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      1 /*	$NetBSD: floatunditf_ieee754.c,v 1.1 2014/01/30 15:06:18 joerg Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2014 Joerg Sonnenberger <joerg (at) NetBSD.org>.
      5  * All rights reserved.
      6  *
      7  * Redistribution and use in source and binary forms, with or without
      8  * modification, are permitted provided that the following conditions
      9  * are met:
     10  *
     11  * 1. Redistributions of source code must retain the above copyright
     12  *    notice, this list of conditions and the following disclaimer.
     13  * 2. Redistributions in binary form must reproduce the above copyright
     14  *    notice, this list of conditions and the following disclaimer in
     15  *    the documentation and/or other materials provided with the
     16  *    distribution.
     17  *
     18  * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
     19  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
     20  * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
     21  * FOR A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE
     22  * COPYRIGHT HOLDERS OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
     23  * INCIDENTAL, SPECIAL, EXEMPLARY OR CONSEQUENTIAL DAMAGES (INCLUDING,
     24  * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
     25  * LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
     26  * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
     27  * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
     28  * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
     29  * SUCH DAMAGE.
     30  */
     31 
     32 #include <sys/cdefs.h>
     33 __RCSID("$NetBSD: floatunditf_ieee754.c,v 1.1 2014/01/30 15:06:18 joerg Exp $");
     34 
     35 #include <math.h>
     36 #include <machine/ieee.h>
     37 #include <limits.h>
     38 
     39 #ifdef __HAVE_LONG_DOUBLE
     40 
     41 long double __floatunditf(uint64_t x);
     42 
     43 /*
     44  * Convert uint64_t to long double.
     45  */
     46 long double
     47 __floatunditf(uint64_t x)
     48 {
     49 	int exponent, zeros;
     50 	union ieee_ext_u ux;
     51 
     52 	/* Use the easier conversion routine for uint32_t if possible. */
     53 	if (x <= UINT32_MAX)
     54 		return (long double)(uint32_t)x;
     55 
     56 	zeros = __builtin_clzll(x);
     57 #ifdef LDBL_IMPLICIT_NBIT
     58 	exponent = 64 - zeros;
     59 	x <<= zeros + 1;
     60 #else
     61 	exponent = 63 - zeros;
     62 	x <<= zeros;
     63 #endif
     64 
     65 	ux.extu_exp = EXT_EXP_BIAS + exponent;
     66 	ux.extu_frach = (x >> (64 - EXT_FRACHBITS));
     67 	x <<= EXT_FRACHBITS;
     68 #ifdef EXT_FRACHMBITS
     69 	ux.extu_frachm = (x >> (64 - EXT_FRACHMBITS));
     70 	x <<= EXT_FRACHMBITS;
     71 #endif
     72 #ifdef EXT_FRACLMBITS
     73 	ux.extu_fraclm = (x >> (64 - EXT_FRACLMBITS));
     74 	x <<= EXT_FRACLMBITS;
     75 #endif
     76 	ux.extu_fracl = (x >> (64 - EXT_FRACLBITS));
     77 	ux.extu_sign = 0;
     78 
     79 	return ux.extu_ld;
     80 }
     81 #endif /* __HAVE_LONG_DOUBLE */
     82