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To: gentoo-performance@g.o
From: Paul de Vrieze <pauldv@g.o>
Subject: Re: best Gcc compilzation flags
Date: Mon, 22 Nov 2004 10:23:59 +0100
On Monday 22 November 2004 08:47, Matthew Groote-Kirsch wrote:
> I settled on:
>
> CFLAGS="-O2 -frename-registers -ftracer -funroll-loops
> -fomit-frame-pointer -pipe -march=athlon"
>
> Looking around on the forums a bit, it seemed like -O2 is recommended
> over -O3.

Aditionally there have been times when -O2 has been shown to be faster 
than -O3. Similarly, the -funroll-loops might actually create slower code 
due to more cache misses. Modern processors are complex systems where 
nondeterministic parts like the cache can have a significant impact on 
performance. The only real way to determine what is fastest would be to 
run real-world (not simple loops) tests (with timing) for each option 
combination.

Paul

-- 
Paul de Vrieze
Gentoo Developer
Mail: pauldv@g.o
Homepage: http://www.devrieze.net
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References:
best Gcc compilzation flags
-- Server Tuneup mission
Re: best Gcc compilzation flags
-- Matthew Groote-Kirsch
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Implementing Optimization for Database Server - Nice story btw :+P


Updated Jun 17, 2009

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