From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S1752445AbYCSTZY (ORCPT ); Wed, 19 Mar 2008 15:25:24 -0400 Received: (majordomo@vger.kernel.org) by vger.kernel.org id S1752197AbYCSTYT (ORCPT ); Wed, 19 Mar 2008 15:24:19 -0400 Received: from terminus.zytor.com ([198.137.202.10]:48491 "EHLO terminus.zytor.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S1750901AbYCSTYQ (ORCPT ); Wed, 19 Mar 2008 15:24:16 -0400 Message-ID: <47E112C7.8020406@zytor.com> Date: Wed, 19 Mar 2008 06:19:03 -0700 From: "H. Peter Anvin" User-Agent: Thunderbird 2.0.0.12 (X11/20080226) MIME-Version: 1.0 To: Jan Beulich CC: Chuck Ebbert , mingo@elte.hu, tglx@linutronix.de, linux-kernel@vger.kernel.org Subject: Re: [RFC] x86: bitops asm constraint fixes References: <47D8FD33.76E4.0078.0@novell.com> <47DAE909.20006@redhat.com> <47DE44F6.76E4.0078.0@novell.com> In-Reply-To: <47DE44F6.76E4.0078.0@novell.com> Content-Type: text/plain; charset=ISO-8859-1; format=flowed Content-Transfer-Encoding: 7bit Sender: linux-kernel-owner@vger.kernel.org List-ID: X-Mailing-List: linux-kernel@vger.kernel.org Jan Beulich wrote: > > That's not very desirable: For one part, because there are uses of > bitops on arrays of ints (and casting these up isn't fully correct on > x86-64 because of the same reason that using the bitops on char > arrays isn't correct (see the other response I sent to Jeremy's reply), > but also because operating on longs requires REX prefixes n x86-64, > hence making the code bigger for no good reason. > It might be worthwhile to find out if 64-bit bitops are faster. Bitops are normally defined only on longs, but since x86 is a littleendian architecture we sometimes fudge that in arch-specific code. -hpa