[sdl_omap.git] / src / video / e_pow.h

/* @(#)e_pow.c 5.1 93/09/24 */
/*
 * ====================================================
 * 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: e_pow.c,v 1.9 1995/05/12 04:57:32 jtc Exp $";
#endif

/* __ieee754_pow(x,y) return x**y
 *
 *		      n
 * Method:  Let x =  2   * (1+f)
 *	1. Compute and return log2(x) in two pieces:
 *		log2(x) = w1 + w2,
 *	   where w1 has 53-24 = 29 bit trailing zeros.
 *	2. Perform y*log2(x) = n+y' by simulating muti-precision
 *	   arithmetic, where |y'|<=0.5.
 *	3. Return x**y = 2**n*exp(y'*log2)
 *
 * Special cases:
 *	1.  (anything) ** 0  is 1
 *	2.  (anything) ** 1  is itself
 *	3.  (anything) ** NAN is NAN
 *	4.  NAN ** (anything except 0) is NAN
 *	5.  +-(|x| > 1) **  +INF is +INF
 *	6.  +-(|x| > 1) **  -INF is +0
 *	7.  +-(|x| < 1) **  +INF is +0
 *	8.  +-(|x| < 1) **  -INF is +INF
 *	9.  +-1         ** +-INF is NAN
 *	10. +0 ** (+anything except 0, NAN)               is +0
 *	11. -0 ** (+anything except 0, NAN, odd integer)  is +0
 *	12. +0 ** (-anything except 0, NAN)               is +INF
 *	13. -0 ** (-anything except 0, NAN, odd integer)  is +INF
 *	14. -0 ** (odd integer) = -( +0 ** (odd integer) )
 *	15. +INF ** (+anything except 0,NAN) is +INF
 *	16. +INF ** (-anything except 0,NAN) is +0
 *	17. -INF ** (anything)  = -0 ** (-anything)
 *	18. (-anything) ** (integer) is (-1)**(integer)*(+anything**integer)
 *	19. (-anything except 0 and inf) ** (non-integer) is NAN
 *
 * Accuracy:
 *	pow(x,y) returns x**y nearly rounded. In particular
 *			pow(integer,integer)
 *	always returns the correct integer provided it is
 *	representable.
 *
 * Constants :
 * The hexadecimal values are the intended ones for the following
 * constants. The decimal values may be used, provided that the
 * compiler will convert from decimal to binary accurately enough
 * to produce the hexadecimal values shown.
 */

/*#include "math.h"*/
#include "math_private.h"

#ifdef __STDC__
static const double
#else
static double
#endif
bp[] = {1.0, 1.5,},
dp_h[] = { 0.0, 5.84962487220764160156e-01,}, /* 0x3FE2B803, 0x40000000 */
dp_l[] = { 0.0, 1.35003920212974897128e-08,}, /* 0x3E4CFDEB, 0x43CFD006 */
	/* poly coefs for (3/2)*(log(x)-2s-2/3*s**3 */
L1  =  5.99999999999994648725e-01, /* 0x3FE33333, 0x33333303 */
L2  =  4.28571428578550184252e-01, /* 0x3FDB6DB6, 0xDB6FABFF */
L3  =  3.33333329818377432918e-01, /* 0x3FD55555, 0x518F264D */
L4  =  2.72728123808534006489e-01, /* 0x3FD17460, 0xA91D4101 */
L5  =  2.30660745775561754067e-01, /* 0x3FCD864A, 0x93C9DB65 */
L6  =  2.06975017800338417784e-01, /* 0x3FCA7E28, 0x4A454EEF */
P1   =  1.66666666666666019037e-01, /* 0x3FC55555, 0x5555553E */
P2   = -2.77777777770155933842e-03, /* 0xBF66C16C, 0x16BEBD93 */
P3   =  6.61375632143793436117e-05, /* 0x3F11566A, 0xAF25DE2C */
P4   = -1.65339022054652515390e-06, /* 0xBEBBBD41, 0xC5D26BF1 */
P5   =  4.13813679705723846039e-08, /* 0x3E663769, 0x72BEA4D0 */
lg2  =  6.93147180559945286227e-01, /* 0x3FE62E42, 0xFEFA39EF */
lg2_h  =  6.93147182464599609375e-01, /* 0x3FE62E43, 0x00000000 */
lg2_l  = -1.90465429995776804525e-09, /* 0xBE205C61, 0x0CA86C39 */
ovt =  8.0085662595372944372e-0017, /* -(1024-log2(ovfl+.5ulp)) */
cp    =  9.61796693925975554329e-01, /* 0x3FEEC709, 0xDC3A03FD =2/(3ln2) */
cp_h  =  9.61796700954437255859e-01, /* 0x3FEEC709, 0xE0000000 =(float)cp */
cp_l  = -7.02846165095275826516e-09, /* 0xBE3E2FE0, 0x145B01F5 =tail of cp_h*/
ivln2    =  1.44269504088896338700e+00, /* 0x3FF71547, 0x652B82FE =1/ln2 */
ivln2_h  =  1.44269502162933349609e+00, /* 0x3FF71547, 0x60000000 =24b 1/ln2*/
ivln2_l  =  1.92596299112661746887e-08; /* 0x3E54AE0B, 0xF85DDF44 =1/ln2 tail*/

#ifdef __STDC__
	double __ieee754_pow(double x, double y)
#else
	double __ieee754_pow(x,y)
	double x, y;
#endif
{
	double z,ax,z_h,z_l,p_h,p_l;
	double y1,t1,t2,r,s,t,u,v,w;
	int32_t i,j,k,yisint,n;
	int32_t hx,hy,ix,iy;
	u_int32_t lx,ly;

	EXTRACT_WORDS(hx,lx,x);
	EXTRACT_WORDS(hy,ly,y);
	ix = hx&0x7fffffff;  iy = hy&0x7fffffff;

    /* y==zero: x**0 = 1 */
	if((iy|ly)==0) return one;

    /* +-NaN return x+y */
	if(ix > 0x7ff00000 || ((ix==0x7ff00000)&&(lx!=0)) ||
	   iy > 0x7ff00000 || ((iy==0x7ff00000)&&(ly!=0)))
		return x+y;

    /* determine if y is an odd int when x < 0
     * yisint = 0	... y is not an integer
     * yisint = 1	... y is an odd int
     * yisint = 2	... y is an even int
     */
	yisint  = 0;
	if(hx<0) {
	    if(iy>=0x43400000) yisint = 2; /* even integer y */
	    else if(iy>=0x3ff00000) {
		k = (iy>>20)-0x3ff;	   /* exponent */
		if(k>20) {
		    j = ly>>(52-k);
		    if((u_int32_t)(j<<(52-k))==ly) yisint = 2-(j&1);
		} else if(ly==0) {
		    j = iy>>(20-k);
		    if((j<<(20-k))==iy) yisint = 2-(j&1);
		}
	    }
	}

    /* special value of y */
	if(ly==0) {
	    if (iy==0x7ff00000) {	/* y is +-inf */
	        if(((ix-0x3ff00000)|lx)==0)
		    return  y - y;	/* inf**+-1 is NaN */
	        else if (ix >= 0x3ff00000)/* (|x|>1)**+-inf = inf,0 */
		    return (hy>=0)? y: zero;
	        else			/* (|x|<1)**-,+inf = inf,0 */
		    return (hy<0)?-y: zero;
	    }
	    if(iy==0x3ff00000) {	/* y is  +-1 */
		if(hy<0) return one/x; else return x;
	    }
	    if(hy==0x40000000) return x*x; /* y is  2 */
	    if(hy==0x3fe00000) {	/* y is  0.5 */
		if(hx>=0)	/* x >= +0 */
		return __ieee754_sqrt(x);
	    }
	}

	ax   = x < 0 ? -x : x; /*fabs(x);*/
    /* special value of x */
	if(lx==0) {
	    if(ix==0x7ff00000||ix==0||ix==0x3ff00000){
		z = ax;			/*x is +-0,+-inf,+-1*/
		if(hy<0) z = one/z;	/* z = (1/|x|) */
		if(hx<0) {
		    if(((ix-0x3ff00000)|yisint)==0) {
			z = (z-z)/(z-z); /* (-1)**non-int is NaN */
		    } else if(yisint==1)
			z = -z;		/* (x<0)**odd = -(|x|**odd) */
		}
		return z;
	    }
	}

    /* (x<0)**(non-int) is NaN */
	if(((((u_int32_t)hx>>31)-1)|yisint)==0) return (x-x)/(x-x);

    /* |y| is huge */
	if(iy>0x41e00000) { /* if |y| > 2**31 */
	    if(iy>0x43f00000){	/* if |y| > 2**64, must o/uflow */
		if(ix<=0x3fefffff) return (hy<0)? huge*huge:tiny*tiny;
		if(ix>=0x3ff00000) return (hy>0)? huge*huge:tiny*tiny;
	    }
	/* over/underflow if x is not close to one */
	    if(ix<0x3fefffff) return (hy<0)? huge*huge:tiny*tiny;
	    if(ix>0x3ff00000) return (hy>0)? huge*huge:tiny*tiny;
	/* now |1-x| is tiny <= 2**-20, suffice to compute
	   log(x) by x-x^2/2+x^3/3-x^4/4 */
	    t = x-1;		/* t has 20 trailing zeros */
	    w = (t*t)*(0.5-t*(0.3333333333333333333333-t*0.25));
	    u = ivln2_h*t;	/* ivln2_h has 21 sig. bits */
	    v = t*ivln2_l-w*ivln2;
	    t1 = u+v;
	    SET_LOW_WORD(t1,0);
	    t2 = v-(t1-u);
	} else {
	    double s2,s_h,s_l,t_h,t_l;
	    n = 0;
	/* take care subnormal number */
	    if(ix<0x00100000)
		{ax *= two53; n -= 53; GET_HIGH_WORD(ix,ax); }
	    n  += ((ix)>>20)-0x3ff;
	    j  = ix&0x000fffff;
	/* determine interval */
	    ix = j|0x3ff00000;		/* normalize ix */
	    if(j<=0x3988E) k=0;		/* |x|<sqrt(3/2) */
	    else if(j<0xBB67A) k=1;	/* |x|<sqrt(3)   */
	    else {k=0;n+=1;ix -= 0x00100000;}
	    SET_HIGH_WORD(ax,ix);

	/* compute s = s_h+s_l = (x-1)/(x+1) or (x-1.5)/(x+1.5) */
	    u = ax-bp[k];		/* bp[0]=1.0, bp[1]=1.5 */
	    v = one/(ax+bp[k]);
	    s = u*v;
	    s_h = s;
	    SET_LOW_WORD(s_h,0);
	/* t_h=ax+bp[k] High */
	    t_h = zero;
	    SET_HIGH_WORD(t_h,((ix>>1)|0x20000000)+0x00080000+(k<<18));
	    t_l = ax - (t_h-bp[k]);
	    s_l = v*((u-s_h*t_h)-s_h*t_l);
	/* compute log(ax) */
	    s2 = s*s;
	    r = s2*s2*(L1+s2*(L2+s2*(L3+s2*(L4+s2*(L5+s2*L6)))));
	    r += s_l*(s_h+s);
	    s2  = s_h*s_h;
	    t_h = 3.0+s2+r;
	    SET_LOW_WORD(t_h,0);
	    t_l = r-((t_h-3.0)-s2);
	/* u+v = s*(1+...) */
	    u = s_h*t_h;
	    v = s_l*t_h+t_l*s;
	/* 2/(3log2)*(s+...) */
	    p_h = u+v;
	    SET_LOW_WORD(p_h,0);
	    p_l = v-(p_h-u);
	    z_h = cp_h*p_h;		/* cp_h+cp_l = 2/(3*log2) */
	    z_l = cp_l*p_h+p_l*cp+dp_l[k];
	/* log2(ax) = (s+..)*2/(3*log2) = n + dp_h + z_h + z_l */
	    t = (double)n;
	    t1 = (((z_h+z_l)+dp_h[k])+t);
	    SET_LOW_WORD(t1,0);
	    t2 = z_l-(((t1-t)-dp_h[k])-z_h);
	}

	s = one; /* s (sign of result -ve**odd) = -1 else = 1 */
	if(((((u_int32_t)hx>>31)-1)|(yisint-1))==0)
	    s = -one;/* (-ve)**(odd int) */

    /* split up y into y1+y2 and compute (y1+y2)*(t1+t2) */
	y1  = y;
	SET_LOW_WORD(y1,0);
	p_l = (y-y1)*t1+y*t2;
	p_h = y1*t1;
	z = p_l+p_h;
	EXTRACT_WORDS(j,i,z);
	if (j>=0x40900000) {				/* z >= 1024 */
	    if(((j-0x40900000)|i)!=0)			/* if z > 1024 */
		return s*huge*huge;			/* overflow */
	    else {
		if(p_l+ovt>z-p_h) return s*huge*huge;	/* overflow */
	    }
	} else if((j&0x7fffffff)>=0x4090cc00 ) {	/* z <= -1075 */
	    if(((j-0xc090cc00)|i)!=0) 		/* z < -1075 */
		return s*tiny*tiny;		/* underflow */
	    else {
		if(p_l<=z-p_h) return s*tiny*tiny;	/* underflow */
	    }
	}
    /*
     * compute 2**(p_h+p_l)
     */
	i = j&0x7fffffff;
	k = (i>>20)-0x3ff;
	n = 0;
	if(i>0x3fe00000) {		/* if |z| > 0.5, set n = [z+0.5] */
	    n = j+(0x00100000>>(k+1));
	    k = ((n&0x7fffffff)>>20)-0x3ff;	/* new k for n */
	    t = zero;
	    SET_HIGH_WORD(t,n&~(0x000fffff>>k));
	    n = ((n&0x000fffff)|0x00100000)>>(20-k);
	    if(j<0) n = -n;
	    p_h -= t;
	}
	t = p_l+p_h;
	SET_LOW_WORD(t,0);
	u = t*lg2_h;
	v = (p_l-(t-p_h))*lg2+t*lg2_l;
	z = u+v;
	w = v-(z-u);
	t  = z*z;
	t1  = z - t*(P1+t*(P2+t*(P3+t*(P4+t*P5))));
	r  = (z*t1)/(t1-two)-(w+z*w);
	z  = one-(r-z);
	GET_HIGH_WORD(j,z);
	j += (n<<20);
	if((j>>20)<=0) z = SDL_NAME(scalbn)(z,n);	/* subnormal output */
	else SET_HIGH_WORD(z,j);
	return s*z;
}
Commit	Line	Data
	1	/* @(#)e_pow.c 5.1 93/09/24 */
	2	/*
	3	* ====================================================
	4	* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
	5	*
	6	* Developed at SunPro, a Sun Microsystems, Inc. business.
	7	* Permission to use, copy, modify, and distribute this
	8	* software is freely granted, provided that this notice
	9	* is preserved.
	10	* ====================================================
	11	*/
	12
	13	#if defined(LIBM_SCCS) && !defined(lint)
	14	static char rcsid[] = "$NetBSD: e_pow.c,v 1.9 1995/05/12 04:57:32 jtc Exp $";
	15	#endif
	16
	17	/* __ieee754_pow(x,y) return x**y
	18	*
	19	* n
	20	* Method: Let x = 2 * (1+f)
	21	* 1. Compute and return log2(x) in two pieces:
	22	* log2(x) = w1 + w2,
	23	* where w1 has 53-24 = 29 bit trailing zeros.
	24	* 2. Perform y*log2(x) = n+y' by simulating muti-precision
	25	* arithmetic, where \|y'\|<=0.5.
	26	* 3. Return xy = 2nexp(y'log2)
	27	*
	28	* Special cases:
	29	* 1. (anything) ** 0 is 1
	30	* 2. (anything) ** 1 is itself
	31	* 3. (anything) ** NAN is NAN
	32	* 4. NAN ** (anything except 0) is NAN
	33	* 5. +-(\|x\| > 1) ** +INF is +INF
	34	* 6. +-(\|x\| > 1) ** -INF is +0
	35	* 7. +-(\|x\| < 1) ** +INF is +0
	36	* 8. +-(\|x\| < 1) ** -INF is +INF
	37	* 9. +-1 ** +-INF is NAN
	38	* 10. +0 ** (+anything except 0, NAN) is +0
	39	* 11. -0 ** (+anything except 0, NAN, odd integer) is +0
	40	* 12. +0 ** (-anything except 0, NAN) is +INF
	41	* 13. -0 ** (-anything except 0, NAN, odd integer) is +INF
	42	* 14. -0 (odd integer) = -( +0 (odd integer) )
	43	* 15. +INF ** (+anything except 0,NAN) is +INF
	44	* 16. +INF ** (-anything except 0,NAN) is +0
	45	* 17. -INF (anything) = -0 (-anything)
	46	* 18. (-anything) (integer) is (-1)(integer)(+anything*integer)
	47	* 19. (-anything except 0 and inf) ** (non-integer) is NAN
	48	*
	49	* Accuracy:
	50	* pow(x,y) returns x**y nearly rounded. In particular
	51	* pow(integer,integer)
	52	* always returns the correct integer provided it is
	53	* representable.
	54	*
	55	* Constants :
	56	* The hexadecimal values are the intended ones for the following
	57	* constants. The decimal values may be used, provided that the
	58	* compiler will convert from decimal to binary accurately enough
	59	* to produce the hexadecimal values shown.
	60	*/
	61
	62	/#include "math.h"/
	63	#include "math_private.h"
	64
	65	#ifdef __STDC__
	66	static const double
	67	#else
	68	static double
	69	#endif
	70	bp[] = {1.0, 1.5,},
	71	dp_h[] = { 0.0, 5.84962487220764160156e-01,}, /* 0x3FE2B803, 0x40000000 */
	72	dp_l[] = { 0.0, 1.35003920212974897128e-08,}, /* 0x3E4CFDEB, 0x43CFD006 */
	73	/* poly coefs for (3/2)(log(x)-2s-2/3s*3 /
	74	L1 = 5.99999999999994648725e-01, /* 0x3FE33333, 0x33333303 */
	75	L2 = 4.28571428578550184252e-01, /* 0x3FDB6DB6, 0xDB6FABFF */
	76	L3 = 3.33333329818377432918e-01, /* 0x3FD55555, 0x518F264D */
	77	L4 = 2.72728123808534006489e-01, /* 0x3FD17460, 0xA91D4101 */
	78	L5 = 2.30660745775561754067e-01, /* 0x3FCD864A, 0x93C9DB65 */
	79	L6 = 2.06975017800338417784e-01, /* 0x3FCA7E28, 0x4A454EEF */
	80	P1 = 1.66666666666666019037e-01, /* 0x3FC55555, 0x5555553E */
	81	P2 = -2.77777777770155933842e-03, /* 0xBF66C16C, 0x16BEBD93 */
	82	P3 = 6.61375632143793436117e-05, /* 0x3F11566A, 0xAF25DE2C */
	83	P4 = -1.65339022054652515390e-06, /* 0xBEBBBD41, 0xC5D26BF1 */
	84	P5 = 4.13813679705723846039e-08, /* 0x3E663769, 0x72BEA4D0 */
	85	lg2 = 6.93147180559945286227e-01, /* 0x3FE62E42, 0xFEFA39EF */
	86	lg2_h = 6.93147182464599609375e-01, /* 0x3FE62E43, 0x00000000 */
	87	lg2_l = -1.90465429995776804525e-09, /* 0xBE205C61, 0x0CA86C39 */
	88	ovt = 8.0085662595372944372e-0017, /* -(1024-log2(ovfl+.5ulp)) */
	89	cp = 9.61796693925975554329e-01, /* 0x3FEEC709, 0xDC3A03FD =2/(3ln2) */
	90	cp_h = 9.61796700954437255859e-01, /* 0x3FEEC709, 0xE0000000 =(float)cp */
	91	cp_l = -7.02846165095275826516e-09, /* 0xBE3E2FE0, 0x145B01F5 =tail of cp_h*/
	92	ivln2 = 1.44269504088896338700e+00, /* 0x3FF71547, 0x652B82FE =1/ln2 */
	93	ivln2_h = 1.44269502162933349609e+00, /* 0x3FF71547, 0x60000000 =24b 1/ln2*/
	94	ivln2_l = 1.92596299112661746887e-08; /* 0x3E54AE0B, 0xF85DDF44 =1/ln2 tail*/
	95
	96	#ifdef __STDC__
	97	double __ieee754_pow(double x, double y)
	98	#else
	99	double __ieee754_pow(x,y)
	100	double x, y;
	101	#endif
	102	{
	103	double z,ax,z_h,z_l,p_h,p_l;
	104	double y1,t1,t2,r,s,t,u,v,w;
	105	int32_t i,j,k,yisint,n;
	106	int32_t hx,hy,ix,iy;
	107	u_int32_t lx,ly;
	108
	109	EXTRACT_WORDS(hx,lx,x);
	110	EXTRACT_WORDS(hy,ly,y);
	111	ix = hx&0x7fffffff; iy = hy&0x7fffffff;
	112
	113	/* y==zero: x*0 = 1 /
	114	if((iy\|ly)==0) return one;
	115
	116	/* +-NaN return x+y */
	117	if(ix > 0x7ff00000 \|\| ((ix==0x7ff00000)&&(lx!=0)) \|\|
	118	iy > 0x7ff00000 \|\| ((iy==0x7ff00000)&&(ly!=0)))
	119	return x+y;
	120
	121	/* determine if y is an odd int when x < 0
	122	* yisint = 0 ... y is not an integer
	123	* yisint = 1 ... y is an odd int
	124	* yisint = 2 ... y is an even int
	125	*/
	126	yisint = 0;
	127	if(hx<0) {
	128	if(iy>=0x43400000) yisint = 2; /* even integer y */
	129	else if(iy>=0x3ff00000) {
	130	k = (iy>>20)-0x3ff; /* exponent */
	131	if(k>20) {
	132	j = ly>>(52-k);
	133	if((u_int32_t)(j<<(52-k))==ly) yisint = 2-(j&1);
	134	} else if(ly==0) {
	135	j = iy>>(20-k);
	136	if((j<<(20-k))==iy) yisint = 2-(j&1);
	137	}
	138	}
	139	}
	140
	141	/* special value of y */
	142	if(ly==0) {
	143	if (iy==0x7ff00000) { /* y is +-inf */
	144	if(((ix-0x3ff00000)\|lx)==0)
	145	return y - y; /* inf*+-1 is NaN /
	146	else if (ix >= 0x3ff00000)/* (\|x\|>1)*+-inf = inf,0 /
	147	return (hy>=0)? y: zero;
	148	else /* (\|x\|<1)*-,+inf = inf,0 /
	149	return (hy<0)?-y: zero;
	150	}
	151	if(iy==0x3ff00000) { /* y is +-1 */
	152	if(hy<0) return one/x; else return x;
	153	}
	154	if(hy==0x40000000) return xx; / y is 2 */
	155	if(hy==0x3fe00000) { /* y is 0.5 */
	156	if(hx>=0) /* x >= +0 */
	157	return __ieee754_sqrt(x);
	158	}
	159	}
	160
	161	ax = x < 0 ? -x : x; /fabs(x);/
	162	/* special value of x */
	163	if(lx==0) {
	164	if(ix==0x7ff00000\|\|ix==0\|\|ix==0x3ff00000){
	165	z = ax; /x is +-0,+-inf,+-1/
	166	if(hy<0) z = one/z; /* z = (1/\|x\|) */
	167	if(hx<0) {
	168	if(((ix-0x3ff00000)\|yisint)==0) {
	169	z = (z-z)/(z-z); /* (-1)*non-int is NaN /
	170	} else if(yisint==1)
	171	z = -z; /* (x<0)odd = -(\|x\|odd) */
	172	}
	173	return z;
	174	}
	175	}
	176
	177	/* (x<0)*(non-int) is NaN /
	178	if(((((u_int32_t)hx>>31)-1)\|yisint)==0) return (x-x)/(x-x);
	179
	180	/* \|y\| is huge */
	181	if(iy>0x41e00000) { /* if \|y\| > 2*31 /
	182	if(iy>0x43f00000){ /* if \|y\| > 2*64, must o/uflow /
	183	if(ix<=0x3fefffff) return (hy<0)? hugehuge:tinytiny;
	184	if(ix>=0x3ff00000) return (hy>0)? hugehuge:tinytiny;
	185	}
	186	/* over/underflow if x is not close to one */
	187	if(ix<0x3fefffff) return (hy<0)? hugehuge:tinytiny;
	188	if(ix>0x3ff00000) return (hy>0)? hugehuge:tinytiny;
	189	/* now \|1-x\| is tiny <= 2**-20, suffice to compute
	190	log(x) by x-x^2/2+x^3/3-x^4/4 */
	191	t = x-1; /* t has 20 trailing zeros */
	192	w = (tt)(0.5-t(0.3333333333333333333333-t0.25));
	193	u = ivln2_ht; / ivln2_h has 21 sig. bits */
	194	v = tivln2_l-wivln2;
	195	t1 = u+v;
	196	SET_LOW_WORD(t1,0);
	197	t2 = v-(t1-u);
	198	} else {
	199	double s2,s_h,s_l,t_h,t_l;
	200	n = 0;
	201	/* take care subnormal number */
	202	if(ix<0x00100000)
	203	{ax *= two53; n -= 53; GET_HIGH_WORD(ix,ax); }
	204	n += ((ix)>>20)-0x3ff;
	205	j = ix&0x000fffff;
	206	/* determine interval */
	207	ix = j\|0x3ff00000; /* normalize ix */
	208	if(j<=0x3988E) k=0; /* \|x\|<sqrt(3/2) */
	209	else if(j<0xBB67A) k=1; /* \|x\|<sqrt(3) */
	210	else {k=0;n+=1;ix -= 0x00100000;}
	211	SET_HIGH_WORD(ax,ix);
	212
	213	/* compute s = s_h+s_l = (x-1)/(x+1) or (x-1.5)/(x+1.5) */
	214	u = ax-bp[k]; /* bp[0]=1.0, bp[1]=1.5 */
	215	v = one/(ax+bp[k]);
	216	s = u*v;
	217	s_h = s;
	218	SET_LOW_WORD(s_h,0);
	219	/* t_h=ax+bp[k] High */
	220	t_h = zero;
	221	SET_HIGH_WORD(t_h,((ix>>1)\|0x20000000)+0x00080000+(k<<18));
	222	t_l = ax - (t_h-bp[k]);
	223	s_l = v((u-s_ht_h)-s_h*t_l);
	224	/* compute log(ax) */
	225	s2 = s*s;
	226	r = s2s2(L1+s2(L2+s2(L3+s2(L4+s2(L5+s2*L6)))));
	227	r += s_l*(s_h+s);
	228	s2 = s_h*s_h;
	229	t_h = 3.0+s2+r;
	230	SET_LOW_WORD(t_h,0);
	231	t_l = r-((t_h-3.0)-s2);
	232	/* u+v = s(1+...) /
	233	u = s_h*t_h;
	234	v = s_lt_h+t_ls;
	235	/* 2/(3log2)(s+...) /
	236	p_h = u+v;
	237	SET_LOW_WORD(p_h,0);
	238	p_l = v-(p_h-u);
	239	z_h = cp_hp_h; / cp_h+cp_l = 2/(3log2) /
	240	z_l = cp_lp_h+p_lcp+dp_l[k];
	241	/* log2(ax) = (s+..)2/(3log2) = n + dp_h + z_h + z_l */
	242	t = (double)n;
	243	t1 = (((z_h+z_l)+dp_h[k])+t);
	244	SET_LOW_WORD(t1,0);
	245	t2 = z_l-(((t1-t)-dp_h[k])-z_h);
	246	}
	247
	248	s = one; /* s (sign of result -ve*odd) = -1 else = 1 /
	249	if(((((u_int32_t)hx>>31)-1)\|(yisint-1))==0)
	250	s = -one;/* (-ve)*(odd int) /
	251
	252	/* split up y into y1+y2 and compute (y1+y2)(t1+t2) /
	253	y1 = y;
	254	SET_LOW_WORD(y1,0);
	255	p_l = (y-y1)t1+yt2;
	256	p_h = y1*t1;
	257	z = p_l+p_h;
	258	EXTRACT_WORDS(j,i,z);
	259	if (j>=0x40900000) { /* z >= 1024 */
	260	if(((j-0x40900000)\|i)!=0) /* if z > 1024 */
	261	return shugehuge; /* overflow */
	262	else {
	263	if(p_l+ovt>z-p_h) return shugehuge; /* overflow */
	264	}
	265	} else if((j&0x7fffffff)>=0x4090cc00 ) { /* z <= -1075 */
	266	if(((j-0xc090cc00)\|i)!=0) /* z < -1075 */
	267	return stinytiny; /* underflow */
	268	else {
	269	if(p_l<=z-p_h) return stinytiny; /* underflow */
	270	}
	271	}
	272	/*
	273	* compute 2**(p_h+p_l)
	274	*/
	275	i = j&0x7fffffff;
	276	k = (i>>20)-0x3ff;
	277	n = 0;
	278	if(i>0x3fe00000) { /* if \|z\| > 0.5, set n = [z+0.5] */
	279	n = j+(0x00100000>>(k+1));
	280	k = ((n&0x7fffffff)>>20)-0x3ff; /* new k for n */
	281	t = zero;
	282	SET_HIGH_WORD(t,n&~(0x000fffff>>k));
	283	n = ((n&0x000fffff)\|0x00100000)>>(20-k);
	284	if(j<0) n = -n;
	285	p_h -= t;
	286	}
	287	t = p_l+p_h;
	288	SET_LOW_WORD(t,0);
	289	u = t*lg2_h;
	290	v = (p_l-(t-p_h))lg2+tlg2_l;
	291	z = u+v;
	292	w = v-(z-u);
	293	t = z*z;
	294	t1 = z - t(P1+t(P2+t(P3+t(P4+t*P5))));
	295	r = (zt1)/(t1-two)-(w+zw);
	296	z = one-(r-z);
	297	GET_HIGH_WORD(j,z);
	298	j += (n<<20);
	299	if((j>>20)<=0) z = SDL_NAME(scalbn)(z,n); /* subnormal output */
	300	else SET_HIGH_WORD(z,j);
	301	return s*z;
	302	}