xref: /illumos-gate/usr/src/lib/libm/common/m9x/lroundl.c (revision 25c28e83beb90e7c80452a7c818c5e6f73a07dc8)
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 lroundl = __lroundl
32 #endif
33 
34 #include <sys/isa_defs.h>	/* _ILP32 */
35 #include "libm.h"
36 
37 #if defined(_ILP32)
38 #if defined(__sparc)
39 long
40 lroundl(long double x) {
41 	union {
42 		unsigned i[4];
43 		long double q;
44 	} xx;
45 	union {
46 		unsigned i;
47 		float f;
48 	} tt;
49 	unsigned hx, sx, frac, l;
50 	int j;
51 
52 	xx.q = x;
53 	sx = xx.i[0] & 0x80000000;
54 	hx = xx.i[0] & ~0x80000000;
55 
56 	/* handle trivial cases */
57 	if (hx > 0x401e0000) { /* |x| > 2^31 + ... or x is nan */
58 		/* convert an out-of-range float */
59 		tt.i = sx | 0x7f000000;
60 		return ((long) tt.f);
61 	}
62 
63 	/* handle |x| < 1 */
64 	if (hx < 0x3fff0000) {
65 		if (hx >= 0x3ffe0000)
66 			return (sx ? -1L : 1L);
67 		return (0L);
68 	}
69 
70 	/* extract the integer and fractional parts of x */
71 	j = 0x406f - (hx >> 16);		/* 91 <= j <= 112 */
72 	xx.i[0] = 0x10000 | (xx.i[0] & 0xffff);
73 	if (j >= 96) {				/* 96 <= j <= 112 */
74 		l = xx.i[0] >> (j - 96);
75 		frac = ((xx.i[0] << 1) << (127 - j)) | (xx.i[1] >> (j - 96));
76 		if (((xx.i[1] << 1) << (127 - j)) | xx.i[2] | xx.i[3])
77 			frac |= 1;
78 	} else {				/* 91 <= j <= 95 */
79 		l = (xx.i[0] << (96 - j)) | (xx.i[1] >> (j - 64));
80 		frac = (xx.i[1] << (96 - j)) | (xx.i[2] >> (j - 64));
81 		if ((xx.i[2] << (96 - j)) | xx.i[3])
82 			frac |= 1;
83 	}
84 
85 	/* round */
86 	if (frac >= 0x80000000U)
87 		l++;
88 
89 	/* check for result out of range (note that z is |x| at this point) */
90 	if (l > 0x80000000U || (l == 0x80000000U && !sx)) {
91 		tt.i = sx | 0x7f000000;
92 		return ((long) tt.f);
93 	}
94 
95 	/* negate result if need be */
96 	if (sx)
97 		l = -l;
98 	return ((long) l);
99 }
100 #elif defined(__x86)
101 long
102 lroundl(long double x) {
103 	union {
104 		unsigned i[3];
105 		long double e;
106 	} xx;
107 	int ex, sx, i;
108 
109 	xx.e = x;
110 	ex = xx.i[2] & 0x7fff;
111 	sx = xx.i[2] & 0x8000;
112 	if (ex < 0x403e) {	/* |x| < 2^63 */
113 		if (ex < 0x3fff) {	/* |x| < 1 */
114 			if (ex >= 0x3ffe)
115 				return (sx ? -1L : 1L);
116 			return (0L);
117 		}
118 
119 		/* round x at the integer bit */
120 		if (ex < 0x401e) {
121 			i = 1 << (0x401d - ex);
122 			xx.i[1] = (xx.i[1] + i) & ~(i | (i - 1));
123 			xx.i[0] = 0;
124 		} else {
125 			i = 1 << (0x403d - ex);
126 			xx.i[0] += i;
127 			if (xx.i[0] < i)
128 				xx.i[1]++;
129 			xx.i[0] &= ~(i | (i - 1));
130 		}
131 		if (xx.i[1] == 0) {
132 			xx.i[2] = sx | ++ex;
133 			xx.i[1] = 0x80000000U;
134 		}
135 	}
136 
137 	/* now x is nan, inf, or integral */
138 	return ((long) xx.e);
139 }
140 #else
141 #error Unknown architecture
142 #endif	/* defined(__sparc) || defined(__x86) */
143 #else
144 #error Unsupported architecture
145 #endif	/* defined(_ILP32) */
146