1 /* 2 * Copyright (c) 1992, 1993 3 * The Regents of the University of California. All rights reserved. 4 * 5 * This software was developed by the Computer Systems Engineering group 6 * at Lawrence Berkeley Laboratory under DARPA contract BG 91-66 and 7 * contributed to Berkeley. 8 * 9 * All advertising materials mentioning features or use of this software 10 * must display the following acknowledgement: 11 * This product includes software developed by the University of 12 * California, Lawrence Berkeley Laboratory. 13 * 14 * %sccs.include.redist.c% 15 * 16 * @(#)ieee.h 8.1 (Berkeley) 06/11/93 17 * 18 * from: $Header: ieee.h,v 1.7 92/11/26 02:04:37 torek Exp $ 19 */ 20 21 /* 22 * ieee.h defines the machine-dependent layout of the machine's IEEE 23 * floating point. It does *not* define (yet?) any of the rounding 24 * mode bits, exceptions, and so forth. 25 */ 26 27 /* 28 * Define the number of bits in each fraction and exponent. 29 * 30 * k k+1 31 * Note that 1.0 x 2 == 0.1 x 2 and that denorms are represented 32 * 33 * (-exp_bias+1) 34 * as fractions that look like 0.fffff x 2 . This means that 35 * 36 * -126 37 * the number 0.10000 x 2 , for instance, is the same as the normalized 38 * 39 * -127 -128 40 * float 1.0 x 2 . Thus, to represent 2 , we need one leading zero 41 * 42 * -129 43 * in the fraction; to represent 2 , we need two, and so on. This 44 * 45 * (-exp_bias-fracbits+1) 46 * implies that the smallest denormalized number is 2 47 * 48 * for whichever format we are talking about: for single precision, for 49 * 50 * -126 -149 51 * instance, we get .00000000000000000000001 x 2 , or 1.0 x 2 , and 52 * 53 * -149 == -127 - 23 + 1. 54 */ 55 #define SNG_EXPBITS 8 56 #define SNG_FRACBITS 23 57 58 #define DBL_EXPBITS 11 59 #define DBL_FRACBITS 52 60 61 #ifdef notyet 62 #define E80_EXPBITS 15 63 #define E80_FRACBITS 64 64 #endif 65 66 #define EXT_EXPBITS 15 67 #define EXT_FRACBITS 112 68 69 struct ieee_single { 70 u_int sng_sign:1; 71 u_int sng_exp:8; 72 u_int sng_frac:23; 73 }; 74 75 struct ieee_double { 76 u_int dbl_sign:1; 77 u_int dbl_exp:11; 78 u_int dbl_frach:20; 79 u_int dbl_fracl; 80 }; 81 82 struct ieee_ext { 83 u_int ext_sign:1; 84 u_int ext_exp:15; 85 u_int ext_frach:16; 86 u_int ext_frachm; 87 u_int ext_fraclm; 88 u_int ext_fracl; 89 }; 90 91 /* 92 * Floats whose exponent is in [1..INFNAN) (of whatever type) are 93 * `normal'. Floats whose exponent is INFNAN are either Inf or NaN. 94 * Floats whose exponent is zero are either zero (iff all fraction 95 * bits are zero) or subnormal values. 96 * 97 * A NaN is a `signalling NaN' if its QUIETNAN bit is clear in its 98 * high fraction; if the bit is set, it is a `quiet NaN'. 99 */ 100 #define SNG_EXP_INFNAN 255 101 #define DBL_EXP_INFNAN 2047 102 #define EXT_EXP_INFNAN 32767 103 104 #if 0 105 #define SNG_QUIETNAN (1 << 22) 106 #define DBL_QUIETNAN (1 << 19) 107 #define EXT_QUIETNAN (1 << 15) 108 #endif 109 110 /* 111 * Exponent biases. 112 */ 113 #define SNG_EXP_BIAS 127 114 #define DBL_EXP_BIAS 1023 115 #define EXT_EXP_BIAS 16383 116