From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from mail-lf1-x133.google.com (mail-lf1-x133.google.com [IPv6:2a00:1450:4864:20::133]) by sourceware.org (Postfix) with ESMTPS id E03A5385AC2D for ; Fri, 28 Oct 2022 15:51:45 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org E03A5385AC2D 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-lf1-x133.google.com with SMTP id g7so8984348lfv.5 for ; Fri, 28 Oct 2022 08:51:45 -0700 (PDT) DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=gmail.com; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:from:to:cc:subject:date:message-id:reply-to; bh=uOxBlZBcFYEN65HdQXqiRujulbwhvzH6OI6isLt6ZEk=; b=AhVfy+nJdUsgu/44m30xKZcRx0gMapFU7KBPnwj2R+C/upV8wJUdRxTUnolfcHR14n Scr7di4PWUdqXYDhfzhwH2aFE9+/cRVNioeHHs0YOmaRc5XUdfYCfWgImiH84qI/WZ3H pjJpdomRiiQJQ/Gdudkq0TgIxD+2qnm0BTyx+xGVFdynOI4gXZzMaDXBCQZ0uDL3fpAY p8SIsnSyRV5uu39RmJsUOQwupvSSNEgrmykJTWyecT/MYhodC6O5IykMQ6Y1gfrGKDb6 TFv9lzG23mNsFGbkmmI33VXQ1Ti/AT0FzSd7Wvn1TixCk1eyw9g2D6nLeimmWcQVuyoQ jwnw== X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20210112; h=cc:to:subject:message-id:date:from:in-reply-to:references :mime-version:x-gm-message-state:from:to:cc:subject:date:message-id :reply-to; bh=uOxBlZBcFYEN65HdQXqiRujulbwhvzH6OI6isLt6ZEk=; b=8IV8+BIqHVBTV+nZCVGh2qO5ELhSCN/QWkk+688xA6gGhhoMTX8KWeKfAgUdfkxUk7 QAhcgmv1DPEMtEeoTCnRdgGuZVhpCxG66IA0be2IYCI6StdCZ26I04t5qO2kXcLM8+hC rH7ATDfCyJn5jzq2gNEvhDrs8OfvVoD/cbV0EJm/Nsca2NK5zhtWXIu0g+/l1oPITdHf vL5KWQtEfKMmErn0pGF9K8ADrKwIHS2ZcTK+VCm2m/BZB0CbHsE/yCO8acmwNq59LVx6 pmCFY4gpFR2Wp8tsqik0vv42xgNMgpTiR4ubmW4ImAElmq6BT5vLxIWbaIRiLeV+Q80D d0YQ== X-Gm-Message-State: ACrzQf1q5C2Taqg2DigRr+Srjn/xNsPpIaaDiBuzjzW85K0B6TgTNLdj KMjURrdLxSrDWWgmfgpqk5wB1yXIjZO6tjn5h64= X-Google-Smtp-Source: AMsMyM7bFPKWgLlENsqV7Htxj00ZScIlkT9fthT7d59o3VYaiqP6xRLKvkvZpuPsoezyQfO7kjbicM6kmnk2SASFw/c= X-Received: by 2002:a05:6512:3403:b0:48c:9727:50b0 with SMTP id i3-20020a056512340300b0048c972750b0mr19636884lfr.309.1666972304123; Fri, 28 Oct 2022 08:51:44 -0700 (PDT) MIME-Version: 1.0 References: <20221026185857.234023-1-hjl.tools@gmail.com> <4752529.GXAFRqVoOG@fomalhaut> In-Reply-To: <4752529.GXAFRqVoOG@fomalhaut> From: "H.J. Lu" Date: Fri, 28 Oct 2022 08:51:07 -0700 Message-ID: Subject: Re: [PATCH] x86: Replace ne:CCC/ne:CCO with UNSPEC_CC_NE in neg patterns To: Eric Botcazou Cc: gcc-patches@gcc.gnu.org, Uros Bizjak Content-Type: text/plain; charset="UTF-8" X-Spam-Status: No, score=-3016.7 required=5.0 tests=BAYES_00,DKIM_SIGNED,DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,FREEMAIL_FROM,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 Fri, Oct 28, 2022 at 1:35 AM Eric Botcazou wrote: > > > (set (reg:SI 93) > > (neg:SI (ltu:SI (reg:CCC 17 flags) (const_int 0 [0])))) > > > > as > > > > (set (reg:SI 93) > > (neg:SI (ltu:SI (const_int 1) (const_int 0 [0])))) > > > > which leads to incorrect results since LTU on MODE_CC register isn't the > > same as "unsigned less than" in x86 backend. > > That's not specific to the x86 back-end, i.e. it's a generic caveat. > > > PR target/107172 > > * config/i386/i386.md (UNSPEC_CC_NE): New. > > Replace ne:CCC/ne:CCO with UNSPEC_CC_NE in neg patterns. > > FWIW the SPARC back-end uses a COMPARE instead of an UNSPEC here. COMPARE may also set CC register to a constant when both operands are known constants. -- H.J.