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 58283C71153 for ; Sun, 10 Sep 2023 21:21:10 +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:Cc:List-Subscribe:List-Help:List-Post: List-Archive:List-Unsubscribe:List-Id:MIME-Version:In-Reply-To:References: Message-ID:Date:Subject:To:From:Reply-To:Content-ID:Content-Description: Resent-Date:Resent-From:Resent-Sender:Resent-To:Resent-Cc:Resent-Message-ID: List-Owner; bh=hyooVNlKjWkACRm4Dv1eMkIckvMxmVIAhd86jhVFAs0=; b=OEpLZUDVyR7Wdg 1AYkHdDR6nHZJDvAWk5N0sKF1CmptkW7ZK2z15aNpifcFgNUfuDdHRYKHFw23PCQrVRDNFCjbI/30 FZRiIgT0HPVemEnTmuRd5q/COTDTYJa74xQUtbizAaD+PF3yQ5haZ6wyR4Wz0nQKjpFMqqfIrMkjH CdSmoXhS7M+MoxVH7Z4aM69B/tEWbsV1rUdoqk+avWpUud3w7VJU6hpMu4NxFy0KqsmulA4q16qlR t01KJZqR8uRersORneM8UOxjV5Si0Y4N6l1QTUmScdQDCypxMdnG+C10j8HLNbjpJtEhiBW/VRxSB UR4KkdEpANcQRg6cwEQg==; Received: from localhost ([::1] helo=bombadil.infradead.org) by bombadil.infradead.org with esmtp (Exim 4.96 #2 (Red Hat Linux)) id 1qfRrZ-00GuNd-0c; Sun, 10 Sep 2023 21:21:01 +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 1qfRrW-00GuN0-1P for linux-riscv@lists.infradead.org; Sun, 10 Sep 2023 21:21:00 +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-146-jIjh0yxkNzCFrfh3QFoU7A-1; Sun, 10 Sep 2023 22:20:42 +0100 X-MC-Unique: jIjh0yxkNzCFrfh3QFoU7A-1 Received: from AcuMS.Aculab.com (10.202.163.4) by AcuMS.aculab.com (10.202.163.4) with Microsoft SMTP Server (TLS) id 15.0.1497.48; Sun, 10 Sep 2023 22:20:33 +0100 Received: from AcuMS.Aculab.com ([::1]) by AcuMS.aculab.com ([::1]) with mapi id 15.00.1497.048; Sun, 10 Sep 2023 22:20:33 +0100 From: David Laight To: 'Charlie Jenkins' , Conor Dooley Subject: RE: [PATCH v2 1/5] riscv: Checksum header Thread-Topic: [PATCH v2 1/5] riscv: Checksum header Thread-Index: AQHZ4bMJWeMEu2xwd0uaIDwvnyVCgbAUlGVw Date: Sun, 10 Sep 2023 21:20:33 +0000 Message-ID: References: <20230905-optimize_checksum-v2-0-ccd658db743b@rivosinc.com> <20230905-optimize_checksum-v2-1-ccd658db743b@rivosinc.com> <20230907-f8c8993dbeb24d5ea5310ec7@fedora> In-Reply-To: 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-20230910_142058_742191_9A979501 X-CRM114-Status: UNSURE ( 8.30 ) 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: , Cc: Albert Ou , "linux-kernel@vger.kernel.org" , Palmer Dabbelt , Paul Walmsley , "linux-riscv@lists.infradead.org" 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 ... > > > +/* > > > + * Fold a partial checksum without adding pseudo headers > > > + */ > > > +static inline __sum16 csum_fold(__wsum sum) > > > +{ > > > + sum += (sum >> 16) | (sum << 16); > > > + return (__force __sum16)(~(sum >> 16)); > > > +} I'm intrigued, gcc normally compiler that quite well. The very similar (from arch/arc): return (~sum - rol32(sum, 16)) >> 16; is slightly better on most architectures. (Especially if the ~sum and rol() can be executed together.) The only odd archs I saw were sparc32 (carry flag bug no rotate) and arm (barrel shifter on all instructions). It is better than the current asm for a lot of archs including x64. 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