xref: /illumos-gate/usr/src/lib/libm/common/m9x/llrintl.c (revision 241c90a0)
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 __llrintl = llrintl
31 #if defined(__sparcv9) || defined(__amd64)
32 #pragma weak lrintl = llrintl
33 #pragma weak __lrintl = llrintl
34 #endif
35 
36 #include "libm.h"
37 
38 #if defined(__sparc)
39 
40 #include "fma.h"
41 #include "fenv_inlines.h"
42 
43 long long
44 llrintl(long double x) {
45 	union {
46 		unsigned i[4];
47 		long double q;
48 	} xx;
49 	union {
50 		unsigned i[2];
51 		long long l;
52 	} zz;
53 	union {
54 		unsigned i;
55 		float f;
56 	} tt;
57 	unsigned int hx, sx, frac, fsr;
58 	int rm, j;
59 	volatile float dummy;
60 
61 	xx.q = x;
62 	sx = xx.i[0] & 0x80000000;
63 	hx = xx.i[0] & ~0x80000000;
64 
65 	/* handle trivial cases */
66 	if (hx > 0x403e0000) { /* |x| > 2^63 + ... or x is nan */
67 		/* convert an out-of-range float */
68 		tt.i = sx | 0x7f000000;
69 		return ((long long) tt.f);
70 	} else if ((hx | xx.i[1] | xx.i[2] | xx.i[3]) == 0) /* x is zero */
71 		return (0LL);
72 
73 	/* get the rounding mode */
74 	__fenv_getfsr32(&fsr);
75 	rm = fsr >> 30;
76 
77 	/* flip the sense of directed roundings if x is negative */
78 	if (sx)
79 		rm ^= rm >> 1;
80 
81 	/* handle |x| < 1 */
82 	if (hx < 0x3fff0000) {
83 		dummy = 1.0e30f; /* x is nonzero, so raise inexact */
84 		dummy += 1.0e-30f;
85 		if (rm == FSR_RP || (rm == FSR_RN && (hx >= 0x3ffe0000 &&
86 			((hx & 0xffff) | xx.i[1] | xx.i[2] | xx.i[3]))))
87 			return (sx ? -1LL : 1LL);
88 		return (0LL);
89 	}
90 
91 	/* extract the integer and fractional parts of x */
92 	j = 0x406f - (hx >> 16);
93 	xx.i[0] = 0x10000 | (xx.i[0] & 0xffff);
94 	if (j >= 96) {
95 		zz.i[0] = 0;
96 		zz.i[1] = xx.i[0] >> (j - 96);
97 		frac = ((xx.i[0] << 1) << (127 - j)) | (xx.i[1] >> (j - 96));
98 		if (((xx.i[1] << 1) << (127 - j)) | xx.i[2] | xx.i[3])
99 			frac |= 1;
100 	} else if (j >= 64) {
101 		zz.i[0] = xx.i[0] >> (j - 64);
102 		zz.i[1] = ((xx.i[0] << 1) << (95 - j)) | (xx.i[1] >> (j - 64));
103 		frac = ((xx.i[1] << 1) << (95 - j)) | (xx.i[2] >> (j - 64));
104 		if (((xx.i[2] << 1) << (95 - j)) | xx.i[3])
105 			frac |= 1;
106 	} else {
107 		zz.i[0] = ((xx.i[0] << 1) << (63 - j)) | (xx.i[1] >> (j - 32));
108 		zz.i[1] = ((xx.i[1] << 1) << (63 - j)) | (xx.i[2] >> (j - 32));
109 		frac = ((xx.i[2] << 1) << (63 - j)) | (xx.i[3] >> (j - 32));
110 		if ((xx.i[3] << 1) << (63 - j))
111 			frac |= 1;
112 	}
113 
114 	/* round */
115 	if (frac && (rm == FSR_RP || (rm == FSR_RN && (frac > 0x80000000u ||
116 		(frac == 0x80000000 && (zz.i[1] & 1)))))) {
117 		if (++zz.i[1] == 0)
118 			zz.i[0]++;
119 	}
120 
121 	/* check for result out of range (note that z is |x| at this point) */
122 	if (zz.i[0] > 0x80000000u || (zz.i[0] == 0x80000000 && (zz.i[1] ||
123 		!sx))) {
124 		tt.i = sx | 0x7f000000;
125 		return ((long long) tt.f);
126 	}
127 
128 	/* raise inexact if need be */
129 	if (frac) {
130 		dummy = 1.0e30F;
131 		dummy += 1.0e-30F;
132 	}
133 
134 	/* negate result if need be */
135 	if (sx) {
136 		zz.i[0] = ~zz.i[0];
137 		zz.i[1] = -zz.i[1];
138 		if (zz.i[1] == 0)
139 			zz.i[0]++;
140 	}
141 	return (zz.l);
142 }
143 #elif defined(__x86)
144 long long
145 llrintl(long double x) {
146 	/*
147 	 * Note: The following code works on x86 (in the default rounding
148 	 * precision mode), but one ought to just use the fistpll instruction
149 	 * instead.
150 	 */
151 	union {
152 		unsigned i[3];
153 		long double e;
154 	} xx, yy;
155 	int ex;
156 
157 	xx.e = x;
158 	ex = xx.i[2] & 0x7fff;
159 
160 	if (ex < 0x403e) { /* |x| < 2^63 */
161 		/* add and subtract a power of two to round x to an integer */
162 		yy.i[2] = (xx.i[2] & 0x8000) | 0x403e;
163 		yy.i[1] = 0x80000000;
164 		yy.i[0] = 0;
165 		x = (x + yy.e) - yy.e;
166 	}
167 
168 	/* now x is nan, inf, or integral */
169 	return ((long long) x);
170 }
171 #else
172 #error Unknown architecture
173 #endif
174