From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 28071 invoked by alias); 13 Jun 2012 09:44:07 -0000 Received: (qmail 28059 invoked by uid 22791); 13 Jun 2012 09:44:06 -0000 X-SWARE-Spam-Status: No, hits=-4.3 required=5.0 tests=ALL_TRUSTED,AWL,BAYES_00,KHOP_THREADED 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, 13 Jun 2012 09:43:53 +0000 From: "rguenth at gcc dot gnu.org" To: gcc-bugs@gcc.gnu.org Subject: [Bug rtl-optimization/53533] [4.7/4.8 regression] vectorization causes loop unrolling test slowdown as measured by Adobe's C++Benchmark Date: Wed, 13 Jun 2012 09:44:00 -0000 X-Bugzilla-Reason: CC X-Bugzilla-Type: changed X-Bugzilla-Watch-Reason: None X-Bugzilla-Product: gcc X-Bugzilla-Component: rtl-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: --- 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 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: 2012-06/txt/msg00765.txt.bz2 http://gcc.gnu.org/bugzilla/show_bug.cgi?id=53533 --- Comment #13 from Richard Guenther 2012-06-13 09:43:15 UTC --- (In reply to comment #12) > (In reply to comment #10) > > But maybe allowing const_vector in (some of) the define_insn_and_split would > > be the way to go ... > > Maybe. It certainly would ease some of the simplifications. > At the moment I don't think we can go from > > mem -> const -> simplify -> const ->newmem > > On the other hand, for this particular test case, where all > of the vector_cst elements are the same, and a reasonably > small number of bits set, it would be great to be able to > leverage synth_mult. I agree, though that should possibly be done earlier. > The main complexity for sse2_mulv4si3 is due to the fact that > we have to decompose the operation into V8HImode multiplies. > Whereas if we decompose the multiply, we have the shifts and > adds in V4SImode. Well, for a constant multiplier one can avoid the shuffles of the multiplier - we seem to use v2si -> v2di multiplies with sse2_mulv4si3.