k_tanf.c revision 2116
12116Sjkh/* k_tanf.c -- float version of k_tan.c 22116Sjkh * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com. 32116Sjkh */ 42116Sjkh 52116Sjkh/* 62116Sjkh * ==================================================== 72116Sjkh * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. 82116Sjkh * 92116Sjkh * Developed at SunPro, a Sun Microsystems, Inc. business. 102116Sjkh * Permission to use, copy, modify, and distribute this 112116Sjkh * software is freely granted, provided that this notice 122116Sjkh * is preserved. 132116Sjkh * ==================================================== 142116Sjkh */ 152116Sjkh 162116Sjkh#ifndef lint 172116Sjkhstatic char rcsid[] = "$Id: k_tanf.c,v 1.2 1994/08/18 23:06:18 jtc Exp $"; 182116Sjkh#endif 192116Sjkh 202116Sjkh#include "math.h" 212116Sjkh#include "math_private.h" 222116Sjkh#ifdef __STDC__ 232116Sjkhstatic const float 242116Sjkh#else 252116Sjkhstatic float 262116Sjkh#endif 272116Sjkhone = 1.0000000000e+00, /* 0x3f800000 */ 282116Sjkhpio4 = 7.8539812565e-01, /* 0x3f490fda */ 292116Sjkhpio4lo= 3.7748947079e-08, /* 0x33222168 */ 302116SjkhT[] = { 312116Sjkh 3.3333334327e-01, /* 0x3eaaaaab */ 322116Sjkh 1.3333334029e-01, /* 0x3e088889 */ 332116Sjkh 5.3968254477e-02, /* 0x3d5d0dd1 */ 342116Sjkh 2.1869488060e-02, /* 0x3cb327a4 */ 352116Sjkh 8.8632395491e-03, /* 0x3c11371f */ 362116Sjkh 3.5920790397e-03, /* 0x3b6b6916 */ 372116Sjkh 1.4562094584e-03, /* 0x3abede48 */ 382116Sjkh 5.8804126456e-04, /* 0x3a1a26c8 */ 392116Sjkh 2.4646313977e-04, /* 0x398137b9 */ 402116Sjkh 7.8179444245e-05, /* 0x38a3f445 */ 412116Sjkh 7.1407252108e-05, /* 0x3895c07a */ 422116Sjkh -1.8558637748e-05, /* 0xb79bae5f */ 432116Sjkh 2.5907305826e-05, /* 0x37d95384 */ 442116Sjkh}; 452116Sjkh 462116Sjkh#ifdef __STDC__ 472116Sjkh float __kernel_tanf(float x, float y, int iy) 482116Sjkh#else 492116Sjkh float __kernel_tanf(x, y, iy) 502116Sjkh float x,y; int iy; 512116Sjkh#endif 522116Sjkh{ 532116Sjkh float z,r,v,w,s; 542116Sjkh int32_t ix,hx; 552116Sjkh GET_FLOAT_WORD(hx,x); 562116Sjkh ix = hx&0x7fffffff; /* high word of |x| */ 572116Sjkh if(ix<0x31800000) /* x < 2**-28 */ 582116Sjkh {if((int)x==0) { /* generate inexact */ 592116Sjkh if((ix|(iy+1))==0) return one/fabsf(x); 602116Sjkh else return (iy==1)? x: -one/x; 612116Sjkh } 622116Sjkh } 632116Sjkh if(ix>=0x3f2ca140) { /* |x|>=0.6744 */ 642116Sjkh if(hx<0) {x = -x; y = -y;} 652116Sjkh z = pio4-x; 662116Sjkh w = pio4lo-y; 672116Sjkh x = z+w; y = 0.0; 682116Sjkh } 692116Sjkh z = x*x; 702116Sjkh w = z*z; 712116Sjkh /* Break x^5*(T[1]+x^2*T[2]+...) into 722116Sjkh * x^5(T[1]+x^4*T[3]+...+x^20*T[11]) + 732116Sjkh * x^5(x^2*(T[2]+x^4*T[4]+...+x^22*[T12])) 742116Sjkh */ 752116Sjkh r = T[1]+w*(T[3]+w*(T[5]+w*(T[7]+w*(T[9]+w*T[11])))); 762116Sjkh v = z*(T[2]+w*(T[4]+w*(T[6]+w*(T[8]+w*(T[10]+w*T[12]))))); 772116Sjkh s = z*x; 782116Sjkh r = y + z*(s*(r+v)+y); 792116Sjkh r += T[0]*s; 802116Sjkh w = x+r; 812116Sjkh if(ix>=0x3f2ca140) { 822116Sjkh v = (float)iy; 832116Sjkh return (float)(1-((hx>>30)&2))*(v-(float)2.0*(x-(w*w/(w+v)-r))); 842116Sjkh } 852116Sjkh if(iy==1) return w; 862116Sjkh else { /* if allow error up to 2 ulp, 872116Sjkh simply return -1.0/(x+r) here */ 882116Sjkh /* compute -1.0/(x+r) accurately */ 892116Sjkh float a,t; 902116Sjkh int32_t i; 912116Sjkh z = w; 922116Sjkh GET_FLOAT_WORD(i,z); 932116Sjkh SET_FLOAT_WORD(z,i&0xfffff000); 942116Sjkh v = r-(z - x); /* z+v = r+x */ 952116Sjkh t = a = -(float)1.0/w; /* a = -1.0/w */ 962116Sjkh GET_FLOAT_WORD(i,t); 972116Sjkh SET_FLOAT_WORD(t,i&0xfffff000); 982116Sjkh s = (float)1.0+t*z; 992116Sjkh return t+a*(s+t*v); 1002116Sjkh } 1012116Sjkh} 102