From owner-cvs-all Thu May 23 7:25:37 2002 Delivered-To: cvs-all@freebsd.org Received: from mail.speakeasy.net (mail16.speakeasy.net [216.254.0.216]) by hub.freebsd.org (Postfix) with ESMTP id B92AF37B401 for ; Thu, 23 May 2002 07:25:15 -0700 (PDT) Received: (qmail 30497 invoked from network); 23 May 2002 14:25:14 -0000 Received: from unknown (HELO server.baldwin.cx) ([216.27.160.63]) (envelope-sender ) by mail16.speakeasy.net (qmail-ldap-1.03) with DES-CBC3-SHA encrypted SMTP for ; 23 May 2002 14:25:14 -0000 Received: from laptop.baldwin.cx (gw1.twc.weather.com [216.133.140.1]) by server.baldwin.cx (8.11.6/8.11.6) with ESMTP id g4NEPDF04373; Thu, 23 May 2002 10:25:13 -0400 (EDT) (envelope-from jhb@FreeBSD.org) Message-ID: X-Mailer: XFMail 1.5.2 on FreeBSD X-Priority: 3 (Normal) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8bit MIME-Version: 1.0 In-Reply-To: <20020523070814.Q25907@stylus.haikugeek.com> Date: Thu, 23 May 2002 10:24:52 -0400 (EDT) From: John Baldwin To: Jonathan Mini Subject: Re: cvs commit: src/sys/kern kern_mutex.c Cc: cvs-committers@FreeBSD.org, cvs-all@FreeBSD.org, Peter Jeremy Sender: owner-cvs-all@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On 23-May-2002 Jonathan Mini wrote: > John Baldwin [jhb@FreeBSD.org] wrote : > >> In Intel's documentation they said that all current look-alikes worked as >> well. It's the opcode for 'rep mov'. I am curious if some implementations >> trash %ecx, and if we are paranoid we could always clobber %ecx in the >> constraints. [ ... ] > > The rep prefix doesn't modify any registers. You do need to make > sure that %ecx was zero when you dispatch a rep mov (unles you're > dispatching a rep mov $0, %ecx), or you'll get an infinite loop. Bah, it's rep nop, not rep mov. rep does modify %ecx when used with, say string instructions. It decrements %[e]cx once for each interation. -- John Baldwin <>< http://www.FreeBSD.org/~jhb/ "Power Users Use the Power to Serve!" - http://www.FreeBSD.org/ To Unsubscribe: send mail to majordomo@FreeBSD.org with "unsubscribe cvs-all" in the body of the message