__LO(z) = 0;
u.d = z; __LO(u) = 0; z = u.d;
	double __kernel_tan(double x, double y, int iy)#else	double __kernel_tan(x, y, iy)	double x,y; int iy;#endif{	double z,r,v,w,s;	int ix,hx;	hx = __HI(x);	/* high word of x */	ix = hx&0x7fffffff;	/* high word of |x| */	if(ix<0x3e300000)			/* x < 2**-28 */	    {if((int)x==0) {			/* generate inexact */		if(((ix|__LO(x))|(iy+1))==0) return one/fd_fabs(x);		else return (iy==1)? x: -one/x;	    }	    }	if(ix>=0x3FE59428) { 			/* |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>=0x3FE59428) {	    v = (double)iy;	    return (double)(1-((hx>>30)&2))*(v-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 */	    double a,t;	    z  = w;	    __LO(z) = 0;	    v  = r-(z - x); 	/* z+v = r+x */	    t = a  = -1.0/w;	/* a = -1.0/w */	    __LO(t) = 0;	    s  = 1.0+t*z;	    return t+a*(s+t*v);	}}