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[Bug tree-optimization/50905] Gcc4.6.x's -ftree-parallelize-loops is effective only when using "-O2/-O3 -ffast-math"
- From: "xunxun1982 at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Fri, 28 Oct 2011 19:53:47 +0000
- Subject: [Bug tree-optimization/50905] Gcc4.6.x's -ftree-parallelize-loops is effective only when using "-O2/-O3 -ffast-math"
- Auto-submitted: auto-generated
- References: <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.