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 __cosl = cosl
31
32 /* INDENT OFF */
33 /* cosl(x)
34 * Table look-up algorithm by K.C. Ng, November, 1989.
35 *
36 * kernel function:
37 * __k_sinl ... sin function on [-pi/4,pi/4]
38 * __k_cosl ... cos function on [-pi/4,pi/4]
39 * __rem_pio2l ... argument reduction routine
40 *
41 * Method.
42 * Let S and C denote the sin and cos respectively on [-PI/4, +PI/4].
43 * 1. Assume the argument x is reduced to y1+y2 = x-k*pi/2 in
44 * [-pi/2 , +pi/2], and let n = k mod 4.
45 * 2. Let S=S(y1+y2), C=C(y1+y2). Depending on n, we have
46 *
47 * n sin(x) cos(x) tan(x)
48 * ----------------------------------------------------------
49 * 0 S C S/C
50 * 1 C -S -C/S
51 * 2 -S -C S/C
52 * 3 -C S -C/S
53 * ----------------------------------------------------------
54 *
55 * Special cases:
56 * Let trig be any of sin, cos, or tan.
57 * trig(+-INF) is NaN, with signals;
58 * trig(NaN) is that NaN;
59 *
60 * Accuracy:
61 * computer TRIG(x) returns trig(x) nearly rounded.
62 */
63 /* INDENT ON */
64
65 #include "libm.h"
66 #include "longdouble.h"
67
68 long double
cosl(long double x)69 cosl(long double x) {
70 long double y[2], z = 0.0L;
71 int n, ix;
72 int *px = (int *) &x;
73
74 /* trig(Inf or NaN) is NaN */
75 if (!finitel(x))
76 return x - x;
77
78 /* High word of x. */
79 #if defined(__i386) || defined(__amd64)
80 XTOI(px, ix);
81 #else
82 ix = px[0];
83 #endif
84
85 /* |x| ~< pi/4 */
86 ix &= 0x7fffffff;
87 if (ix <= 0x3ffe9220)
88 return __k_cosl(x, z);
89
90 /* argument reduction needed */
91 else {
92 n = __rem_pio2l(x, y);
93 switch (n & 3) {
94 case 0:
95 return __k_cosl(y[0], y[1]);
96 case 1:
97 return -__k_sinl(y[0], y[1]);
98 case 2:
99 return -__k_cosl(y[0], y[1]);
100 case 3:
101 return __k_sinl(y[0], y[1]);
102 /* NOTREACHED */
103 }
104 }
105 return 0.0L;
106 }
107