xref: /illumos-gate/usr/src/lib/libm/common/C/significand.c (revision a160fd9a3a7d4d2a7b2979af5e53de5d0ad961aa)
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 __significand = significand
31 
32 #include "libm.h"
33 
34 double
35 significand(double x) {
36 	int ix = ((int *) &x)[HIWORD] & ~0x80000000;
37 
38 	/* weed out 0/+-Inf/NaN because C99 ilogb raises invalid on them */
39 	if ((ix | ((int *) &x)[LOWORD]) == 0 || ix >= 0x7ff00000)
40 #if defined(FPADD_TRAPS_INCOMPLETE_ON_NAN)
41 		return ((ix & 0x80000) != 0 ? x : x + x);
42 		/* assumes sparc-like QNaN */
43 #else
44 		return (x + x);
45 #endif
46 	else
47 		return (scalbn(x, -ilogb(x)));
48 }
49