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From: "abel at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/60043] -fschedule-insns2 breaks anti-dependency
Date: Tue, 04 Feb 2014 06:59:00 -0000	[thread overview]
Message-ID: <bug-60043-4-mMOniw9QA1@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-60043-4@http.gcc.gnu.org/bugzilla/>

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60043

Andrey Belevantsev <abel at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |abel at gcc dot gnu.org

--- Comment #1 from Andrey Belevantsev <abel at gcc dot gnu.org> ---
I don't follow the reasoning of this example and the original ML thread.  The
load of *b follows the store to *a, thus the scheduler is checking for the
presence of the _true_ dependence between them:

gcc/sched-deps.c:
2660                 if (true_dependence (XEXP (pending_mem, 0), VOIDmode, t)
2661                     && ! sched_insns_conditions_mutex_p (insn,
2662                                                          XEXP (pending,
0)))
2663                   note_mem_dep (t, XEXP (pending_mem, 0), XEXP (pending,
0),
2664                                 sched_deps_info->generate_spec_deps
2665                                 ? BEGIN_DATA | DEP_TRUE : DEP_TRUE);

which does not exist because the mems have different alias sets.  But you have
agreed that TBAA can be used for true dependences in the ML thread, no?  What
is then required from the scheduler?


  reply	other threads:[~2014-02-04  6:59 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2014-02-03 13:18 [Bug rtl-optimization/60043] New: " rguenth at gcc dot gnu.org
2014-02-04  6:59 ` abel at gcc dot gnu.org [this message]
2014-02-04  7:14 ` [Bug rtl-optimization/60043] " abel at gcc dot gnu.org
2014-02-04  9:26 ` rguenther at suse dot de
2014-02-04  9:27 ` rguenth at gcc dot gnu.org
2014-02-04  9:37 ` abel at gcc dot gnu.org

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