1 /* e_acosf.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 "math.h"
17 #include "math_private.h"
18
19 static const float
20 one = 1.0000000000e+00, /* 0x3F800000 */
21 pi = 3.1415925026e+00, /* 0x40490fda */
22 pio2_hi = 1.5707962513e+00, /* 0x3fc90fda */
23 pio2_lo = 7.5497894159e-08, /* 0x33a22168 */
24 pS0 = 1.6666667163e-01, /* 0x3e2aaaab */
25 pS1 = -3.2556581497e-01, /* 0xbea6b090 */
26 pS2 = 2.0121252537e-01, /* 0x3e4e0aa8 */
27 pS3 = -4.0055535734e-02, /* 0xbd241146 */
28 pS4 = 7.9153501429e-04, /* 0x3a4f7f04 */
29 pS5 = 3.4793309169e-05, /* 0x3811ef08 */
30 qS1 = -2.4033949375e+00, /* 0xc019d139 */
31 qS2 = 2.0209457874e+00, /* 0x4001572d */
32 qS3 = -6.8828397989e-01, /* 0xbf303361 */
33 qS4 = 7.7038154006e-02; /* 0x3d9dc62e */
34
35 float
acosf(float x)36 acosf(float x)
37 {
38 float z,p,q,r,w,s,c,df;
39 int32_t hx,ix;
40 GET_FLOAT_WORD(hx,x);
41 ix = hx&0x7fffffff;
42 if(ix==0x3f800000) { /* |x|==1 */
43 if(hx>0) return 0.0; /* acos(1) = 0 */
44 else return pi+(float)2.0*pio2_lo; /* acos(-1)= pi */
45 } else if(ix>0x3f800000) { /* |x| >= 1 */
46 return (x-x)/(x-x); /* acos(|x|>1) is NaN */
47 }
48 if(ix<0x3f000000) { /* |x| < 0.5 */
49 if(ix<=0x23000000) return pio2_hi+pio2_lo;/*if|x|<2**-57*/
50 z = x*x;
51 p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
52 q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
53 r = p/q;
54 return pio2_hi - (x - (pio2_lo-x*r));
55 } else if (hx<0) { /* x < -0.5 */
56 z = (one+x)*(float)0.5;
57 p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
58 q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
59 s = sqrtf(z);
60 r = p/q;
61 w = r*s-pio2_lo;
62 return pi - (float)2.0*(s+w);
63 } else { /* x > 0.5 */
64 int32_t idf;
65 z = (one-x)*(float)0.5;
66 s = sqrtf(z);
67 df = s;
68 GET_FLOAT_WORD(idf,df);
69 SET_FLOAT_WORD(df,idf&0xfffff000);
70 c = (z-df*df)/(s+df);
71 p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
72 q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
73 r = p/q;
74 w = r*s+c;
75 return (float)2.0*(df+w);
76 }
77 }
78