The Design and Implementation of the FreeBSD Operating System, Second Edition
Now available: The Design and Implementation of the FreeBSD Operating System (Second Edition)


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FreeBSD/Linux Kernel Cross Reference
sys/mips/include/ieee.h

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    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  *      @(#)ieee.h      8.1 (Berkeley) 6/11/93
   43  *
   44  * $FreeBSD$
   45  *
   46  */
   47 
   48 /*
   49  * NOTICE: This is not a standalone file.  To use it, #include it in
   50  * your port's ieee.h header.
   51  */
   52 
   53 #include <machine/endian.h>
   54 
   55 /*
   56  * <sys/ieee754.h> defines the layout of IEEE 754 floating point types.
   57  * Only single-precision and double-precision types are defined here;
   58  * extended types, if available, are defined in the machine-dependent
   59  * header.
   60  */
   61 
   62 /*
   63  * Define the number of bits in each fraction and exponent.
   64  *
   65  *                   k           k+1
   66  * Note that  1.0 x 2  == 0.1 x 2      and that denorms are represented
   67  *
   68  *                                        (-exp_bias+1)
   69  * as fractions that look like 0.fffff x 2             .  This means that
   70  *
   71  *                       -126
   72  * the number 0.10000 x 2    , for instance, is the same as the normalized
   73  *
   74  *              -127                       -128
   75  * float 1.0 x 2    .  Thus, to represent 2    , we need one leading zero
   76  *
   77  *                                -129
   78  * in the fraction; to represent 2    , we need two, and so on.  This
   79  *
   80  *                                                   (-exp_bias-fracbits+1)
   81  * implies that the smallest denormalized number is 2
   82  *
   83  * for whichever format we are talking about: for single precision, for
   84  *
   85  *                                              -126            -149
   86  * instance, we get .00000000000000000000001 x 2    , or 1.0 x 2    , and
   87  *
   88  * -149 == -127 - 23 + 1.
   89  */
   90 #define SNG_EXPBITS     8
   91 #define SNG_FRACBITS    23
   92 
   93 #define DBL_EXPBITS     11
   94 #define DBL_FRACBITS    52
   95 
   96 struct ieee_single {
   97 #if _BYTE_ORDER == _BIG_ENDIAN
   98         u_int   sng_sign:1;
   99         u_int   sng_exp:8;
  100         u_int   sng_frac:23;
  101 #else
  102         u_int   sng_frac:23;
  103         u_int   sng_exp:8;
  104         u_int   sng_sign:1;
  105 #endif
  106 };
  107 
  108 struct ieee_double {
  109 #if _BYTE_ORDER == _BIG_ENDIAN
  110         u_int   dbl_sign:1;
  111         u_int   dbl_exp:11;
  112         u_int   dbl_frach:20;
  113         u_int   dbl_fracl;
  114 #else
  115         u_int   dbl_fracl;
  116         u_int   dbl_frach:20;
  117         u_int   dbl_exp:11;
  118         u_int   dbl_sign:1;
  119 #endif
  120 };
  121 
  122 /*
  123  * Floats whose exponent is in [1..INFNAN) (of whatever type) are
  124  * `normal'.  Floats whose exponent is INFNAN are either Inf or NaN.
  125  * Floats whose exponent is zero are either zero (iff all fraction
  126  * bits are zero) or subnormal values.
  127  *
  128  * A NaN is a `signalling NaN' if its QUIETNAN bit is clear in its
  129  * high fraction; if the bit is set, it is a `quiet NaN'.
  130  */
  131 #define SNG_EXP_INFNAN  255
  132 #define DBL_EXP_INFNAN  2047
  133 
  134 #if 0
  135 #define SNG_QUIETNAN    (1 << 22)
  136 #define DBL_QUIETNAN    (1 << 19)
  137 #endif
  138 
  139 /*
  140  * Exponent biases.
  141  */
  142 #define SNG_EXP_BIAS    127
  143 #define DBL_EXP_BIAS    1023
  144 
  145 /*
  146  * Convenience data structures.
  147  */
  148 union ieee_single_u {
  149         float                   sngu_f;
  150         struct ieee_single      sngu_sng;
  151 };
  152 
  153 union ieee_double_u {
  154         double                  dblu_d;
  155         struct ieee_double      dblu_dbl;
  156 };

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