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[Bug tree-optimization/18694] [4.0 regression] loop miscompilation at -O1 (-ftree-ch)
- From: "rakdver at atrey dot karlin dot mff dot cuni dot cz" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 10 Dec 2004 18:38:08 -0000
- Subject: [Bug tree-optimization/18694] [4.0 regression] loop miscompilation at -O1 (-ftree-ch)
- References: <20041127224610.18694.falk@debian.org>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Additional Comments From rakdver at atrey dot karlin dot mff dot cuni dot cz 2004-12-10 18:38 -------
Subject: Re: [4.0 regression] loop miscompilation at -O1 (-ftree-ch)
> > or simply use dominated_by_p, which is not too expensive -
> > only a couple of "if" statements, assuming the dominator infomatino is
> > available.
> EDGE_DFS_BACK would have been more efficient. But I don't think it's
> 100% safe right now.
not that much. Since you do not change cfg in the progress of dominator
optimizations, you should have fast query structure for dominators
up-to-date; i.e. testing whether a basic block dominates other takes only
two comparisons of integers.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18694