xref: /illumos-gate/usr/src/lib/libm/common/Q/rintl.c (revision 3ba944265c4ae1fcf23ef758537c2e4f4feec16e)
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 __rintl = rintl
31 
32 /*
33  * rintl(long double x) return x rounded to integral according to
34  * the prevailing rounding direction
35  *
36  * NOTE: aintl(x), anintl(x), ceill(x), floorl(x), and rintl(x) return result
37  * with the same sign as x's, including 0.0L.
38  */
39 
40 #include "libm.h"
41 #include "longdouble.h"
42 
43 extern enum fp_precision_type __swapRP(enum fp_precision_type);
44 
45 static const double one = 1.0;
46 static const long double qzero = 0.0L;
47 
48 long double
49 rintl(long double x) {
50 	enum fp_precision_type rp;
51 	long double t, w, two112;
52 	int *pt = (int *) &two112;
53 
54 	if (!finitel(x))
55 		return (x + x);
56 
57 	if (*(int *) &one != 0) {	/* set two112 = 2^112 */
58 		pt[0] = 0x406f0000;
59 		pt[1] = pt[2] = pt[3] = 0;
60 	} else {
61 		pt[3] = 0x406f0000;
62 		pt[0] = pt[1] = pt[2] = 0;
63 	}
64 
65 	if (fabsl(x) >= two112)
66 		return (x);	/* already an integer */
67 	t = copysignl(two112, x);
68 	rp = __swapRP(fp_extended);	/* make sure precision is long double */
69 	w = x + t;			/* x+sign(x)*2^112 rounded to integer */
70 	(void) __swapRP(rp);		/* restore precision mode */
71 	if (w == t)
72 		return (copysignl(qzero, x));	/* x rounded to zero */
73 	else
74 		return (w - t);
75 }
76