From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from us-smtp-delivery-124.mimecast.com (us-smtp-delivery-124.mimecast.com [216.205.24.124]) by sourceware.org (Postfix) with ESMTP id 551C8388C032 for ; Thu, 6 May 2021 15:09:06 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 551C8388C032 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-383-HHJBLMbgOgKovelPxkjvuA-1; Thu, 06 May 2021 11:09:04 -0400 X-MC-Unique: HHJBLMbgOgKovelPxkjvuA-1 Received: from smtp.corp.redhat.com (int-mx04.intmail.prod.int.phx2.redhat.com [10.5.11.14]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx01.redhat.com (Postfix) with ESMTPS id AC842805EF2; Thu, 6 May 2021 15:09:02 +0000 (UTC) Received: from oldenburg.str.redhat.com (ovpn-112-137.ams2.redhat.com [10.36.112.137]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 5C1015D9E2; Thu, 6 May 2021 15:09:01 +0000 (UTC) From: Florian Weimer To: Szabolcs Nagy via Libc-alpha Cc: "naohirot@fujitsu.com" , Szabolcs Nagy , 'Wilco Dijkstra' Subject: Re: [PATCH 0/5] Added optimized memcpy/memmove/memset for A64FX References: <20210506142658.GA9028@arm.com> Date: Thu, 06 May 2021 17:09:19 +0200 In-Reply-To: <20210506142658.GA9028@arm.com> (Szabolcs Nagy via Libc-alpha's message of "Thu, 6 May 2021 15:26:59 +0100") Message-ID: <875yzvhpb4.fsf@oldenburg.str.redhat.com> User-Agent: Gnus/5.13 (Gnus v5.13) Emacs/27.2 (gnu/linux) MIME-Version: 1.0 X-Scanned-By: MIMEDefang 2.79 on 10.5.11.14 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain X-Spam-Status: No, score=-6.8 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_LOW, RCVD_IN_MSPIKE_H4, RCVD_IN_MSPIKE_WL, SPF_HELO_NONE, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org 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: , X-List-Received-Date: Thu, 06 May 2021 15:09:09 -0000 * Szabolcs Nagy via Libc-alpha: > this means a64fx implemented hint space instructions > (such as bti c) slower than plain nops, which is not > expected and will cause slowdowns with distros that > try to distribute binaries with bti c, this problem > goes beyond string functions. And we are using -mbranch-protection=standard on AArch64 going forward, for example: | optflags: aarch64 %{__global_compiler_flags} -mbranch-protection=standard -fasynchronous-unwind-tables %[ "%{toolchain}" == "gcc" ? "-fstack-clash-protection" : "" ] (Fedora is similar. This is why I find this issue so worrying. Thanks, Florian