From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 24555 invoked by alias); 12 Feb 2015 23:04:36 -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 15038 invoked by uid 48); 12 Feb 2015 22:56:41 -0000 From: "law at redhat dot com" To: gcc-bugs@gcc.gnu.org Subject: [Bug middle-end/61409] [4.9/5 regression] -Wmaybe-uninitialized false-positive with -O2 Date: Thu, 12 Feb 2015 23:04:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: middle-end X-Bugzilla-Version: 4.9.0 X-Bugzilla-Keywords: X-Bugzilla-Severity: enhancement X-Bugzilla-Who: law at redhat dot com X-Bugzilla-Status: NEW X-Bugzilla-Priority: P2 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: 4.9.3 X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: cc 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: 2015-02/txt/msg01416.txt.bz2 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=61409 Jeffrey A. Law changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |law at redhat dot com --- Comment #10 from Jeffrey A. Law --- Of particular interest is this PHI node at the start of BB6: # mw_1 = PHI I vaguely remember that we had code that would optimize this case, specifically we would ignore PHI alternatives associated with undefined uses. If we did that, then we'd create an equivalence mw_1 = h33 which would then propagate to the use of mw_1 and replace it with h33 and avoid the false positive. I thought that was in the vrp/ccp propagation engine.