From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: from esa1.mentor.iphmx.com (esa1.mentor.iphmx.com [68.232.129.153]) by sourceware.org (Postfix) with ESMTPS id 4E5EE3894C11 for ; Tue, 1 Sep 2020 21:16:38 +0000 (GMT) DMARC-Filter: OpenDMARC Filter v1.3.2 sourceware.org 4E5EE3894C11 Authentication-Results: sourceware.org; dmarc=none (p=none dis=none) header.from=codesourcery.com Authentication-Results: sourceware.org; spf=pass smtp.mailfrom=joseph_myers@mentor.com IronPort-SDR: dzka/iC++O2qNJEaHHnSz5LY67nyICHnCfiyXuqqQ8v+ezQDlC80Q+DJ80675iSeS4fyjULYj9 OJlRQI7IHqDxX7cMMN6BtojWubWpvz4gXTm/CXJZlV6C++Uab+Pd0OuYnNXQJVOmZrHEzZBWaW hrlmwgX8+yfA9yDCFvh9Wiyhddae1XbMwMhsxz8wr0D+35g/VIaurrRlbMxozgSrrXXbtWT/wo j+5P7m6xSRELoxLUWCEIAyCgJFblzNt3VJRDsWfK5os7NjZlZ/To42gjgkzqScv942vsVFk+hw OqE= X-IronPort-AV: E=Sophos;i="5.76,380,1592899200"; d="scan'208";a="54661645" Received: from orw-gwy-01-in.mentorg.com ([192.94.38.165]) by esa1.mentor.iphmx.com with ESMTP; 01 Sep 2020 13:16:37 -0800 IronPort-SDR: 8BFx4LrQzzEvQqN9K1CzxipPsGjEVip93zMDjUlKRtNNdiEonlQ9HHr17SPljgamFmDKwTweH5 Xd9Y+V2cpgaLrGn3TvNvlJ7mVAJ2GgcJ+ECbidn3QJ/evTcq8tF3F+dqHpBM5bk2Rnd2ZOND4W n23nOC7G8z67jAN4UUAm9oQWI562R1iJDIoqZqG9bbEmeYvjyC/Xjr+0zWHN3rje9lWR8bDc9J 6ikU5QbG9bQS5Q1RA4vUp2tCD9oEyKNqsYwlVOqQT/DNARysI5yQUX3a9VNd7gOaGJc5OAeiKr tYs= Date: Tue, 1 Sep 2020 21:16:31 +0000 From: Joseph Myers X-X-Sender: jsm28@digraph.polyomino.org.uk To: Keith Packard CC: Sebastian Huber , Subject: Re: [PATCH 0/3] ARM with only 32-bit floats do not have fast 64-bit FMA In-Reply-To: <87wo1db8kt.fsf@keithp.com> Message-ID: References: <20200808223413.4015633-1-keithp@keithp.com> <1fc07c90-694b-01ea-cedc-0656eccdd827@embedded-brains.de> <87wo1db8kt.fsf@keithp.com> User-Agent: Alpine 2.21 (DEB 202 2017-01-01) MIME-Version: 1.0 Content-Type: text/plain; charset="US-ASCII" X-Originating-IP: [137.202.0.90] X-ClientProxiedBy: SVR-IES-MBX-07.mgc.mentorg.com (139.181.222.7) To SVR-IES-MBX-03.mgc.mentorg.com (139.181.222.3) X-Spam-Status: No, score=-3127.6 required=5.0 tests=BAYES_00, HEADER_FROM_DIFFERENT_DOMAINS, KAM_DMARC_STATUS, SPF_HELO_PASS, SPF_PASS, TXREP autolearn=ham autolearn_force=no version=3.4.2 X-Spam-Checker-Version: SpamAssassin 3.4.2 (2018-09-13) on server2.sourceware.org X-BeenThere: newlib@sourceware.org X-Mailman-Version: 2.1.29 Precedence: list List-Id: Newlib mailing list List-Unsubscribe: , List-Archive: List-Post: List-Help: List-Subscribe: , X-List-Received-Date: Tue, 01 Sep 2020 21:16:39 -0000 On Tue, 1 Sep 2020, Keith Packard via Newlib wrote: > If not, then one of the two versions of fma should be getting compiled > as they have opposite tests -- newlib/libm/machine/arm/s_fma.c checks > for '#if HAVE_FAST_FMA' while newlib/libm/common/s_fma.c checks for > '#if !HAVE_FAST_FMA'. But note that newlib/libm/common/s_fma.c doesn't actually do anything useful; it's not a fused operation. Implementing correct fma in software is highly nontrivial, especially when you want to handle exceptions and rounding modes correctly (including machine-specific differences in whether tininess is detected before or after rounding). -- Joseph S. Myers joseph@codesourcery.com