From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 77910 invoked by alias); 12 Apr 2018 16:11:36 -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 77893 invoked by uid 89); 12 Apr 2018 16:11:36 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.6 required=5.0 tests=AWL,BAYES_00,FREEMAIL_FROM,RCVD_IN_DNSWL_NONE,SPF_PASS autolearn=ham version=3.3.2 spammy=PERIOD X-HELO: mail-ot0-f174.google.com Received: from mail-ot0-f174.google.com (HELO mail-ot0-f174.google.com) (74.125.82.174) by sourceware.org (qpsmtpd/0.93/v0.84-503-g423c35a) with ESMTP; Thu, 12 Apr 2018 16:11:34 +0000 Received: by mail-ot0-f174.google.com with SMTP id a14-v6so6626958otf.6 for ; Thu, 12 Apr 2018 09:11:34 -0700 (PDT) X-Google-DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=1e100.net; s=20161025; h=x-gm-message-state:mime-version:in-reply-to:references:from:date :message-id:subject:to:cc; bh=f0OFKQf5/oKDE1qExMj1esoEqWhju+bbYGder+gYslI=; b=Mb8YlC5BZVwer3WMqc4pBuyOPovMhOLbRZFz5wksgCKSGJa5MGIEDYsX4giRBhGJBv UJgXPw8w84gSLLoRYJxECQqXi0dsb2n2iQuswd6MaHS0X+TQuTj7i4eXgU4CLNUXf9dU mPJ8HDSLFXcjq4Nb27OntZHjK2+mp5M7ImqTRYw63OvHqA0bnH3hFl8mUzc8TyQQzdEC zJBo63Zje5+4fHWL0ZUvmEtPH5+PPvZEzKNf9Xbf+uhlGBWkMrRVn5fBEoCPMU+wDwSZ JlAcgEY+LsANEMrzBZKe807ICLcxDhR/eClastKLV5hB/w3c7FLeaeYnU0werFEoX39i yv1g== X-Gm-Message-State: ALQs6tB+1MWr8McCNmpNBmdOVQ23yLmlW/au9TLGJEwfih6DN1bOK5tO acDAIqkh6CvwtWea3LaRabwWqemPWYQdN3KZRaI= X-Google-Smtp-Source: AIpwx4+psJSKwtypJxUaj/zMNZHaiZJADV7bCHRTGIOax/bHKGKhWip74IaeqMTyFudbS/xKInilQZ275l8jhTnIc48= X-Received: by 2002:a9d:4479:: with SMTP id f54-v6mr1136647otj.125.1523549492935; Thu, 12 Apr 2018 09:11:32 -0700 (PDT) MIME-Version: 1.0 Received: by 10.74.190.152 with HTTP; Thu, 12 Apr 2018 09:11:32 -0700 (PDT) In-Reply-To: References: From: "H.J. Lu" Date: Thu, 12 Apr 2018 16:11:00 -0000 Message-ID: Subject: Re: [PATCH] Prefer mempcpy to memcpy on x86_64 target (PR middle-end/81657). To: Wilco Dijkstra Cc: Jakub Jelinek , Richard Biener , nd , "mliska@suse.cz" , "ubizjak@gmail.com" , GCC Patches , "marc.glisse@inria.fr" , Jan Hubicka Content-Type: text/plain; charset="UTF-8" X-IsSubscribed: yes X-SW-Source: 2018-04/txt/msg00617.txt.bz2 On Thu, Apr 12, 2018 at 8:53 AM, Wilco Dijkstra wrote: > So generally it's a good idea to change mempcpy into memcpy by default. It's > not slower than calling mempcpy even if you have a fast implementation, it's faster > if you use an up to date GLIBC which calls memcpy, and it's significantly better > when using an old GLIBC. > It is a BAD idea for x86. We don't want to turn mempcpy to to memcpy on x86. PERIOD. -- H.J.