1 /* ef_acos.c -- float version of e_acos.c.
2  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
3  */
4 
5 /*
6  * ====================================================
7  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8  *
9  * Developed at SunPro, a Sun Microsystems, Inc. business.
10  * Permission to use, copy, modify, and distribute this
11  * software is freely granted, provided that this notice
12  * is preserved.
13  * ====================================================
14  */
15 
16 #include "fdlibm.h"
17 
18 static const float one = 1.0000000000e+00, /* 0x3F800000 */
19     pi = 3.1415925026e+00, /* 0x40490fda */
20     pio2_hi = 1.5707962513e+00, /* 0x3fc90fda */
21     pio2_lo = 7.5497894159e-08, /* 0x33a22168 */
22     pS0 = 1.6666667163e-01, /* 0x3e2aaaab */
23     pS1 = -3.2556581497e-01, /* 0xbea6b090 */
24     pS2 = 2.0121252537e-01, /* 0x3e4e0aa8 */
25     pS3 = -4.0055535734e-02, /* 0xbd241146 */
26     pS4 = 7.9153501429e-04, /* 0x3a4f7f04 */
27     pS5 = 3.4793309169e-05, /* 0x3811ef08 */
28     qS1 = -2.4033949375e+00, /* 0xc019d139 */
29     qS2 = 2.0209457874e+00, /* 0x4001572d */
30     qS3 = -6.8828397989e-01, /* 0xbf303361 */
31     qS4 = 7.7038154006e-02; /* 0x3d9dc62e */
32 
33 float
acosf(float x)34 acosf(float x)
35 {
36     float z, p, q, r, w, s, c, df;
37     __int32_t hx, ix;
38     GET_FLOAT_WORD(hx, x);
39     ix = hx & 0x7fffffff;
40     if (ix == 0x3f800000) { /* |x|==1 */
41         if (hx > 0)
42             return 0.0; /* acos(1) = 0  */
43         else
44             return pi + (float)2.0 * pio2_lo; /* acos(-1)= pi */
45     } else if (ix > 0x3f800000) { /* |x| >= 1 */
46         return __math_invalidf(x); /* acos(|x|>1) is NaN */
47     }
48     if (ix < 0x3f000000) { /* |x| < 0.5 */
49         if (ix <= 0x23000000)
50             return pio2_hi + pio2_lo; /*if|x|<2**-57*/
51         z = x * x;
52         p = z * (pS0 + z * (pS1 + z * (pS2 + z * (pS3 + z * (pS4 + z * pS5)))));
53         q = one + z * (qS1 + z * (qS2 + z * (qS3 + z * qS4)));
54         r = p / q;
55         return pio2_hi - (x - (pio2_lo - x * r));
56     } else if (hx < 0) { /* x < -0.5 */
57         z = (one + x) * (float)0.5;
58         p = z * (pS0 + z * (pS1 + z * (pS2 + z * (pS3 + z * (pS4 + z * pS5)))));
59         q = one + z * (qS1 + z * (qS2 + z * (qS3 + z * qS4)));
60         s = sqrtf(z);
61         r = p / q;
62         w = r * s - pio2_lo;
63         return pi - (float)2.0 * (s + w);
64     } else { /* x > 0.5 */
65         __int32_t idf;
66         z = (one - x) * (float)0.5;
67         s = sqrtf(z);
68         df = s;
69         GET_FLOAT_WORD(idf, df);
70         SET_FLOAT_WORD(df, idf & 0xfffff000);
71         c = (z - df * df) / (s + df);
72         p = z * (pS0 + z * (pS1 + z * (pS2 + z * (pS3 + z * (pS4 + z * pS5)))));
73         q = one + z * (qS1 + z * (qS2 + z * (qS3 + z * qS4)));
74         r = p / q;
75         w = r * s + c;
76         return (float)2.0 * (df + w);
77     }
78 }
79 
80 _MATH_ALIAS_f_f(acos)
81