From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on dcvr.yhbt.net X-Spam-Level: X-Spam-ASN: AS17314 8.43.84.0/22 X-Spam-Status: No, score=-3.7 required=3.0 tests=AWL,BAYES_00,DKIM_SIGNED, DKIM_VALID,DKIM_VALID_AU,DKIM_VALID_EF,MAILING_LIST_MULTI, RCVD_IN_DNSWL_MED,RDNS_DYNAMIC,SPF_HELO_PASS,SPF_PASS shortcircuit=no autolearn=ham autolearn_force=no version=3.4.2 Received: from sourceware.org (ip-8-43-85-97.sourceware.org [8.43.85.97]) (using TLSv1.3 with cipher TLS_AES_256_GCM_SHA384 (256/256 bits) key-exchange X25519 server-signature RSA-PSS (4096 bits) server-digest SHA256) (No client certificate requested) by dcvr.yhbt.net (Postfix) with ESMTPS id 39CEE1F8C6 for ; Tue, 14 Sep 2021 05:43:05 +0000 (UTC) Received: from server2.sourceware.org (localhost [IPv6:::1]) by sourceware.org (Postfix) with ESMTP id 0DFED385842C for ; Tue, 14 Sep 2021 05:43:04 +0000 (GMT) DKIM-Filter: OpenDKIM Filter v2.11.0 sourceware.org 0DFED385842C DKIM-Signature: v=1; a=rsa-sha256; c=relaxed/relaxed; d=sourceware.org; s=default; t=1631598184; bh=k1PtraA02Kj6rq0tvfJbh0I3NHw42Np+agwejWBpSvI=; h=To:Subject:In-Reply-To:Date:List-Id:List-Unsubscribe:List-Archive: List-Post:List-Help:List-Subscribe:From:Reply-To:Cc:From; b=wa5/vZdh2dRKTKdOAf2DkXHtC1wyIaTZlPM/aSMbugh7OWYtQPaY50LWInh5zcmH2 gQE5E+5zFgLhESigoK6k7BL8mbm08uqHsBBdI/gHQze0Fw9MMPqHlZPgYPJnGiIQwN n9p932qFgS6t1kJ4SscG74YvwL68zWnm1jlxnkbE= Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [170.10.133.124]) by sourceware.org (Postfix) with ESMTP id D87AF3858402 for ; Tue, 14 Sep 2021 05:42:45 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org D87AF3858402 Received: from mimecast-mx01.redhat.com (mimecast-mx01.redhat.com [209.132.183.4]) (Using TLS) by relay.mimecast.com with ESMTP id us-mta-586-OuFVpuNuM7mNQ2LqhaJ_dQ-1; Tue, 14 Sep 2021 01:42:42 -0400 X-MC-Unique: OuFVpuNuM7mNQ2LqhaJ_dQ-1 Received: from smtp.corp.redhat.com (int-mx03.intmail.prod.int.phx2.redhat.com [10.5.11.13]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id 7EA7D1084681; Tue, 14 Sep 2021 05:42:41 +0000 (UTC) Received: from greed.delorie.com (ovpn-112-2.rdu2.redhat.com [10.10.112.2]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6EC082B399; Tue, 14 Sep 2021 05:42:38 +0000 (UTC) Received: from greed.delorie.com.redhat.com (localhost [127.0.0.1]) by greed.delorie.com (8.15.2/8.15.2) with ESMTP id 18E5gach1799619; Tue, 14 Sep 2021 01:42:37 -0400 To: Noah Goldstein Subject: Re: [PATCH 5/5] x86_64: Add evex optimized bcmp implementation in bcmp-evex.S In-Reply-To: Date: Tue, 14 Sep 2021 01:42:36 -0400 Message-ID: MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.13 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-BeenThere: libc-alpha@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Libc-alpha mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , From: DJ Delorie via Libc-alpha Reply-To: DJ Delorie Cc: libc-alpha@sourceware.org Errors-To: libc-alpha-bounces+e=80x24.org@sourceware.org Sender: "Libc-alpha" Noah Goldstein writes: > I'm not 100% sure what you mean? memcmp can correctly implement bcmp > but not the vice versa. glibc does not have a separate implementation of bcmp(). Any calls to bcmp() end up calling memcmp() (through that weak alias). So your patch is not *optimizing* bcmp, it is *adding* bcmp. The new version you are adding is no longer using the optimized versions of memcmp, so you'd have to either (1) be very careful to not introduce a performance regression, or (2) optimize the existing memcmp()s further instead.