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

["kazu at cs dot umass dot edu" <gcc-bugzilla at gcc dot gnu dot org>]

------- Additional Comments From kazu at cs dot umass dot edu  2004-12-09 19:22 -------
Jeff,

With my new patch, stmt.i gets one fewer jump threading opportunities
(compared to what the vanilla mainline produces).
So it's very plausible that we are miscompiling stmt.c quietly.

This difference comes from DOM1 while compiling stmt.c:expand_asm_operands.

I hope this helps.

With my old patch, I got one more jump threading opportunity
(compared to what the vanilla mainline produces).
It was one of loop.i, stmt.i, and predict.i.

Since my old patch gives less information to lookup routines,
the increase in the number of opportunity seems very strange.

If you want, I can find out which of DOM[123] is causing this problem
on which function in which file for you.


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