From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 10271 invoked by alias); 20 May 2013 14:10:33 -0000 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 Received: (qmail 10211 invoked by uid 48); 20 May 2013 14:10:29 -0000 From: "ppluzhnikov at google dot com" To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/57199] [4.8/4.9 Regression] Bogus warning: iteration NNNN invokes undefined behavior -Waggressive-loop-optimizations Date: Mon, 20 May 2013 14:10:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: tree-optimization X-Bugzilla-Version: 4.9.0 X-Bugzilla-Keywords: X-Bugzilla-Severity: normal X-Bugzilla-Who: ppluzhnikov at google dot com X-Bugzilla-Status: REOPENED X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: 4.8.1 X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-SW-Source: 2013-05/txt/msg01320.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57199 --- Comment #4 from Paul Pluzhnikov --- (In reply to Jakub Jelinek from comment #3) > it can't prove the following loop that uses _8 as upper bound is dead, ... Do we need a separate "may invoke undefined behavior" warning? In our codebase of 100+ million lines of C++, we've found ~20 instances of real "invokes undefined behavior" (so we don't want to turn the -Waggressive-loop-optimizations off). But we also have ~5 instances where the warning is bogus, and there is no easy way to turn them off, short of sprinkling -Wno-aggresive-loop-optimizations over our BUILD files.