From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 32596 invoked by alias); 28 Dec 2008 10:12:34 -0000 Received: (qmail 32583 invoked by uid 22791); 28 Dec 2008 10:12:34 -0000 X-SWARE-Spam-Status: No, hits=-2.6 required=5.0 tests=BAYES_00 X-Spam-Check-By: sourceware.org Received: from web31405.mail.mud.yahoo.com (HELO web31405.mail.mud.yahoo.com) (68.142.198.117) by sourceware.org (qpsmtpd/0.43rc1) with SMTP; Sun, 28 Dec 2008 10:11:54 +0000 Received: (qmail 3670 invoked by uid 60001); 28 Dec 2008 10:11:51 -0000 Received: from [72.163.216.217] by web31405.mail.mud.yahoo.com via HTTP; Sun, 28 Dec 2008 02:11:51 PST Date: Sun, 28 Dec 2008 12:24:00 -0000 From: tom gogh Reply-To: tomgogh20@yahoo.com Subject: Re: core2 flag for arch on gcc 4.3.2 To: tprince@computer.org Cc: gcc-help@gcc.gnu.org In-Reply-To: <49570D1C.4000400@sbcglobal.net> MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Message-ID: <869404.1220.qm@web31405.mail.mud.yahoo.com> Mailing-List: contact gcc-help-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-help-owner@gcc.gnu.org X-SW-Source: 2008-12/txt/msg00260.txt.bz2 Hi Tim, sorry for not making it clear. I am building Gentoo 2008.0 and gcc supported is 4.1.2 which only supports -mnocona for core 2 duo processor. By migrating to gcc 4.3.2 I will get tunning for core 2 with flag -mcore2 but, it involves going to unsupported gcc for Gentoo. So, I want to know what is the difference between -mnocona flag of gcc versus -mcore2 flag of gcc 4.3.2. Is it worth in terms of speed optimization? --- On Sun, 12/28/08, Tim Prince wrote: > From: Tim Prince > Subject: Re: core2 flag for arch on gcc 4.3.2 > To: "tom gogh" > Cc: gcc-help@gcc.gnu.org > Date: Sunday, December 28, 2008, 12:22 AM > tom gogh wrote: > > > I am planning to migrate my linux to 4.3.2 but, > current flag for core 2 duo is nocona. > > I couldn't find elaborate explanation of core2 > flag compare to nocona. > > What is difference between core2 and nocona flags? > > Do they behave identical or core2 offers better > performance/tunning? > > Not knowing where you're trying to go with this, > default for 64-bit gcc is > good for Core 2, from no difference up to 50% better > throughput than > nocona in my tests. -msse3 is available for either Nocona > or Core 2 CPUs. > You probably wouldn't want the nocona option even for > the older CPU. I > can't imagine why you don't simply try the options > you have in mind, nor > do I understand what you mean by nocona being a current > flag. Maybe you > mean the best option for some old version of gcc which > predates Core 2. > I don't think -mtune=barcelona is available until more > recent versions of > gcc; it may often give better vectorization even on Core 2, > particularly > for Fortran, maybe for C, not so much for C++.