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[Bug tree-optimization/18694] [4.0 regression] loop miscompilation at -O1 (-ftree-ch)



------- 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.


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18694

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