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[Bug rtl-optimization/33928] [4.3/4.4/4.5 Regression] 30% performance slowdown in floating-point code caused by r118475
- From: "lucier at math dot purdue dot edu" <gcc-bugzilla at gcc dot gnu dot org>
- To: gcc-bugs at gcc dot gnu dot org
- Date: 7 May 2009 16:31:44 -0000
- Subject: [Bug rtl-optimization/33928] [4.3/4.4/4.5 Regression] 30% performance slowdown in floating-point code caused by r118475
- References: <bug-33928-271@http.gcc.gnu.org/bugzilla/>
- Reply-to: gcc-bugzilla at gcc dot gnu dot org
------- Comment #75 from lucier at math dot purdue dot edu 2009-05-07 16:31 -------
Subject: Re: [4.3/4.4/4.5 Regression] 30% performance slowdown in
floating-point code caused by r118475
On May 7, 2009, at 12:21 PM, bonzini at gnu dot org wrote:
> ------- Comment #74 from bonzini at gnu dot org 2009-05-07 16:21
> -------
> Ok. One step at a time. :-) To recap, here is the situation:
>
> - that scheduling is necessary now and not in 4.2.x, probably is
> just a matter
> of luck
If you mean -fschedule-insns2, it has always been part of the options
list.
> - at least we have a set of options providing good performance on this
> testcase, and guidance towards better tuning of the various
> problematic
> optimizations
OK, but -fforward-propagate is not viable in general for these
machine-generated codes.
>
Brad
--
http://gcc.gnu.org/bugzilla/show_bug.cgi?id=33928