From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 27469 invoked by alias); 10 Jan 2012 16:59:42 -0000 Received: (qmail 27446 invoked by uid 22791); 10 Jan 2012 16:59:41 -0000 X-SWARE-Spam-Status: No, hits=-2.9 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00,TW_TM 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 16:59:28 +0000 From: "rguenth at gcc dot gnu.org" To: java-prs@gcc.gnu.org Subject: [Bug java/21855] array bounds checking elimination Date: Tue, 10 Jan 2012 16:59:00 -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: rguenth 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/msg00013.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=21855 --- Comment #20 from Richard Guenther 2012-01-10 16:55:52 UTC --- (In reply to comment #19) > > > No. What you can do is, via the method I outlined, tell GCC that > > args is to be treated similar to a local automatic variable - thus > > it cannot be refered to from other functions (unless you pass them > > its address of course). > > But that doesn't help. args *can* potentially be referred to by other > functions. The special property we need to make use of its that fact that once > an array is created, its length can never change. That is something we cannot express at the moment, and I think it would be hard to implement reliably (thinking of the RTX_UNCHANGING saga - we do have to exclude the stmts that initialize the length field).