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[Bug tree-optimization/35653] [4.3/4.4 Regression]: gcc-4.3 -O3/-ftree-vectorize regression: incorrect code generation
- From: "victork at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 25 Mar 2008 10:47:53 -0000
- Subject: [Bug tree-optimization/35653] [4.3/4.4 Regression]: gcc-4.3 -O3/-ftree-vectorize regression: incorrect code generation
- References: <bug-35653-15165@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #15 from victork at gcc dot gnu dot org 2008-03-25 10:47 -------
Just to make clear my previous comment. I think that it *is* possible that
original code violates c/c++ aliasing rules, but the example given by Richard
Guenther is not-vectorized since currently we do not vectorize structures with
a single member. We may want to open a missed-optimization bug report, but this
problem is not related to the possible bug in the subject.
Actually, the possible problem rises only when we try enforce alignment using
loop peeling. If we enforce alignment using loop versioning, a run-time check
will discover misalignment and a non-vectorized version of loop will be
executed.
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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35653