/* 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 <float.h>

#include <math.h>

#include <math_private.h>

#include <math-underflow.h>

static const float

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 */

};

float __kernel_tanf(float x, float y, int iy)

{

	float z,r,v,w,s;

	int32_t ix,hx;

	GET_FLOAT_WORD(hx,x);

	ix = hx&0x7fffffff;	/* high word of |x| */

	if(ix<0x39000000)			/* x < 2**-13 */

	    {if((int)x==0) {			/* generate inexact */

		if((ix|(iy+1))==0) return one/fabsf(x);

		else if (iy == 1)

		  {

		    math_check_force_underflow (x);

		    return x;

		  }

		else

		  return -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;

	    if (fabsf (x) < 0x1p-13f)

		return (1 - ((hx >> 30) & 2)) * iy * (1.0f - 2 * iy * x);

	}

	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);

	}

}