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[Bug rtl-optimization/42511] [4.5 Regression] bootstrap error in stage3 on alpha-linux-gnu
- From: "ebotcazou at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 7 Jan 2010 07:39:43 -0000
- Subject: [Bug rtl-optimization/42511] [4.5 Regression] bootstrap error in stage3 on alpha-linux-gnu
- References: <bug-42511-5724@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #21 from ebotcazou at gcc dot gnu dot org 2010-01-07 07:39 -------
> Because at the point of propagation, propagated constant _is_ equal to
> whatever REG_EQUAL says. Removing this note at the point of propagation
> would IMO disable much more optimization opportunities.
What kind of opportunities exactly? The insn is more precise that the note.
> BTW: This fixup happens in very rare occasions. Although the loop looks scary,
> it usually processes very small BBs (I didn't found the case where more than
> one assignment was moved at the top of the test BB.
Yes, but removing REG_EQUAL notes pointing to constants seems a bad idea.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42511