Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753654Ab0KHMUE (ORCPT ); Mon, 8 Nov 2010 07:20:04 -0500 Received: from cantor2.suse.de ([195.135.220.15]:50220 "EHLO mx2.suse.de" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1752454Ab0KHMUD (ORCPT ); Mon, 8 Nov 2010 07:20:03 -0500 Date: Mon, 8 Nov 2010 13:20:01 +0100 (CET) From: Michael Matz To: Andi Kleen Cc: Richard Guenther , Andreas Schwab , Jim , Linux Kernel Mailing List , gcc@gcc.gnu.org Subject: Re: gcc 4.5.1 / as 2.20.51.0.11 miscompiling drivers/char/i8k.c ? In-Reply-To: <877hgorrj1.fsf@basil.nowhere.org> Message-ID: References: <4CD538CA.8010901@xs4all.nl> <87wroostw3.fsf@basil.nowhere.org> <87k4kospnd.fsf@basil.nowhere.org> <877hgorrj1.fsf@basil.nowhere.org> 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 Content-Length: 1248 Lines: 38 Hi, On Mon, 8 Nov 2010, Andi Kleen wrote: > Richard Guenther writes: > > > On Mon, Nov 8, 2010 at 12:03 AM, Andi Kleen wrote: > >> Andreas Schwab writes: > >>> > >>> The asm fails to mention that it modifies *regs. > >> > >> It has a memory clobber, that should be enough, no? > > > > No. A memory clobber does not cover automatic storage. > > That's a separate problem. > > > Btw, I can't see a testcase anywhere so I just assume Andreas got > > it right as usual. > > An asm with live inputs and outputs should never be optimized > way. If 4.5.1 started doing that it's seriously broken. You know the drill: testcase -> gcc.gnu.org/bugzilla/ (In particular up to now it's only speculation in some forum that the asm really is optimized away, which I agree would be a bug, or if it isn't merely that regs->eax isn't reloaded after the asm(), which would be caused by the problem Andreas mentioned) Ciao, Michael. -- 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/