xref: /illumos-gate/usr/src/lib/libm/common/m9x/lrint.c (revision ddc0e0b53c661f6e439e3b7072b3ef353eadb4af)
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 __lrint = lrint
31 
32 /*
33  * lrint(x) rounds its argument to the nearest integer according
34  * to the current rounding direction and converts the result to
35  * a 32 bit signed integer.
36  *
37  * If x is NaN, infinite, or so large that the nearest integer
38  * would exceed 32 bits, the invalid operation exception is raised.
39  * If x is not an integer, the inexact exception is raised.
40  */
41 
42 #include <sys/isa_defs.h>	/* _ILP32 */
43 #include "libm.h"
44 
45 #if defined(_ILP32)
46 long
lrint(double x)47 lrint(double x) {
48 	/*
49 	 * Note: The following code works on x86 (in the default rounding
50 	 * precision mode), but one should just use the fistpl instruction
51 	 * instead.
52 	 */
53 	union {
54 		unsigned i[2];
55 		double d;
56 	} xx, yy;
57 	unsigned hx;
58 
59 	xx.d = x;
60 	hx = xx.i[HIWORD] & ~0x80000000;
61 	if (hx < 0x43300000) { /* |x| < 2^52 */
62 		/* add and subtract a power of two to round x to an integer */
63 #if defined(__sparc)
64 		yy.i[HIWORD] = (xx.i[HIWORD] & 0x80000000) | 0x43300000;
65 #elif defined(__x86)
66 		yy.i[HIWORD] = (xx.i[HIWORD] & 0x80000000) | 0x43e00000;
67 #else
68 #error Unknown architecture
69 #endif
70 		yy.i[LOWORD] = 0;
71 		x = (x + yy.d) - yy.d;
72 	}
73 
74 	/* now x is nan, inf, or integral */
75 	return ((long) x);
76 }
77 #else
78 #error Unsupported architecture
79 #endif	/* defined(_ILP32) */
80