xref: /illumos-gate/usr/src/lib/libm/common/C/isnan.c (revision c5bab7026b8e0ac44b25ee08507ea360f177d844)
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  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
23  */
24 /*
25  * Copyright 2006 Sun Microsystems, Inc.  All rights reserved.
26  * Use is subject to license terms.
27  */
28 
29 #pragma weak isnan = __isnan
30 #pragma weak _isnan = __isnan
31 #pragma weak _isnand = __isnan
32 #pragma weak isnand = __isnan
33 
34 #include "libm.h"
35 
36 /*
37  * The following implementation assumes fast 64-bit integer arith-
38  * metic.  This is fine for sparc because we build libm in v8plus
39  * mode.  It's also fine for sparcv9 and amd64.  For x86, it would
40  * be better to use 32-bit code, but we have assembly for x86.
41  */
42 int
43 __isnan(double x) {
44 	long long	llx;
45 
46 	llx = *(long long *)&x & ~0x8000000000000000ull;
47 	return ((unsigned long long)(0x7ff0000000000000ll - llx) >> 63);
48 }
49