1/* Compute cosine of argument.
2 Copyright (C) 2018-2022 Free Software Foundation, Inc.
3 This file is part of the GNU C Library.
4
5 The GNU C Library is free software; you can redistribute it and/or
6 modify it under the terms of the GNU Lesser General Public
7 License as published by the Free Software Foundation; either
8 version 2.1 of the License, or (at your option) any later version.
9
10 The GNU C Library is distributed in the hope that it will be useful,
11 but WITHOUT ANY WARRANTY; without even the implied warranty of
12 MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
13 Lesser General Public License for more details.
14
15 You should have received a copy of the GNU Lesser General Public
16 License along with the GNU C Library; if not, see
17 <https://www.gnu.org/licenses/>. */
18
19#include <stdint.h>
20#include <math.h>
21#include <math-barriers.h>
22#include <libm-alias-float.h>
23#include "math_config.h"
24#include "s_sincosf.h"
25
26#ifndef SECTION
27# define SECTION
28#endif
29
30#ifndef COSF
31# define COSF_FUNC __cosf
32#else
33# define COSF_FUNC COSF
34#endif
35
36/* Fast cosf implementation. Worst-case ULP is 0.5607, maximum relative
37 error is 0.5303 * 2^-23. A single-step range reduction is used for
38 small values. Large inputs have their range reduced using fast integer
39 arithmetic.
40*/
41float
42SECTION
43COSF_FUNC (float y)
44{
45 double x = y;
46 double s;
47 int n;
48 const sincos_t *p = &__sincosf_table[0];
49
50 if (abstop12 (y) < abstop12 (pio4))
51 {
52 double x2 = x * x;
53
54 if (__glibc_unlikely (abstop12 (y) < abstop12 (0x1p-12f)))
55 return 1.0f;
56
57 return sinf_poly (x, x2, p, 1);
58 }
59 else if (__glibc_likely (abstop12 (y) < abstop12 (120.0f)))
60 {
61 x = reduce_fast (x, p, &n);
62
63 /* Setup the signs for sin and cos. */
64 s = p->sign[n & 3];
65
66 if (n & 2)
67 p = &__sincosf_table[1];
68
69 return sinf_poly (x * s, x * x, p, n ^ 1);
70 }
71 else if (abstop12 (y) < abstop12 (INFINITY))
72 {
73 uint32_t xi = asuint (y);
74 int sign = xi >> 31;
75
76 x = reduce_large (xi, &n);
77
78 /* Setup signs for sin and cos - include original sign. */
79 s = p->sign[(n + sign) & 3];
80
81 if ((n + sign) & 2)
82 p = &__sincosf_table[1];
83
84 return sinf_poly (x * s, x * x, p, n ^ 1);
85 }
86 else
87 return __math_invalidf (y);
88}
89
90#ifndef COSF
91libm_alias_float (__cos, cos)
92#endif
93