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
98struct 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
110struct 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 */
155union ieee_single_u {
156 float sngu_f;
157 struct ieee_single sngu_sng;
158};
159
160union ieee_double_u {
161 double dblu_d;
162 struct ieee_double dblu_dbl;
163};