linux-kernel - Re: kernel + gcc 4.1 = several problems

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Message-ID: <Pine.LNX.4.63.0701031128420.14187@alpha.polcom.net>
Date:	Wed, 3 Jan 2007 11:32:00 +0100 (CET)
From:	Grzegorz Kulewski <kangur@...com.net>
To:	Alan <alan@...rguk.ukuu.org.uk>
Cc:	Mikael Pettersson <mikpe@...uu.se>, s0348365@....ed.ac.uk,
	torvalds@...l.org, 76306.1226@...puserve.com, akpm@...l.org,
	bunk@...sta.de, greg@...ah.com, linux-kernel@...r.kernel.org,
	yanmin_zhang@...ux.intel.com
Subject: Re: kernel + gcc 4.1 = several problems

On Wed, 3 Jan 2007, Alan wrote:
> The proper fix for all of this mess is to fix the gcc compiler suite to
> actually generate i686 code when told to use i686. CMOV is an optional
> i686 extension which gcc uses without checking. In early PIV days it made
> sense but on modern processors CMOV is so pointless the bug should be
> fixed. At that point an i686 kernel would contain i686 instructions and
> actually run on all i686 processors ending all the i586 pain for most
> users and distributions.

Could you explain why CMOV is pointless now? Are there any benchmarks 
proving that?


Thanks,

Grzegorz Kulewski

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