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 vger.kernel.org (vger.kernel.org [23.128.96.18]) by smtp.lore.kernel.org (Postfix) with ESMTP id BBA2CC83F10 for ; Thu, 31 Aug 2023 08:43:32 +0000 (UTC) Received: (majordomo@vger.kernel.org) by vger.kernel.org via listexpand id S232909AbjHaInd convert rfc822-to-8bit (ORCPT ); Thu, 31 Aug 2023 04:43:33 -0400 Received: from lindbergh.monkeyblade.net ([23.128.96.19]:33122 "EHLO lindbergh.monkeyblade.net" rhost-flags-OK-OK-OK-OK) by vger.kernel.org with ESMTP id S234879AbjHaInd (ORCPT ); Thu, 31 Aug 2023 04:43:33 -0400 Received: from eu-smtp-delivery-151.mimecast.com (eu-smtp-delivery-151.mimecast.com [185.58.86.151]) by lindbergh.monkeyblade.net (Postfix) with ESMTPS id 0E75BCF2 for ; Thu, 31 Aug 2023 01:43:28 -0700 (PDT) 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-311-LRFvNPzzO7iMs2R3ZDsrzw-1; Thu, 31 Aug 2023 09:37:14 +0100 X-MC-Unique: LRFvNPzzO7iMs2R3ZDsrzw-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; Thu, 31 Aug 2023 09:37:12 +0100 Received: from AcuMS.Aculab.com ([::1]) by AcuMS.aculab.com ([::1]) with mapi id 15.00.1497.048; Thu, 31 Aug 2023 09:37:12 +0100 From: David Laight To: 'Zhangjin Wu' CC: "ammarfaizi2@gnuweeb.org" , "arnd@arndb.de" , "linux-kernel@vger.kernel.org" , "linux-kselftest@vger.kernel.org" , "tanyuan@tinylab.org" , "thomas@t-8ch.de" , "w@1wt.eu" Subject: RE: [RFC] tools/nolibc: replace duplicated -ENOSYS return with single -ENOSYS return Thread-Topic: [RFC] tools/nolibc: replace duplicated -ENOSYS return with single -ENOSYS return Thread-Index: AdnbXfVru8RTG9gTQ+SsAG5ax7hYowAeEOWAAANtgiA= Date: Thu, 31 Aug 2023 08:37:11 +0000 Message-ID: References: <2d52dbd55e6240d5a91ebdce67fe0b7b@AcuMS.aculab.com> <20230831074151.7900-1-falcon@tinylab.org> In-Reply-To: <20230831074151.7900-1-falcon@tinylab.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 Content-Type: text/plain; charset=UTF-8 Content-Transfer-Encoding: 8BIT Precedence: bulk List-ID: X-Mailing-List: linux-kselftest@vger.kernel.org ... > We also need this style of checking for the delta logic in __atoi_add(). have > randomly tried different clang and gcc versions, seems all of them work > correctly, but the compiling speed is not that good if we want to support the > worst cases like "((0x900000 + 0x0f0000) + 5)", the shorter one > "((0x900000+0x0f0000)+5)" is used by ARM+OABI (not supported by nolibc > currently), therefore, we can strip some tailing branches but it is either not > that fast, of course, the other architectures/variants can use faster > __atoi_add() versions with less branches and without hex detection, comparison > and calculating. If there are only a few prefix offsets then the code can be optimised to explicitly detect them - rather than decoding arbitrary hex values. After all it only needs to decode the values that actually appear. The code also needs a compile-time assert that the result is constant (__buitin_constant_p() will do the check. But you can't use _Static_assert() to report the error because that requires an 'integer constant expression'. David - Registered Address Lakeside, Bramley Road, Mount Farm, Milton Keynes, MK1 1PT, UK Registration No: 1397386 (Wales)