1/* s_tanl.c -- long double version of s_tan.c. 2 * Conversion to IEEE quad long double by Jakub Jelinek, jj@ultra.linux.cz. 3 */ 4 5/* @(#)s_tan.c 5.1 93/09/24 */ 6/* 7 * ==================================================== 8 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 9 * 10 * Developed at SunPro, a Sun Microsystems, Inc. business. 11 * Permission to use, copy, modify, and distribute this 12 * software is freely granted, provided that this notice 13 * is preserved. 14 * ==================================================== 15 */ 16 17/* tanq(x) 18 * Return tangent function of x. 19 * 20 * kernel function: 21 * __quadmath_kernel_tanq ... tangent 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 tanq(__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) return __quadmath_kernel_tanq(x,z,1); 60 61 /* tanq(Inf or NaN) is NaN */ 62 else if (ix>=0x7fff000000000000LL) { 63 if (ix == 0x7fff000000000000LL) { 64 GET_FLT128_LSW64(n,x); 65 if (n == 0) 66 errno = EDOM; 67 } 68 return x-x; /* NaN */ 69 } 70 71 /* argument reduction needed */ 72 else { 73 n = __quadmath_rem_pio2q(x,y); 74 return __quadmath_kernel_tanq(y[0],y[1],1-((n&1)<<1)); /* 1 -- n even 75 -1 -- n odd */ 76 } 77} 78