From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759322AbXLQN0r (ORCPT ); Mon, 17 Dec 2007 08:26:47 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1755217AbXLQN0k (ORCPT ); Mon, 17 Dec 2007 08:26:40 -0500 Received: from mx2.mail.elte.hu ([157.181.151.9]:34154 "EHLO mx2.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754784AbXLQN0j (ORCPT ); Mon, 17 Dec 2007 08:26:39 -0500 Date: Mon, 17 Dec 2007 14:26:19 +0100 From: Ingo Molnar To: Jan Beulich Cc: tglx@linutronix.de, mingo@redhat.com, hpa@zytor.com, linux-kernel@vger.kernel.org, Andrew Morton Subject: Re: [PATCH] x86-64: make pda's cpunumber and nodenumber unsigned Message-ID: <20071217132619.GB1870@elte.hu> References: <47610530.76E4.0078.0@novell.com> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <47610530.76E4.0078.0@novell.com> User-Agent: Mutt/1.5.17 (2007-11-01) X-ELTE-VirusStatus: clean X-ELTE-SpamScore: -1.5 X-ELTE-SpamLevel: X-ELTE-SpamCheck: no X-ELTE-SpamVersion: ELTE 2.0 X-ELTE-SpamCheck-Details: score=-1.5 required=5.9 tests=BAYES_00 autolearn=no SpamAssassin version=3.2.3 -1.5 BAYES_00 BODY: Bayesian spam probability is 0 to 1% [score: 0.0000] Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org * Jan Beulich wrote: > This generally allows better code to be generated, since the zero- > extension during 32-bit operations comes for free (needed when the > result is used as array index or similar), whereas sign extension must > be done explicitly and frequently requires a one byte larger > instruction due to the necessary rex64 prefix. good catch! Applied your patch to x86.git - queued it up for v2.6.25. I bet there are tons of other instances where we use signed instead of unsigned and get worse code generation. Ingo