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[Bug middle-end/27986] [4.0/4.1/4.2 Regression] jump to middle of loop on entry with using old version of an variable
- From: "amacleod at redhat dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 2 Oct 2006 14:01:26 -0000
- Subject: [Bug middle-end/27986] [4.0/4.1/4.2 Regression] jump to middle of loop on entry with using old version of an variable
- References: <bug-27986-5748@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #5 from amacleod at redhat dot com 2006-10-02 14:01 -------
I guess you can flatten the goto slightly.
this is still something that is not really in the scope of out of ssa. part of
the root of this problem is that the PHI is really just a copy, but the fact
that it remains a PHI prevents anyone from moving it.
Its possible that we might be able to do something about it with some of the
RABLET work. it doesnt really reduce any register pressure, but we might be
able to recoginze that it flatten the cfg a bit... I'm not crazy about putting
it there tho.
Of course, any optimization could do the same thing. A quick pass to look for
these cases and transform those PHIs into copies at the appropriate place would
accomplish the same thing.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=27986