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From: "dorit at gcc dot gnu dot org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug middle-end/35343] Sum-reduction loop not recognized
Date: Mon, 25 Feb 2008 10:22:00 -0000 [thread overview]
Message-ID: <20080225102149.15542.qmail@sourceware.org> (raw)
In-Reply-To: <bug-35343-9436@http.gcc.gnu.org/bugzilla/>
------- Comment #1 from dorit at gcc dot gnu dot org 2008-02-25 10:21 -------
(In reply to comment #0)
> It is beneficial to unroll reduction loop (and split the reduction target) to
> reduce dependence height due to recurrence, but GCC does not perform such
> optimization (-O3 -fno-tree-vectorize)
it does, if you use -fvariable-expansion-in-unroller -funroll-loops
(this splits the reduction target into 2 accumulators. For more agressive
spiltting you can use --param max-variable-expansions-in-unrolle=[n])
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35343
next prev parent reply other threads:[~2008-02-25 10:22 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2008-02-24 4:28 [Bug middle-end/35343] New: " xinliangli at gmail dot com
2008-02-24 21:56 ` [Bug middle-end/35343] " rguenth at gcc dot gnu dot org
2008-02-25 10:22 ` dorit at gcc dot gnu dot org [this message]
2008-02-25 21:37 ` xinliangli at gmail dot com
2008-12-29 6:32 ` [Bug middle-end/35343] Sum-reduction loop not recognized (enable -fvariable-expansion-in-unroller by default) pinskia at gcc dot gnu dot org
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