From owner-cvs-src@FreeBSD.ORG Wed Aug 16 14:34:35 2006 Return-Path: X-Original-To: cvs-src@FreeBSD.org Delivered-To: cvs-src@FreeBSD.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id E777F16A4DD; Wed, 16 Aug 2006 14:34:35 +0000 (UTC) (envelope-from bde@zeta.org.au) Received: from mailout2.pacific.net.au (mailout2.pacific.net.au [61.8.0.115]) by mx1.FreeBSD.org (Postfix) with ESMTP id 75BDA43D4C; Wed, 16 Aug 2006 14:34:35 +0000 (GMT) (envelope-from bde@zeta.org.au) Received: from mailproxy1.pacific.net.au (mailproxy1.pacific.net.au [61.8.2.162]) by mailout2.pacific.net.au (Postfix) with ESMTP id 4536B149255; Thu, 17 Aug 2006 00:34:34 +1000 (EST) Received: from katana.zip.com.au (katana.zip.com.au [61.8.7.246]) by mailproxy1.pacific.net.au (8.13.4/8.13.4/Debian-3sarge1) with ESMTP id k7GEYVPl002004; Thu, 17 Aug 2006 00:34:32 +1000 Date: Thu, 17 Aug 2006 00:34:31 +1000 (EST) From: Bruce Evans X-X-Sender: bde@delplex.bde.org To: John Baldwin In-Reply-To: <200608151052.49421.jhb@freebsd.org> Message-ID: <20060817003125.I38538@delplex.bde.org> References: <200608151245.k7FCjpJo077372@repoman.freebsd.org> <200608152134.46359.davidxu@freebsd.org> <20060815135517.GB41562@deviant.kiev.zoral.com.ua> <200608151052.49421.jhb@freebsd.org> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed Cc: Kostik Belousov , cvs-src@FreeBSD.org, src-committers@FreeBSD.org, David Xu , cvs-all@FreeBSD.org Subject: Re: cvs commit: src/sys/amd64/amd64 support.S X-BeenThere: cvs-src@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: CVS commit messages for the src tree List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Wed, 16 Aug 2006 14:34:36 -0000 On Tue, 15 Aug 2006, John Baldwin wrote: > On Tuesday 15 August 2006 09:55, Kostik Belousov wrote: >> So, it seems that xorq %rax, %rax and xorl %eax, %eax will make the >> same results, but in the different ways. And xorq requires REX prefix, >> that shall make the decoding longer. > > Ok, thanks! David, can you revert your change? I had almost gone through > earlier and fixed all the places that did this a while back until I realized > that it must have been intentional. It is logged as intentional in the commit that went through and optimized all places that used xorq: %%% RCS file: /home/ncvs/src/sys/amd64/amd64/support.S,v Working file: support.S head: 1.118 ... ---------------------------- revision 1.116 date: 2005/09/27 18:32:46; author: peter; state: Exp; lines: +11 -11 Fix a minor nit that has been bugging me for a while. Fix the obvious cases of using a 64 bit operation to zero a register. 32 bit opcodes are smaller and supposedly faster, and clear the upper 32 bits for free. ---------------------------- %%% Bruce