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e409716d | 1 | /* s_cosl.c -- long double version of s_cos.c. |
87969c8c | 2 | * Conversion to long double by Jakub Jelinek, jj@ultra.linux.cz. |
3 | */ | |
4 | ||
5 | /* | |
6 | * ==================================================== | |
7 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. | |
8 | * | |
9 | * Developed at SunPro, a Sun Microsystems, Inc. business. | |
10 | * Permission to use, copy, modify, and distribute this | |
11 | * software is freely granted, provided that this notice | |
12 | * is preserved. | |
13 | * ==================================================== | |
14 | */ | |
15 | ||
4a2f7ea2 | 16 | /* cosq(x) |
87969c8c | 17 | * Return cosine function of x. |
18 | * | |
19 | * kernel function: | |
e409716d | 20 | * __quadmath_kernel_sinq ... sine function on [-pi/4,pi/4] |
21 | * __quadmath_kernel_cosq ... cosine function on [-pi/4,pi/4] | |
4a2f7ea2 | 22 | * __quadmath_rem_pio2q ... argument reduction routine |
87969c8c | 23 | * |
24 | * Method. | |
25 | * Let S,C and T denote the sin, cos and tan respectively on | |
26 | * [-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2 | |
27 | * in [-pi/4 , +pi/4], and let n = k mod 4. | |
28 | * We have | |
29 | * | |
30 | * n sin(x) cos(x) tan(x) | |
31 | * ---------------------------------------------------------- | |
32 | * 0 S C T | |
33 | * 1 C -S -1/T | |
34 | * 2 -S -C T | |
35 | * 3 -C S -1/T | |
36 | * ---------------------------------------------------------- | |
37 | * | |
38 | * Special cases: | |
39 | * Let trig be any of sin, cos, or tan. | |
40 | * trig(+-INF) is NaN, with signals; | |
41 | * trig(NaN) is that NaN; | |
42 | * | |
43 | * Accuracy: | |
44 | * TRIG(x) returns trig(x) nearly rounded | |
45 | */ | |
46 | ||
47 | #include "quadmath-imp.h" | |
48 | ||
e409716d | 49 | __float128 cosq(__float128 x) |
87969c8c | 50 | { |
e409716d | 51 | __float128 y[2],z=0; |
87969c8c | 52 | int64_t n, ix; |
53 | ||
54 | /* High word of x. */ | |
55 | GET_FLT128_MSW64(ix,x); | |
56 | ||
57 | /* |x| ~< pi/4 */ | |
58 | ix &= 0x7fffffffffffffffLL; | |
59 | if(ix <= 0x3ffe921fb54442d1LL) | |
0aa903b3 | 60 | return __quadmath_kernel_cosq(x,z); |
87969c8c | 61 | |
62 | /* cos(Inf or NaN) is NaN */ | |
63 | else if (ix>=0x7fff000000000000LL) { | |
64 | if (ix == 0x7fff000000000000LL) { | |
65 | GET_FLT128_LSW64(n,x); | |
e409716d | 66 | if (n == 0) |
67 | errno = EDOM; | |
87969c8c | 68 | } |
69 | return x-x; | |
70 | } | |
71 | ||
72 | /* argument reduction needed */ | |
73 | else { | |
0aa903b3 | 74 | n = __quadmath_rem_pio2q(x,y); |
87969c8c | 75 | switch(n&3) { |
0aa903b3 | 76 | case 0: return __quadmath_kernel_cosq(y[0],y[1]); |
77 | case 1: return -__quadmath_kernel_sinq(y[0],y[1],1); | |
78 | case 2: return -__quadmath_kernel_cosq(y[0],y[1]); | |
87969c8c | 79 | default: |
0aa903b3 | 80 | return __quadmath_kernel_sinq(y[0],y[1],1); |
87969c8c | 81 | } |
82 | } | |
83 | } |