From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 78948 invoked by alias); 26 Jul 2016 15:38:07 -0000 Mailing-List: contact gcc-patches-help@gcc.gnu.org; run by ezmlm Precedence: bulk List-Id: List-Archive: List-Post: List-Help: Sender: gcc-patches-owner@gcc.gnu.org Received: (qmail 78936 invoked by uid 89); 26 Jul 2016 15:38:06 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.6 required=5.0 tests=BAYES_00,FREEMAIL_FROM,RCVD_IN_DNSWL_LOW,SPF_PASS autolearn=ham version=3.3.2 spammy=Hx-languages-length:1443, opportunity, 2016-07-26 X-HELO: mail-ua0-f179.google.com Received: from mail-ua0-f179.google.com (HELO mail-ua0-f179.google.com) (209.85.217.179) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with (AES128-GCM-SHA256 encrypted) ESMTPS; Tue, 26 Jul 2016 15:38:03 +0000 Received: by mail-ua0-f179.google.com with SMTP id l32so2524058ual.2 for ; Tue, 26 Jul 2016 08:38:03 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20130820; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=+3EUnddbH2dmE4TXZc4mWg47Xih+CbvpNVH3h3+8vbw=; b=XkfTf9zK9OCiV1s2ICRtKoAseopT5pJGU/S0cQlHqmEsTTlAk7cmvamyiawCeHjidg jsfIUNZWdMR+YOtZU2R+GiewQzYNU5BbtcjkXrq/t0/MahSYmh2NO72N+XyH2vlRmu5M PQJK40lN1FieZbv0pbcQ9lHtFJWoS6jRhkKojg1e+l2/P0MjtNFni5ejbBjuukVMqwZ7 xkiETxavtHGn+MuFElDnyIKPFOz1fEenMZIqhfGANBvXQvUVYlZrLHHp6VJy+O48HQ07 RjSK/clnDUZqNFdhC1oXiUafcCNu9Ad+CNVnb7p5GDh5cuvxDS15LZI/smP3Wm654aU0 uc1Q== X-Gm-Message-State: AEkoouswG3xPsihTvJc0GpBPBoph33KM/fVI8AOq65SeMJZ4tyPUg7ipRiGvz84v8/3YWe0aV8MmpsjFSSBFzg== X-Received: by 10.159.40.102 with SMTP id c93mr10041228uac.78.1469547481041; Tue, 26 Jul 2016 08:38:01 -0700 (PDT) MIME-Version: 1.0 Received: by 10.176.2.244 with HTTP; Tue, 26 Jul 2016 08:38:00 -0700 (PDT) In-Reply-To: <37fbe5e6-6e44-ffff-5467-21e162919586@redhat.com> References: <20160519194450.GH40563@msticlxl57.ims.intel.com> <18ccae1a-30c3-c23c-e28f-287f9d41eaa0@redhat.com> <20160628122439.GB4143@msticlxl57.ims.intel.com> <20160720143705.GA2605@msticlxl57.ims.intel.com> <4bb744cb-92df-ca29-54e2-82162216e88c@redhat.com> <5cacdc29-e916-f460-3c44-5fa6450a24a9@redhat.com> <37fbe5e6-6e44-ffff-5467-21e162919586@redhat.com> From: Ilya Enkovich Date: Tue, 26 Jul 2016 15:38:00 -0000 Message-ID: Subject: Re: [PATCH, vec-tails 07/10] Support loop epilogue combining To: Jeff Law Cc: Richard Biener , gcc-patches , Yuri Rumyantsev , Igor Zamyatin Content-Type: text/plain; charset=UTF-8 X-IsSubscribed: yes X-SW-Source: 2016-07/txt/msg01726.txt.bz2 2016-07-26 18:26 GMT+03:00 Jeff Law : > On 07/26/2016 03:57 AM, Ilya Enkovich wrote: >>> >>> >>> Ilya, what's the fundamental reason why we need to run >>> if-conversion again? Yes, I know you want to if-convert the >>> epilogue, but why? >>> >>> What are the consequences of not doing if-conversion on the >>> epilogue? Presumably we miss a vectorization opportunity on the >>> tail. But that may be a reasonable limitation to allow the >>> existing work to move forward while you go back and revamp things a >>> little. >> >> >> If we have some control-flow in a loop then we have to if-convert it >> for vectorizer. We need to preserve both versions: if-converted one >> for vectorizer and the original one to be used if vectorization >> fails. For epilogues we have similar situation and need two >> versions. I do it by running if-conversion on a copy of original >> loop. Note that it doesn't run full if-conversion pass. If-conversion >> is called for epilogue loop only. > > Right. So what I think Richi wants you to try is to use the if-converted > loop to construct the if-converted epilogue. It seems conceptually simple > and low cost -- the question is on the implementation side. I have no clue > how painful that would be. Probably another part of if-conversion may be re-used to build required epilogue. I'll have a look. Thanks, Ilya > > jeff >