From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 40808 invoked by alias); 26 Apr 2016 14:16:21 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Received: (qmail 40791 invoked by uid 89); 26 Apr 2016 14:16:21 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-2.9 required=5.0 tests=BAYES_00,RP_MATCHES_RCVD,SPF_HELO_PASS autolearn=ham version=3.3.2 spammy= X-HELO: mx1.redhat.com Subject: Re: [PATCH 2/4] S390: Use 64bit instruction to check for copies of > 1MB with mvcle. To: Stefan Liebler , libc-alpha@sourceware.org References: <1461672469-2107-1-git-send-email-stli@linux.vnet.ibm.com> <1461672469-2107-2-git-send-email-stli@linux.vnet.ibm.com> Cc: carlos@redhat.com, Wilco.Dijkstra@arm.com, neleai@seznam.cz From: Florian Weimer Message-ID: <571F7826.5050402@redhat.com> Date: Tue, 26 Apr 2016 14:16:00 -0000 User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:38.0) Gecko/20100101 Thunderbird/38.7.1 MIME-Version: 1.0 In-Reply-To: <1461672469-2107-2-git-send-email-stli@linux.vnet.ibm.com> Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 7bit X-SW-Source: 2016-04/txt/msg00647.txt.bz2 On 04/26/2016 02:07 PM, Stefan Liebler wrote: > The __memcpy_default variant on s390 64bit calculates the number of > 256byte blocks in a 64bit register and checks, if they exceed 1MB > to jump to mvcle. Otherwise a mvc-loop is used. The compare-instruction > only checks a 32bit value. > This patch uses a 64bit compare. This is purely an optimization, right? Did the previous implementation still perform a complete copy (although perhaps in a less efficient way)? Thanks, Florian