Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1750714AbXACLwQ (ORCPT ); Wed, 3 Jan 2007 06:52:16 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1750719AbXACLwQ (ORCPT ); Wed, 3 Jan 2007 06:52:16 -0500 Received: from srv5.dvmed.net ([207.36.208.214]:50996 "EHLO mail.dvmed.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750714AbXACLwP (ORCPT ); Wed, 3 Jan 2007 06:52:15 -0500 Message-ID: <459B98C9.1040309@garzik.org> Date: Wed, 03 Jan 2007 06:51:37 -0500 From: Jeff Garzik User-Agent: Thunderbird 1.5.0.9 (X11/20061219) MIME-Version: 1.0 To: Grzegorz Kulewski CC: Alan , Mikael Pettersson , s0348365@sms.ed.ac.uk, torvalds@osdl.org, 76306.1226@compuserve.com, akpm@osdl.org, bunk@stusta.de, greg@kroah.com, linux-kernel@vger.kernel.org, yanmin_zhang@linux.intel.com Subject: Re: kernel + gcc 4.1 = several problems References: <200701030212.l032CDXe015365@harpo.it.uu.se> <20070103102944.09e81786@localhost.localdomain> In-Reply-To: Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Score: -4.3 (----) X-Spam-Report: SpamAssassin version 3.1.7 on srv5.dvmed.net summary: Content analysis details: (-4.3 points, 5.0 required) Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1027 Lines: 26 Grzegorz Kulewski wrote: > 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? In theory modern processors should have no trouble converting a test/move sequence into the same uops generated by a cmov instruction, for one. Jeff - To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@vger.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/