Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1755765Ab0DNOcK (ORCPT ); Wed, 14 Apr 2010 10:32:10 -0400 Received: from mx1.redhat.com ([209.132.183.28]:32711 "EHLO mx1.redhat.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755521Ab0DNOcH (ORCPT ); Wed, 14 Apr 2010 10:32:07 -0400 Message-ID: <4BC5D19A.8000605@redhat.com> Date: Wed, 14 Apr 2010 17:30:50 +0300 From: Avi Kivity User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.1.9) Gecko/20100330 Fedora/3.0.4-1.fc12 Thunderbird/3.0.4 MIME-Version: 1.0 To: David Howells CC: Linus Torvalds , Matthew Wilcox , Ralf Baechle , mingo@elte.hu, tglx@linutronix.de, linux-arch@vger.kernel.org, linux-kernel@vger.kernel.org Subject: Re: [PATCH 1/3] X86: Optimise fls(), ffs() and fls64() References: <20100406133026.GD20577@parisc-linux.org> <20100326144241.8583.95617.stgit@warthog.procyon.org.uk> <28287.1269625325@redhat.com> <20100326175827.GD20055@linux-mips.org> <17213.1271245760@redhat.com> In-Reply-To: <17213.1271245760@redhat.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 925 Lines: 25 On 04/14/2010 02:49 PM, David Howells wrote: > Matthew Wilcox wrote: > > >> I don't know whether we can get it /documented/, but the architect I >> asked said "We'll never get away with reverting to the older behavior, >> so in essence the architecture is set to not overwrite." >> > Does that mean we can rely on it? Linus? > Even if Intel processors behave that way, other processors (real and emulated) use those manuals as a specification. Emulated processors are unlikely to touch an undefined register, but real processors may. (qemu tcg appears not to touch the output) -- error compiling committee.c: too many arguments to function -- 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/