/src/moddable/xs/tools/fdlibm/s_cos.c
Line | Count | Source (jump to first uncovered line) |
1 | | /* |
2 | | * ==================================================== |
3 | | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
4 | | * |
5 | | * Developed at SunPro, a Sun Microsystems, Inc. business. |
6 | | * Permission to use, copy, modify, and distribute this |
7 | | * software is freely granted, provided that this notice |
8 | | * is preserved. |
9 | | * ==================================================== |
10 | | */ |
11 | | |
12 | | /* cos(x) |
13 | | * Return cosine function of x. |
14 | | * |
15 | | * kernel function: |
16 | | * __kernel_sin ... sine function on [-pi/4,pi/4] |
17 | | * __kernel_cos ... cosine function on [-pi/4,pi/4] |
18 | | * __ieee754_rem_pio2 ... argument reduction routine |
19 | | * |
20 | | * Method. |
21 | | * Let S,C and T denote the sin, cos and tan respectively on |
22 | | * [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2 |
23 | | * in [-pi/4 , +pi/4], and let n = k mod 4. |
24 | | * We have |
25 | | * |
26 | | * n sin(x) cos(x) tan(x) |
27 | | * ---------------------------------------------------------- |
28 | | * 0 S C T |
29 | | * 1 C -S -1/T |
30 | | * 2 -S -C T |
31 | | * 3 -C S -1/T |
32 | | * ---------------------------------------------------------- |
33 | | * |
34 | | * Special cases: |
35 | | * Let trig be any of sin, cos, or tan. |
36 | | * trig(+-INF) is NaN, with signals; |
37 | | * trig(NaN) is that NaN; |
38 | | * |
39 | | * Accuracy: |
40 | | * TRIG(x) returns trig(x) nearly rounded |
41 | | */ |
42 | | |
43 | | #define INLINE_REM_PIO2 |
44 | | #include "math_private.h" |
45 | | #include "e_rem_pio2.c" |
46 | | |
47 | | double |
48 | | s_cos(double x) |
49 | 407k | { |
50 | 407k | double y[2],z=0.0; |
51 | 407k | int32_t n, ix; |
52 | | |
53 | | /* High word of x. */ |
54 | 407k | GET_HIGH_WORD(ix,x); |
55 | | |
56 | | /* |x| ~< pi/4 */ |
57 | 407k | ix &= 0x7fffffff; |
58 | 407k | if(ix <= 0x3fe921fb) { |
59 | 26.7k | if(ix<0x3e46a09e) /* if x < 2**-27 * sqrt(2) */ |
60 | 2.09k | if(((int)x)==0) return 1.0; /* generate inexact */ |
61 | 24.6k | return __kernel_cos(x,z); |
62 | 26.7k | } |
63 | | |
64 | | /* cos(Inf or NaN) is NaN */ |
65 | 380k | else if (ix>=0x7ff00000) return x-x; |
66 | | |
67 | | /* argument reduction needed */ |
68 | 379k | else { |
69 | 379k | n = __ieee754_rem_pio2(x,y); |
70 | 379k | switch(n&3) { |
71 | 32.1k | case 0: return __kernel_cos(y[0],y[1]); |
72 | 284k | case 1: return -__kernel_sin(y[0],y[1],1); |
73 | 31.0k | case 2: return -__kernel_cos(y[0],y[1]); |
74 | 32.0k | default: |
75 | 32.0k | return __kernel_sin(y[0],y[1],1); |
76 | 379k | } |
77 | 379k | } |
78 | 407k | } |