xref: /illumos-gate/usr/src/lib/libm/common/m9x/lrintl.c (revision 152f805526ab714ed4b76c4ff672f34c8dda62ea)
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 __lrintl = lrintl
31 
32 #include <sys/isa_defs.h>	/* _ILP32 */
33 #include "libm.h"
34 
35 #if defined(_ILP32)
36 #if defined(__sparc)
37 
38 #include "fma.h"
39 #include "fenv_inlines.h"
40 
41 long
42 lrintl(long double x) {
43 	union {
44 		unsigned int i[4];
45 		long double q;
46 	} xx;
47 	union {
48 		unsigned int i;
49 		float f;
50 	} tt;
51 	unsigned int hx, sx, frac, l, fsr;
52 	int rm, j;
53 	volatile float dummy;
54 
55 	xx.q = x;
56 	sx = xx.i[0] & 0x80000000;
57 	hx = xx.i[0] & ~0x80000000;
58 
59 	/* handle trivial cases */
60 	if (hx > 0x401e0000) { /* |x| > 2^31 + ... or x is nan */
61 		/* convert an out-of-range float */
62 		tt.i = sx | 0x7f000000;
63 		return ((long) tt.f);
64 	} else if ((hx | xx.i[1] | xx.i[2] | xx.i[3]) == 0) /* x is zero */
65 		return (0L);
66 
67 	/* get the rounding mode */
68 	__fenv_getfsr32(&fsr);
69 	rm = fsr >> 30;
70 
71 	/* flip the sense of directed roundings if x is negative */
72 	if (sx)
73 		rm ^= rm >> 1;
74 
75 	/* handle |x| < 1 */
76 	if (hx < 0x3fff0000) {
77 		dummy = 1.0e30F; /* x is nonzero, so raise inexact */
78 		dummy += 1.0e-30F;
79 		if (rm == FSR_RP || (rm == FSR_RN && (hx >= 0x3ffe0000 &&
80 			((hx & 0xffff) | xx.i[1] | xx.i[2] | xx.i[3]))))
81 			return (sx ? -1L : 1L);
82 		return (0L);
83 	}
84 
85 	/* extract the integer and fractional parts of x */
86 	j = 0x406f - (hx >> 16);		/* 91 <= j <= 112 */
87 	xx.i[0] = 0x10000 | (xx.i[0] & 0xffff);
88 	if (j >= 96) {				/* 96 <= j <= 112 */
89 		l = xx.i[0] >> (j - 96);
90 		frac = ((xx.i[0] << 1) << (127 - j)) | (xx.i[1] >> (j - 96));
91 		if (((xx.i[1] << 1) << (127 - j)) | xx.i[2] | xx.i[3])
92 			frac |= 1;
93 	} else {				/* 91 <= j <= 95 */
94 		l = (xx.i[0] << (96 - j)) | (xx.i[1] >> (j - 64));
95 		frac = (xx.i[1] << (96 - j)) | (xx.i[2] >> (j - 64));
96 		if ((xx.i[2] << (96 - j)) | xx.i[3])
97 			frac |= 1;
98 	}
99 
100 	/* round */
101 	if (frac && (rm == FSR_RP || (rm == FSR_RN && (frac > 0x80000000U ||
102 		(frac == 0x80000000 && (l & 1))))))
103 		l++;
104 
105 	/* check for result out of range (note that z is |x| at this point) */
106 	if (l > 0x80000000U || (l == 0x80000000U && !sx)) {
107 		tt.i = sx | 0x7f000000;
108 		return ((long) tt.f);
109 	}
110 
111 	/* raise inexact if need be */
112 	if (frac) {
113 		dummy = 1.0e30F;
114 		dummy += 1.0e-30F;
115 	}
116 
117 	/* negate result if need be */
118 	if (sx)
119 		l = -l;
120 	return ((long) l);
121 }
122 #elif defined(__x86)
123 long
124 lrintl(long double x) {
125 	/*
126 	 * Note: The following code works on x86 (in the default rounding
127 	 * precision mode), but one ought to just use the fistpl instruction
128 	 * instead.
129 	 */
130 	union {
131 		unsigned i[3];
132 		long double e;
133 	} xx, yy;
134 	int ex;
135 
136 	xx.e = x;
137 	ex = xx.i[2] & 0x7fff;
138 	if (ex < 0x403e) {	/* |x| < 2^63 */
139 		/* add and subtract a power of two to round x to an integer */
140 		yy.i[2] = (xx.i[2] & 0x8000) | 0x403e;
141 		yy.i[1] = 0x80000000;
142 		yy.i[0] = 0;
143 		x = (x + yy.e) - yy.e;
144 	}
145 
146 	/* now x is nan, inf, or integral */
147 	return ((long) x);
148 }
149 #else
150 #error Unknown architecture
151 #endif	/* defined(__sparc) || defined(__x86) */
152 #else
153 #error Unsupported architecture
154 #endif	/* defined(_ILP32) */
155