From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 18335 invoked by alias); 28 Nov 2012 09:55:05 -0000 Received: (qmail 18326 invoked by uid 22791); 28 Nov 2012 09:55:04 -0000 X-SWARE-Spam-Status: No, hits=-3.0 required=5.0 tests=AWL,BAYES_00,KHOP_THREADED X-Spam-Check-By: sourceware.org Received: from mel.act-europe.fr (HELO mel.act-europe.fr) (194.98.77.210) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Wed, 28 Nov 2012 09:54:59 +0000 Received: from localhost (localhost [127.0.0.1]) by filtered-smtp.eu.adacore.com (Postfix) with ESMTP id 937A7CB255D; Wed, 28 Nov 2012 10:55:02 +0100 (CET) Received: from mel.act-europe.fr ([127.0.0.1]) by localhost (smtp.eu.adacore.com [127.0.0.1]) (amavisd-new, port 10024) with ESMTP id WkgYupcQU9L2; Wed, 28 Nov 2012 10:55:02 +0100 (CET) Received: from polaris.localnet (bon31-6-88-161-99-133.fbx.proxad.net [88.161.99.133]) (using TLSv1 with cipher DHE-RSA-AES256-SHA (256/256 bits)) (No client certificate requested) by mel.act-europe.fr (Postfix) with ESMTP id 60B19CB160B; Wed, 28 Nov 2012 10:55:02 +0100 (CET) From: Eric Botcazou To: Marek Polacek Cc: gcc-patches@gcc.gnu.org Subject: Re: [PATCH] Don't bypass blocks with multiple latch edges (PR middle-end/54838) Date: Wed, 28 Nov 2012 09:55:00 -0000 Message-ID: <1544820.Re9E01eJrW@polaris> User-Agent: KMail/4.7.2 (Linux/3.1.10-1.16-desktop; KDE/4.7.2; x86_64; ; ) In-Reply-To: <20121126142843.GH17362@redhat.com> References: <20121126142843.GH17362@redhat.com> MIME-Version: 1.0 Content-Transfer-Encoding: 7Bit Content-Type: text/plain; charset="us-ascii" Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org X-SW-Source: 2012-11/txt/msg02298.txt.bz2 > We then end up with > Redirecting fallthru edge 3->4 to 6 > JUMP-BYPASS: Proved reg 59 in jump_insn 15 equals constant (const_int 1 > [0x1]) Bypass edge from 3->4 to 6 > Redirecting fallthru edge 9->4 to 5 > JUMP-BYPASS: Proved reg 59 in jump_insn 15 equals constant (const_int 3 > [0x3]) Bypass edge from 9->4 to 5 > i.e., it is assumed that in one reg there "are" two constants, that can't > be right, right?! No, I don't think that's the problem. The above messages are admittedly a bit terse, they should say: JUMP-BYPASS: Proved reg 59 in jump_insn 15 equals constant (const_int 3 [0x3]) when BB 4 is entered from BB 9. Redirect edge 9->4 to 5. so you can have different constants for BB 3 and BB 9. The patch to tweak the dump messages along these lines is pre-approved. The ICE in merge_latch_edges means that the loop structure and the CFG aren't in sync anymore. Does the cprop pass modify the former without declaring it? -- Eric Botcazou