From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 97524 invoked by alias); 11 Mar 2015 21:45:31 -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 97456 invoked by uid 48); 11 Mar 2015 21:45:27 -0000 From: "law at redhat dot com" To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/65177] [5 Regression]: extend jump thread for finite state automata causes miscompilation Date: Wed, 11 Mar 2015 21:45:00 -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: 5.0 X-Bugzilla-Keywords: wrong-code X-Bugzilla-Severity: normal X-Bugzilla-Who: law at redhat dot com X-Bugzilla-Status: UNCONFIRMED X-Bugzilla-Priority: P1 X-Bugzilla-Assigned-To: spop at gcc dot gnu.org X-Bugzilla-Target-Milestone: 5.0 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: 2015-03/txt/msg01266.txt.bz2 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65177 --- Comment #15 from Jeffrey A. Law --- Basically the way this works is we record the SSA_NAMEs that are being duplicated during block copying. For any duplicated SSA_NAME, if > 1 instance of it is live at a join point in the CFG, then update_ssa will create a PHI and merge the values. I can't offhand think of any reason why it wouldn't work here if the names were properly marked. But I haven't looked at the before/after CFGs to see if there's something unique in this case. In fact, I haven't looked at it at all at this point.