From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 9721 invoked by alias); 9 Jan 2019 09:50:15 -0000 Mailing-List: contact gcc-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-owner@gcc.gnu.org Received: (qmail 9710 invoked by uid 89); 9 Jan 2019 09:50:15 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-1.9 required=5.0 tests=BAYES_00,KAM_SHORT,SPF_HELO_PASS autolearn=ham version=3.3.2 spammy=plenty, Kay, H*f:sk:41ea83c, user-visible X-HELO: mx1.redhat.com Received: from mx1.redhat.com (HELO mx1.redhat.com) (209.132.183.28) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Wed, 09 Jan 2019 09:50:13 +0000 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mx1.redhat.com (Postfix) with ESMTPS id 7076A81DEC; Wed, 9 Jan 2019 09:50:12 +0000 (UTC) Received: from zebedee.pink (ovpn-126-138.rdu2.redhat.com [10.10.126.138]) by smtp.corp.redhat.com (Postfix) with ESMTP id 213E35ED5B; Wed, 9 Jan 2019 09:50:09 +0000 (UTC) Subject: Re: autovectorization in gcc To: Kyrill Tkachov , "Kay F. Jahnke" , "gcc@gcc.gnu.org" References: <41ea83cd-0ce8-4f25-35e5-888513d69c7b@gmail.com> <5C35C2C2.1050106@foss.arm.com> From: Andrew Haley Openpgp: preference=signencrypt Message-ID: <2721bb39-ee4b-0202-d81d-e0b36d2059fa@redhat.com> Date: Wed, 09 Jan 2019 09:50:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:60.0) Gecko/20100101 Thunderbird/60.3.0 MIME-Version: 1.0 In-Reply-To: <5C35C2C2.1050106@foss.arm.com> Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: 7bit X-IsSubscribed: yes X-SW-Source: 2019-01/txt/msg00047.txt.bz2 On 1/9/19 9:45 AM, Kyrill Tkachov wrote: > Hi Kay, > > On 09/01/19 08:29, Kay F. Jahnke wrote: >> Hi there! >> >> I am developing software which tries to deliberately exploit the >> compiler's autovectorization facilities by feeding data in >> autovectorization-friendly loops. I'm currently using both g++ and >> clang++ to see how well this approach works. Using simple arithmetic, I >> often get good results. To widen the scope of my work, I was looking for >> documentation on which constructs would be recognized by the >> autovectorization stage, and found >> >> https://www.gnu.org/software/gcc/projects/tree-ssa/vectorization.html >> > > Yeah, that page hasn't been updated in ages AFAIK. > >> By the looks of it, this document has not seen any changes for several >> years. Has development on the autovectorization stage stopped, or is >> there simply no documentation? >> > > There's plenty of work being done on auto-vectorisation in GCC. > Auto-vectorisation is a performance optimisation and as such is not really > a user-visible feature that absolutely requires user documentation. I don't agree. Sometimes vectorization is critical. It would be nice to have a warning which would fire if vectorization failed. That would surely help the OP. -- Andrew Haley Java Platform Lead Engineer Red Hat UK Ltd. EAC8 43EB D3EF DB98 CC77 2FAD A5CD 6035 332F A671