| /* k_tanf.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. |
| * ==================================================== |
| */ |
| |
| #if defined(LIBM_SCCS) && !defined(lint) |
| static char rcsid[] = "$NetBSD: k_tanf.c,v 1.4 1995/05/10 20:46:39 jtc Exp $"; |
| #endif |
| |
| #include "math.h" |
| #include "math_private.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); |
| } |
| } |
