[Bug tree-optimization/40676] [4.5 Regression] internal compiler error: verify_ssa error: definition in block 5 does not dominate use in block 7

[hubicka at ucw dot cz]

------- Comment #5 from hubicka at ucw dot cz  2009-07-11 22:45 -------
Subject: Re:  [4.5 Regression] internal compiler error: verify_ssa error:
definition in block 5 does not dominate use in block 7

Thinking about this more, we change here dominance relation in
not-so-obvious way.  It is not really textbook case with presence of
both abnormal edges that might prevent forwarding consistently
everything across the empty BBs and virtual operands that may remain in
the BBs otherwise empty.

I think we need
1) forward the edges in the tree-ssa-dce itself (i.e. don't do the edge
forwarding only when control flow stmt becomes dead but for every edge
leading to dead BB that is not abnormal)
2) for empty BBs that remains in the program (only reason would be
because they are destination of abnormal edge), send all virtual PHIs
for updating since we can not be sure dominance relations are preserved.

Sounds sane?  If so, I will give it a try tomorrow.

Honza


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=40676