Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S932851AbYCFWEu (ORCPT ); Thu, 6 Mar 2008 17:04:50 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1754526AbYCFWEk (ORCPT ); Thu, 6 Mar 2008 17:04:40 -0500 Received: from one.firstfloor.org ([213.235.205.2]:45820 "EHLO one.firstfloor.org" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1755051AbYCFWEk (ORCPT ); Thu, 6 Mar 2008 17:04:40 -0500 Date: Thu, 6 Mar 2008 23:06:10 +0100 From: Andi Kleen To: "H. Peter Anvin" Cc: Richard Guenther , Joe Buck , Andi Kleen , Andrew Haley , Aurelien Jarno , Michael Matz , linux-kernel@vger.kernel.org, gcc@gcc.gnu.org Subject: Re: Linux doesn't follow x86/x86-64 ABI wrt direction flag Message-ID: <20080306220610.GB31833@one.firstfloor.org> References: <20080305202319.GA17053@volta.aurel32.net> <47CF0627.2070200@zytor.com> <47CF07FE.10200@aurel32.net> <47CFBF28.4060309@redhat.com> <871w6ogjnu.fsf@basil.nowhere.org> <84fc9c000803060406u7dfa0d38ve8af3154bf5064f9@mail.gmail.com> <20080306173438.GH17267@synopsys.com> <84fc9c000803061254i5865f68ev11fcfd08b698c58f@mail.gmail.com> <47D05A70.40008@zytor.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <47D05A70.40008@zytor.com> User-Agent: Mutt/1.4.2.1i Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1059 Lines: 28 On Thu, Mar 06, 2008 at 12:56:16PM -0800, H. Peter Anvin wrote: > Richard Guenther wrote: > > > >A patched GCC IMHO makes only sense if it is always-on, yet another option > >won't help in corner cases. And corner cases is exactly what people seem > >to care about. For this reason that we have this single release, 4.3.0, > >that > >behaves "bad" is already a problem. > > > > The option will help embedded vendors who can guarantee that it's not a > problem. For very very low values of "help". To be realistic it is very unlikely anybody will measure a difference from a few more or a few less clds in a program. It's not that they're expensive instructions and they normally don't happen in inner loops either. "If you enable this option you will get an optimization that you cannot measure" @) -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/