1 /* $NetBSD: ieee754.h,v 1.4 2003/10/27 02:30:26 simonb Exp $ */ 2 3 /*- 4 * SPDX-License-Identifier: BSD-3-Clause 5 * 6 * Copyright (c) 1992, 1993 7 * The Regents of the University of California. All rights reserved. 8 * 9 * This software was developed by the Computer Systems Engineering group 10 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and 11 * contributed to Berkeley. 12 * 13 * All advertising materials mentioning features or use of this software 14 * must display the following acknowledgement: 15 * This product includes software developed by the University of 16 * California, Lawrence Berkeley Laboratory. 17 * 18 * Redistribution and use in source and binary forms, with or without 19 * modification, are permitted provided that the following conditions 20 * are met: 21 * 1. Redistributions of source code must retain the above copyright 22 * notice, this list of conditions and the following disclaimer. 23 * 2. Redistributions in binary form must reproduce the above copyright 24 * notice, this list of conditions and the following disclaimer in the 25 * documentation and/or other materials provided with the distribution. 26 * 3. Neither the name of the University nor the names of its contributors 27 * may be used to endorse or promote products derived from this software 28 * without specific prior written permission. 29 * 30 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND 31 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE 32 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE 33 * ARE DISCLAIMED. IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE 34 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL 35 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS 36 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) 37 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT 38 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY 39 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF 40 * SUCH DAMAGE. 41 * 42 */ 43 44 /* 45 * NOTICE: This is not a standalone file. To use it, #include it in 46 * your port's ieee.h header. 47 */ 48 49 #include <machine/endian.h> 50 51 /* 52 * <sys/ieee754.h> defines the layout of IEEE 754 floating point types. 53 * Only single-precision and double-precision types are defined here; 54 * extended types, if available, are defined in the machine-dependent 55 * header. 56 */ 57 58 /* 59 * Define the number of bits in each fraction and exponent. 60 * 61 * k k+1 62 * Note that 1.0 x 2 == 0.1 x 2 and that denorms are represented 63 * 64 * (-exp_bias+1) 65 * as fractions that look like 0.fffff x 2 . This means that 66 * 67 * -126 68 * the number 0.10000 x 2 , for instance, is the same as the normalized 69 * 70 * -127 -128 71 * float 1.0 x 2 . Thus, to represent 2 , we need one leading zero 72 * 73 * -129 74 * in the fraction; to represent 2 , we need two, and so on. This 75 * 76 * (-exp_bias-fracbits+1) 77 * implies that the smallest denormalized number is 2 78 * 79 * for whichever format we are talking about: for single precision, for 80 * 81 * -126 -149 82 * instance, we get .00000000000000000000001 x 2 , or 1.0 x 2 , and 83 * 84 * -149 == -127 - 23 + 1. 85 */ 86 #define SNG_EXPBITS 8 87 #define SNG_FRACBITS 23 88 89 #define DBL_EXPBITS 11 90 #define DBL_FRACBITS 52 91 92 #if defined(__VFP_FP__) || defined(__ARM_EABI__) 93 #define _IEEE_WORD_ORDER _BYTE_ORDER 94 #else 95 #define _IEEE_WORD_ORDER _BIG_ENDIAN 96 #endif 97 98 struct ieee_single { 99 #if _BYTE_ORDER == _BIG_ENDIAN 100 u_int sng_sign:1; 101 u_int sng_exp:8; 102 u_int sng_frac:23; 103 #else 104 u_int sng_frac:23; 105 u_int sng_exp:8; 106 u_int sng_sign:1; 107 #endif 108 }; 109 110 struct ieee_double { 111 #if _BYTE_ORDER == _BIG_ENDIAN 112 u_int dbl_sign:1; 113 u_int dbl_exp:11; 114 u_int dbl_frach:20; 115 u_int dbl_fracl; 116 #else 117 #if _IEEE_WORD_ORDER == _LITTLE_ENDIAN 118 u_int dbl_fracl; 119 #endif 120 u_int dbl_frach:20; 121 u_int dbl_exp:11; 122 u_int dbl_sign:1; 123 #if _IEEE_WORD_ORDER == _BIG_ENDIAN 124 u_int dbl_fracl; 125 #endif 126 #endif 127 }; 128 129 /* 130 * Floats whose exponent is in [1..INFNAN) (of whatever type) are 131 * `normal'. Floats whose exponent is INFNAN are either Inf or NaN. 132 * Floats whose exponent is zero are either zero (iff all fraction 133 * bits are zero) or subnormal values. 134 * 135 * A NaN is a `signalling NaN' if its QUIETNAN bit is clear in its 136 * high fraction; if the bit is set, it is a `quiet NaN'. 137 */ 138 #define SNG_EXP_INFNAN 255 139 #define DBL_EXP_INFNAN 2047 140 141 #if 0 142 #define SNG_QUIETNAN (1 << 22) 143 #define DBL_QUIETNAN (1 << 19) 144 #endif 145 146 /* 147 * Exponent biases. 148 */ 149 #define SNG_EXP_BIAS 127 150 #define DBL_EXP_BIAS 1023 151 152 /* 153 * Convenience data structures. 154 */ 155 union ieee_single_u { 156 float sngu_f; 157 struct ieee_single sngu_sng; 158 }; 159 160 union ieee_double_u { 161 double dblu_d; 162 struct ieee_double dblu_dbl; 163 }; 164