 ` Alexandre Oliva
2015-08-20 17:03 ` Jeff Law
2015-08-21 7:57 ` Alexandre Oliva
2015-08-21 8:38 ` Richard Biener
2015-08-21 12:17 ` Andreas Schwab
2015-08-21 8:11 ` Alexandre Oliva
2015-08-21 8:37 ` Richard Biener
2015-09-02 17:09 ` Alan Lawrence
2015-09-02 22:34 ` Alexandre Oliva
2015-09-03 10:58 ` Alan Lawrence
2015-09-18 15:49 ` Alan Lawrence
2015-09-23 20:44 ` Alexandre Oliva
2015-09-25 11:39 ` Richard Biener
2015-10-09 5:26 ` [PR67828] don't unswitch loops on undefined SSA values (was: Re: [PR64164] drop copyrename, integrate into expand) Alexandre Oliva
2015-10-09 9:35 ` Richard Biener
2015-10-09 5:36 ` [PR67766] reorder return value copying from PARALLELs and CONCATs " Alexandre Oliva
2015-10-09 7:33 ` [PR67891] drop is_gimple_reg test from set_parm_rtl (was: [PR67766] reorder return value copying from PARALLELs and CONCATs) Alexandre Oliva
2015-10-09 9:40 ` Richard Biener
2015-10-10 13:20 ` [PR67891] drop is_gimple_reg test from set_parm_rtl Alexandre Oliva
2015-10-12 10:22 ` Richard Biener
2015-10-14 3:25 ` Alexandre Oliva
2015-10-14 9:28 ` Richard Biener
2015-11-03 1:11 ` Alexandre Oliva
2015-11-03 3:14 ` Jeff Law
2015-11-03 4:29 ` Alexandre Oliva
2022-10-17 12:08 ` Tag 'gcc/gimple-expr.cc:mark_addressable_2' as 'static' (was: [PR67891] drop is_gimple_reg test from set_parm_rtl) Thomas Schwinge
2015-10-09 9:36 ` [PR67766] reorder return value copying from PARALLELs and CONCATs (was: Re: [PR64164] drop copyrename, integrate into expand) Richard Biener
2015-09-29 11:31 ` [PR64164] drop copyrename, integrate into expand Szabolcs Nagy
2015-10-07 22:37 ` Alexandre Oliva
2015-10-08 10:00 ` Richard Biener [this message]
2015-10-09 21:10 ` Jeff Law
2015-11-05 5:09 ` Alexandre Oliva
2015-11-05 13:44 ` Richard Biener
2015-11-10 15:31 ` Alan Lawrence
2015-11-10 22:59 ` Alexandre Oliva
2015-11-10 23:43 ` Jeff Law
2015-11-11 18:10 ` Alexandre Oliva
2015-11-13 6:33 ` Jeff Law
2015-11-17 0:07 ` Alexandre Oliva
2015-11-24 5:41 ` Jeff Law
2015-07-24 18:21 ` Alexandre Oliva
2015-07-29 20:32 ` Alexandre Oliva
2015-04-29 3:51 ` Jeff Law
2015-03-31 6:55 ` Steven Bosscher
2015-03-31 13:30 ` Richard Biener
2015-03-31 14:06 ` Richard Biener
2015-04-03 13:30 ` Alexandre Oliva
2015-04-06 15:57 ` Jeff Law
2015-12-04 12:45 ` Dominik Vogt
2015-06-09 16:19 David Edelsohn
2015-06-09 18:36 ` Alexandre Oliva
2015-06-09 20:24 ` Alexandre Oliva
2015-06-09 20:59 ` Jakub Jelinek
2015-06-09 21:36 ` Eric Botcazou
2015-06-09 21:38 ` David Edelsohn
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