From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 33380 invoked by alias); 3 Mar 2015 09:42:23 -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 Received: (qmail 33332 invoked by uid 48); 3 Mar 2015 09:42:20 -0000 From: "rguenth at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug testsuite/63175] [4.9/5 regression] FAIL: gcc.dg/vect/costmodel/ppc/costmodel-bb-slp-9a.c scan-tree-dump-times slp2" basic block vectorized using SLP" 1 Date: Tue, 03 Mar 2015 09:42:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: testsuite X-Bugzilla-Version: 4.9.1 X-Bugzilla-Keywords: 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: unassigned at gcc dot gnu.org X-Bugzilla-Target-Milestone: 4.9.3 X-Bugzilla-Flags: X-Bugzilla-Changed-Fields: Message-ID: In-Reply-To: References: Content-Type: text/plain; charset="UTF-8" Content-Transfer-Encoding: 7bit X-Bugzilla-URL: http://gcc.gnu.org/bugzilla/ Auto-Submitted: auto-generated MIME-Version: 1.0 X-SW-Source: 2015-03/txt/msg00266.txt.bz2 https://gcc.gnu.org/bugzilla/show_bug.cgi?id=63175 --- Comment #26 from Richard Biener --- David - please clarify the cost of misaligned stores/loads. I tried to understand the PPC ISA document but can't really find the appropriate place where it talks about misalign cost (I only can see it still assumes element alignment). Btw with double-word alignment I get t.c:10:10: note: Cost model analysis: Vector inside of basic block cost: 8 Vector prologue cost: 0 Vector epilogue cost: 0 Scalar cost of basic block: 8 t.c:10:10: note: not vectorized: vectorization is not profitable. So currently on a tie we don't vectorize basic-blocks (same with GCC 4.8). That's kind of arbitrary, but given instruction encoding size on x86 for example it makes sense. Note that we seem to prefer optimized re-alignment loads over misaligned loads (even if double-word aligned) - the vectorizer is not set up to decide that based on costs (the misaligned load would cost 2 while the optimized re-aligned load costs 6 - two aligned loads (2), one vector stmt for mask compute (1) and one permute (3)). I think we are regression free compared to 4.8 (if you enable -fvect-cost-model there).