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[Bug tree-optimization/37916] [4.2/4.3/4.4 Regression] SSA names causing register pressure; unnecessarily many simultaneously "live" names.
- From: "hp at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 27 Oct 2008 16:09:50 -0000
- Subject: [Bug tree-optimization/37916] [4.2/4.3/4.4 Regression] SSA names causing register pressure; unnecessarily many simultaneously "live" names.
- References: <bug-37916-507@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #12 from hp at gcc dot gnu dot org 2008-10-27 16:09 -------
I had an "old" native x86_64-unknown-linux-gnu tree around from
[trunk revision 139963], and I see the corresponding effect there.
Of all four combinations of {,-fno-tree-reassoc} {,-fschedule-insns
-fschedule-insns2}, together with -fno-ivopts -fno-reorder-blocks -fno-gcse, it
was plain -fno-tree-reassoc (no scheduling) that produces the smallest
stack-frame and *at a glance* smaller, faster code. (FWIW, I'm a bit surprised
to see that -fschedule-insns -fschedule-insns2 is not the default for this
arch.)
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=37916