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 #pragma weak __log1pl = log1pl 31 32 /* 33 * log1pl(x) 34 * Kahan's trick based on log(1+x)/x being a slow varying function. 35 */ 36 37 #include "libm.h" 38 39 #if defined(__x86) 40 #define __swapRD __swap87RD 41 #endif 42 extern enum fp_direction_type __swapRD(enum fp_direction_type); 43 44 long double log1pl(long double x)45log1pl(long double x) { 46 long double y; 47 enum fp_direction_type rd; 48 49 if (x != x) 50 return (x + x); 51 if (x < -1.L) 52 return (logl(x)); 53 rd = __swapRD(fp_nearest); 54 y = 1.L + x; 55 if (y != 1.L) { 56 if (y == x) 57 x = logl(x); 58 else 59 x *= logl(y) / (y - 1.L); 60 } 61 if (rd != fp_nearest) 62 (void) __swapRD(rd); 63 return (x); 64 } 65