Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S261669AbVAXVYV (ORCPT ); Mon, 24 Jan 2005 16:24:21 -0500 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S261667AbVAXVWJ (ORCPT ); Mon, 24 Jan 2005 16:22:09 -0500 Received: from waste.org ([216.27.176.166]:22709 "EHLO waste.org") by vger.kernel.org with ESMTP id S261595AbVAXVVI (ORCPT ); Mon, 24 Jan 2005 16:21:08 -0500 Date: Mon, 24 Jan 2005 13:20:37 -0800 From: Matt Mackall To: Felipe Alfaro Solana Cc: Andi Kleen , Neil Brown , linux-kernel@vger.kernel.org, Buck Huppmann , Trond Myklebust , Andreas Gruenbacher , "Andries E. Brouwer" , Andrew Morton , Olaf Kirch Subject: Re: [patch 1/13] Qsort Message-ID: <20050124212037.GJ3867@waste.org> References: <20050122203326.402087000@blunzn.suse.de> <20050122203618.962749000@blunzn.suse.de> <5ADB1D78-6CFB-11D9-86B4-000D9352858E@mac.com> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <5ADB1D78-6CFB-11D9-86B4-000D9352858E@mac.com> User-Agent: Mutt/1.5.6+20040907i Sender: linux-kernel-owner@vger.kernel.org X-Mailing-List: linux-kernel@vger.kernel.org Content-Length: 1018 Lines: 27 On Sun, Jan 23, 2005 at 05:58:00AM +0100, Felipe Alfaro Solana wrote: > On 23 Jan 2005, at 03:39, Andi Kleen wrote: > > >Felipe Alfaro Solana writes: > >> > >>AFAIK, XOR is quite expensive on IA32 when compared to simple MOV > >>operatings. Also, since the original patch uses 3 MOVs to perform the > >>swapping, and your version uses 3 XOR operations, I don't see any > >>gains. > > > >Both are one cycle latency for register<->register on all x86 cores > >I've looked at. What makes you think differently? > > I thought XOR was more expensie. Anyways, I still don't see any > advantage in replacing 3 MOVs with 3 XORs. Again, no temporaries needed. But I benched it and it was quite a bit slower. -- Mathematics is the supreme nostalgia of our time. - 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/