1/* origin: FreeBSD /usr/src/lib/msun/src/e_acosl.c */
2/*
3 * ====================================================
4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
5 *
6 * Developed at SunSoft, 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 * See comments in acos.c.
14 * Converted to long double by David Schultz <das@FreeBSD.ORG>.
15 */
16
17#include "libm.h"
18
19#if LDBL_MANT_DIG == 53 && LDBL_MAX_EXP == 1024
20long double acosl(long double x)
21{
22	return acos(x);
23}
24#elif (LDBL_MANT_DIG == 64 || LDBL_MANT_DIG == 113) && LDBL_MAX_EXP == 16384
25#include "__invtrigl.h"
26#if LDBL_MANT_DIG == 64
27#define CLEARBOTTOM(u) (u.i.m &= -1ULL << 32)
28#elif LDBL_MANT_DIG == 113
29#define CLEARBOTTOM(u) (u.i.lo = 0)
30#endif
31
32long double acosl(long double x)
33{
34	union ldshape u = {x};
35	long double z, s, c, f;
36	uint16_t e = u.i.se & 0x7fff;
37
38	/* |x| >= 1 or nan */
39	if (e >= 0x3fff) {
40		if (x == 1)
41			return 0;
42		if (x == -1)
43			return 2*pio2_hi + 0x1p-120f;
44		return 0/(x-x);
45	}
46	/* |x| < 0.5 */
47	if (e < 0x3fff - 1) {
48		if (e < 0x3fff - LDBL_MANT_DIG - 1)
49			return pio2_hi + 0x1p-120f;
50		return pio2_hi - (__invtrigl_R(x*x)*x - pio2_lo + x);
51	}
52	/* x < -0.5 */
53	if (u.i.se >> 15) {
54		z = (1 + x)*0.5;
55		s = sqrtl(z);
56		return 2*(pio2_hi - (__invtrigl_R(z)*s - pio2_lo + s));
57	}
58	/* x > 0.5 */
59	z = (1 - x)*0.5;
60	s = sqrtl(z);
61	u.f = s;
62	CLEARBOTTOM(u);
63	f = u.f;
64	c = (z - f*f)/(s + f);
65	return 2*(__invtrigl_R(z)*s + c + f);
66}
67#endif
68