From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1753946Ab1GOXH2 (ORCPT ); Fri, 15 Jul 2011 19:07:28 -0400 Received: from terminus.zytor.com ([198.137.202.10]:33882 "EHLO mail.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1753564Ab1GOXH1 (ORCPT ); Fri, 15 Jul 2011 19:07:27 -0400 Message-ID: <4E20C80A.4050307@zytor.com> Date: Fri, 15 Jul 2011 16:06:50 -0700 From: "H. Peter Anvin" User-Agent: Mozilla/5.0 (X11; U; Linux x86_64; en-US; rv:1.9.2.17) Gecko/20110428 Fedora/3.1.10-1.fc15 Thunderbird/3.1.10 MIME-Version: 1.0 To: Jeremy Fitzhardinge CC: Peter Zijlstra , Linus Torvalds , Ingo Molnar , the arch/x86 maintainers , Linux Kernel Mailing List , Nick Piggin , Jeremy Fitzhardinge , "H.J. Lu" Subject: Re: [PATCH RFC 0/7] x86: convert ticketlocks to C and remove duplicate code References: <4E0506A8.3010102@zytor.com> <4E0512BC.5010900@goop.org> <1ade2577-044b-4391-a607-91a4a989c3ff@email.android.com> <4E2077E1.4060606@goop.org> In-Reply-To: <4E2077E1.4060606@goop.org> Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org On 07/15/2011 10:24 AM, Jeremy Fitzhardinge wrote: > > I posted a bug about gcc not generating cmp %ah, %al in this case, but the general consensus was that > it's not a good choice on current Intel chips, because it causes a partial word stall, and that the > current generated code is better. (And gcc can generate "cmp %Xh, %Xl" if it wants to - see below.) > Which version of gcc is this, and also, do you have the gcc bug report number? I was talking to H.J. and he said he thought it sounded strange. -hpa