xref: /illumos-gate/usr/src/lib/libm/common/m9x/modff.c (revision a6bde1a23b60f140c7ed78df979c2e22b1ed9b2c)
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 modff = __modff
32 #pragma weak _modff = __modff
33 #endif
34 
35 #include "libm.h"
36 
37 float
38 __modff(float x, float *iptr) {
39 	union {
40 		unsigned i;
41 		float f;
42 	} xx, yy;
43 	unsigned hx, s;
44 
45 	xx.f = x;
46 	hx = xx.i & ~0x80000000;
47 
48 	if (hx >= 0x4b000000) {	/* x is NaN, infinite, or integral */
49 		*iptr = x;
50 		if (hx <= 0x7f800000)
51 			xx.i &= 0x80000000;
52 		return (xx.f);
53 	}
54 
55 	if (hx < 0x3f800000) {	/* |x| < 1 */
56 		xx.i &= 0x80000000;
57 		*iptr = xx.f;
58 		return (x);
59 	}
60 
61 	/* split x at the binary point */
62 	s = xx.i & 0x80000000;
63 	yy.i = xx.i & ~((1 << (0x96 - (hx >> 23))) - 1);
64 	*iptr = yy.f;
65 	xx.f -= yy.f;
66 	xx.i = (xx.i & ~0x80000000) | s;
67 				/* restore sign in case difference is 0 */
68 	return (xx.f);
69 }
70