Date: Fri, 7 Mar 2008 15:09:40 +0100 (CET)
From: Michael Matz <matz@suse.de>
To: Andi Kleen <andi@firstfloor.org>
Cc: "H. Peter Anvin" <hpa@zytor.com>,
       Richard Guenther <richard.guenther@gmail.com>,
       Joe Buck <Joe.Buck@synopsys.com>, Andrew Haley <aph@redhat.com>,
       Aurelien Jarno <aurelien@aurel32.net>, linux-kernel@vger.kernel.org,
       gcc@gcc.gnu.org
Subject: Re: Linux doesn't follow x86/x86-64 ABI wrt direction flag
In-Reply-To: <20080306220610.GB31833@one.firstfloor.org>
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Hi,

On Thu, 6 Mar 2008, Andi Kleen wrote:

> To be realistic it is very unlikely anybody will measure a difference 
> from a few more or a few less clds in a program.

Only an assumption, and in fact wrong.  See upthread for a benchmark.  
IIRC Uros also made measurements to justify the removal of cld (on P4 I 
think), where it helps tremendously on small memcpy loops.


Ciao,
Michael.
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