xref: /illumos-gate/usr/src/lib/libm/common/m9x/ldexp.c (revision d48be21240dfd051b689384ce2b23479d757f2d8)
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 __ldexp = ldexp
31 
32 #include "libm.h"
33 #include <errno.h>
34 
35 double
36 ldexp(double x, int n) {
37 	int *px = (int *) &x, ix = px[HIWORD] & ~0x80000000;
38 
39 	if (ix >= 0x7ff00000 || (px[LOWORD] | ix) == 0)
40 #if defined(FPADD_TRAPS_INCOMPLETE_ON_NAN)
41 		return (ix >= 0x7ff80000 ? x : x + x);
42 		/* assumes sparc-like QNaN */
43 #else
44 		return (x + x);
45 #endif
46 	x = scalbn(x, n);
47 	ix = px[HIWORD] & ~0x80000000;
48 	/*
49 	 * SVID3 requires both overflow and underflow cases to set errno
50 	 * XPG3/XPG4/XPG4.2/SUSv2 requires overflow to set errno
51 	 */
52 	if (ix >= 0x7ff00000 || (px[LOWORD] | ix) == 0)
53 		errno = ERANGE;
54 	return (x);
55 }
56