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[/] [openrisc/] [trunk/] [gnu-stable/] [newlib-1.18.0/] [newlib/] [libm/] [math/] [kf_tan.c] - Rev 858
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/* kf_tan.c -- float version of k_tan.c * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. */ /* * ==================================================== * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. * * Developed at SunPro, a Sun Microsystems, Inc. business. * Permission to use, copy, modify, and distribute this * software is freely granted, provided that this notice * is preserved. * ==================================================== */ #include "fdlibm.h" #ifdef __STDC__ static const float #else static float #endif one = 1.0000000000e+00, /* 0x3f800000 */ pio4 = 7.8539812565e-01, /* 0x3f490fda */ pio4lo= 3.7748947079e-08, /* 0x33222168 */ T[] = { 3.3333334327e-01, /* 0x3eaaaaab */ 1.3333334029e-01, /* 0x3e088889 */ 5.3968254477e-02, /* 0x3d5d0dd1 */ 2.1869488060e-02, /* 0x3cb327a4 */ 8.8632395491e-03, /* 0x3c11371f */ 3.5920790397e-03, /* 0x3b6b6916 */ 1.4562094584e-03, /* 0x3abede48 */ 5.8804126456e-04, /* 0x3a1a26c8 */ 2.4646313977e-04, /* 0x398137b9 */ 7.8179444245e-05, /* 0x38a3f445 */ 7.1407252108e-05, /* 0x3895c07a */ -1.8558637748e-05, /* 0xb79bae5f */ 2.5907305826e-05, /* 0x37d95384 */ }; #ifdef __STDC__ float __kernel_tanf(float x, float y, int iy) #else float __kernel_tanf(x, y, iy) float x,y; int iy; #endif { float z,r,v,w,s; __int32_t ix,hx; GET_FLOAT_WORD(hx,x); ix = hx&0x7fffffff; /* high word of |x| */ if(ix<0x31800000) /* x < 2**-28 */ {if((int)x==0) { /* generate inexact */ if((ix|(iy+1))==0) return one/fabsf(x); else return (iy==1)? x: -one/x; } } if(ix>=0x3f2ca140) { /* |x|>=0.6744 */ if(hx<0) {x = -x; y = -y;} z = pio4-x; w = pio4lo-y; x = z+w; y = 0.0; } z = x*x; w = z*z; /* Break x^5*(T[1]+x^2*T[2]+...) into * x^5(T[1]+x^4*T[3]+...+x^20*T[11]) + * x^5(x^2*(T[2]+x^4*T[4]+...+x^22*[T12])) */ r = T[1]+w*(T[3]+w*(T[5]+w*(T[7]+w*(T[9]+w*T[11])))); v = z*(T[2]+w*(T[4]+w*(T[6]+w*(T[8]+w*(T[10]+w*T[12]))))); s = z*x; r = y + z*(s*(r+v)+y); r += T[0]*s; w = x+r; if(ix>=0x3f2ca140) { v = (float)iy; return (float)(1-((hx>>30)&2))*(v-(float)2.0*(x-(w*w/(w+v)-r))); } if(iy==1) return w; else { /* if allow error up to 2 ulp, simply return -1.0/(x+r) here */ /* compute -1.0/(x+r) accurately */ float a,t; __int32_t i; z = w; GET_FLOAT_WORD(i,z); SET_FLOAT_WORD(z,i&0xfffff000); v = r-(z - x); /* z+v = r+x */ t = a = -(float)1.0/w; /* a = -1.0/w */ GET_FLOAT_WORD(i,t); SET_FLOAT_WORD(t,i&0xfffff000); s = (float)1.0+t*z; return t+a*(s+t*v); } }
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