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[Bug tree-optimization/20643] [4.0/4.1/4.2 Regression] Tree loop optimizer does worse job than RTL loop optimizer
- From: "rakdver at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 17 Jul 2006 11:54:48 -0000
- Subject: [Bug tree-optimization/20643] [4.0/4.1/4.2 Regression] Tree loop optimizer does worse job than RTL loop optimizer
- References: <bug-20643-3107@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #13 from rakdver at gcc dot gnu dot org 2006-07-17 11:54 -------
(In reply to comment #12)
> The test case in comment #11 looks like a classic store motion opportunity to
> me. GCC 3.3 performs the store motion, GCC 4.2 r115467 does not.
>
> Zdenek, I thought tree-ssa-lim should be able to do store motion in loops?
Yes, however again, the alias analysis does not tell it that a[0] does not
alias a[1]; once that is fixed, tree-ssa-lim should work just fine.
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20643