From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 10684 invoked by alias); 13 Dec 2002 14:52:52 -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 10619 invoked from network); 13 Dec 2002 14:52:50 -0000 Received: from unknown (HELO thales.mathematik.uni-ulm.de) (134.60.66.5) by sources.redhat.com with SMTP; 13 Dec 2002 14:52:50 -0000 Received: (qmail 20338 invoked by uid 642); 13 Dec 2002 14:52:49 -0000 Message-ID: <20021213145249.20337.qmail@thales.mathematik.uni-ulm.de> From: "Christian Ehrhardt" Date: Fri, 13 Dec 2002 07:34:00 -0000 To: Eric Botcazou Cc: nejataydin@superonline.com, gcc-gnats@gcc.gnu.org, gcc@gcc.gnu.org, gcc-bugs@gcc.gnu.org, nobody@gcc.gnu.org Subject: Re: optimization/7799: [3.2/3.3 regression] Loop bug with optimization flag -Os in gcc References: <20021213133626.29733.qmail@theseus.mathematik.uni-ulm.de> <200212131449.01528.ebotcazou@libertysurf.fr> Mime-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Disposition: inline In-Reply-To: <200212131449.01528.ebotcazou@libertysurf.fr> User-Agent: Mutt/1.3.25i X-SW-Source: 2002-12/txt/msg00725.txt.bz2 On Fri, Dec 13, 2002 at 02:49:01PM +0100, Eric Botcazou wrote: > > This transformation is IMHO illegal because there is no way to make the > > comparison in general equivialent to that in the original for loop. > > If p is initially 0x7ffffffc the comparison must be treated as unsigned, > > however, if p is initially 0xfffffffc the comparison must be treated as > > signed. > > Well-known deficiency of the strength reduction pass (see the testcase > testsuite/gcc.c-torture/execute/loop-2e.c which is XFAILed on x86 at -Os). Thanks for the clarification. This means that we can close the report? I can confirm that using -fno-strength-reduce fixes the problem. regards Christian -- THAT'S ALL FOLKS!