From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 1239 invoked by alias); 10 Jan 2012 17:08:48 -0000 Received: (qmail 1222 invoked by uid 22791); 10 Jan 2012 17:08:48 -0000 X-SWARE-Spam-Status: No, hits=-2.9 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00 X-Spam-Check-By: sourceware.org Received: from localhost (HELO gcc.gnu.org) (127.0.0.1) by sourceware.org (qpsmtpd/0.43rc1) with ESMTP; Tue, 10 Jan 2012 17:08:35 +0000 From: "aph at gcc dot gnu.org" To: java-prs@gcc.gnu.org Subject: [Bug java/21855] array bounds checking elimination Date: Tue, 10 Jan 2012 17:08:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: java X-Bugzilla-Keywords: alias, missed-optimization X-Bugzilla-Severity: normal X-Bugzilla-Who: aph at gcc dot gnu.org X-Bugzilla-Status: NEW X-Bugzilla-Priority: P2 X-Bugzilla-Assigned-To: dnovillo at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated Content-Type: text/plain; charset="UTF-8" MIME-Version: 1.0 Mailing-List: contact java-prs-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: java-prs-owner@gcc.gnu.org X-SW-Source: 2012-q1/txt/msg00014.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21855 --- Comment #22 from Andrew Haley 2012-01-10 17:08:30 UTC --- (In reply to comment #21) > The Java frontend could handle this by performing loads of the length field > via a SAVE_EXPR and sharing this across a function. That way CSE would > happen automagically. Now that's a nice idea. In this specific case it should be easy, because array.length is used in the control expression for the loop. So. we can create the SAVE_EXPR when the loop is initialized. The problem with doing this in general is that we don't have a CFG, so we don't always know when to create that SAVE_EXPR. If we can find an initial use of an array that dominates all other uses we can create the SAVE_EXPR at that point.