From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 10450 invoked by alias); 27 Aug 2010 13:49:42 -0000 Received: (qmail 10433 invoked by uid 22791); 27 Aug 2010 13:49:41 -0000 X-SWARE-Spam-Status: No, hits=-1.1 required=5.0 tests=AWL,BAYES_05,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,FREEMAIL_FROM,RCVD_IN_DNSWL_NONE X-Spam-Check-By: sourceware.org Received: from mail-vw0-f47.google.com (HELO mail-vw0-f47.google.com) (209.85.212.47) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Fri, 27 Aug 2010 13:48:51 +0000 Received: by vws9 with SMTP id 9so37670vws.20 for ; Fri, 27 Aug 2010 06:48:49 -0700 (PDT) MIME-Version: 1.0 Received: by 10.220.71.136 with SMTP id h8mr498906vcj.275.1282916929453; Fri, 27 Aug 2010 06:48:49 -0700 (PDT) Received: by 10.220.78.193 with HTTP; Fri, 27 Aug 2010 06:48:49 -0700 (PDT) In-Reply-To: <1282916665.2100.39.camel@MILLC-COREY> References: <1282916665.2100.39.camel@MILLC-COREY> Date: Fri, 27 Aug 2010 14:20:00 -0000 Message-ID: Subject: Re: Better performance on older version of GCC From: "H.J. Lu" To: Corey Kasten Cc: gcc@gcc.gnu.org Content-Type: text/plain; charset=ISO-8859-1 X-IsSubscribed: yes Mailing-List: contact gcc-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-owner@gcc.gnu.org X-SW-Source: 2010-08/txt/msg00393.txt.bz2 On Fri, Aug 27, 2010 at 6:44 AM, Corey Kasten wrote: > Hello all, > > I have two computers with two different versions of GCC. Otherwise the > two systems have identical hardware. I have a processor and memory > intensive benchmark program which I compile on both systems and I cannot > understand why the system with older GCC version compiles faster code. > > System A has GCC version "4.1.2 20070925 (Red Hat 4.1.2-33)" > System B has GCC version "4.3.0 20080428 (Red Hat 4.3.0-8)" > > I find that the executable compiled on system A runs faster (on both > systems) than the executable compiled on system B (on both system), by a > factor about approximately 4 times. I have attempted to play with the > GCC optimizer flags and have not been able to get System B (with the > later GCC version) to compile code with any better performance. Could > someone please help figure this out? > Can you try gcc 4.5.1? -- H.J.