[Bug tree-optimization/50905] Gcc4.6.x's -ftree-parallelize-loops is effective only when using "-O2/-O3 -ffast-math"

[xunxun1982 at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50905

xunxun <xunxun1982 at gmail dot com> changed:

           What    |Removed                     |Added
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             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.