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[Bug target/31897] [4.3 Regression] 30% speed regression with -m32 on Opteron with rnflow
- From: "ubizjak at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 4 Jul 2007 12:29:36 -0000
- Subject: [Bug target/31897] [4.3 Regression] 30% speed regression with -m32 on Opteron with rnflow
- References: <bug-31897-13404@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #3 from ubizjak at gmail dot com 2007-07-04 12:29 -------
(In reply to comment #2)
> Can't reproduce this, gcc 4.3 actually seems to be faster (tests done on Intel
> quadcore Core2):
On core2 the bug doesn't trigger, but it shows on FC4 with:
vendor_id : GenuineIntel
cpu family : 15
model : 4
model name : Intel(R) Xeon(TM) CPU 3.60GHz
stepping : 10
cpu MHz : 3600.970
cache size : 2048 KB
This is one of most mysterious bugs I've ever seen. The _idamax routine is
exactly the same for both builds, but it shows such a difference. I have
analyzed this with cachegrind but nothing sticks out there.
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=31897