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