From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 14833 invoked by alias); 9 Jan 2019 10:47:54 -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 14820 invoked by uid 89); 9 Jan 2019 10:47:53 -0000 Authentication-Results: sourceware.org; auth=none X-Spam-SWARE-Status: No, score=-1.9 required=5.0 tests=BAYES_00,FREEMAIL_FROM,KAM_SHORT,RCVD_IN_DNSWL_NONE,SPF_PASS autolearn=ham version=3.3.2 spammy=googlemail.com, googlemailcom, H*F:D*googlemail.com, UD:googlemail.com X-HELO: mail-vs1-f67.google.com Received: from mail-vs1-f67.google.com (HELO mail-vs1-f67.google.com) (209.85.217.67) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Wed, 09 Jan 2019 10:47:51 +0000 Received: by mail-vs1-f67.google.com with SMTP id x64so4438377vsa.5 for ; Wed, 09 Jan 2019 02:47:51 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=googlemail.com; s=20161025; h=mime-version:references:in-reply-to:from:date:message-id:subject:to :cc; bh=pti9xSx8KfCn2+/K0Bg63tbzmr8UD4+fAZoXCeSWNDU=; b=H7gQvT8RygZqmkNmPs7KaEiYj0W8GZpwccIHfy1H8XbR6Xt3hQBnNsyHpFrC2ChQnw HC9SiEG305bH2uuoBdYKCy66uNlfMn62ziAJfYZLXVsZXIWlcmgOOA7c38ihXtKZC3Nj 3LrmIe872SaDpAmepIcJgbeDQdL4XDKH5b/TNdQsmyFdtO63Kf1q8CTz38Tbn+PFd4+J 3j8mX1Fi4D08eRIYGW6gxCOrtyO/grqYgBjGDN9si+JHD0MuCjvbrtz+XZCbfOiBUG/2 QMqBJ2pTTLIjS2/gpu8ExGZjFABCnKGksyofyjDoYwDj2UcspSWt5bMlBFBSl+cOntR6 IDRg== MIME-Version: 1.0 References: <41ea83cd-0ce8-4f25-35e5-888513d69c7b@gmail.com> <5C35C2C2.1050106@foss.arm.com> <2721bb39-ee4b-0202-d81d-e0b36d2059fa@redhat.com> In-Reply-To: <2721bb39-ee4b-0202-d81d-e0b36d2059fa@redhat.com> From: Ramana Radhakrishnan Date: Wed, 09 Jan 2019 10:47:00 -0000 Message-ID: Subject: Re: autovectorization in gcc To: Andrew Haley Cc: Kyrill Tkachov , "Kay F. Jahnke" , "gcc@gcc.gnu.org" Content-Type: text/plain; charset="UTF-8" X-IsSubscribed: yes X-SW-Source: 2019-01/txt/msg00050.txt.bz2 On Wed, Jan 9, 2019 at 9:50 AM Andrew Haley wrote: > > 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. That would help certainly : the user could get some information out today with the debug dumps - however they are designed more for the compiler writers rather than users. regards Ramana