0,0 → 1,102 |
/* Copyright (C) 1994 DJ Delorie, see COPYING.DJ for details */ |
/* 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[] = "$Id: k_tanf.c,v 1.2 1994/08/18 23:06:18 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); |
} |
} |