xref: /illumos-gate/usr/src/lib/libm/common/m9x/lroundl.c (revision 1a2d662a91cee3bf82f41cd47c7ae6f3825d9db2)
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 __lroundl = lroundl
31 
32 #include <sys/isa_defs.h>	/* _ILP32 */
33 #include "libm.h"
34 
35 #if defined(_ILP32)
36 #if defined(__sparc)
37 long
38 lroundl(long double x) {
39 	union {
40 		unsigned i[4];
41 		long double q;
42 	} xx;
43 	union {
44 		unsigned i;
45 		float f;
46 	} tt;
47 	unsigned hx, sx, frac, l;
48 	int j;
49 
50 	xx.q = x;
51 	sx = xx.i[0] & 0x80000000;
52 	hx = xx.i[0] & ~0x80000000;
53 
54 	/* handle trivial cases */
55 	if (hx > 0x401e0000) { /* |x| > 2^31 + ... or x is nan */
56 		/* convert an out-of-range float */
57 		tt.i = sx | 0x7f000000;
58 		return ((long) tt.f);
59 	}
60 
61 	/* handle |x| < 1 */
62 	if (hx < 0x3fff0000) {
63 		if (hx >= 0x3ffe0000)
64 			return (sx ? -1L : 1L);
65 		return (0L);
66 	}
67 
68 	/* extract the integer and fractional parts of x */
69 	j = 0x406f - (hx >> 16);		/* 91 <= j <= 112 */
70 	xx.i[0] = 0x10000 | (xx.i[0] & 0xffff);
71 	if (j >= 96) {				/* 96 <= j <= 112 */
72 		l = xx.i[0] >> (j - 96);
73 		frac = ((xx.i[0] << 1) << (127 - j)) | (xx.i[1] >> (j - 96));
74 		if (((xx.i[1] << 1) << (127 - j)) | xx.i[2] | xx.i[3])
75 			frac |= 1;
76 	} else {				/* 91 <= j <= 95 */
77 		l = (xx.i[0] << (96 - j)) | (xx.i[1] >> (j - 64));
78 		frac = (xx.i[1] << (96 - j)) | (xx.i[2] >> (j - 64));
79 		if ((xx.i[2] << (96 - j)) | xx.i[3])
80 			frac |= 1;
81 	}
82 
83 	/* round */
84 	if (frac >= 0x80000000U)
85 		l++;
86 
87 	/* check for result out of range (note that z is |x| at this point) */
88 	if (l > 0x80000000U || (l == 0x80000000U && !sx)) {
89 		tt.i = sx | 0x7f000000;
90 		return ((long) tt.f);
91 	}
92 
93 	/* negate result if need be */
94 	if (sx)
95 		l = -l;
96 	return ((long) l);
97 }
98 #elif defined(__x86)
99 long
100 lroundl(long double x) {
101 	union {
102 		unsigned i[3];
103 		long double e;
104 	} xx;
105 	int ex, sx, i;
106 
107 	xx.e = x;
108 	ex = xx.i[2] & 0x7fff;
109 	sx = xx.i[2] & 0x8000;
110 	if (ex < 0x403e) {	/* |x| < 2^63 */
111 		if (ex < 0x3fff) {	/* |x| < 1 */
112 			if (ex >= 0x3ffe)
113 				return (sx ? -1L : 1L);
114 			return (0L);
115 		}
116 
117 		/* round x at the integer bit */
118 		if (ex < 0x401e) {
119 			i = 1 << (0x401d - ex);
120 			xx.i[1] = (xx.i[1] + i) & ~(i | (i - 1));
121 			xx.i[0] = 0;
122 		} else {
123 			i = 1 << (0x403d - ex);
124 			xx.i[0] += i;
125 			if (xx.i[0] < i)
126 				xx.i[1]++;
127 			xx.i[0] &= ~(i | (i - 1));
128 		}
129 		if (xx.i[1] == 0) {
130 			xx.i[2] = sx | ++ex;
131 			xx.i[1] = 0x80000000U;
132 		}
133 	}
134 
135 	/* now x is nan, inf, or integral */
136 	return ((long) xx.e);
137 }
138 #else
139 #error Unknown architecture
140 #endif	/* defined(__sparc) || defined(__x86) */
141 #else
142 #error Unsupported architecture
143 #endif	/* defined(_ILP32) */
144