Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1756970AbZKSPty (ORCPT ); Thu, 19 Nov 2009 10:49:54 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754895AbZKSPtx (ORCPT ); Thu, 19 Nov 2009 10:49:53 -0500 Received: from mail-pw0-f42.google.com ([209.85.160.42]:54275 "EHLO mail-pw0-f42.google.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754175AbZKSPtw convert rfc822-to-8bit (ORCPT ); Thu, 19 Nov 2009 10:49:52 -0500 DomainKey-Signature: a=rsa-sha1; c=nofws; d=gmail.com; s=gamma; h=mime-version:in-reply-to:references:date:message-id:subject:from:to :cc:content-type:content-transfer-encoding; b=e86hIK8hZr1JpU/0YLEBJsVJVnSs6X7CRREUDN5UYgfN1WqhlPKA+L5GbpAynNNdes rHuJPPCPyrewcANXJdIeIvVf8TUnL40JF8GRrfd8WdqDIG5F5bpJbNP0FOzqrQ9UEomM h9nIYx6C5wvFSj2eQ37KY2zWw6coj5iJJ6RVM= MIME-Version: 1.0 In-Reply-To: <4B056820.1050104@zytor.com> References: <20091119072040.GA23579@elte.hu> <4B056820.1050104@zytor.com> Date: Thu, 19 Nov 2009 16:49:57 +0100 Message-ID: <84fc9c000911190749y294381a2q16f4547991525cee@mail.gmail.com> Subject: Re: BUG: GCC-4.4.x changes the function frame on some functions From: Richard Guenther To: "H. Peter Anvin" Cc: Thomas Gleixner , Ingo Molnar , LKML , Andrew Morton , Heiko Carstens , feng.tang@intel.com, "Fr??d??ric Weisbecker" , Steven Rostedt , Peter Zijlstra , jakub@redhat.com, gcc@gcc.gnu.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1120 Lines: 31 On Thu, Nov 19, 2009 at 4:45 PM, H. Peter Anvin wrote: > On 11/19/2009 07:37 AM, Thomas Gleixner wrote: >> >> modified function start on a handful of functions only seen with gcc >> 4.4.x on x86 32 bit: >> >> ? ? ? push ? %edi >> ? ? ? lea ? ?0x8(%esp),%edi >> ? ? ? and ? ?$0xfffffff0,%esp >> ? ? ? pushl ?-0x4(%edi) >> ? ? ? push ? %ebp >> ? ? ? mov ? ?%esp,%ebp >> ? ? ? ... >> ? ? ? call ? mcount >> > > The real questions is why we're aligning the stack in the kernel. ?It is > probably not what we want -- we don't use SSE for anything but a handful > of special cases in the kernel, and we don't want the overhead. It's likely because you have long long vars on the stack which is faster when they are aligned. -mno-stackrealign may do what you want (or may not, I have not checked). I assume you already use -mpreferred-stack-boundary=2. Richard. -- 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/