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[Bug target/56309] -O3 optimizer generates conditional moves instead of compare and branch resulting in almost 2x slower code
- From: "jakub at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Fri, 15 Feb 2013 07:14:44 +0000
- Subject: [Bug target/56309] -O3 optimizer generates conditional moves instead of compare and branch resulting in almost 2x slower code
- Auto-submitted: auto-generated
- References: <bug-56309-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56309
Jakub Jelinek <jakub at gcc dot gnu.org> changed:
What |Removed |Added
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CC| |jakub at gcc dot gnu.org
--- Comment #22 from Jakub Jelinek <jakub at gcc dot gnu.org> 2013-02-15 07:14:44 UTC ---
Yeah. We need to either find another way how to present vectorizer with the
ifconverted statement (perhaps similar to how pattern matching works, I think
if-conversion only handles inner-most loops, so maybe just as an alternative
gimple_seq for the single bb of the loop body?), or we need some kind of
if-unconversion pass.
See the http://gcc.gnu.org/ml/gcc-patches/2012-11/msg01659.html patch which
contains much more limited version of if-unconversion, unfortunately it is
going to be harder to handle more complex conditions efficiently.