From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 19611 invoked by alias); 10 Nov 2010 12:32:33 -0000 Received: (qmail 19600 invoked by uid 22791); 10 Nov 2010 12:32:33 -0000 X-SWARE-Spam-Status: No, hits=-2.8 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; Wed, 10 Nov 2010 12:32:28 +0000 From: "rguenth at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/35290] Missing dead store elimination X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: tree-optimization X-Bugzilla-Keywords: missed-optimization, TREE X-Bugzilla-Severity: enhancement X-Bugzilla-Who: rguenth at gcc dot gnu.org X-Bugzilla-Status: ASSIGNED X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: rguenth at gcc dot gnu.org X-Bugzilla-Target-Milestone: --- X-Bugzilla-Changed-Fields: Status AssignedTo 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 Date: Wed, 10 Nov 2010 12:32:00 -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 X-SW-Source: 2010-11/txt/msg01274.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=35290 Richard Guenther changed: What |Removed |Added ---------------------------------------------------------------------------- Status|NEW |ASSIGNED AssignedTo|unassigned at gcc dot |rguenth at gcc dot gnu.org |gnu.org | --- Comment #4 from Richard Guenther 2010-11-10 12:32:16 UTC --- Well, it's not working on the tree level to make it cheaper: /* We deliberately stop on clobbering statements and not only on killing ones to make walking cheaper. Otherwise we can just continue walking until both stores have equal reference trees. */ while (!stmt_may_clobber_ref_p (temp, gimple_assign_lhs (stmt))); changing that to while (!stmt_kills_ref_p (temp, gimple_assign_lhs (stmt))); will make it work (and slower). Also needs (possibly unsafe in general if used cross loop iteration) Index: gcc/tree-ssa-alias.c =================================================================== --- gcc/tree-ssa-alias.c (revision 166526) +++ gcc/tree-ssa-alias.c (working copy) @@ -1577,7 +1577,12 @@ stmt_kills_ref_p_1 (gimple stmt, ao_ref base = get_ref_base_and_extent (lhs, &offset, &size, &max_size); /* We can get MEM[symbol: sZ, index: D.8862_1] here, so base == ref->base does not always hold. */ - if (base == ref->base) + if (base == ref->base + || (TREE_CODE (base) == MEM_REF + && TREE_CODE (ref->base) == MEM_REF + && TREE_OPERAND (base, 0) == TREE_OPERAND (ref->base, 0) + && tree_int_cst_equal (TREE_OPERAND (base, 1), + TREE_OPERAND (ref->base, 1)))) { /* For a must-alias check we need to be able to constrain the accesses properly. */