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SFS:(4636009)(396003)(136003)(376002)(39860400002)(346002)(46966005)(356005)(956004)(47076004)(7696005)(6666004)(70586007)(2616005)(8936002)(82740400003)(336012)(5660300002)(70206006)(16526019)(1076003)(186003)(86362001)(8676002)(33656002)(26005)(36906005)(81166007)(8886007)(36756003)(82310400002)(478600001)(44832011)(2906002)(83380400001)(316002)(55016002); DIR:OUT; SFP:1101; X-OriginatorOrg: arm.com X-MS-Exchange-CrossTenant-OriginalArrivalTime: 10 Aug 2020 14:43:30.8612 (UTC) X-MS-Exchange-CrossTenant-Network-Message-Id: faee752f-0b0b-4bd2-610c-08d83d3bc028 X-MS-Exchange-CrossTenant-Id: f34e5979-57d9-4aaa-ad4d-b122a662184d X-MS-Exchange-CrossTenant-OriginalAttributedTenantConnectingIp: TenantId=f34e5979-57d9-4aaa-ad4d-b122a662184d; Ip=[63.35.35.123]; Helo=[64aa7808-outbound-1.mta.getcheckrecipient.com] X-MS-Exchange-CrossTenant-AuthSource: AM5EUR03FT033.eop-EUR03.prod.protection.outlook.com X-MS-Exchange-CrossTenant-AuthAs: Anonymous X-MS-Exchange-CrossTenant-FromEntityHeader: HybridOnPrem X-MS-Exchange-Transport-CrossTenantHeadersStamped: AM8PR08MB5860 X-Spam-Status: No, score=-9.8 required=5.0 tests=BAYES_00, DKIM_SIGNED, DKIM_VALID, MSGID_FROM_MTA_HEADER, RCVD_IN_DNSWL_NONE, RCVD_IN_MSPIKE_H2, SPF_HELO_PASS, SPF_PASS, TXREP, UNPARSEABLE_RELAY 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: Mon, 10 Aug 2020 14:43:34 -0000 The 08/10/2020 11:30, Corinna Vinschen wrote: > Hi Szabolcs, > > ok to push? > this looks ok. i would have used the arm specific macros ( __ARM_FEATURE_FMA, __ARM_FP) directly in arm specific code. but using HAVE_FAST_FMA{F} works too. (note that these macros currently only do something useful on aarch64 and arm.) > > Thanks, > Corinna > > On Aug 8 15:34, Keith Packard via Newlib wrote: > > I added some new test configurations to my CI system for picolibc and > > discovered that when the new math code was built on 32-bit ARM > > processors with only single-precision floating hardware, several math > > functions were returning imprecise results. I got the expected results > > on processors with no FPU and on processors with both 32- and 64- bit > > FPUs. > > > > I discovered that the affected functions were using the 'fma' function > > on this hardware, even though (lacking 64-bit HW support), that > > function was being emulated without the required precision. > > > > This all boiled down to math_config.h incorrectly detecting 64-bit FMA > > support on ARM processors. > > > > This patch series contains three changes: > > > > 1. fix the fast FMA process so that 32-bit ARM processors without 64-bit FMA > > support don't use 'fma' for the new math functions > > > > 2. Add detection of fast FMAF, which 32-bit ARM processors with only > > 32-bit FPUs *do* support. > > > > 3. Add ARM versions of fma and fmaf which are used when those > > instructions are available. > > > > -- > Corinna Vinschen > Cygwin Maintainer > Red Hat > --