xref: /illumos-gate/usr/src/lib/libm/common/m9x/llroundf.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 __llroundf = llroundf
31 #if defined(__sparcv9) || defined(__amd64)
32 #pragma weak lroundf = llroundf
33 #pragma weak __lroundf = llroundf
34 #endif
35 
36 #include "libm.h"
37 
38 long long
39 llroundf(float x) {
40 	union {
41 		unsigned i;
42 		float f;
43 	} xx;
44 	unsigned hx, sx, i;
45 
46 	xx.f = x;
47 	hx = xx.i & ~0x80000000;
48 	sx = xx.i & 0x80000000;
49 
50 	if (hx < 0x4b000000) { /* |x| < 2^23 */
51 		/* handle |x| < 1 */
52 		if (hx < 0x3f800000) {
53 			if (hx >= 0x3f000000)
54 				return (sx ? -1LL : 1LL);
55 			return (0LL);
56 		}
57 
58 		/* round x at the integer bit */
59 		i = 1 << (0x95 - (hx >> 23));
60 		xx.i = (xx.i + i) & ~((i << 1) - 1);
61 
62 		/*
63 		 * on LP32 architectures, we can just convert x to a 32-bit
64 		 * integer and sign-extend it
65 		 */
66 		return ((long) xx.f);
67 	}
68 
69 	/* now x is nan, inf, or integral */
70 	return ((long long) x);
71 }
72