xref: /titanic_41/usr/src/lib/libm/common/C/significand.c (revision bb3db448291a7208a0162997e1d17d3fa993871a)
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 #if defined(ELFOBJ)
31 #pragma weak significand = __significand
32 #endif
33 
34 #include "libm.h"
35 
36 double
37 significand(double x) {
38 	int ix = ((int *) &x)[HIWORD] & ~0x80000000;
39 
40 	/* weed out 0/+-Inf/NaN because C99 ilogb raises invalid on them */
41 	if ((ix | ((int *) &x)[LOWORD]) == 0 || ix >= 0x7ff00000)
42 #if defined(FPADD_TRAPS_INCOMPLETE_ON_NAN)
43 		return ((ix & 0x80000) != 0 ? x : x + x);
44 		/* assumes sparc-like QNaN */
45 #else
46 		return (x + x);
47 #endif
48 	else
49 		return (scalbn(x, -ilogb(x)));
50 }
51