xref: /illumos-gate/usr/src/lib/libm/common/R/tanf.c (revision f20211217f12ce291fd518e61065cd273f23e4ea)
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  * Copyright 2011 Nexenta Systems, Inc.  All rights reserved.
23  */
24 /*
25  * Copyright 2005 Sun Microsystems, Inc.  All rights reserved.
26  * Use is subject to license terms.
27  */
28 
29 #pragma weak __tanf = tanf
30 
31 #include "libm.h"
32 
33 extern const int _TBL_ipio2_inf[];
34 extern int __rem_pio2m(double *, double *, int, int, int, const int *);
35 #if defined(__i386) && !defined(__amd64)
36 extern int __swapRP(int);
37 #endif
38 
39 static const double C[] = {
40 	1.0,
41 	4.46066928428959230679140546271810308098793029785e-0003,
42 	4.92165316309189027066395283327437937259674072266e+0000,
43 	-7.11410648161473480044492134766187518835067749023e-0001,
44 	4.08549808374053391446523164631798863410949707031e+0000,
45 	2.50411070398050927821032018982805311679840087891e+0000,
46 	1.11492064560251158411574579076841473579406738281e+0001,
47 	-1.50565540968422650891511693771462887525558471680e+0000,
48 	-1.81484378878349295050043110677506774663925170898e+0000,
49 	3.333335997532835641297409611782510896641e-0001,
50 	2.999997598248363761541668282006867229939e+00,
51 	0.636619772367581343075535,	/* 2^ -1  * 1.45F306DC9C883 */
52 	0.5,
53 	1.570796326734125614166,	/* 2^  0  * 1.921FB54400000 */
54 	6.077100506506192601475e-11,	/* 2^-34  * 1.0B4611A626331 */
55 };
56 
57 #define	one	C[0]
58 #define	P0	C[1]
59 #define	P1	C[2]
60 #define	P2	C[3]
61 #define	P3	C[4]
62 #define	P4	C[5]
63 #define	P5	C[6]
64 #define	P6	C[7]
65 #define	P7	C[8]
66 #define	T0	C[9]
67 #define	T1	C[10]
68 #define	invpio2	C[11]
69 #define	half	C[12]
70 #define	pio2_1  C[13]
71 #define	pio2_t	C[14]
72 
73 float
74 tanf(float x)
75 {
76 	double	y, z, w;
77 	float	f;
78 	int	n, ix, hx, hy;
79 	volatile int i __unused;
80 
81 	hx = *((int *)&x);
82 	ix = hx & 0x7fffffff;
83 
84 	y = (double)x;
85 
86 	if (ix <= 0x4016cbe4) {		/* |x| < 3*pi/4 */
87 		if (ix <= 0x3f490fdb) {		/* |x| < pi/4 */
88 			if (ix < 0x3c000000) {		/* |x| < 2**-7 */
89 				if (ix <= 0x39800000) {	/* |x| < 2**-12 */
90 					i = (int)y;
91 #ifdef lint
92 					i = i;
93 #endif
94 					return (x);
95 				}
96 				return ((float)((y * T0) * (T1 + y * y)));
97 			}
98 			z = y * y;
99 			return ((float)(((P0 * y) * (P1 + z * (P2 + z)) *
100 			    (P3 + z * (P4 + z))) *
101 			    (P5 + z * (P6 + z * (P7 + z)))));
102 		}
103 		if (hx > 0)
104 			y = (y - pio2_1) - pio2_t;
105 		else
106 			y = (y + pio2_1) + pio2_t;
107 		hy = ((int *)&y)[HIWORD] & ~0x80000000;
108 		if (hy < 0x3f800000) {		/* |y| < 2**-7 */
109 			z = (y * T0) * (T1 + y * y);
110 			return ((float)(-one / z));
111 		}
112 		z = y * y;
113 		w = ((P0 * y) * (P1 + z * (P2 + z)) * (P3 + z * (P4 + z))) *
114 		    (P5 + z * (P6 + z * (P7 + z)));
115 		return ((float)(-one / w));
116 	}
117 
118 	if (ix <= 0x49c90fdb) {	/* |x| < 2^19*pi */
119 #if defined(__i386) && !defined(__amd64)
120 		int	rp;
121 
122 		rp = __swapRP(fp_extended);
123 #endif
124 		w = y * invpio2;
125 		if (hx < 0)
126 			n = (int)(w - half);
127 		else
128 			n = (int)(w + half);
129 		y = (y - n * pio2_1) - n * pio2_t;
130 #if defined(__i386) && !defined(__amd64)
131 		if (rp != fp_extended)
132 			(void) __swapRP(rp);
133 #endif
134 	} else {
135 		if (ix >= 0x7f800000)
136 			return (x / x);	/* sin(Inf or NaN) is NaN */
137 		hy = ((int *)&y)[HIWORD];
138 		n = ((hy >> 20) & 0x7ff) - 1046;
139 		((int *)&w)[HIWORD] = (hy & 0xfffff) | 0x41600000;
140 		((int *)&w)[LOWORD] = ((int *)&y)[LOWORD];
141 		n = __rem_pio2m(&w, &y, n, 1, 0, _TBL_ipio2_inf);
142 		if (hy < 0) {
143 			y = -y;
144 			n = -n;
145 		}
146 	}
147 
148 	hy = ((int *)&y)[HIWORD] & ~0x80000000;
149 	if (hy < 0x3f800000) {		/* |y| < 2**-7 */
150 		z = (y * T0) * (T1 + y * y);
151 		f = ((n & 1) == 0)? (float)z : (float)(-one / z);
152 		return (f);
153 	}
154 	z = y * y;
155 	w = ((P0 * y) * (P1 + z * (P2 + z)) * (P3 + z * (P4 + z))) *
156 	    (P5 + z * (P6 + z * (P7 + z)));
157 	f = ((n & 1) == 0)? (float)w : (float)(-one / w);
158 	return (f);
159 }
160