#include <float.h>
#include "math.h"

#include "math_private.h"

static const double
	one     = 1.00000000000000000000e+00, /* 0x3FF00000, 0x00000000 */
	huge    = 1.000e+300,
	pio2_hi = 1.57079632679489655800e+00, /* 0x3FF921FB, 0x54442D18 */
	pio2_lo = 6.12323399573676603587e-17, /* 0x3C91A626, 0x33145C07 */
	pio4_hi = 7.85398163397448278999e-01, /* 0x3FE921FB, 0x54442D18 */
	/* coefficient for R(x^2) */
	pS0 = 1.66666666666666657415e-01, /* 0x3FC55555, 0x55555555 */
	pS1 = -3.25565818622400915405e-01, /* 0xBFD4D612, 0x03EB6F7D */
	pS2 = 2.01212532134862925881e-01, /* 0x3FC9C155, 0x0E884455 */
	pS3 = -4.00555345006794114027e-02, /* 0xBFA48228, 0xB5688F3B */
	pS4 = 7.91534994289814532176e-04, /* 0x3F49EFE0, 0x7501B288 */
	pS5 = 3.47933107596021167570e-05, /* 0x3F023DE1, 0x0DFDF709 */
	qS1 = -2.40339491173441421878e+00, /* 0xC0033A27, 0x1C8A2D4B */
	qS2 = 2.02094576023350569471e+00, /* 0x40002AE5, 0x9C598AC8 */
	qS3 = -6.88283971605453293030e-01, /* 0xBFE6066C, 0x1B8D0159 */
	qS4 = 7.70381505559019352791e-02; /* 0x3FB3B8C5, 0xB12E9282 */

double asin(double x)
{
	double t = 0.0, w, p, q, c, r, s;
	int32_t hx, ix;
	GET_HIGH_WORD(hx, x);
	ix = hx & 0x7fffffff;
	if (ix >= 0x3ff00000) { /* |x|>= 1 */
		u_int32_t lx;
		GET_LOW_WORD(lx, x);
		if (((ix - 0x3ff00000) | lx) == 0)
			/* asin(1)=+-pi/2 with inexact */
			return x * pio2_hi + x * pio2_lo;
		return (x - x) / (x - x); /* asin(|x|>1) is NaN */
	} else if (ix < 0x3fe00000) { /* |x|<0.5 */
		if (ix < 0x3e500000) { /* if |x| < 2**-26 */
			if (huge + x > one)
				return x; /* return x with inexact if x!=0*/
		}
		t = x * x;
		p = t * (pS0 + t * (pS1 + t * (pS2 + t * (pS3 + t * (pS4 + t * pS5)))));
		q = one + t * (qS1 + t * (qS2 + t * (qS3 + t * qS4)));
		w = p / q;
		return x + x * w;
	}
	/* 1> |x|>= 0.5 */
	w = one - fabs(x);
	t = w * 0.5;
	p = t * (pS0 + t * (pS1 + t * (pS2 + t * (pS3 + t * (pS4 + t * pS5)))));
	q = one + t * (qS1 + t * (qS2 + t * (qS3 + t * qS4)));
	s = sqrt(t);
	if (ix >= 0x3FEF3333) { /* if |x| > 0.975 */
		w = p / q;
		t = pio2_hi - (2.0 * (s + s * w) - pio2_lo);
	} else {
		w = s;
		SET_LOW_WORD(w, 0);
		c = (t - w * w) / (s + w);
		r = p / q;
		p = 2.0 * s * r - (pio2_lo - 2.0 * c);
		q = pio4_hi - 2.0 * w;
		t = pio4_hi - (p - q);
	}
	if (hx > 0)
		return t;
	else
		return -t;
}
/*
#if LDBL_MANT_DIG == 53
openlibm_weak_reference(asin, asinl);
#endif
*/