xref: /titanic_41/usr/src/lib/libm/common/m9x/lrint.c (revision 018207534e5d18020ddb86fea48c6d68c7a2626d)
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 lrint = __lrint
32 #endif
33 
34 /*
35  * lrint(x) rounds its argument to the nearest integer according
36  * to the current rounding direction and converts the result to
37  * a 32 bit signed integer.
38  *
39  * If x is NaN, infinite, or so large that the nearest integer
40  * would exceed 32 bits, the invalid operation exception is raised.
41  * If x is not an integer, the inexact exception is raised.
42  */
43 
44 #include <sys/isa_defs.h>	/* _ILP32 */
45 #include "libm.h"
46 
47 #if defined(_ILP32)
48 long
49 lrint(double x) {
50 	/*
51 	 * Note: The following code works on x86 (in the default rounding
52 	 * precision mode), but one should just use the fistpl instruction
53 	 * instead.
54 	 */
55 	union {
56 		unsigned i[2];
57 		double d;
58 	} xx, yy;
59 	unsigned hx;
60 
61 	xx.d = x;
62 	hx = xx.i[HIWORD] & ~0x80000000;
63 	if (hx < 0x43300000) { /* |x| < 2^52 */
64 		/* add and subtract a power of two to round x to an integer */
65 #if defined(__sparc)
66 		yy.i[HIWORD] = (xx.i[HIWORD] & 0x80000000) | 0x43300000;
67 #elif defined(__x86)
68 		yy.i[HIWORD] = (xx.i[HIWORD] & 0x80000000) | 0x43e00000;
69 #else
70 #error Unknown architecture
71 #endif
72 		yy.i[LOWORD] = 0;
73 		x = (x + yy.d) - yy.d;
74 	}
75 
76 	/* now x is nan, inf, or integral */
77 	return ((long) x);
78 }
79 #else
80 #error Unsupported architecture
81 #endif	/* defined(_ILP32) */
82