From owner-freebsd-arch@FreeBSD.ORG Tue Nov 11 09:02:06 2003 Return-Path: Delivered-To: freebsd-arch@freebsd.org Received: from mx1.FreeBSD.org (mx1.freebsd.org [216.136.204.125]) by hub.freebsd.org (Postfix) with ESMTP id 348B516A4CE for ; Tue, 11 Nov 2003 09:02:06 -0800 (PST) Received: from mailout01.sul.t-online.com (mailout01.sul.t-online.com [194.25.134.80]) by mx1.FreeBSD.org (Postfix) with ESMTP id E074D43FE0 for ; Tue, 11 Nov 2003 09:02:04 -0800 (PST) (envelope-from Alexander@Leidinger.net) Received: from fwd00.aul.t-online.de by mailout01.sul.t-online.com with smtp id 1AJbnA-0003Z9-02; Tue, 11 Nov 2003 17:55:00 +0100 Received: from Andro-Beta.Leidinger.net (G-ExAsZvQeLJ6kgV+8iRtUPCnJM7e8Ct5ZOBBMSteoRHgtRDOXYckm@[217.83.23.62]) by fmrl00.sul.t-online.com with esmtp id 1AJbmo-0lPprs0; Tue, 11 Nov 2003 17:54:38 +0100 Received: from Magelan.Leidinger.net (Magellan [192.168.1.1]) hABGsVsm091826; Tue, 11 Nov 2003 17:54:32 +0100 (CET) (envelope-from Alexander@Leidinger.net) Received: from Magelan.Leidinger.net (netchild@localhost [127.0.0.1]) hABGspkP069179; Tue, 11 Nov 2003 17:54:51 +0100 (CET) (envelope-from Alexander@Leidinger.net) Date: Tue, 11 Nov 2003 17:54:51 +0100 From: Alexander Leidinger To: Guido van Rooij , Marius Strobl Message-Id: <20031111175451.7b836abf.Alexander@Leidinger.net> In-Reply-To: <20031111153142.GA42684@gvr.gvr.org> References: <20031110222221.36a11979.Alexander@Leidinger.net> <20031111153142.GA42684@gvr.gvr.org> X-Mailer: Sylpheed version 0.9.6claws (GTK+ 1.2.10; i386-portbld-freebsd5.1) Mime-Version: 1.0 Content-Type: text/plain; charset=US-ASCII Content-Transfer-Encoding: 7bit X-Seen: false X-ID: G-ExAsZvQeLJ6kgV+8iRtUPCnJM7e8Ct5ZOBBMSteoRHgtRDOXYckm@t-dialin.net cc: arch@freebsd.org Subject: Re: Patches to compile the kernel with Intel's C/C++ compiler X-BeenThere: freebsd-arch@freebsd.org X-Mailman-Version: 2.1.1 Precedence: list List-Id: Discussion related to FreeBSD architecture List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 11 Nov 2003 17:02:06 -0000 On Tue, 11 Nov 2003 16:31:42 +0100 Guido van Rooij wrote: > What are the benefits of running an icc compiled kernel? The same as every other program gets. a) Icc knows better to schedule instructions for a P4 than gcc does. b) If you have an application which stresses some critical path in the kernel, icc may be able to optimize parts of it and allows you to get a little bit more out of it. c) Someone is working on getting the icc profiling information out of the linux kernel back into icc to optimize the system based upon the measured values (think about branch prediction and probabilities). When this matures, it's very likely that we also get support for it. d) If 2 compilers agree on the behavior of the same code, either both compilers a buggy, or your code is fine (yes, an overly optimistic point of view, but a pragmatic one). If one of 2 compilers disagrees, something is wrong with one of the compilers, or with your code. Or perhaps you're just religious and want to use as less (L)GPLed code as possible. ;-) Obviously not everyone needs to run an icc compiled kernel or userland, but it doesn't hurts (modulo bugs in icc (as FreeBSD has a commercial license of icc, we get commercial support, and Intel fixed already some ICE issues for us) or in the code, but there could be/are bugs in gcc too) to run or to be able to run one. BTW.: even if Intel doesn't like it, but: icc produces the fastest 32bit code for AMD CPUs too (in specific applications of course). Bye, Alexander. -- It's not a bug, it's tradition! http://www.Leidinger.net Alexander @ Leidinger.net GPG fingerprint = C518 BC70 E67F 143F BE91 3365 79E2 9C60 B006 3FE7