From owner-svn-src-all@FreeBSD.ORG  Fri Jul 27 07:36:28 2012
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Date: Fri, 27 Jul 2012 17:36:19 +1000 (EST)
From: Bruce Evans <brde@optusnet.com.au>
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To: Luigi Rizzo <rizzo@iet.unipi.it>
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Cc: svn-src-head@FreeBSD.org, Roman Divacky <rdivacky@FreeBSD.org>,
	src-committers@FreeBSD.org, Luigi Rizzo <luigi@FreeBSD.org>,
	svn-src-all@FreeBSD.org
Subject: Re: svn commit: r238818 - head/sys/dev/netmap
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On Fri, 27 Jul 2012, Luigi Rizzo wrote:

> On Thu, Jul 26, 2012 at 11:39:59PM +0200, Roman Divacky wrote:
>> Why dont you use __builtin_prefetch() ?
>
> ignorance :)
>
> thanks for the pointer, i'll look at it.
> i suppose it works for clang too ?

Even gcc-3.3.1 has it (I expected it not to).  And it works quite
well (defaults to nothing from -mi386, and gives prefetcht0 for
-march=athlon-xp and later).  Other builtins that I have tried
didn't work so well (IIRC, many generate a call to a library
function instead of nothing, when the CPU or compiler doesn't
really support them).

Bruce