1/* cosq.c -- __float128 version of s_cos.c. 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 16/* cosq(x) 17 * Return cosine function of x. 18 * 19 * kernel function: 20 * __quadmath_kernel_sinq ... sine function on [-pi/4,pi/4] 21 * __quadmath_kernel_cosq ... cosine function on [-pi/4,pi/4] 22 * __quadmath_rem_pio2q ... argument reduction routine 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 49__float128 50cosq (__float128 x) 51{ 52 __float128 y[2],z=0.0Q; 53 int64_t n, ix; 54 55 /* High word of x. */ 56 GET_FLT128_MSW64(ix,x); 57 58 /* |x| ~< pi/4 */ 59 ix &= 0x7fffffffffffffffLL; 60 if(ix <= 0x3ffe921fb54442d1LL) 61 return __quadmath_kernel_cosq(x,z); 62 63 /* cos(Inf or NaN) is NaN */ 64 else if (ix>=0x7fff000000000000LL) { 65 if (ix == 0x7fff000000000000LL) { 66 GET_FLT128_LSW64(n,x); 67 } 68 return x-x; 69 } 70 71 /* argument reduction needed */ 72 else { 73 n = __quadmath_rem_pio2q(x,y); 74 switch(n&3) { 75 case 0: return __quadmath_kernel_cosq(y[0],y[1]); 76 case 1: return -__quadmath_kernel_sinq(y[0],y[1],1); 77 case 2: return -__quadmath_kernel_cosq(y[0],y[1]); 78 default: 79 return __quadmath_kernel_sinq(y[0],y[1],1); 80 } 81 } 82} 83