From owner-freebsd-hackers Mon Jan 7 11:56:24 2002 Delivered-To: freebsd-hackers@freebsd.org Received: from mail6.speakeasy.net (mail6.speakeasy.net [216.254.0.206]) by hub.freebsd.org (Postfix) with ESMTP id 8E11337B41A for ; Mon, 7 Jan 2002 11:56:06 -0800 (PST) Received: (qmail 15038 invoked from network); 7 Jan 2002 19:56:05 -0000 Received: from unknown (HELO laptop.baldwin.cx) ([64.81.54.73]) (envelope-sender ) by mail6.speakeasy.net (qmail-ldap-1.03) with SMTP for ; 7 Jan 2002 19:56:05 -0000 Message-ID: X-Mailer: XFMail 1.4.0 on FreeBSD X-Priority: 3 (Normal) Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 8bit MIME-Version: 1.0 In-Reply-To: <3C39F804.43A242DD@math.missouri.edu> Date: Mon, 07 Jan 2002 11:55:34 -0800 (PST) From: John Baldwin To: Stephen Montgomery-Smith Subject: Re: Tell gcc I have a i686 Cc: "Matthew D. Fuller" , freebsd-hackers@FreeBSD.org Sender: owner-freebsd-hackers@FreeBSD.ORG Precedence: bulk List-ID: List-Archive: (Web Archive) List-Help: (List Instructions) List-Subscribe: List-Unsubscribe: X-Loop: FreeBSD.ORG On 07-Jan-02 Stephen Montgomery-Smith wrote: > John Baldwin wrote: >> >> > You know, I have no idea. It is someone elses code. These are the >> > instructions. Can anyone tell me? >> > >> > "movl 32(%0),%1\n" >> > "adcl %1,32(%0)\n" >> > >> > Also, from this discussion, what I have decided to do is provide it as >> > an option for the user to add by editing the Makefile - not to do it >> > automatically. >> >> These instructions are 386 instructions. What we need to see are the >> contraints (the stuff after the actual instructions with colons in them) to >> see >> if it is somehow using Pentium Pro+ specific registers. And actually, just >> for >> the record, a PPro is a 686. :) >> > > OK, this is it in context: > > register Word32 *_x = x; > register int _a = 0; > > asm("xorl %1,%1\n" /* clear C */ > "movl 124(%0),%1\n" > "adcl %1,124(%0)\n" > : : "r" (_x), "r" (_a) > ); Looks like rather silly code to double the value at x + 124. I say silly casue it clears carry and then does a addcl. However, since CF is zero, this is the same as doing an addl. Since it is just doubling the value, a shl would make more sense (and only be 1 instruction.) -- 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 freebsd-hackers" in the body of the message