1 /* $NetBSD: s_scalbnl.c,v 1.9 2013/05/20 19:40:09 joerg Exp $ */ 2 3 /*- 4 * Copyright (c) 2011 The NetBSD Foundation, Inc. 5 * All rights reserved. 6 * 7 * This code is derived from software contributed to The NetBSD Foundation 8 * by Joerg Sonnenberger. 9 * 10 * Redistribution and use in source and binary forms, with or without 11 * modification, are permitted provided that the following conditions 12 * are met: 13 * 1. Redistributions of source code must retain the above copyright 14 * notice, this list of conditions and the following disclaimer. 15 * 2. Redistributions in binary form must reproduce the above copyright 16 * notice, this list of conditions and the following disclaimer in the 17 * documentation and/or other materials provided with the distribution. 18 * 19 * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS 20 * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED 21 * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR 22 * PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS 23 * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR 24 * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF 25 * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS 26 * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN 27 * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) 28 * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE 29 * POSSIBILITY OF SUCH DAMAGE. 30 */ 31 32 #include <sys/cdefs.h> 33 __RCSID("$NetBSD: s_scalbnl.c,v 1.9 2013/05/20 19:40:09 joerg Exp $"); 34 35 #include "namespace.h" 36 37 #include <float.h> 38 #include <math.h> 39 #include <machine/ieee.h> 40 41 #ifdef __HAVE_LONG_DOUBLE 42 43 #ifdef _LP64 44 long double 45 scalbnl(long double x, int n) 46 { 47 return scalblnl(x, n); 48 } 49 #else 50 __strong_alias(_scalbnl, _scalblnl) 51 #endif 52 53 __weak_alias(scalbnl, _scalbnl) 54 __weak_alias(scalblnl, _scalblnl) 55 __weak_alias(ldexpl, _scalbnl) 56 57 #if LDBL_MANT_DIG == 64 58 #define FROM_UNDERFLOW 0x1p65L 59 #define TO_UNDERFLOW 0x1p-65L 60 #elif LDBL_MANT_DIG == 113 61 #define FROM_UNDERFLOW 0x1p114L 62 #define TO_UNDERFLOW 0x1p-114L 63 #else 64 #error Unsupported long double format 65 #endif 66 67 long double 68 scalblnl(long double x, long n) 69 { 70 union ieee_ext_u u; 71 72 /* Trivial cases first */ 73 if (n == 0 || x == 0.0L) 74 return x; 75 76 u.extu_ld = x; 77 78 /* NaN and infinite don't change either, but trigger exception */ 79 if (u.extu_ext.ext_exp == EXT_EXP_INFNAN) 80 return x + x; 81 82 /* Protect against integer overflow in calculation of new exponent */ 83 if (n > LDBL_MAX_EXP - LDBL_MIN_EXP + LDBL_MANT_DIG) 84 goto overflow; 85 if (n < LDBL_MIN_EXP - LDBL_MAX_EXP - LDBL_MANT_DIG) 86 goto underflow; 87 88 /* Scale denormalized numbers slightly, so that they are normal */ 89 if (u.extu_ext.ext_exp == 0) { 90 u.extu_ld *= FROM_UNDERFLOW; 91 n -= LDBL_MANT_DIG + 1; 92 } 93 94 n += u.extu_ext.ext_exp; 95 if (n >= LDBL_MAX_EXP + EXT_EXP_BIAS) 96 goto overflow; 97 /* Positive exponent (incl. bias) means normal result */ 98 if (n > 0) { 99 u.extu_ext.ext_exp = n; 100 return u.extu_ld; 101 } 102 /* Shift the exponent and let the multiply below handle subnormal */ 103 n += LDBL_MANT_DIG + 1; 104 if (n <= 0) 105 goto underflow; 106 u.extu_ext.ext_exp = n; 107 return u.extu_ld * TO_UNDERFLOW; 108 109 underflow: 110 return LDBL_MIN * copysignl(LDBL_MIN, x); 111 112 overflow: 113 return LDBL_MAX * copysignl(LDBL_MAX, x); 114 } 115 116 #endif 117