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[Bug tree-optimization/42586] New: load-modify-store on x86 should be \ single instruction
- From: "pinskia at gcc dot gnu dot org" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 3 Jan 2010 07:07:27 -0000
- Subject: [Bug tree-optimization/42586] New: load-modify-store on x86 should be \ single instruction
- References: <bug-42586-7834@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #12 from pinskia at gcc dot gnu dot org 2010-01-03 07:07 -------
(In reply to comment #11)
> My naive assumption was that the read-modify-write pattern is handled late by
> the RTL backend when generating instructions while SRA is somewhere early in
> the tree oriented middle end.
Well the other issue is that only post-reload-cse deletes the load/stores
without SRA doing what needs to be done. And since the deletion happens so
late, combine does not combine the three instruction which does the
read-modify-write. :).
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42586