1 /*
2 * CDDL HEADER START
3 *
4 * The contents of this file are subject to the terms of the
5 * Common Development and Distribution License (the "License").
6 * You may not use this file except in compliance with the License.
7 *
8 * You can obtain a copy of the license at usr/src/OPENSOLARIS.LICENSE
9 * or http://www.opensolaris.org/os/licensing.
10 * See the License for the specific language governing permissions
11 * and limitations under the License.
12 *
13 * When distributing Covered Code, include this CDDL HEADER in each
14 * file and include the License file at usr/src/OPENSOLARIS.LICENSE.
15 * If applicable, add the following below this CDDL HEADER, with the
16 * fields enclosed by brackets "[]" replaced with your own identifying
17 * information: Portions Copyright [yyyy] [name of copyright owner]
18 *
19 * CDDL HEADER END
20 */
21
22 /*
23 * Copyright 2011 Nexenta Systems, Inc. All rights reserved.
24 */
25 /*
26 * Copyright 2006 Sun Microsystems, Inc. All rights reserved.
27 * Use is subject to license terms.
28 */
29
30 #pragma weak __exp2l = exp2l
31
32 #include "libm.h"
33 #include "longdouble.h"
34
35 /*
36 * exp2l(x) = 2**x = 2**((x-anint(x))+anint(x))
37 * = 2**anint(x)*2**(x-anint(x))
38 * = 2**anint(x)*exp((x-anint(x))*ln2)
39 */
40
41 #define TINY 1.0e-20L /* single: 1e-5, double: 1e-10, quad: 1e-20 */
42 #define OVFLEXP 16400 /* single: 130, double 1030, quad: 16400 */
43 #define UNFLEXP -16520 /* single:-155, double -1080, quad:-16520 */
44
45 static const long double
46 zero = 0.0L,
47 tiny = TINY * TINY,
48 half = 0.5L,
49 ln2 = 6.931471805599453094172321214581765680755e-0001L,
50 one = 1.0L;
51
52 static const int
53 ovflexp = OVFLEXP,
54 unflexp = UNFLEXP;
55
56 long double
exp2l(long double x)57 exp2l(long double x) {
58 long double t;
59
60 if (!finitel(x)) {
61 if (isnanl(x) || x > zero)
62 return (x + x);
63 else
64 return (zero);
65 }
66 t = fabsl(x);
67 if (t < half) {
68 if (t < tiny)
69 return (one + x);
70 else
71 return (expl(ln2 * x));
72 }
73 t = anintl(x);
74 if (t < ovflexp) {
75 if (t >= unflexp)
76 return (scalbnl(expl(ln2 * (x - t)), (int) t));
77 else
78 return (scalbnl(one, unflexp)); /* underflow */
79 } else
80 return (scalbnl(one, ovflexp)); /* overflow */
81 }
82