[Bug tree-optimization/18694] [4.0 regression] loop miscompilation at -O1 (-ftree-ch)
------- Additional Comments From kazu at cs dot umass dot edu 2004-12-10 18:53 -------
Subject: Re: [4.0 regression] loop
miscompilation at -O1 (-ftree-ch)
Hi Zdenek,
> > > 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.
Right. If we have dominator information available,
mark_dfs_back_edges does nothing but duplicates a part of what the
dominator information has to offer. (It's not that
mark_dfs_back_edges is very flow, but ....)
Kazu Hirata
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=18694
------- You are receiving this mail because: -------
You are on the CC list for the bug, or are watching someone who is.
Reply to: