From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 27253 invoked by alias); 14 Dec 2009 17:49:28 -0000 Received: (qmail 27245 invoked by uid 22791); 14 Dec 2009 17:49:27 -0000 X-SWARE-Spam-Status: No, hits=-1.8 required=5.0 tests=AWL,BAYES_00,SARE_MSGID_LONG40,SPF_PASS X-Spam-Check-By: sourceware.org Received: from mail-bw0-f211.google.com (HELO mail-bw0-f211.google.com) (209.85.218.211) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Mon, 14 Dec 2009 17:49:24 +0000 Received: by bwz3 with SMTP id 3so2360363bwz.16 for ; Mon, 14 Dec 2009 09:49:22 -0800 (PST) MIME-Version: 1.0 Received: by 10.204.32.204 with SMTP id e12mr3036047bkd.51.1260812961575; Mon, 14 Dec 2009 09:49:21 -0800 (PST) In-Reply-To: References: <4B265B23.1010102@cs.utah.edu> <87hbrty1k5.fsf@basil.nowhere.org> Date: Mon, 14 Dec 2009 17:49:00 -0000 Message-ID: <571f6b510912140949h50a97fa6redffc1c152b1fd3d@mail.gmail.com> Subject: Re: detailed comparison of generated code size for GCC and other compilers From: Steven Bosscher To: John Regehr Cc: Andi Kleen , gcc@gcc.gnu.org Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: quoted-printable 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: 2009-12/txt/msg00182.txt.bz2 On Mon, Dec 14, 2009 at 5:30 PM, John Regehr wrote: >> I wonder if the original program was already broken or was this >> something your conversion introduced? > > Not sure about this specific case but I'm sure there's some of each. > > I also noticed these testcases but decided to leave them in for now. > Obviously the code is useless, but it can still be interpreted according = to > the C standard, and code can be generated. =A0Once you start going down t= he > road of exploiting undefined behavior to create better code -- and gcc > already does this pretty aggressively -- why not keep going? > > That said, if there's a clear sentiment that this kind of test case is > undesirable, I'll make an effort to get rid of these for subsequent runs. +1 for undesirable. Benchmarks are already always artificial, but benchmarks of undefined code are not going to give useful comparisons. Ciao! Steven