From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 23402 invoked by alias); 21 Dec 2012 14:27:44 -0000 Received: (qmail 23296 invoked by uid 48); 21 Dec 2012 14:27:20 -0000 From: "rguenth at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug tree-optimization/55334] [4.8 Regression] mgrid regression (ipa-cp disables vectorization) Date: Fri, 21 Dec 2012 14:27:00 -0000 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 X-Bugzilla-Severity: normal X-Bugzilla-Who: rguenth at gcc dot gnu.org X-Bugzilla-Status: NEW X-Bugzilla-Priority: P3 X-Bugzilla-Assigned-To: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: 4.8.0 X-Bugzilla-Changed-Fields: CC 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 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: 2012-12/txt/msg02132.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55334 Richard Biener changed: What |Removed |Added ---------------------------------------------------------------------------- CC| |rguenth at gcc dot gnu.org --- Comment #23 from Richard Biener 2012-12-21 14:27:18 UTC --- In fact there are a few dependences we can solve: 191: versioning for alias required: can't determine dependence between MEM[(real(kind=8)[0:D.1986] *)&x + 20247552B][_20] and MEM[(real(kind=8)[0:D.1989] *)&x + 37823552B][_20] from Creating dr for MEM[(real(kind=8)[0:D.1986] *)&x + 20247552B][_20] analyze_innermost: success. base_address: &x offset from base address: (ssizetype) ((sizetype) (((_7 - stride.11_6) + pretmp_791) + pretmp_813) * 8) constant offset from base address: 20247568 step: 8 aligned to: 8 base_object: MEM[(real(kind=8)[0:D.1986] *)&x + 20247552B] Access function 0: {{(stride.9_4 * 2 + pretmp_792) + 2, +, stride.9_4}_2, +, 1}_3 and Creating dr for MEM[(real(kind=8)[0:D.1983] *)&x][_20] analyze_innermost: success. base_address: &x offset from base address: (ssizetype) ((sizetype) (((_7 - stride.11_6) + pretmp_791) + pretmp_813) * 8) constant offset from base address: 16 step: 8 aligned to: 8 base_object: MEM[(real(kind=8)[0:D.1983] *)&x] Access function 0: {{(stride.9_4 * 2 + pretmp_792) + 2, +, stride.9_4}_2, +, 1}_3 we hit: /* If the references do not access the same object, we do not know whether they alias or not. */ if (!operand_equal_p (DR_BASE_OBJECT (a), DR_BASE_OBJECT (b), 0)) { DDR_ARE_DEPENDENT (res) = chrec_dont_know; return res; } but for the case the access functions are the same we can conclude the accesses cannot alias if the base_objects cannot alias (danger! data-ref does not record an "access size", so with the same access function but only 1-byte offset in base_object this can lead to false disambiguations, so it might in the end not be that easy ...) This size issue is also why we cannot translate the base_object internal offset into an access function (see testcases I added for bugs we had there)