k_tanf.c revision 152647
1/* k_tanf.c -- float version of k_tan.c 2 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. 3 */ 4 5/* 6 * ==================================================== 7 * Copyright 2004 Sun Microsystems, Inc. All Rights Reserved. 8 * 9 * Permission to use, copy, modify, and distribute this 10 * software is freely granted, provided that this notice 11 * is preserved. 12 * ==================================================== 13 */ 14 15#ifndef INLINE_KERNEL_TANF 16#ifndef lint 17static char rcsid[] = "$FreeBSD: head/lib/msun/src/k_tanf.c 152647 2005-11-21 04:57:12Z bde $"; 18#endif 19#endif 20 21#include "math.h" 22#include "math_private.h" 23 24static const float 25pio4 = 7.8539812565e-01, /* 0x3f490fda */ 26pio4lo= 3.7748947079e-08, /* 0x33222168 */ 27/* |tan(x)/x - t(x)| < 2**-29.2 (~[-1.73e-09, 1.724e-09]). */ 28T[] = { 29 0xaaaaa3.0p-25, /* 0.33333310485 */ 30 0x888b06.0p-26, /* 0.13334283238 */ 31 0xdc84c8.0p-28, /* 0.053837567568 */ 32 0xb9d8f1.0p-29, /* 0.022686453536 */ 33 0xcfe632.0p-31, /* 0.0063445800915 */ 34 0xeaf97e.0p-31, /* 0.0071708550677 */ 35}; 36 37#ifdef INLINE_KERNEL_TANF 38extern inline 39#endif 40float 41__kernel_tanf(float x, float y, int iy) 42{ 43 float z,r,v,w,s; 44 int32_t ix,hx; 45 46 GET_FLOAT_WORD(hx,x); 47 ix = hx&0x7fffffff; 48 if(ix>=0x3f2ca140) { /* |x|>=0.67434 */ 49 if(hx<0) {x = -x; y = -y;} 50 z = pio4-x; 51 w = pio4lo-y; 52 x = z+w; y = 0.0; 53 } 54 z = x*x; 55 w = z*z; 56 /* Break x^5*(T[1]+x^2*T[2]+...) into 57 * x^5*(T[1]+x^4*T[3]+x^8*T[5]) + 58 * x^5*(x^2*(T[2]+x^4*T[4])) 59 */ 60 r = T[1]+w*(T[3]+w*T[5]); 61 v = z*(T[2]+w*T[4]); 62 s = z*x; 63 r = y + z*(s*(r+v)+y); 64 r += T[0]*s; 65 w = x+r; 66 if(ix>=0x3f2ca140) { 67 v = (float)iy; 68 return (float)(1-((hx>>30)&2))*(v-(float)2.0*(x-(w*w/(w+v)-r))); 69 } 70 if(iy==1) return w; 71 else return -1.0/((double)x+r); 72} 73