170Ssundar/* s_cosl.c -- long double version of s_cos.c.
270Ssundar * Conversion to long double by Jakub Jelinek, jj@ultra.linux.cz.
370Ssundar */
4877Sattila
570Ssundar/*
670Ssundar * ====================================================
770Ssundar * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8877Sattila *
970Ssundar * Developed at SunPro, a Sun Microsystems, Inc. business.
1070Ssundar * Permission to use, copy, modify, and distribute this
1170Ssundar * software is freely granted, provided that this notice
1270Ssundar * is preserved.
1370Ssundar * ====================================================
14877Sattila */
1570Ssundar
1670Ssundar/* cosq(x)
1770Ssundar * Return cosine function of x.
18877Sattila *
1970Ssundar * kernel function:
2070Ssundar *	__quadmath_kernel_sinq		... sine function on [-pi/4,pi/4]
2170Ssundar *	__quadmath_kernel_cosq		... cosine function on [-pi/4,pi/4]
2270Ssundar *	__quadmath_rem_pio2q	... argument reduction routine
2370Ssundar *
2469Ssundar * Method.
2569Ssundar *      Let S,C and T denote the sin, cos and tan respectively on
2669Ssundar *	[-PI/4, +PI/4]. Reduce the argument x to y1+y2 = x-k*pi/2
2769Ssundar *	in [-pi/4 , +pi/4], and let n = k mod 4.
2869Ssundar *	We have
2969Ssundar *
3069Ssundar *          n        sin(x)      cos(x)        tan(x)
3169Ssundar *     ----------------------------------------------------------
3269Ssundar *	    0	       S	   C		 T
3369Ssundar *	    1	       C	  -S		-1/T
3469Ssundar *	    2	      -S	  -C		 T
3569Ssundar *	    3	      -C	   S		-1/T
3669Ssundar *     ----------------------------------------------------------
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
49__float128 cosq(__float128 x)
50{
51	__float128 y[2],z=0;
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)
60	  return __quadmath_kernel_cosq(x,z);
61
62    /* cos(Inf or NaN) is NaN */
63	else if (ix>=0x7fff000000000000LL) {
64	    if (ix == 0x7fff000000000000LL) {
65		GET_FLT128_LSW64(n,x);
66		if (n == 0)
67		    errno = EDOM;
68	    }
69	    return x-x;
70	}
71
72    /* argument reduction needed */
73	else {
74	    n = __quadmath_rem_pio2q(x,y);
75	    switch(n&3) {
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]);
79		default:
80		        return  __quadmath_kernel_sinq(y[0],y[1],1);
81	    }
82	}
83}
84