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From: "rguenth at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/53676] [4.7 regression] empty loop is not always removed now
Date: Wed, 22 Aug 2012 08:48:00 -0000	[thread overview]
Message-ID: <bug-53676-4-L14BO0t4dZ@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-53676-4@http.gcc.gnu.org/bugzilla/>

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53676

--- Comment #13 from Richard Guenther <rguenth at gcc dot gnu.org> 2012-08-22 08:46:54 UTC ---
(In reply to comment #12)
> I've been doing research into LLVM 3.1 and other GCC versions. LLVM 3.1
> correctly eliminate the (near) empty loop, and their current trunk does not
> regress like 4.7 has.
> 
> Is the trunk patch coupled to other changes that are too invasive for 4.7? I'm
> confused and curious about what optimization regressions are serious enough to
> warrant a back port, if any.

No, it's only the commit referenced in this PR.  No optimization regressions
warrant a backport as they always come with the risk of regressing something
worse than performance.  Trivial restoring of old behavior might be worth
backporting but the patch introduces a completely new non-trivial transform
into a core analysis engine that is shared among many passes.


  parent reply	other threads:[~2012-08-22  8:48 UTC|newest]

Thread overview: 23+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2012-06-14 22:47 [Bug middle-end/53676] New: [4.7/4.8 regression] constant folding regression, shown as slowdown as measured by Adobe's C++Benchmark matt at use dot net
2012-06-14 22:49 ` [Bug middle-end/53676] " matt at use dot net
2012-06-14 23:00 ` matt at use dot net
2012-06-14 23:13 ` [Bug middle-end/53676] [4.7/4.8 regression] empty loop is not always removed now pinskia at gcc dot gnu.org
2012-06-15  0:02 ` hjl.tools at gmail dot com
2012-06-19 13:18 ` rguenth at gcc dot gnu.org
2012-06-25  8:19 ` rguenth at gcc dot gnu.org
2012-06-25 13:41 ` rguenth at gcc dot gnu.org
2012-06-27 11:33 ` rguenth at gcc dot gnu.org
2012-06-27 11:33 ` [Bug middle-end/53676] [4.7 " rguenth at gcc dot gnu.org
2012-06-27 11:33 ` rguenth at gcc dot gnu.org
2012-06-27 18:27 ` matt at use dot net
2012-06-28  8:26 ` rguenther at suse dot de
2012-08-21 21:40 ` matt at use dot net
2012-08-22  8:48 ` rguenth at gcc dot gnu.org [this message]
2012-08-22  8:56 ` steven at gcc dot gnu.org
2012-08-22  9:18 ` rguenth at gcc dot gnu.org
2012-08-23 18:01 ` matt at use dot net
2012-09-06 15:21 ` rguenth at gcc dot gnu.org
2012-09-20 10:16 ` jakub at gcc dot gnu.org
2013-04-10  8:11 ` rguenth at gcc dot gnu.org
2013-04-11  7:59 ` rguenth at gcc dot gnu.org
2014-05-06 11:58 ` rguenth at gcc dot gnu.org

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