From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pl1-x62b.google.com (mail-pl1-x62b.google.com [IPv6:2607:f8b0:4864:20::62b]) by sourceware.org (Postfix) with ESMTPS id 4E5733858410 for ; Thu, 14 Oct 2021 14:23:12 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 4E5733858410 Received: by mail-pl1-x62b.google.com with SMTP id c4so4289321pls.6 for ; Thu, 14 Oct 2021 07:23:12 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=x-gm-message-state:subject:to:cc:references:from:message-id:date :user-agent:mime-version:in-reply-to:content-transfer-encoding :content-language; bh=AdNF+FQPbMmOKE/wXK8a+rf7+qX6+4fR80veK7wIwMU=; b=26yurtVhIKgXQZxuzKJN1RfHqsRH0Wqkm/0f6Ybe1qmeULVsmKlwVB/dyID0bnfBol nYL1jaNZjlCys98nttgKiw7PJa+UqB+D3O2C0C+LMn3vDlaEcjNYZe/oDzH65fIVGq1J 8SfXK3XI3JpsPu3F1nwMtxGH7Braj0V6mPPNuAy2HxQK3TeD9uOfuuFt6IPaj/rW5VpC cZTal4pjoilhFatzqJVkNRoEcUk5p0r44EEjIMGH8BGjaYWKB8ZTv2AwfHEImJ3TRpOC OSj7hsKycDdJGRg4Ohv22kL0HarCyTK0uPo5YJrOwu394fWP2O7k0O+B4qJYvug7HmNl XRsw== X-Gm-Message-State: AOAM533FUljA/6Yeno9O44VSZEDdkL9aZw4ftpwpq1RtfNK+sRvEKDY3 eVL+VW/gyzdZKX2xScRuHqU8OJb/g10= X-Google-Smtp-Source: ABdhPJxcTPIHjZrP3yOXJ7NfrjpzikDjBTHOxH5SEIjuPg5bXjgqElbADY0kC6prvmNTZpPWmi14Zg== X-Received: by 2002:a17:902:8b8b:b0:13d:e91c:a1b9 with SMTP id ay11-20020a1709028b8b00b0013de91ca1b9mr5357507plb.60.1634221391173; Thu, 14 Oct 2021 07:23:11 -0700 (PDT) Received: from [172.31.0.175] (c-98-202-48-222.hsd1.ut.comcast.net. [98.202.48.222]) by smtp.gmail.com with ESMTPSA id f30sm2835548pfq.142.2021.10.14.07.23.10 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Thu, 14 Oct 2021 07:23:10 -0700 (PDT) Subject: Re: [RFC] More jump threading restrictions in the presence of loops. To: Aldy Hernandez , Richard Biener , Michael Matz Cc: Andrew MacLeod , GCC patches References: <20211004094313.1596556-1-aldyh@redhat.com> From: Jeff Law Message-ID: Date: Thu, 14 Oct 2021 08:23:09 -0600 User-Agent: Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:78.0) Gecko/20100101 Thunderbird/78.14.0 MIME-Version: 1.0 In-Reply-To: Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 7bit Content-Language: en-US X-Spam-Status: No, score=-2.5 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, FREEMAIL_FROM, NICE_REPLY_A, RCVD_IN_DNSWL_NONE, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.4 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on server2.sourceware.org X-BeenThere: gcc-patches@gcc.gnu.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Gcc-patches mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Thu, 14 Oct 2021 14:23:13 -0000 On 10/14/2021 3:25 AM, Aldy Hernandez wrote: > PING. > > Note, that there are no PRs and nothing really dependent on this > patch. This has just been suggested as the right thing to do wrt > loops. > > This patch fixes 6 XFAILs in our testsuite and has the added > side-effect of fixing the aarch64 bootstrap problem (though the > problem in the uninit code is still there). > > This is a fundamental change in what we've traditionally allowed for > jump threading, but I think it's a good thing. It also paves the way > for combining the validity models for both the forward and the > backward threaders. > > I am happy to field the PRs this may bring about, since every change > in the cost model has us questioning whether we should or shouldn't > thread a path. But I may need some help from y'all if there's a > missing thread that causes a regression in some other pass. That > being said, most of the issues that have come with the threader > changes haven't been because we thread less, but because we thread > more-- so perhaps restricting things is a good thing ;-). Just chasing down fallout from the vectorizer changes first :-) jeff