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From: "ebotcazou at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug rtl-optimization/52060] [4.7 regression] Invalid constant simplification in combine with parallel result
Date: Tue, 07 Feb 2012 08:48:00 -0000	[thread overview]
Message-ID: <bug-52060-4-Xjl9YAw3SX@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-52060-4@http.gcc.gnu.org/bugzilla/>

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=52060

--- Comment #7 from Eric Botcazou <ebotcazou at gcc dot gnu.org> 2012-02-07 08:46:39 UTC ---
> I think the important question is if it is ok that combine_simplify_rtx may
> modify the given rtl in place, as opposed to keeping it unmodified and just
> allocating new rtx and returning it.  A brief look at combine.c suggests that
> SUBST () is used in so many places that it is meant to be ok to modify it in
> place.
> 
> Then we for added_sets_{1,2} should just make copies of i1src resp. i0src
> upfront, which means perhaps slightly bigger amount of GC, but at least it
> won't miscompile things.

I'm a little uncomfortable with the patch, because I think it's annoying to
have to copy a pattern that you're going to substitute for.  On the other hand,
given that combine_simplify_rtx is allowed to SUBST, that's the most reasonable
fix.

Why do you need 2 copies of I0SRC though?


  parent reply	other threads:[~2012-02-07  8:48 UTC|newest]

Thread overview: 16+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-01-30 21:36 [Bug rtl-optimization/52060] New: Incorrect mask/and (ARM "bic") instruction generated for shifted expression parameter, triggered by -O2 -finline-functions swarren at nvidia dot com
2012-01-30 23:17 ` [Bug rtl-optimization/52060] " swarren at nvidia dot com
2012-01-30 23:57 ` [Bug target/52060] " swarren at nvidia dot com
2012-02-03 16:50 ` ibolton at gcc dot gnu.org
2012-02-03 18:50 ` ramana at gcc dot gnu.org
2012-02-06 14:28 ` [Bug rtl-optimization/52060] " rearnsha at gcc dot gnu.org
2012-02-06 17:46 ` [Bug rtl-optimization/52060] [4.7 regression] Invalid constant simplification in combine with parallel result jakub at gcc dot gnu.org
2012-02-07  8:48 ` ebotcazou at gcc dot gnu.org [this message]
2012-02-07  9:20 ` [Bug rtl-optimization/52060] [4.6/4.7 Regression] " rguenth at gcc dot gnu.org
2012-02-07  9:22 ` jakub at gcc dot gnu.org
2012-02-07 15:52 ` jakub at gcc dot gnu.org
2012-02-07 16:17 ` [Bug rtl-optimization/52060] [4.6 " jakub at gcc dot gnu.org
2012-02-09 17:32 ` jakub at gcc dot gnu.org
2012-02-09 17:50 ` jakub at gcc dot gnu.org
2012-02-24  9:17 ` rguenth at gcc dot gnu.org
2012-03-02  1:03 ` jingyu at gcc dot gnu.org

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