1/*-
2 * Copyright (c) 2007 Steven G. Kargl
3 * All rights reserved.
4 *
5 * Redistribution and use in source and binary forms, with or without
6 * modification, are permitted provided that the following conditions
7 * are met:
8 * 1. Redistributions of source code must retain the above copyright
9 *    notice unmodified, this list of conditions, and the following
10 *    disclaimer.
11 * 2. Redistributions in binary form must reproduce the above copyright
12 *    notice, this list of conditions and the following disclaimer in the
13 *    documentation and/or other materials provided with the distribution.
14 *
15 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR
16 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES
17 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED.
18 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT,
19 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT
20 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE,
21 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY
22 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT
23 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF
24 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
25 */
26
27#include <sys/cdefs.h>
28__FBSDID("$FreeBSD$");
29
30/*
31 * Limited testing on pseudorandom numbers drawn within [0:4e8] shows
32 * an accuracy of <= 1.5 ULP where 247024 values of x out of 40 million
33 * possibles resulted in tan(x) that exceeded 0.5 ULP (ie., 0.6%).
34 */
35
36#include <float.h>
37#ifdef __i386__
38#include <ieeefp.h>
39#endif
40
41#include "math.h"
42#include "math_private.h"
43#if LDBL_MANT_DIG == 64
44#include "../ld80/e_rem_pio2l.h"
45#elif LDBL_MANT_DIG == 113
46#include "../ld128/e_rem_pio2l.h"
47#else
48#error "Unsupported long double format"
49#endif
50
51long double
52tanl(long double x)
53{
54	union IEEEl2bits z;
55	int e0, s;
56	long double y[2];
57	long double hi, lo;
58
59	z.e = x;
60	s = z.bits.sign;
61	z.bits.sign = 0;
62
63	/* If x = +-0 or x is subnormal, then tan(x) = x. */
64	if (z.bits.exp == 0)
65		return (x);
66
67	/* If x = NaN or Inf, then tan(x) = NaN. */
68	if (z.bits.exp == 32767)
69		return ((x - x) / (x - x));
70
71	ENTERI();
72
73	/* Optimize the case where x is already within range. */
74	if (z.e < M_PI_4) {
75		hi = __kernel_tanl(z.e, 0, 0);
76		RETURNI(s ? -hi : hi);
77	}
78
79	e0 = __ieee754_rem_pio2l(x, y);
80	hi = y[0];
81	lo = y[1];
82
83	switch (e0 & 3) {
84	case 0:
85	case 2:
86	    hi = __kernel_tanl(hi, lo, 0);
87	    break;
88	case 1:
89	case 3:
90	    hi = __kernel_tanl(hi, lo, 1);
91	    break;
92	}
93
94	RETURNI(hi);
95}
96