1 /* Compute cosine of argument.
2 Copyright (C) 2018-2021 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 COSF
27 # define COSF_FUNC __cosf
28 #else
29 # define COSF_FUNC COSF
30 #endif
31
32 /* Fast cosf implementation. Worst-case ULP is 0.5607, maximum relative
33 error is 0.5303 * 2^-23. A single-step range reduction is used for
34 small values. Large inputs have their range reduced using fast integer
35 arithmetic.
36 */
37 float
COSF_FUNC(float y)38 COSF_FUNC (float y)
39 {
40 double x = y;
41 double s;
42 int n;
43 const sincos_t *p = &__sincosf_table[0];
44
45 if (abstop12 (y) < abstop12 (pio4))
46 {
47 double x2 = x * x;
48
49 if (__glibc_unlikely (abstop12 (y) < abstop12 (0x1p-12f)))
50 return 1.0f;
51
52 return sinf_poly (x, x2, p, 1);
53 }
54 else if (__glibc_likely (abstop12 (y) < abstop12 (120.0f)))
55 {
56 x = reduce_fast (x, p, &n);
57
58 /* Setup the signs for sin and cos. */
59 s = p->sign[n & 3];
60
61 if (n & 2)
62 p = &__sincosf_table[1];
63
64 return sinf_poly (x * s, x * x, p, n ^ 1);
65 }
66 else if (abstop12 (y) < abstop12 (INFINITY))
67 {
68 uint32_t xi = asuint (y);
69 int sign = xi >> 31;
70
71 x = reduce_large (xi, &n);
72
73 /* Setup signs for sin and cos - include original sign. */
74 s = p->sign[(n + sign) & 3];
75
76 if ((n + sign) & 2)
77 p = &__sincosf_table[1];
78
79 return sinf_poly (x * s, x * x, p, n ^ 1);
80 }
81 else
82 return __math_invalidf (y);
83 }
84
85 #ifndef COSF
86 libm_alias_float (__cos, cos)
87 #endif
88