From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 17749 invoked by alias); 19 Sep 2004 14:02:42 -0000 Mailing-List: contact gcc-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Archive: List-Post: List-Help: Sender: gcc-owner@gcc.gnu.org Received: (qmail 17738 invoked from network); 19 Sep 2004 14:02:41 -0000 Received: from unknown (HELO ppsw-5.csi.cam.ac.uk) (131.111.8.135) by sourceware.org with SMTP; 19 Sep 2004 14:02:41 -0000 Received: from cass41.ast.cam.ac.uk ([131.111.69.186]:63903) by ppsw-5.csi.cam.ac.uk (mx.cam.ac.uk [131.111.8.145]:25) with esmtp (Exim 4.34) id 1C92H0-0007PL-21 (return-path jss@ast.cam.ac.uk); Sun, 19 Sep 2004 15:02:38 +0100 Received: from xserv1.ast.cam.ac.uk (IDENT:/8tcqwLqDnumrhOlkkK9LFnTKx8qRXMQ@xserv1.ast.cam.ac.uk [131.111.69.235]) by cass41.ast.cam.ac.uk (8.12.10+Sun/8.12.10) with ESMTP id i8JE2b0I007165; Sun, 19 Sep 2004 15:02:37 +0100 (BST) Received: from xpc5.ast.cam.ac.uk (IDENT:vVG07Gu0BjbXsxKfQAAXQuiZ0UkvBl1v@xpc5.ast.cam.ac.uk [131.111.68.220]) by xserv1.ast.cam.ac.uk (8.11.6/8.11.6) with ESMTP id i8JE2bf04421; Sun, 19 Sep 2004 15:02:37 +0100 Date: Sun, 19 Sep 2004 14:55:00 -0000 From: Jeremy Sanders To: Richard Guenther cc: Scott Robert Ladd , gcc mailing list Subject: Re: Comparing Linux C and C++ Compilers: Benchmarks and Analysis In-Reply-To: <84fc9c0004091810315b26815a@mail.gmail.com> Message-ID: References: <84fc9c0004091810315b26815a@mail.gmail.com> MIME-Version: 1.0 Content-Type: TEXT/PLAIN; charset=US-ASCII; format=flowed X-Cam-ScannerInfo: http://www.cam.ac.uk/cs/email/scanner/ X-Cam-AntiVirus: No virus found X-Cam-SpamDetails: Not scanned X-SW-Source: 2004-09/txt/msg01129.txt.bz2 On Sat, 18 Sep 2004, Richard Guenther wrote: > You may want to check gcc 4.0s auto-vectorizing capabilities by using > -ftree-vectorize. I believe Intel compiler does this by default with > your optimization settings, and also unrolls loops where profitable > (-funroll-loops for all gcc versions). While I personally do not have > success with auto-vectorizing (neither with Intel nor with gcc), loop > unrolling shows very positive effects on my numerical codes. I tried compiling scimark with gcc 4 with -ftree-vectorize -msse2 -fdump-tree-vect-stats and again with the lno branch. This was with a P4 on Fedora Core 2. Looking at the generated .vect files, it looked like gcc wasn't able to vectorize any of the loops in scimark, which is a bit diappointing. It's possible I didn't use it correctly I suppose. Jeremy -- Jeremy Sanders http://www-xray.ast.cam.ac.uk/~jss/ X-Ray Group, Institute of Astronomy, University of Cambridge, UK. Public Key Server PGP Key ID: E1AAE053