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 [170.10.129.124]) by sourceware.org (Postfix) with ESMTPS id 1A2093857349 for ; Fri, 13 May 2022 10:58:12 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.4.1 sourceware.org 1A2093857349 Received: from mimecast-mx02.redhat.com (mimecast-mx02.redhat.com [66.187.233.88]) by relay.mimecast.com with ESMTP with STARTTLS (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_GCM_SHA384) id us-mta-665-i3w1IGAWP2uwYddyNpG4UA-1; Fri, 13 May 2022 06:58:10 -0400 X-MC-Unique: i3w1IGAWP2uwYddyNpG4UA-1 Received: from smtp.corp.redhat.com (int-mx08.intmail.prod.int.rdu2.redhat.com [10.11.54.8]) (using TLSv1.2 with cipher AECDH-AES256-SHA (256/256 bits)) (No client certificate requested) by mimecast-mx02.redhat.com (Postfix) with ESMTPS id 4AEE3185A7A4; Fri, 13 May 2022 10:58:10 +0000 (UTC) Received: from oldenburg.str.redhat.com (unknown [10.39.192.147]) by smtp.corp.redhat.com (Postfix) with ESMTPS id 6DD58C44AE2; Fri, 13 May 2022 10:58:08 +0000 (UTC) From: Florian Weimer To: Christoph =?utf-8?Q?M=C3=BCllner?= via Binutils Cc: Palmer Dabbelt , Christoph =?utf-8?Q?M=C3=BCllner?= , Philipp Tomsich , GNU C Library , GCC Patches , gdb-patches@sourceware.org Subject: Re: Supporting RISC-V Vendor Extensions in the GNU Toolchain References: Date: Fri, 13 May 2022 12:58:06 +0200 In-Reply-To: ("Christoph =?utf-8?Q?M=C3=BCllner?= via Binutils"'s message of "Fri, 13 May 2022 12:00:21 +0200") Message-ID: <87y1z5d7i9.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 2.85 on 10.11.54.8 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: redhat.com Content-Type: text/plain; charset=utf-8 Content-Transfer-Encoding: quoted-printable X-Spam-Status: No, score=-5.1 required=5.0 tests=BAYES_00, DKIMWL_WL_HIGH, DKIM_SIGNED, DKIM_VALID, DKIM_VALID_AU, DKIM_VALID_EF, RCVD_IN_DNSWL_LOW, SPF_HELO_NONE, SPF_NONE, TXREP, T_SCC_BODY_TEXT_LINE autolearn=ham autolearn_force=no version=3.4.6 X-Spam-Checker-Version: SpamAssassin 3.4.6 (2021-04-09) on server2.sourceware.org X-BeenThere: binutils@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Binutils mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Fri, 13 May 2022 10:58:13 -0000 * Christoph M=C3=BCllner via Binutils: > I'd like to add two points to this topic and raise two questions. > > 1) Accepting vendor extensions =3D avoidance of fragmentation > > RISC-V implementors are actively encouraged to implement their > own ISA extensions. To avoid fragmentation in the SW ecosystem > (every vendor maintains a fork of tools, distros and binaries) there > needs to be a principle acceptance to get vendor extension support > upstream. If you eventually want portable binaries, it's necessary to converge on a small set of widely implemented extensions. x86 didn't have this, and adoption was poor outside specialized libraries (and JIT, of course). Yet everything was as upstream as possible (ISA manuals, assemblers, compiler intrinsics, even automated adoption by optimizers). So upstreaming is only the first step. Not every useful CPU feature can be adopted through run-time dispatching (IFUNCs, function multi-versionining). Thanks, Florian