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