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 X-Spam-Level: X-Spam-Status: No, score=-1.0 required=3.0 tests=HEADER_FROM_DIFFERENT_DOMAINS, MAILING_LIST_MULTI,SPF_PASS autolearn=ham autolearn_force=no version=3.4.0 Received: from mail.kernel.org (mail.kernel.org [198.145.29.99]) by smtp.lore.kernel.org (Postfix) with ESMTP id 559ADC43441 for ; Fri, 23 Nov 2018 10:53:36 +0000 (UTC) Received: from vger.kernel.org (vger.kernel.org [209.132.180.67]) by mail.kernel.org (Postfix) with ESMTP id 22FEE20820 for ; Fri, 23 Nov 2018 10:53:36 +0000 (UTC) DMARC-Filter: OpenDMARC Filter v1.3.2 mail.kernel.org 22FEE20820 Authentication-Results: mail.kernel.org; dmarc=none (p=none dis=none) header.from=ACULAB.COM Authentication-Results: mail.kernel.org; spf=none smtp.mailfrom=linux-kernel-owner@vger.kernel.org Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S2503549AbeKWVhV convert rfc822-to-8bit (ORCPT ); Fri, 23 Nov 2018 16:37:21 -0500 Received: from eu-smtp-delivery-151.mimecast.com ([146.101.78.151]:29247 "EHLO eu-smtp-delivery-151.mimecast.com" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S2390373AbeKWVhV (ORCPT ); Fri, 23 Nov 2018 16:37:21 -0500 Received: from AcuMS.aculab.com (156.67.243.126 [156.67.243.126]) (Using TLS) by relay.mimecast.com with ESMTP id uk-mta-99-GPDCUzThP7OsQ6S8j4J4iA-1; Fri, 23 Nov 2018 10:53:30 +0000 Received: from AcuMS.Aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) by AcuMS.aculab.com (fd9f:af1c:a25b:0:43c:695e:880f:8750) with Microsoft SMTP Server (TLS) id 15.0.1347.2; Fri, 23 Nov 2018 10:53:37 +0000 Received: from AcuMS.Aculab.com ([fe80::43c:695e:880f:8750]) by AcuMS.aculab.com ([fe80::43c:695e:880f:8750%12]) with mapi id 15.00.1347.000; Fri, 23 Nov 2018 10:53:37 +0000 From: David Laight To: 'Vincent Chen' , "green.hu@gmail.com" , "arnd@arndb.de" CC: "linux-kernel@vger.kernel.org" , Nickhu Subject: RE: [PATCH v4 2/5] nds32: Support FP emulation Thread-Topic: [PATCH v4 2/5] nds32: Support FP emulation Thread-Index: AQHUghG4/qfbmySOskGwd6CmLmV7sqVdK4Ig Date: Fri, 23 Nov 2018 10:53:37 +0000 Message-ID: References: <1542856478-795-1-git-send-email-vincentc@andestech.com> <1542856478-795-3-git-send-email-vincentc@andestech.com> In-Reply-To: <1542856478-795-3-git-send-email-vincentc@andestech.com> Accept-Language: en-GB, en-US Content-Language: 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-MC-Unique: GPDCUzThP7OsQ6S8j4J4iA-1 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Sender: linux-kernel-owner@vger.kernel.org Precedence: bulk List-ID: X-Mailing-List: linux-kernel@vger.kernel.org From: Vincent Chen > Sent: 22 November 2018 03:15 > > The Andes FPU coprocessor does not support denormalized number handling. > According to the specification, FPU generates a denorm input exception > that requires the kernel to deal with this instrution operation when it > encounters denormalized operands. Hence an nds32 FPU ISA emulator in the > kernel is required to meet requirement. What does the FPU generate for results near zero? If it doesn't generate denormalised results (but does detect them) then I assume it never generates FP values with exponent zero. (So the gap around zero is even larger than it would be if exponent zero values had a hidden bit.) So is it really worth doing anything other than treating denormalised values as zero? David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)