From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 9102 invoked by alias); 7 Apr 2014 11:31:49 -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 9052 invoked by uid 48); 7 Apr 2014 11:31:45 -0000 From: "glisse at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/60770] disappearing clobbers Date: Mon, 07 Apr 2014 11:31:00 -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: diagnostic X-Bugzilla-Severity: normal X-Bugzilla-Who: glisse at gcc dot gnu.org X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- 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: 2014-04/txt/msg00463.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=60770 --- Comment #4 from Marc Glisse --- Catching it earlier may be hard, even for these trivial examples we only have from einline (18) to esra (24) or from eh (10) to ccp1 (21) and in more complicated examples I fear the interval will be empty, but we can try... CCP looks like the most natural choice in the interval 18-21. Manuel, for the CCP thing, it looks a bit different from PR 18501. There, you had something that was either 42 or undefined, so we picked 42. Here, we have something that must be undefined, and we are still picking whatever value it might have had before becoming undefined (but the write of that old value may have already been removed because it sees the value becomes undefined later...). Not that it is necessarily easier to do anything about it.