Date: Wed, 10 Mar 1999 01:11:45 +0100
To: "pgcc AT delorie DOT com" <pgcc AT delorie DOT com>
Subject: Re: Optimizations questions
Message-ID: <19990310011145.N360@cerebro.laendle>
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In-Reply-To: <Pine.LNX.4.04.9903091514430.11608-100000@coffee.phys.unm.edu>; from Dmitri A. Sergatskov on Tue, Mar 09, 1999 at 03:41:52PM -0700
X-Operating-System: Linux version 2.2.2 (marc AT cerebro) (gcc driver version pgcc-2.93.04 19990131 (gcc2 ss-980929 experimental) executing gcc version 2.7.2.3) 
From: Marc Lehmann <pcg AT goof DOT com>
Reply-To: pgcc AT delorie DOT com
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On Tue, Mar 09, 1999 at 03:41:52PM -0700, Dmitri A. Sergatskov wrote:
> On Tue, 9 Mar 1999, Marc Lehmann wrote:
> 
> > On Mon, Mar 08, 1999 at 08:45:32PM -0600, Steve Bergman wrote:
> > > I'm getting ready to recompile my RH5.2 system and 2.2.2 kernel.  I have an
> > > AMDK6-2/300.  Would "-O6 -march=amdk6 -mcpu=amdk6" be reasonable options to set
> > > in rpmrc?  What is the status of "-fstrength-reduce" and "-funroll-all-loops"
> > 
> > strength-reduce is fixed. it was never broken enough to warrant turning it
> > off in the first place.
> > 
> 
> The question with strength-reduce popped up few times on egcs list and
> Michael Meissner recommended to turn it off for all register starved
> CPU archs (which I think means all x86 CPUs).

pgcc should be able to compensate. even more, you can't do loop unrolling
without biv+giv analysis (done by the strength-reduce opt).

So, unless benchmarks claim otherwise, -fstrength-reduce should not be turned
off (with pgcc, that is).

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