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      1 /*	$NetBSD: floatundisf_ieee754.c,v 1.2 2013/08/24 00:51:48 matt Exp $	*/
      2 
      3 /*-
      4  * Copyright (c) 2013 The NetBSD Foundation, Inc.
      5  * All rights reserved.
      6  *
      7  * This code is derived from software contributed to The NetBSD Foundation
      8  * by Matt Thomas of 3am Software Foundry.
      9  *
     10  * Redistribution and use in source and binary forms, with or without
     11  * modification, are permitted provided that the following conditions
     12  * are met:
     13  * 1. Redistributions of source code must retain the above copyright
     14  *    notice, this list of conditions and the following disclaimer.
     15  * 2. Redistributions in binary form must reproduce the above copyright
     16  *    notice, this list of conditions and the following disclaimer in the
     17  *    documentation and/or other materials provided with the distribution.
     18  *
     19  * THIS SOFTWARE IS PROVIDED BY THE NETBSD FOUNDATION, INC. AND CONTRIBUTORS
     20  * ``AS IS'' AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED
     21  * TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR
     22  * PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE FOUNDATION OR CONTRIBUTORS
     23  * BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
     24  * CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
     25  * SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
     26  * INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
     27  * CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
     28  * ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
     29  * POSSIBILITY OF SUCH DAMAGE.
     30  */
     31 
     32 #include <sys/cdefs.h>
     33 #if defined(LIBC_SCCS) && !defined(lint)
     34 __RCSID("$NetBSD: floatundisf_ieee754.c,v 1.2 2013/08/24 00:51:48 matt Exp $");
     35 #endif /* LIBC_SCCS and not lint */
     36 
     37 #if defined(SOFTFLOAT) || defined(__ARM_EABI__)
     38 #include "softfloat/softfloat-for-gcc.h"
     39 #endif
     40 
     41 #include <machine/ieee.h>
     42 #include "quad.h"
     43 
     44 float __floatundisf(u_quad_t);
     45 
     46 /*
     47  * Convert unsigned quad to float.
     48  */
     49 float
     50 __floatundisf(u_quad_t x)
     51 {
     52 	union ieee_single_u ux = { .sngu_f = 0.0 };
     53 
     54 	if (x == 0)
     55 		return 0.0;
     56 	if (x == 1)
     57 		return 1.0;
     58 
     59 #if defined(_LP64) || defined(__mips_n32)
     60 	u_int l = __builtin_clzll(x);
     61 	x <<= (l + 1);	/* clear implicit bit */
     62 
     63 	ux.sngu_frac = x >> (64 - SNG_FRACBITS);
     64 #else
     65 	union uu u = { .uq = x };
     66 	uint32_t frac;
     67 	u_int l;
     68 	if (u.ul[H] == 0) {
     69 		l = __builtin_clz(u.ul[L]);
     70 		frac = u.ul[L] << (l + 1);	/* clear implicit bit */
     71 		l += 32;
     72 	} else {
     73 		l = __builtin_clz(u.ul[H]);
     74 		frac = u.ul[H] << (l + 1);	/* clear implicit bit */
     75 		frac |= u.ul[L] >> (32 - (l + 1));
     76 	}
     77 
     78 	ux.sngu_frac = frac >> (32 - SNG_FRACBITS);
     79 #endif
     80 	ux.sngu_exp = SNG_EXP_BIAS + 63 - l;
     81 
     82 	return ux.sngu_f;
     83 }
     84