1/*-
2 * SPDX-License-Identifier: BSD-2-Clause-FreeBSD
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#include <sys/cdefs.h>
30__FBSDID("$FreeBSD$");
31
32/*
33 * Limited testing on pseudorandom numbers drawn within [0:4e8] shows
34 * an accuracy of <= 1.5 ULP where 247024 values of x out of 40 million
35 * possibles resulted in tan(x) that exceeded 0.5 ULP (ie., 0.6%).
36 */
37
38#include <float.h>
39#ifdef __i386__
40#include <ieeefp.h>
41#endif
42
43#include "math.h"
44#include "math_private.h"
45#if LDBL_MANT_DIG == 64
46#include "../ld80/e_rem_pio2l.h"
47#elif LDBL_MANT_DIG == 113
48#include "../ld128/e_rem_pio2l.h"
49#else
50#error "Unsupported long double format"
51#endif
52
53long double
54tanl(long double x)
55{
56	union IEEEl2bits z;
57	int e0, s;
58	long double y[2];
59	long double hi, lo;
60
61	z.e = x;
62	s = z.bits.sign;
63	z.bits.sign = 0;
64
65	/* If x = +-0 or x is subnormal, then tan(x) = x. */
66	if (z.bits.exp == 0)
67		return (x);
68
69	/* If x = NaN or Inf, then tan(x) = NaN. */
70	if (z.bits.exp == 32767)
71		return ((x - x) / (x - x));
72
73	ENTERI();
74
75	/* Optimize the case where x is already within range. */
76	if (z.e < M_PI_4) {
77		hi = __kernel_tanl(z.e, 0, 0);
78		RETURNI(s ? -hi : hi);
79	}
80
81	e0 = __ieee754_rem_pio2l(x, y);
82	hi = y[0];
83	lo = y[1];
84
85	switch (e0 & 3) {
86	case 0:
87	case 2:
88	    hi = __kernel_tanl(hi, lo, 0);
89	    break;
90	case 1:
91	case 3:
92	    hi = __kernel_tanl(hi, lo, 1);
93	    break;
94	}
95
96	RETURNI(hi);
97}
98