[Bug tree-optimization/23286] missed fully redundant expression

[steven at gcc dot gnu dot org]

------- Comment #16 from steven at gcc dot gnu dot org  2008-11-23 13:07 -------
Created an attachment (id=16751)
 --> (http://gcc.gnu.org/bugzilla/attachment.cgi?id=16751&action=view)
Proof-of-concept patch

It is not terribly complicated to add hoisting to tree-ssa-pre.c.  I have
attached the result of roughly half a day of hacking.  It is a proof-of-concept
patch that demonstrates how hoisting could be added.  It's not finished,
tested, or even correct ;-) but it shows the general idea.  For a
"production-quality" version, one would have to make sure not to hoist
expressions up too far (e.g. not further up than above the first block that
generates the expression).


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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23286