Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1757671AbXEQNic (ORCPT ); Thu, 17 May 2007 09:38:32 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1753981AbXEQNiZ (ORCPT ); Thu, 17 May 2007 09:38:25 -0400 Received: from ns2.suse.de ([195.135.220.15]:49300 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1754312AbXEQNiY (ORCPT ); Thu, 17 May 2007 09:38:24 -0400 From: Andi Kleen To: Mikulas Patocka , Jan Hubicka Subject: Re: stack alignment on i386 Date: Thu, 17 May 2007 15:37:57 +0200 User-Agent: KMail/1.9.1 Cc: Linus Torvalds , linux-kernel@vger.kernel.org References: In-Reply-To: MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Content-Transfer-Encoding: 7bit Content-Disposition: inline Message-Id: <200705171537.57893.ak@suse.de> Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1953 Lines: 57 On Wednesday 16 May 2007 07:24, Mikulas Patocka wrote: > > [PATCH] x86: Drop cc-options call for all options supported in gcc > >3.2+ > > > > The kernel only supports gcc 3.2+ now so it doesn't make sense > > anymore to explicitely check for options this compiler version > > already has. > > > > This actually fixes a bug. The -mprefered-stack-boundary check > > never worked because gcc rightly complains > > > > CC arch/i386/kernel/asm-offsets.s > > cc1: -mpreferred-stack-boundary=2 is not between 4 and 12 > > Hi > > Your patch for stack alignment on i386 is wrong. -mprefered-stack-boundary > is log2 of the stack alignment (read gcc man page). Ah just using the real number would have been too easy I guess. > On AMD64 16-byte > alignment is enforced because of SSE, on i386 minimal alignment is 4 > bytes. Ok fixed now > See the code in gcc that triggered your error: > i = atoi (ix86_preferred_stack_boundary_string); > if (i < (TARGET_64BIT ? 4 : 2) || i > 12) > error ("-mpreferred-stack-boundary=%d is not between %d and 12", > i, > TARGET_64BIT ? 4 : 2); > else > ix86_preferred_stack_boundary = (1 << i) * BITS_PER_UNIT; > > You are actually dealing with gcc bug, not Linux bug --- when gcc is > compiled with AMD64 support it enforces 16-byte alignment even in 32-bit > mode. Honza? > Rather let it be as it was, adding -mpreferred-stack-boundary=4 doesn't > make sense, because it is default. Hmm, maybe that was different on older gcc versions. There must have been some reason this option was originally added. Linus can you please just revert c8fdd247255a3a027cd9f66dcf93e6847d1d2f85 -Andi - 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/