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      1 /*	$NetBSD: floatdisf_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: floatdisf_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 <limits.h>
     42 #include <machine/ieee.h>
     43 #include "quad.h"
     44 
     45 float __floatdisf(quad_t);
     46 
     47 /*
     48  * Convert signed quad to float.
     49  */
     50 float
     51 __floatdisf(quad_t x)
     52 {
     53 	union ieee_single_u ux = { .sngu_f = 0.0 };
     54 
     55 	if (x == 0)
     56 		return 0.0;
     57 	if (x == 1)
     58 		return 1.0;
     59 
     60 	if (x < 0) {
     61 		if (x == QUAD_MIN)
     62 			return -0x1.0p63;
     63 		ux.sngu_sign = 1;
     64 		x = -x;
     65 	}
     66 #if defined(_LP64) || defined(__mips_n32)
     67 	u_int l = __builtin_clzll(x);
     68 	x <<= (l + 1);	/* clear implicit bit */
     69 
     70 	ux.sngu_frac = (u_quad_t)x >> (64 - SNG_FRACBITS);
     71 #else
     72 	union uu u = { .uq = x };
     73 	uint32_t frac;
     74 	u_int l;
     75 	if (u.ul[H] == 0) {
     76 		l = __builtin_clz(u.ul[L]);
     77 		frac = u.ul[L] << (l + 1);	/* clear implicit bit */
     78 		l += 32;
     79 	} else {
     80 		l = __builtin_clz(u.ul[H]);
     81 		frac = u.ul[H] << (l + 1);	/* clear implicit bit */
     82 		frac |= u.ul[L] >> (32 - (l + 1));
     83 	}
     84 
     85 	ux.sngu_frac = frac >> (32 - SNG_FRACBITS);
     86 #endif
     87 	ux.sngu_exp = SNG_EXP_BIAS + 63 - l;
     88 
     89 	return ux.sngu_f;
     90 }
     91