From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 18661 invoked by alias); 13 Nov 2005 16:17:22 -0000 Mailing-List: contact gcc-bugs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Archive: List-Post: List-Help: Sender: gcc-bugs-owner@gcc.gnu.org Received: (qmail 18498 invoked by uid 48); 13 Nov 2005 16:17:20 -0000 Date: Sun, 13 Nov 2005 16:17:00 -0000 Message-ID: <20051113161720.18496.qmail@sourceware.org> X-Bugzilla-Reason: CC References: Subject: [Bug tree-optimization/23821] [4.0/4.1 Regression] DOM and VRP creating harder to optimize code In-Reply-To: Reply-To: gcc-bugzilla@gcc.gnu.org To: gcc-bugs@gcc.gnu.org From: "steven at gcc dot gnu dot org" X-SW-Source: 2005-11/txt/msg01918.txt.bz2 List-Id: ------- Comment #4 from steven at gcc dot gnu dot org 2005-11-13 16:17 ------- What happens here is just copy propagation by DOM and VRP for "conditional copies", e.g. with "if (a==b) ..." we can record b as a copy of a, or a as a copy of b. In this case, copy propagation just happens to make IV analysis hard (or impossible). Now, this sounds bad. But does this code really happen often enough in real world code to justify spending hours on figuring out how to fix this? Zdenek, where does your example come from? -- http://gcc.gnu.org/bugzilla/show_bug.cgi?id=23821