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From: "xunxun1982 at gmail dot com" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug tree-optimization/50905] Gcc4.6.x's -ftree-parallelize-loops is effective only when using "-O2/-O3 -ffast-math"
Date: Fri, 28 Oct 2011 19:54:00 -0000 [thread overview]
Message-ID: <bug-50905-4-IajOyqr5pL@http.gcc.gnu.org/bugzilla/> (raw)
In-Reply-To: <bug-50905-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50905
xunxun <xunxun1982 at gmail dot com> changed:
What |Removed |Added
----------------------------------------------------------------------------
Status|RESOLVED |UNCONFIRMED
Resolution|INVALID |
--- Comment #2 from xunxun <xunxun1982 at gmail dot com> 2011-10-28 19:53:47 UTC ---
(In reply to comment #1)
> >Am I right?
> Yes but the reason comes down to fp math is not associative which means it is
> impossible to do reductions with fp math unless you have -ffast-math (or really
> -fassociative-math) turned on.
But -ffast-math -ftree-parallelize-loops=2 is also no use.
We must combine -ffast-math and -O2/-O3.
next prev parent reply other threads:[~2011-10-28 19:54 UTC|newest]
Thread overview: 5+ messages / expand[flat|nested] mbox.gz Atom feed top
2011-10-28 19:37 [Bug tree-optimization/50905] New: " xunxun1982 at gmail dot com
2011-10-28 19:45 ` [Bug tree-optimization/50905] " pinskia at gcc dot gnu.org
2011-10-28 19:54 ` xunxun1982 at gmail dot com [this message]
2011-10-28 20:07 ` pinskia at gcc dot gnu.org
2011-10-28 20:14 ` xunxun1982 at gmail dot com
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