/* origin: FreeBSD /usr/src/lib/msun/src/e_asinl.c */
/*
 * ====================================================
 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
 *
 * Developed at SunSoft, a Sun Microsystems, Inc. business.
 * Permission to use, copy, modify, and distribute this
 * software is freely granted, provided that this notice
 * is preserved.
 * ====================================================
 */
/*
 * See comments in asin.c.
 * Converted to long double by David Schultz <das@FreeBSD.ORG>.
 */

#include "libm.h" // for ldshape, ldshape::(anonymous), FORCE_EVAL

#include <float.h>  // for LDBL_MANT_DIG, LDBL_MAX_EXP
#include <math.h>   // for asinl, fabsl, sqrtl
#include <stdint.h> // for uint16_t

#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
long double asinl(long double x)
{
	return asin(x);
}
#elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
#include "__invtrigl.h" // for __invtrigl_R, pio2_hi, pio2_lo
#if LDBL_MANT_DIG == 64
#define CLOSETO1(u)    ((u).i.m >> 56 >= 0xf7)
#define CLEARBOTTOM(u) ((u).i.m &= -1ULL << 32)
#elif LDBL_MANT_DIG == 113
#define CLOSETO1(u)    (u.i.top >= 0xee00)
#define CLEARBOTTOM(u) (u.i.lo = 0)
#endif

long double asinl(long double x)
{
	union ldshape u = { x };
	long double z, r, s;
	uint16_t e = u.i.se & 0x7fff;
	int sign = u.i.se >> 15;

	if (e >= 0x3fff) { /* |x| >= 1 or nan */
		/* asin(+-1)=+-pi/2 with inexact */
		if (x == 1 || x == -1)
			return x * pio2_hi + 0x1p-120f;
		return 0 / (x - x);
	}
	if (e < 0x3fff - 1) { /* |x| < 0.5 */
		if (e < 0x3fff - (LDBL_MANT_DIG + 1) / 2) {
			/* return x with inexact if x!=0 */
			FORCE_EVAL(x + 0x1p120f);
			return x;
		}
		return x + x * __invtrigl_R(x * x);
	}
	/* 1 > |x| >= 0.5 */
	z = (1.0 - fabsl(x)) * 0.5;
	s = sqrtl(z);
	r = __invtrigl_R(z);
	if (CLOSETO1(u)) {
		x = pio2_hi - (2 * (s + s * r) - pio2_lo);
	} else {
		long double f, c;
		u.f = s;
		CLEARBOTTOM(u);
		f = u.f;
		c = (z - f * f) / (s + f);
		x = 0.5 * pio2_hi -
		    (2 * s * r - (pio2_lo - 2 * c) - (0.5 * pio2_hi - 2 * f));
	}
	return sign ? -x : x;
}
#endif