From mboxrd@z Thu Jan  1 00:00:00 1970
Return-Path: <gcc-return-158217-listarch-gcc=gcc.gnu.org@gcc.gnu.org>
Received: (qmail 32419 invoked by alias); 23 Nov 2009 09:17:20 -0000
Received: (qmail 32395 invoked by uid 22791); 23 Nov 2009 09:17:18 -0000
X-SWARE-Spam-Status: No, hits=-2.5 required=5.0 	tests=AWL,BAYES_00,SPF_HELO_PASS,SPF_PASS
X-Spam-Check-By: sourceware.org
Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28)     by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Mon, 23 Nov 2009 09:16:14 +0000
Received: from int-mx05.intmail.prod.int.phx2.redhat.com (int-mx05.intmail.prod.int.phx2.redhat.com [10.5.11.18]) 	by mx1.redhat.com (8.13.8/8.13.8) with ESMTP id nAN9G7Au023522 	(version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=OK); 	Mon, 23 Nov 2009 04:16:07 -0500
Received: from hs20-bc2-1.build.redhat.com (hs20-bc2-1.build.redhat.com [10.10.28.34]) 	by int-mx05.intmail.prod.int.phx2.redhat.com (8.13.8/8.13.8) with ESMTP id nAN9G5iY001366 	(version=TLSv1/SSLv3 cipher=DHE-RSA-AES256-SHA bits=256 verify=NO); 	Mon, 23 Nov 2009 04:16:06 -0500
Received: from hs20-bc2-1.build.redhat.com (localhost.localdomain [127.0.0.1]) 	by hs20-bc2-1.build.redhat.com (8.13.1/8.13.1) with ESMTP id nAN9G5Nj032162; 	Mon, 23 Nov 2009 04:16:05 -0500
Received: (from jakub@localhost) 	by hs20-bc2-1.build.redhat.com (8.13.1/8.13.1/Submit) id nAN9G2ls032158; 	Mon, 23 Nov 2009 04:16:02 -0500
Date: Mon, 23 Nov 2009 09:17:00 -0000
From: Jakub Jelinek <jakub@redhat.com>
To: Thomas Gleixner <tglx@linutronix.de>
Cc: Linus Torvalds <torvalds@linux-foundation.org>,         Andrew Haley <aph@redhat.com>,         Richard Guenther <richard.guenther@gmail.com>, rostedt@goodmis.org,         Ingo Molnar <mingo@elte.hu>, "H. Peter Anvin" <hpa@zytor.com>,         LKML <linux-kernel@vger.kernel.org>,         Andrew Morton <akpm@linux-foundation.org>,         Heiko Carstens <heiko.carstens@de.ibm.com>, feng.tang@intel.com,         Fr??d??ric Weisbecker <fweisbec@gmail.com>,         Peter Zijlstra <peterz@infradead.org>, gcc@gcc.gnu.org
Subject: Re: BUG: GCC-4.4.x changes the function frame on some functions
Message-ID: <20091123091602.GB22813@hs20-bc2-1.build.redhat.com>
Reply-To: Jakub Jelinek <jakub@redhat.com>
References: <alpine.LFD.2.00.0911191423190.24119@localhost.localdomain> <alpine.LFD.2.00.0911191607440.24119@localhost.localdomain> <alpine.LFD.2.00.0911190934070.2793@localhost.localdomain> <1258653562.22249.682.camel@gandalf.stny.rr.com> <84fc9c000911191003t244eb864o3d5b355ab5485f@mail.gmail.com> <4B058CCD.8050605@redhat.com> <alpine.LFD.2.00.0911191039470.2793@localhost.localdomain> <alpine.LFD.2.00.0911191041471.2793@localhost.localdomain> <alpine.LFD.2.00.0911191047350.2793@localhost.localdomain> <alpine.LFD.2.00.0911191958470.24119@localhost.localdomain>
Mime-Version: 1.0
Content-Type: text/plain; charset=us-ascii
Content-Disposition: inline
In-Reply-To: <alpine.LFD.2.00.0911191958470.24119@localhost.localdomain>
User-Agent: Mutt/1.4.1i
Mailing-List: contact gcc-help@gcc.gnu.org; run by ezmlm
Precedence: bulk
List-Id: <gcc.gcc.gnu.org>
List-Archive: <http://gcc.gnu.org/ml/gcc/>
List-Post: <mailto:gcc@gcc.gnu.org>
List-Help: <http://gcc.gnu.org/ml/>
Sender: gcc-owner@gcc.gnu.org
X-SW-Source: 2009-11/txt/msg00617.txt.bz2

On Thu, Nov 19, 2009 at 08:01:57PM +0100, Thomas Gleixner wrote:
> Just compiled with -mincoming-stack-boundary=4 and the problem goes
> away as gcc now thinks that the incoming stack is already 16 byte
> aligned. But that might break code which actually uses SSE

Please don't do this, lying to the compiler is just going to result in
wrong-code sooner or later, with the above switch gcc will assume the
incoming stack is 16-byte aligned (which is not true in the ix86 kernel)
and could very well e.g. optimize away code that looks at
alignment of stack variables etc.

	Jakub