From owner-freebsd-current@FreeBSD.ORG Mon May 8 03:13:07 2006 Return-Path: X-Original-To: freebsd-current@freebsd.org Delivered-To: freebsd-current@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 04DCB16A400 for ; Mon, 8 May 2006 03:13:07 +0000 (UTC) (envelope-from des@des.no) Received: from tim.des.no (tim.des.no [194.63.250.121]) by mx1.FreeBSD.org (Postfix) with ESMTP id 3BE1043D48 for ; Mon, 8 May 2006 03:13:06 +0000 (GMT) (envelope-from des@des.no) Received: from tim.des.no (localhost [127.0.0.1]) by spam.des.no (Postfix) with ESMTP id C14592086; Mon, 8 May 2006 05:13:00 +0200 (CEST) X-Spam-Tests: AWL,BAYES_00,FORGED_RCVD_HELO X-Spam-Learn: ham X-Spam-Score: -2.4/3.0 X-Spam-Checker-Version: SpamAssassin 3.1.1 (2006-03-10) on tim.des.no Received: from xps.des.no (des.no [80.203.243.180]) by tim.des.no (Postfix) with ESMTP id B442B2085; Mon, 8 May 2006 05:13:00 +0200 (CEST) Received: by xps.des.no (Postfix, from userid 1001) id 92A2833C8D; Mon, 8 May 2006 05:13:00 +0200 (CEST) From: des@des.no (Dag-Erling =?iso-8859-1?Q?Sm=F8rgrav?=) To: "Vincent Blondel" References: <61809.192.168.1.21.1147030254.squirrel@192.168.1.21> Date: Mon, 08 May 2006 05:13:00 +0200 In-Reply-To: <61809.192.168.1.21.1147030254.squirrel@192.168.1.21> (Vincent Blondel's message of "Sun, 7 May 2006 21:30:54 +0200 (CEST)") Message-ID: <86d5epp5tv.fsf@xps.des.no> User-Agent: Gnus/5.110003 (No Gnus v0.3) Emacs/21.3 (berkeley-unix) MIME-Version: 1.0 Content-Type: text/plain; charset=iso-8859-1 Content-Transfer-Encoding: quoted-printable Cc: freebsd-current@freebsd.org Subject: Re: I_686 MMX / 3DNOW / SSE / SSE2 ? X-BeenThere: freebsd-current@freebsd.org X-Mailman-Version: 2.1.5 Precedence: list List-Id: Discussions about the use of FreeBSD-current List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Mon, 08 May 2006 03:13:07 -0000 "Vincent Blondel" writes: > So in this context, I use 'CFLAGS=3D -O2 -pipe -fno-strict-aliasing' > and 'CPUTYPE?=3Dathlon-xp' for compiling kernel but when I look at > file /usr/src/sys/conf/kern.mk I see all kind of mmx/3dnow/sse/sse2 > are disabled [...] We don't want to use floating point within the kernel, for a variety of reasons (one of them being that saving and restoring the floating point context when switching in and out of the kernel is very expensive). > So, finally, there is something I don't understand, what is the goal > of 'CPU_ENABLE_SSE' [...] The (now standard) CPU_ENABLE_SSE option adds code to save / restore SSE registers when necesary. This allows userland applications to use SSE without getting clobbering eachother's data. DES --=20 Dag-Erling Sm=F8rgrav - des@des.no