From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-pj1-x1031.google.com (mail-pj1-x1031.google.com [IPv6:2607:f8b0:4864:20::1031]) by sourceware.org (Postfix) with ESMTPS id 04E1A384C34E for ; Sat, 17 Dec 2022 00:33:43 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 04E1A384C34E Authentication-Results: sourceware.org; dmarc=pass (p=none dis=none) header.from=gmail.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=gmail.com Received: by mail-pj1-x1031.google.com with SMTP id e7-20020a17090a77c700b00216928a3917so7675519pjs.4 for ; Fri, 16 Dec 2022 16:33:42 -0800 (PST) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :from:to:cc:subject:date:message-id:reply-to; bh=yC6BosapkinreV1/n2fBcCnX0Sxa7chMWkKb1WC6kp4=; b=Nk92gyw61LKhJkZdnNoFl0swyGEsFXcDCgNaHhrhRimDHATA2XjBAj0YB3qKroWEqG lXoWc8WBomk4xrhFzYdIAJ6O7UEf+0H0mt4evvJH12VeN4j6jciTYxxN+UVkQRATS+KZ czB0a5fsA3l8cTFfHOn+HG9ruCMe/uI1xXVfkwge9CtXsUh+pQATNasKwX66E/VkQuip v2lcMaWsqM/w0wStSuSeOMENO0vudz2nN4ER19CKBCOVHe3+ehFcbLR+jXNzrwUW98w3 LX55+ciM2yHsGugaLNXgbrBz5CDZoqIsjQ8S1CDdK7mfD6TlwMNFuyuNVTBiwutsFzY6 f2+w== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=content-transfer-encoding:in-reply-to:from:references:cc:to :content-language:subject:user-agent:mime-version:date:message-id :x-gm-message-state:from:to:cc:subject:date:message-id:reply-to; bh=yC6BosapkinreV1/n2fBcCnX0Sxa7chMWkKb1WC6kp4=; b=DdTsnCcU7otS4hAsUKlLTb3HMOnLN4ZCud9ZH93K+mpDUoi8Su9G4+YmCL7JD1iivh FgFEYDr3iYc7DfUCmiR03tcD67KDdn2UqPB6HbIyPvCu3y/zilkZbEuVKXecgT1Ln5Iz qqbl4hhrOFmsjdjv1+UOML6g8FX1/H6QDoPsJ7nS62mVdza2UfcHu8zSHayKUc9NnZlm 6GyVJfMpO9K1sIw45/O2oxcdoYcd12AwLrVP3Gaj+8dV8YvXfxZ8sdr3vF5bRty7bj3q jNs4JvuKwX2PBfsNzxrVduKyFKmVQ9KuL8cSyvmYl8XqSv1IrdiQwte5HfuxTFl2XpKI zKkQ== X-Gm-Message-State: AFqh2kp2OeGBPhov66hNpVrCy332xznob0RDaYpzP1wCQbSOwmhOz8aj ZOlasjEHxlmzqeQtScqwLWY= X-Google-Smtp-Source: AMrXdXu5jG16+zraqxw8DWm0lYCq31Jds1y9XKUPm0Y1IK8WhC7YbxNb34kpMBgLJABmygKFmxzaGQ== X-Received: by 2002:a05:6a20:4f16:b0:af:9c65:5ba5 with SMTP id gi22-20020a056a204f1600b000af9c655ba5mr9373362pzb.60.1671237221843; Fri, 16 Dec 2022 16:33:41 -0800 (PST) Received: from ?IPV6:2601:681:8600:13d0::f0a? ([2601:681:8600:13d0::f0a]) by smtp.gmail.com with ESMTPSA id nl16-20020a17090b385000b00218f529e486sm5487669pjb.0.2022.12.16.16.33.40 (version=TLS1_3 cipher=TLS_AES_128_GCM_SHA256 bits=128/128); Fri, 16 Dec 2022 16:33:41 -0800 (PST) Message-ID: <8de37756-4b6f-48fc-e878-40a966db61b0@gmail.com> Date: Fri, 16 Dec 2022 17:33:40 -0700 MIME-Version: 1.0 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:102.0) Gecko/20100101 Thunderbird/102.5.0 Subject: Re: Possible regression in DF analysis Content-Language: en-US To: Claudiu Zissulescu Ianculescu , Eric Botcazou Cc: gcc@gcc.gnu.org References: <2858689.e9J7NaK4W3@fomalhaut> From: Jeff Law In-Reply-To: Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 7bit X-Spam-Status: No, score=-2.4 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=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org List-Id: On 12/8/22 04:51, Claudiu Zissulescu Ianculescu via Gcc wrote: > Hi Eric, > The problem shows in loop-doloop.c when I introduce a loop end pattern > that replaces the first jump instruction (JUMP_INSN 15) with a pattern > that clobbers CC reg. However, the DF doesn't look like it works as > the doloop step cannot find the CC reg alive. Please see > loop-doloop.c:766. Hence, it introduces the doloop_end patterns, and > renders the compare instruction (INSN 14) dead code. leading to But simply inserting an instruction that clobbers CC can't be a valid thing to do. You have to verify that the register isn't live at the point where you want to do the insertion. Or is that the core of the problem -- that life analysis is inaccurate or unavailable? Jeff