From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: X-Spam-Checker-Version: SpamAssassin 3.4.0 (2014-02-07) on aws-us-west-2-korg-lkml-1.web.codeaurora.org Received: from bombadil.infradead.org (bombadil.infradead.org [198.137.202.133]) (using TLSv1.2 with cipher ECDHE-RSA-AES256-GCM-SHA384 (256/256 bits)) (No client certificate requested) by smtp.lore.kernel.org (Postfix) with ESMTPS id 4DBF7C61D9B for ; Wed, 22 Nov 2023 11:16:10 +0000 (UTC) DKIM-Signature: v=1; a=rsa-sha256; q=dns/txt; c=relaxed/relaxed; d=lists.infradead.org; s=bombadil.20210309; h=Sender: Content-Transfer-Encoding:Content-Type:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:In-Reply-To:References: Message-ID:Date:Subject:CC:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=bsiEMGQWKE1jlsnixuEZZZO2frkAM9aQc1yRzz9YX7I=; b=SShCCZWsI04yxq t0u9VOhsd6fSPxC8zXLEJ/cdCgVfbbwPYZKN6XUeCxSJRMNtc+3NBYTibVPZWTzGn2REJt+89vNSc pRKF5dDf/GgxZbZb7YGLlqhp9vM91TYRedcFlhJjzW8wIebel2EEme173aM1Nn49dhrmzEI5ZC/Jf aOdlT7rcBAUv24yeAo5cUcCUKSR+HHeW/ZtmD/tstEOpjciPU+nSA6SMYvA1IM4h5Do/4ayePyNb7 IZmEfmH1/FUQi/bTnjdoJgymzd65W2GipVEi9HBzuUMBqvvUNMqULLlFK3MI7B4bQ2rcMrMyG4YaJ V9MFbXMbWFSP346UN9xw==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1r5lDB-001WZp-2g; Wed, 22 Nov 2023 11:16:05 +0000 Received: from eu-smtp-delivery-151.mimecast.com ([185.58.85.151]) by bombadil.infradead.org with esmtps (Exim 4.96 #2 (Red Hat Linux)) id 1r5lD8-001WYj-1h for linux-riscv@lists.infradead.org; Wed, 22 Nov 2023 11:16:04 +0000 Received: from AcuMS.aculab.com (156.67.243.121 [156.67.243.121]) by relay.mimecast.com with ESMTP with both STARTTLS and AUTH (version=TLSv1.2, cipher=TLS_ECDHE_RSA_WITH_AES_256_CBC_SHA384) id uk-mta-72-nmAAUN1cNVK2s83WvssOog-1; Wed, 22 Nov 2023 11:15:53 +0000 X-MC-Unique: nmAAUN1cNVK2s83WvssOog-1 Received: from AcuMS.Aculab.com (10.202.163.6) by AcuMS.aculab.com (10.202.163.6) with Microsoft SMTP Server (TLS) id 15.0.1497.48; Wed, 22 Nov 2023 11:16:23 +0000 Received: from AcuMS.Aculab.com ([::1]) by AcuMS.aculab.com ([::1]) with mapi id 15.00.1497.048; Wed, 22 Nov 2023 11:16:23 +0000 From: David Laight To: 'Jisheng Zhang' , Paul Walmsley , Palmer Dabbelt , Albert Ou CC: "linux-riscv@lists.infradead.org" , "linux-kernel@vger.kernel.org" Subject: RE: [PATCH] riscv: select ARCH_HAS_FAST_MULTIPLIER Thread-Topic: [PATCH] riscv: select ARCH_HAS_FAST_MULTIPLIER Thread-Index: AQHaHIr3F/LmUcOCEUqs//JJARgdtrCGLu+Q Date: Wed, 22 Nov 2023 11:16:23 +0000 Message-ID: <47995b4daafb43348fc839ffb486f56b@AcuMS.aculab.com> References: <20231121144340.3492-1-jszhang@kernel.org> In-Reply-To: <20231121144340.3492-1-jszhang@kernel.org> Accept-Language: en-GB, en-US X-MS-Has-Attach: X-MS-TNEF-Correlator: x-ms-exchange-transport-fromentityheader: Hosted x-originating-ip: [10.202.205.107] MIME-Version: 1.0 X-Mimecast-Spam-Score: 0 X-Mimecast-Originator: aculab.com Content-Language: en-US X-CRM114-Version: 20100106-BlameMichelson ( TRE 0.8.0 (BSD) ) MR-646709E3 X-CRM114-CacheID: sfid-20231122_031602_851843_12F76B71 X-CRM114-Status: UNSURE ( 4.51 ) X-CRM114-Notice: Please train this message. X-BeenThere: linux-riscv@lists.infradead.org X-Mailman-Version: 2.1.34 Precedence: list List-Id: List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , Content-Type: text/plain; charset="us-ascii" Content-Transfer-Encoding: 7bit Sender: "linux-riscv" Errors-To: linux-riscv-bounces+linux-riscv=archiver.kernel.org@lists.infradead.org ... > However, the > situation exists on x86 too, for example, P4 doesn't have fast > integer multiplies ... P4 doesn't have fast anything :-) More interestingly does anything modern not have fast multiplies? (that you'd consider running Linux on). The silicon required isn't that big. IIRC an 'n' bit multiplier requires n^2 full adders and has the latency of 2n adders. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales) _______________________________________________ linux-riscv mailing list linux-riscv@lists.infradead.org http://lists.infradead.org/mailman/listinfo/linux-riscv