xref: /titanic_51/usr/src/lib/libm/common/Q/scalbl.c (revision 177d5b5f8c0e969013441207a0a705ae66b08cf7)
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 scalbl = __scalbl
31 
32 /*
33  * scalbl(x,n): return x * 2^n by manipulating exponent.
34  */
35 
36 #include "libm.h"
37 
38 #define	n0	0
39 
40 long double
41 scalbl(long double x, long double fn) {
42 	int *py = (int *) &fn, n;
43 	long double z;
44 
45 	if (isnanl(x) || isnanl(fn))
46 		return (x * fn);
47 
48 	/*
49 	 * fn is inf or NaN
50 	 */
51 	if ((py[n0] & 0x7fff0000) == 0x7fff0000) {
52 		if ((py[n0] & 0x80000000) != 0)
53 			return (x / (-fn));
54 		else
55 			return (x * fn);
56 	}
57 	if (rintl(fn) != fn)
58 		return ((fn - fn) / (fn - fn));
59 	if (fn > 65000.0L)
60 		z = scalbnl(x, 65000);
61 	else if (-fn > 65000.0L)
62 		z = scalbnl(x, -65000);
63 	else {
64 		n = (int) fn;
65 		z = scalbnl(x, n);
66 	}
67 	return (z);
68 }
69