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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/46781] [4.6 Regression] Missing optimization
Date: Mon, 03 Jan 2011 20:32:00 -0000	[thread overview]
Message-ID: <bug-46781-4-2GZtIV4Ovv@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-46781-4@http.gcc.gnu.org/bugzilla/>

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=46781

--- Comment #4 from Richard Guenther <rguenth at gcc dot gnu.org> 2011-01-03 20:31:55 UTC ---
(In reply to comment #3)
> Comment on attachment 22612 [details]
> Code produced by GCC 4.6.0
> 
> (In reply to comment #2)
> > Where did you get this testcase from?
> 
> May I know why do you ask?

To see if the change indeed causes important regressions in real-world
code.  The change was done to be less surprising when doing TBAA based
disambiguations as people regularly expect void * to be similar to char *
and also do not really handle multiple-indirect pointers the correct
way.  Thus, we now miscompile less not strictly conforming programs.

> IIRC, it was distilled from some large program. There was a difference when
> compiling it with and without LTO, and I reported it as a bug 43201.

Ah, that explains it (LTO did the pointer TBAA thing for a long time).


  parent reply	other threads:[~2011-01-03 20:32 UTC|newest]

Thread overview: 6+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2010-12-03 12:36 [Bug tree-optimization/46781] New: " d.g.gorbachev at gmail dot com
2010-12-03 12:38 ` [Bug tree-optimization/46781] " d.g.gorbachev at gmail dot com
2010-12-03 13:55 ` rguenth at gcc dot gnu.org
2010-12-03 15:39 ` d.g.gorbachev at gmail dot com
2011-01-03 20:32 ` rguenth at gcc dot gnu.org [this message]
2011-02-03  8:55 ` jakub at gcc dot gnu.org

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