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[Bug rtl-optimization/53176] [4.8 Regression] gcc.target/i386/movbe-2.c and gcc.dg/lower-subreg-1.c
- From: "ubizjak at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: Wed, 02 May 2012 17:58:17 +0000
- Subject: [Bug rtl-optimization/53176] [4.8 Regression] gcc.target/i386/movbe-2.c and gcc.dg/lower-subreg-1.c
- Auto-submitted: auto-generated
- References: <bug-53176-4@http.gcc.gnu.org/bugzilla/>
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53176
--- Comment #3 from Uros Bizjak <ubizjak at gmail dot com> 2012-05-02 17:58:17 UTC ---
(In reply to comment #1)
> Lower-subreg is most likely a terrible transformation to do on later x86s but
> is likely to have been useful on the earlier ones. So this regression is
> likely a good thing.
Can you please suggest, what should be added to leave decisions as they were?
We would like to fine tune the cost model in a controlled way, supported by the
data from benchmarks and applications. Forced under-the-hood changes to cost
model just don't fit this approach.