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Date:	Tue, 10 Nov 2009 23:01:26 +0100
From:	Matteo Croce <>
To:	Pavel Machek <>
Cc:	Willy Tarreau <>, "H. Peter Anvin" <>,
	Avi Kivity <>,
	Alan Cox <>,
	Sven-Haegar Koch <>,
	Ingo Molnar <>,
Subject: Re: i686 quirk for AMD Geode

On Tue, Nov 10, 2009 at 9:54 PM, Pavel Machek <> wrote:
> Hi!
>> Indeed, but there is a difference between [cmpxchg, bswap, cmov, nopl]
>> on one side and [sse*] on the other : distros are built assuming the
>> former are always available while they are not always. And the
>> distro
> Well, fix the distros...

$ objdump -d |grep cmov -c

and ask the companies to fix their binaries too?

>> which make the difference have to provide an dedicated build for earlier
>> systems just for compatibility. SSE*, 3dnow* etc... are only used by a
>> handful of media players/converters/encoders which are able to detect
>> themselves what to use and already have the necessary fallbacks because
>> these instruction sets vary too much between processors and vendors.
>> One could argue that cmpxchg/bswap/xadd are supported by 486 and that
>> implementing them for 386 is almost useless now (though it costs almost
>> nothing to provide them, I did a few years ago).
>> CMOV/NOPL are rarely used, thus have no reason to cause a massive
>> performance drop, but are frequent enough (at least cmov) for almost
> *One* CMOV in the inner loop will make your performance go down 20x.

Still better than a browser crashing for a SIGILL
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