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ieee.h revision 1.1 
      1 /*	$NetBSD: ieee.h,v 1.1 1995/02/13 23:07:40 cgd 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. All advertising materials mentioning features or use of this software
     25  *    must display the following acknowledgement:
     26  *	This product includes software developed by the University of
     27  *	California, Berkeley and its contributors.
     28  * 4. Neither the name of the University nor the names of its contributors
     29  *    may be used to endorse or promote products derived from this software
     30  *    without specific prior written permission.
     31  *
     32  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     33  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     34  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     35  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     36  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     37  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     38  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     39  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     40  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     41  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     42  * SUCH DAMAGE.
     43  *
     44  *	@(#)ieee.h	8.1 (Berkeley) 6/11/93
     45  *
     46  * from: Header: ieee.h,v 1.7 92/11/26 02:04:37 torek Exp
     47  */
     48 
     49 /*
     50  * ieee.h defines the machine-dependent layout of the machine's IEEE
     51  * floating point.  It does *not* define (yet?) any of the rounding
     52  * mode bits, exceptions, and so forth.
     53  */
     54 
     55 /*
     56  * Define the number of bits in each fraction and exponent.
     57  *
     58  *		     k	         k+1
     59  * Note that  1.0 x 2  == 0.1 x 2      and that denorms are represented
     60  *
     61  *					  (-exp_bias+1)
     62  * as fractions that look like 0.fffff x 2             .  This means that
     63  *
     64  *			 -126
     65  * the number 0.10000 x 2    , for instance, is the same as the normalized
     66  *
     67  *		-127			   -128
     68  * float 1.0 x 2    .  Thus, to represent 2    , we need one leading zero
     69  *
     70  *				  -129
     71  * in the fraction; to represent 2    , we need two, and so on.  This
     72  *
     73  *						     (-exp_bias-fracbits+1)
     74  * implies that the smallest denormalized number is 2
     75  *
     76  * for whichever format we are talking about: for single precision, for
     77  *
     78  *						-126		-149
     79  * instance, we get .00000000000000000000001 x 2    , or 1.0 x 2    , and
     80  *
     81  * -149 == -127 - 23 + 1.
     82  */
     83 #define	SNG_EXPBITS	8
     84 #define	SNG_FRACBITS	23
     85 
     86 #define	DBL_EXPBITS	11
     87 #define	DBL_FRACBITS	52
     88 
     89 struct ieee_single {
     90 	u_int	sng_frac:23;
     91 	u_int	sng_exp:8;
     92 	u_int	sng_sign:1;
     93 };
     94 
     95 struct ieee_double {
     96 	u_int	dbl_fracl;
     97 	u_int	dbl_frach:20;
     98 	u_int	dbl_exp:11;
     99 	u_int	dbl_sign:1;
    100 };
    101 
    102 /*
    103  * Floats whose exponent is in [1..INFNAN) (of whatever type) are
    104  * `normal'.  Floats whose exponent is INFNAN are either Inf or NaN.
    105  * Floats whose exponent is zero are either zero (iff all fraction
    106  * bits are zero) or subnormal values.
    107  *
    108  * A NaN is a `signalling NaN' if its QUIETNAN bit is clear in its
    109  * high fraction; if the bit is set, it is a `quiet NaN'.
    110  */
    111 #define	SNG_EXP_INFNAN	255
    112 #define	DBL_EXP_INFNAN	2047
    113 
    114 #if 0
    115 #define	SNG_QUIETNAN	(1 << 22)
    116 #define	DBL_QUIETNAN	(1 << 19)
    117 #endif
    118 
    119 /*
    120  * Exponent biases.
    121  */
    122 #define	SNG_EXP_BIAS	127
    123 #define	DBL_EXP_BIAS	1023
    124