1 /*
2  * Single-precision cos function.
3  *
4  * Copyright (c) 2018-2019, Arm Limited.
5  * SPDX-License-Identifier: MIT
6  */
7 
8 #include <stdint.h>
9 #include <math.h>
10 #include "math_config.h"
11 #include "sincosf.h"
12 
13 /* Fast cosf implementation.  Worst-case ULP is 0.5607, maximum relative
14    error is 0.5303 * 2^-23.  A single-step range reduction is used for
15    small values.  Large inputs have their range reduced using fast integer
16    arithmetic.  */
17 float
18 cosf (float y)
19 {
20   double x = y;
21   double s;
22   int n;
23   const sincos_t *p = &__sincosf_table[0];
24 
25   if (abstop12 (y) < abstop12 (pio4f))
26     {
27       double x2 = x * x;
28 
29       if (unlikely (abstop12 (y) < abstop12 (0x1p-12f)))
30 	return 1.0f;
31 
32       return sinf_poly (x, x2, p, 1);
33     }
34   else if (likely (abstop12 (y) < abstop12 (120.0f)))
35     {
36       x = reduce_fast (x, p, &n);
37 
38       /* Setup the signs for sin and cos.  */
39       s = p->sign[n & 3];
40 
41       if (n & 2)
42 	p = &__sincosf_table[1];
43 
44       return sinf_poly (x * s, x * x, p, n ^ 1);
45     }
46   else if (abstop12 (y) < abstop12 (INFINITY))
47     {
48       uint32_t xi = asuint (y);
49       int sign = xi >> 31;
50 
51       x = reduce_large (xi, &n);
52 
53       /* Setup signs for sin and cos - include original sign.  */
54       s = p->sign[(n + sign) & 3];
55 
56       if ((n + sign) & 2)
57 	p = &__sincosf_table[1];
58 
59       return sinf_poly (x * s, x * x, p, n ^ 1);
60     }
61   else
62     return __math_invalidf (y);
63 }
64