1 /* 2 * CDDL HEADER START 3 * 4 * The contents of this file are subject to the terms of the 5 * Common Development and Distribution License (the "License"). 6 * You may not use this file except in compliance with the License. 7 * 8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE 9 * or http://www.opensolaris.org/os/licensing. 10 * See the License for the specific language governing permissions 11 * and limitations under the License. 12 * 13 * When distributing Covered Code, include this CDDL HEADER in each 14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE. 15 * If applicable, add the following below this CDDL HEADER, with the 16 * fields enclosed by brackets "[]" replaced with your own identifying 17 * information: Portions Copyright [yyyy] [name of copyright owner] 18 * 19 * CDDL HEADER END 20 */ 21 22 /* 23 * Copyright 2011 Nexenta Systems, Inc. All rights reserved. 24 */ 25 /* 26 * Copyright 2006 Sun Microsystems, Inc. All rights reserved. 27 * Use is subject to license terms. 28 */ 29 30 #if defined(ELFOBJ) 31 #pragma weak log1pl = __log1pl 32 #endif 33 34 /* 35 * log1pl(x) 36 * Kahan's trick based on log(1+x)/x being a slow varying function. 37 */ 38 39 #include "libm.h" 40 41 #if defined(__x86) 42 #define __swapRD __swap87RD 43 #endif 44 extern enum fp_direction_type __swapRD(enum fp_direction_type); 45 46 long double 47 log1pl(long double x) { 48 long double y; 49 enum fp_direction_type rd; 50 51 if (x != x) 52 return (x + x); 53 if (x < -1.L) 54 return (logl(x)); 55 rd = __swapRD(fp_nearest); 56 y = 1.L + x; 57 if (y != 1.L) { 58 if (y == x) 59 x = logl(x); 60 else 61 x *= logl(y) / (y - 1.L); 62 } 63 if (rd != fp_nearest) 64 (void) __swapRD(rd); 65 return (x); 66 } 67