floatdidf_ieee754.c revision 1.1 
1/*	$NetBSD: floatdidf_ieee754.c,v 1.1 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: floatdidf_ieee754.c,v 1.1 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
45double __floatdidf(quad_t);
46
47/*
48 * Convert signed quad to double.
49 */
50double
51__floatdidf(quad_t x)
52{
53	union ieee_double_u ux = { .dblu_d = 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.dblu_sign = 1;
64		x = -x;
65	}
66	u_int l = __builtin_clzll(x);
67	x <<= (l + 1);	/* clear implicit bit */
68	x >>= 64 - (DBL_FRACHBITS + DBL_FRACLBITS);
69	union uu u = { .uq = x };
70	ux.dblu_frach = u.ul[H];
71	ux.dblu_fracl = u.ul[L];
72	ux.dblu_exp = DBL_EXP_BIAS + 63 - l;
73
74	return ux.dblu_d;
75}
76