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[Bug optimization/13191] [64bit] Redundant sign extends
- From: "kazu at cs dot umass dot edu" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 3 Mar 2004 23:41:34 -0000
- Subject: [Bug optimization/13191] [64bit] Redundant sign extends
- References: <20031125235354.13191.amodra@gcc.gnu.org>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Additional Comments From kazu at cs dot umass dot edu 2004-03-03 23:41 -------
I've implemented an ad hoc rule in tree-ssa like so: Given
b = (type1) a;
c = (type2) b;
I try to eliminate b if b is dead and I can say "c = (type3) a".
It turns out at the end of tree-ssa optimizations, I seem to get two variables
containing the essentially same value, just in different types.
So, yes, the placement is important. I'm reading the paper Falk pointed.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=13191