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 __log10l = log10l 31 32 /* 33 * log10l(X) 34 * 35 * Method : 36 * Let log10_2hi = leading 98(SPARC)/49(x86) bits of log10(2) and 37 * log10_2lo = log10(2) - log10_2hi, 38 * ivln10 = 1/log(10) rounded. 39 * Then 40 * n = ilogb(x), 41 * if (n<0) n = n+1; 42 * x = scalbn(x,-n); 43 * LOG10(x) := n*log10_2hi + (n*log10_2lo + ivln10*log(x)) 44 * 45 * Note1: 46 * For fear of destroying log10(10**n)=n, the rounding mode is 47 * set to Round-to-Nearest. 48 * 49 * Special cases: 50 * log10(x) is NaN with signal if x < 0; 51 * log10(+INF) is +INF with no signal; log10(0) is -INF with signal; 52 * log10(NaN) is that NaN with no signal; 53 * log10(10**N) = N for N=0,1,...,22. 54 * 55 * Constants: 56 * The hexadecimal values are the intended ones for the following constants. 57 * The decimal values may be used, provided that the compiler will convert 58 * from decimal to binary accurately enough to produce the hexadecimal values 59 * shown. 60 */ 61 62 #include "libm.h" 63 #include "longdouble.h" 64 65 #if defined(__x86) 66 #define __swapRD __swap87RD 67 #endif 68 extern enum fp_direction_type __swapRD(enum fp_direction_type); 69 70 static const long double 71 zero = 0.0L, 72 ivln10 = 4.342944819032518276511289189166050822944e-0001L, 73 one = 1.0L, 74 #if defined(__x86) 75 log10_2hi = 3.010299956639803653501985536422580480576e-01L, 76 log10_2lo = 8.298635403410822349787106337291183585413e-16L; 77 #elif defined(__sparc) 78 log10_2hi = 3.010299956639811952137388947242098603469e-01L, 79 log10_2lo = 2.831664213089468167896664371953210945664e-31L; 80 #else 81 #error Unknown Architecture! 82 #endif 83 84 long double 85 log10l(long double x) { 86 long double y, z; 87 enum fp_direction_type rd; 88 int n; 89 90 if (!finitel(x)) 91 return (x + fabsl(x)); /* x is +-INF or NaN */ 92 else if (x > zero) { 93 n = ilogbl(x); 94 if (n < 0) 95 n += 1; 96 rd = __swapRD(fp_nearest); 97 y = n; 98 x = scalbnl(x, -n); 99 z = y * log10_2lo + ivln10 * logl(x); 100 z += y * log10_2hi; 101 if (rd != fp_nearest) 102 (void) __swapRD(rd); 103 return (z); 104 } else if (x == zero) /* -INF */ 105 return (-one / zero); 106 else /* x <0, return NaN */ 107 return (zero / zero); 108 } 109