1 /* $NetBSD: s_scalbnl.c,v 1.4 2013/02/11 02:45:15 christos 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 1.4 2013/02/11 02:45:15 christos 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 #ifndef _LP64 44 __strong_alias(_scalbnl, _scalblnl) 45 #endif 46 47 __weak_alias(scalbnl, _scalbnl) 48 __weak_alias(scalblnl, _scalblnl) 49 __weak_alias(ldexpl, _scalblnl); 50 51 #if LDBL_MANT_DIG == 64 52 #define FROM_UNDERFLOW 0x1p65L 53 #define TO_UNDERFLOW 0x1p-65L 54 #elif LDBL_MANT_DIG == 113 55 #define FROM_UNDERFLOW 0x1p114L 56 #define TO_UNDERFLOW 0x1p-114L 57 #else 58 #error Unsupported long double format 59 #endif 60 61 #ifdef _LP64 62 long double 63 scalbnl(long double x, int n) 64 { 65 return scalblnl(x, n); 66 } 67 #endif 68 69 long double 70 scalblnl(long double x, long n) 71 { 72 union ieee_ext_u u; 73 74 /* Trivial cases first */ 75 if (n == 0 || x == 0.0L) 76 return x; 77 78 u.extu_ld = x; 79 80 /* NaN and infinite don't change either, but trigger exception */ 81 if (u.extu_ext.ext_exp == EXT_EXP_INFNAN) 82 return x + x; 83 84 /* Protect against integer overflow in calculation of new exponent */ 85 if (n > LDBL_MAX_EXP - LDBL_MIN_EXP + LDBL_MANT_DIG) 86 goto overflow; 87 if (n < LDBL_MAX_EXP - LDBL_MIN_EXP + LDBL_MANT_DIG) 88 goto underflow; 89 90 /* Scale denormalized numbers slightly, so that they are normal */ 91 if (u.extu_ext.ext_exp == 0) { 92 u.extu_ld *= FROM_UNDERFLOW; 93 n -= LDBL_MANT_DIG + 1; 94 } 95 96 n += u.extu_ext.ext_exp; 97 if (n >= LDBL_MAX_EXP + EXT_EXP_BIAS) 98 goto overflow; 99 /* Positive exponent (incl. bias) means normal result */ 100 if (n > 0) { 101 u.extu_ext.ext_exp = n; 102 return u.extu_ld; 103 } 104 /* Shift the exponent and let the multiply below handle subnormal */ 105 n += LDBL_MANT_DIG + 1; 106 if (n <= 0) 107 goto underflow; 108 u.extu_ext.ext_exp = n; 109 return u.extu_ld * TO_UNDERFLOW; 110 111 underflow: 112 return LDBL_MIN * copysignl(LDBL_MIN, x); 113 114 overflow: 115 return LDBL_MAX * copysignl(LDBL_MAX, x); 116 } 117 118 #endif 119