From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1759199AbZGCU5W (ORCPT ); Fri, 3 Jul 2009 16:57:22 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1756747AbZGCU5P (ORCPT ); Fri, 3 Jul 2009 16:57:15 -0400 Received: from mail-out.m-online.net ([212.18.0.9]:52620 "EHLO mail-out.m-online.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1756083AbZGCU5O (ORCPT ); Fri, 3 Jul 2009 16:57:14 -0400 From: Andreas Schwab To: Brad Boyer Cc: kernel mailz , linuxppc-dev@ozlabs.org, gcc-help@gcc.gnu.org, linux-kernel@vger.kernel.org Subject: Re: Inline assembly queries [2] References: <20090703174031.GA12410@cynthia.pants.nu> X-Yow: I am a traffic light, and Alan Ginsberg kidnapped my laundry in 1927! Date: Fri, 03 Jul 2009 22:57:12 +0200 In-Reply-To: <20090703174031.GA12410@cynthia.pants.nu> (Brad Boyer's message of "Fri, 3 Jul 2009 10:40:31 -0700") Message-ID: User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/23.0.95 (gnu/linux) MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Brad Boyer writes: > On Fri, Jul 03, 2009 at 12:14:41PM +0530, kernel mailz wrote: >> b. using m or Z with a memory address. I tried replacing m/Z but no change >> Is there some guideline ? >> gcc documentation says Z is obsolete. Is m/Z replaceable ? > > No idea. I don't remember ever seeing 'Z' used in anything. Maybe somebody > else remembers what it used to mean. The 'Z' constraint is required for a memory operand for insns that don't have an update form (which would be selected by the %U modifier). It should only be used together with the %y operand modifier, which makes sure that the first register is never 0. If the 'm' constraint were used the operand could contain a pre-in/decrement operation, and without %U the side effect would be lost. Andreas. -- Andreas Schwab, schwab@linux-m68k.org GPG Key fingerprint = 58CA 54C7 6D53 942B 1756 01D3 44D5 214B 8276 4ED5 "And now for something completely different."