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floatunditf_ieee754.c revision 1.2 
      1 /*	$NetBSD: floatunditf_ieee754.c,v 1.2 2011/07/09 03:16:40 matt 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  * Redistribution and use in source and binary forms, with or without
     12  * modification, are permitted provided that the following conditions
     13  * are met:
     14  * 1. Redistributions of source code must retain the above copyright
     15  *    notice, this list of conditions and the following disclaimer.
     16  * 2. Redistributions in binary form must reproduce the above copyright
     17  *    notice, this list of conditions and the following disclaimer in the
     18  *    documentation and/or other materials provided with the distribution.
     19  * 3. Neither the name of the University nor the names of its contributors
     20  *    may be used to endorse or promote products derived from this software
     21  *    without specific prior written permission.
     22  *
     23  * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
     24  * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
     25  * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
     26  * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
     27  * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
     28  * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
     29  * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
     30  * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
     31  * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
     32  * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     33  * SUCH DAMAGE.
     34  */
     35 
     36 #include <sys/cdefs.h>
     37 #if defined(LIBC_SCCS) && !defined(lint)
     38 #if 0
     39 static char sccsid[] = "@(#)floatunsdidf.c	8.1 (Berkeley) 6/4/93";
     40 #else
     41 __RCSID("$NetBSD: floatunditf_ieee754.c,v 1.2 2011/07/09 03:16:40 matt Exp $");
     42 #endif
     43 #endif /* LIBC_SCCS and not lint */
     44 
     45 #include "quad.h"
     46 #ifdef __vax__
     47 #error vax does not support a distinct long double
     48 #endif
     49 #include <machine/ieee.h>
     50 
     51 /*
     52  * Convert (unsigned) quad to long double.
     53  * This is exactly like floatdidf.c except that negatives never occur.
     54  */
     55 long double
     56 __floatunditf(u_quad_t x)
     57 {
     58 #if 0
     59 	long double ld;
     60 	union uu u;
     61 
     62 	u.uq = x;
     63 	ld = (long double)u.ul[H] * (((int)1 << (INT_BITS - 2)) * 4.0);
     64 	ld += u.ul[L];
     65 	return (ld);
     66 #else
     67 	union ieee_ext_u extu;
     68 	quad_t tmp = x;		/* must be signed */
     69 	size_t width = 64;
     70 	size_t bit = 0;
     71 	quad_t mask = ~(quad_t)0;
     72 
     73 	if (x == 0)
     74 		return 0.0L;
     75 	if (x == 1)
     76 		return 1.0L;
     77 
     78 	while (mask != 0 && (tmp >= 0)) {
     79 		width >>= 1;
     80 		mask <<= width;
     81 		if ((tmp & mask) == 0) {
     82 			tmp <<= width;
     83 			bit += width;
     84 		}
     85 	}
     86 
     87 	x <<= (bit + 1);
     88 	extu.extu_sign = 0;
     89 	extu.extu_exp = EXT_EXP_BIAS + (64 - (bit + 1));
     90 	extu.extu_frach = x >> (64 - EXT_FRACHBITS);
     91 	x <<= EXT_FRACHBITS;
     92 #ifdef EXT_FRACHMBITS
     93 	extu.extu_frachm = x >> (64 - EXT_FRACHMBITS);
     94 	x <<= EXT_FRACHMBITS;
     95 #endif
     96 #ifdef EXT_FRACLMBITS
     97 	extu.extu_fraclm = x >> (64 - EXT_FRACLMBITS);
     98 	x <<= EXT_FRACLMBITS;
     99 #endif
    100 	extu.extu_fracl = x >> (64 - EXT_FRACLBITS);
    101 
    102 	return extu.extu_ld;
    103 #endif
    104 }
    105