ieee.h revision 1.3 
1/*	$OpenBSD: ieee.h,v 1.3 2008/09/07 20:36:06 martynas Exp $	*/
2
3/*
4 * Copyright (c) 1992, 1993
5 *	The Regents of the University of California.  All rights reserved.
6 *
7 * This software was developed by the Computer Systems Engineering group
8 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and
9 * contributed to Berkeley.
10 *
11 * All advertising materials mentioning features or use of this software
12 * must display the following acknowledgement:
13 *	This product includes software developed by the University of
14 *	California, Lawrence Berkeley Laboratory.
15 *
16 * Redistribution and use in source and binary forms, with or without
17 * modification, are permitted provided that the following conditions
18 * are met:
19 * 1. Redistributions of source code must retain the above copyright
20 *    notice, this list of conditions and the following disclaimer.
21 * 2. Redistributions in binary form must reproduce the above copyright
22 *    notice, this list of conditions and the following disclaimer in the
23 *    documentation and/or other materials provided with the distribution.
24 * 3. Neither the name of the University nor the names of its contributors
25 *    may be used to endorse or promote products derived from this software
26 *    without specific prior written permission.
27 *
28 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
29 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
30 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
31 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
32 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
33 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
34 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
35 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
36 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
37 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
38 * SUCH DAMAGE.
39 *
40 *	@(#)ieee.h	8.1 (Berkeley) 6/11/93
41 */
42
43/*
44 * ieee.h defines the machine-dependent layout of the machine's IEEE
45 * floating point.  It does *not* define (yet?) any of the rounding
46 * mode bits, exceptions, and so forth.
47 */
48
49/*
50 * Define the number of bits in each fraction and exponent.
51 *
52 *		     k	         k+1
53 * Note that  1.0 x 2  == 0.1 x 2      and that denorms are represented
54 *
55 *					  (-exp_bias+1)
56 * as fractions that look like 0.fffff x 2             .  This means that
57 *
58 *			 -126
59 * the number 0.10000 x 2    , for instance, is the same as the normalized
60 *
61 *		-127			   -128
62 * float 1.0 x 2    .  Thus, to represent 2    , we need one leading zero
63 *
64 *				  -129
65 * in the fraction; to represent 2    , we need two, and so on.  This
66 *
67 *						     (-exp_bias-fracbits+1)
68 * implies that the smallest denormalized number is 2
69 *
70 * for whichever format we are talking about: for single precision, for
71 *
72 *						-126		-149
73 * instance, we get .00000000000000000000001 x 2    , or 1.0 x 2    , and
74 *
75 * -149 == -127 - 23 + 1.
76 */
77#define	SNG_EXPBITS	8
78#define	SNG_FRACBITS	23
79
80#define	DBL_EXPBITS	11
81#define	DBL_FRACHBITS	20
82#define	DBL_FRACLBITS	32
83#define	DBL_FRACBITS	52
84
85#ifdef notyet
86#define	E80_EXPBITS	15
87#define	E80_FRACBITS	64
88#endif
89
90struct ieee_single {
91	u_int	sng_sign:1;
92	u_int	sng_exp:8;
93	u_int	sng_frac:23;
94};
95
96struct ieee_double {
97	u_int	dbl_sign:1;
98	u_int	dbl_exp:11;
99	u_int	dbl_frach:20;
100	u_int	dbl_fracl;
101};
102
103/*
104 * Floats whose exponent is in [1..INFNAN) (of whatever type) are
105 * `normal'.  Floats whose exponent is INFNAN are either Inf or NaN.
106 * Floats whose exponent is zero are either zero (iff all fraction
107 * bits are zero) or subnormal values.
108 *
109 * A NaN is a `signalling NaN' if its QUIETNAN bit is clear in its
110 * high fraction; if the bit is set, it is a `quiet NaN'.
111 */
112#define	SNG_EXP_INFNAN	255
113#define	DBL_EXP_INFNAN	2047
114
115#if 0
116#define	SNG_QUIETNAN	(1 << 22)
117#define	DBL_QUIETNAN	(1 << 19)
118#endif
119
120/*
121 * Exponent biases.
122 */
123#define	SNG_EXP_BIAS	127
124#define	DBL_EXP_BIAS	1023
125