1/*	$NetBSD: s_ilogbl.c,v 1.4 2016/08/26 08:20:31 christos Exp $	*/
2
3/*-
4 * Copyright (c) 2011 The NetBSD Foundation, Inc.
5 * All rights reserved.
6 *
7 * This code is derived from software contributed to The NetBSD Foundation
8 * by Joerg Sonnenberger.
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__RCSID("$NetBSD: s_ilogbl.c,v 1.4 2016/08/26 08:20:31 christos Exp $");
34
35#include "namespace.h"
36
37#include <float.h>
38#include <math.h>
39#define __TEST_FENV
40#include <fenv.h>
41#ifndef __HAVE_FENV
42#define feraiseexcept(a)
43#endif
44#include <machine/ieee.h>
45
46#ifdef __HAVE_LONG_DOUBLE
47
48#if LDBL_MANT_DIG == 64
49#define	FROM_UNDERFLOW	0x1p65L
50#elif LDBL_MANT_DIG == 113
51#define	FROM_UNDERFLOW	0x1p114L
52#else
53#error Unsupported long double format
54#endif
55
56int
57ilogbl(long double x)
58{
59	union ieee_ext_u u;
60
61	if (x == 0.0L) {
62		feraiseexcept(FE_INVALID);
63		return FP_ILOGB0;	/* ilogbl(0) = 0x80000001 */
64	}
65
66	u.extu_ld = x;
67
68	if (u.extu_ext.ext_exp == EXT_EXP_INFNAN) {
69		feraiseexcept(FE_INVALID);
70		return isnan(x) ? FP_ILOGBNAN : INT_MAX;
71	}
72
73	if (u.extu_ext.ext_exp == 0) {
74		/*
75		 * Scale denormalized numbers slightly,
76		 * so that they are normal.
77		 */
78		u.extu_ld *= FROM_UNDERFLOW;
79		return u.extu_ext.ext_exp - EXT_EXP_BIAS - LDBL_MANT_DIG - 1;
80	}
81	return u.extu_ext.ext_exp - EXT_EXP_BIAS;
82
83}
84
85#endif
86