Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S934523AbZARRim (ORCPT ); Sun, 18 Jan 2009 12:38:42 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1765638AbZARRic (ORCPT ); Sun, 18 Jan 2009 12:38:32 -0500 Received: from mx3.mail.elte.hu ([157.181.1.138]:48107 "EHLO mx3.mail.elte.hu" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1762473AbZARRic (ORCPT ); Sun, 18 Jan 2009 12:38:32 -0500 Date: Sun, 18 Jan 2009 18:38:20 +0100 From: Ingo Molnar To: Brian Gerst Cc: Tejun Heo , linux-kernel@vger.kernel.org Subject: Re: [PATCH 12/17] x86-64: Use absolute displacements for per-cpu accesses. Message-ID: <20090118173820.GA14356@elte.hu> References: <1232115396-26367-6-git-send-email-brgerst@gmail.com> <1232115396-26367-7-git-send-email-brgerst@gmail.com> <1232115396-26367-8-git-send-email-brgerst@gmail.com> <1232115396-26367-9-git-send-email-brgerst@gmail.com> <1232115396-26367-10-git-send-email-brgerst@gmail.com> <1232115396-26367-11-git-send-email-brgerst@gmail.com> <1232115396-26367-12-git-send-email-brgerst@gmail.com> <4972AE71.2030506@kernel.org> <73c1f2160901172036m4d7bb4f8i50b6a5185a63e95@mail.gmail.com> <20090118164246.GA28423@elte.hu> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <20090118164246.GA28423@elte.hu> User-Agent: Mutt/1.5.18 (2008-05-17) 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 Content-Length: 1307 Lines: 36 * Ingo Molnar wrote: > > * Brian Gerst wrote: > > > On Sat, Jan 17, 2009 at 11:22 PM, Tejun Heo wrote: > > > > > Hello, Brian. > > > > > > Brian Gerst wrote: > > > > Accessing memory through %gs should not use rip-relative addressing. > > > > Adding a P prefix for the argument tells gcc to not add (%rip) to > > > > the memory references. > > > > > > Nice catch. I dind't know about the P prefix thing. It also is used > > > in other places too. Hmmm... I can't find anything about the P > > > argument prefix in the gcc info page (4.3). Any ideas where I can > > > find some information about it? It's a bit weird that it's not a > > > constraint prefix but an argument one. > > > > The only place I could confirm that it works is in the gcc source > > itself, and even there it's not well documented. > > does %P support go back as far as gcc 3.2 (the earliest GCC we still > support)? update: Brian pointed it out off-list that switch_to() already uses %P, so we already rely on it. Ingo -- 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/