From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 32098 invoked by alias); 2 Dec 2011 15:04:08 -0000 Received: (qmail 32060 invoked by uid 22791); 2 Dec 2011 15:04:05 -0000 X-SWARE-Spam-Status: No, hits=-2.9 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00 X-Spam-Check-By: sourceware.org Received: from localhost (HELO gcc.gnu.org) (127.0.0.1) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Fri, 02 Dec 2011 15:03:49 +0000 From: "rguenther at suse dot de" To: gcc-bugs@gcc.gnu.org Subject: [Bug rtl-optimization/50904] [4.7 regression] pessimization when -fno-protect-parens is enabled by -Ofast Date: Fri, 02 Dec 2011 15:04:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: rtl-optimization X-Bugzilla-Keywords: missed-optimization X-Bugzilla-Severity: normal X-Bugzilla-Who: rguenther at suse dot de X-Bugzilla-Status: ASSIGNED X-Bugzilla-Priority: P2 X-Bugzilla-Assigned-To: ebotcazou at gcc dot gnu.org X-Bugzilla-Target-Milestone: 4.7.0 X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org X-SW-Source: 2011-12/txt/msg00171.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50904 --- Comment #26 from rguenther at suse dot de 2011-12-02 15:02:27 UTC --- On Fri, 2 Dec 2011, burnus at gcc dot gnu.org wrote: > http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50904 > > Tobias Burnus changed: > > What |Removed |Added > ---------------------------------------------------------------------------- > CC|burnus@net-b.de |dominiq at lps dot ens.fr > > --- Comment #25 from Tobias Burnus 2011-12-02 14:40:48 UTC --- > (In reply to comment #24) > > Every program that would break with non honoring explicit parantheses > > would also break if the bracketed expression would be explicitely > > computed into a temporary (without explicit parantheses). So it > > should be easy to construct a testcase if you have one that breaks > > without -fno-protect-parens. > > I vaguely recall that one of the Polyhedron benchmarks gets minutely out of the > correctness-check tolerance range with -fno-protect-parens while it stays > within without. I think Dominique has a program where the effect is more > disastrous. The trivial example is (x + 2**52) - 2**52 which rounds x to an integer. Without parens we optimize away that rounding effect. Thus, real*8 x, tem x = 1.3d tem = x + 2.d**52 x = tem - 2.d**52 if (x.ne.1.0d) call abort should not fail (minus my fortran coding errors ;)) with -fprotect-parens