xref: /titanic_41/usr/src/lib/libm/common/m9x/lrintf.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 lrintf = __lrintf
32 #endif
33 
34 #include <sys/isa_defs.h>	/* _ILP32 */
35 #include "libm.h"
36 
37 #if defined(_ILP32)
38 long
39 lrintf(float x) {
40 	/*
41 	 * Note: The following code works on x86 (in the default rounding
42 	 * precision mode), but one should just use the fistpl instruction
43 	 * instead.
44 	 */
45 	union {
46 		unsigned i;
47 		float f;
48 	} xx, yy;
49 	unsigned hx;
50 
51 	xx.f = x;
52 	hx = xx.i & ~0x80000000;
53 	if (hx < 0x4b000000) {	/* |x| < 2^23 */
54 		/* add and subtract a power of two to round x to an integer */
55 #if defined(__sparc)
56 		yy.i = (xx.i & 0x80000000) | 0x4b000000;
57 #elif defined(__x86)
58 		/* assume 64-bit precision */
59 		yy.i = (xx.i & 0x80000000) | 0x5f000000;
60 #else
61 #error Unknown architecture
62 #endif
63 		x = (x + yy.f) - yy.f;
64 		return ((long) x);
65 	}
66 
67 	/* now x is nan, inf, or integral */
68 	return ((long) x);
69 }
70 #else
71 #error Unsupported architecture
72 #endif	/* defined(_ILP32) */
73