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Re: PR19039 causes regression of 3.9% in SPEC int
- From: "Giovanni Bajo" <giovannibajo at libero dot it>
- To: "Steven Bosscher" <stevenb at suse dot de>,"Andrew MacLeod" <amacleod at redhat dot com>
- Cc: "Mostafa Hagog" <MUSTAFA at il dot ibm dot com>,<gcc at gcc dot gnu dot org>,"Roger Sayle" <roger at eyesopen dot com>
- Date: Fri, 24 Dec 2004 17:32:49 +0100
- Subject: Re: PR19039 causes regression of 3.9% in SPEC int
- References: <Pine.LNX.4.44.0412240256330.24989-100000@www.eyesopen.com> <200412241426.29440.stevenb@suse.de>
Steven Bosscher <stevenb@suse.de> wrote:
>> Would you mind posting your RTL-based loop header copying patch to
>> gcc-patches? Not only might it be catching more optimizations than
>> out-of-ssa is causing, but as a solution it might be more suitable
>> for gcc 4.0 (depending upon compile-time performance impact,
>> ugliness, intrusivenss, corrections to Andrew's "quick fix", etc...).
>
> I'm unimpressed by either RTL loop header copying, or Andrew's fix,
> both just paper over the underlying problem. The real problem is
> that apparently we are creating a situation where copy propagation
> makes coalescing impossible. Fix that and you don't get the extra
> basic block - bug fixed, done.
Yes, but as you said, we ought to fix this one way or another in 4.0. Mostafa's
patch is at least written and tested, and it shows a big improvement. Andrew,
as the original author of the out-of-ssa pass, do you believe that this bug
(http://gcc.gnu.org/PR19038) can be properly fixed in time for 4.0?
Giovanni Bajo