1 | /* e_acosf.c -- float version of e_acos.c. |
2 | */ |
3 | |
4 | /* |
5 | * ==================================================== |
6 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved. |
7 | * |
8 | * Developed at SunPro, a Sun Microsystems, Inc. business. |
9 | * Permission to use, copy, modify, and distribute this |
10 | * software is freely granted, provided that this notice |
11 | * is preserved. |
12 | * ==================================================== |
13 | */ |
14 | |
15 | #include <math.h> |
16 | #include <math_private.h> |
17 | #include <libm-alias-finite.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 |
36 | __ieee754_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<=0x32800000) return pio2_hi+pio2_lo;/*if|x|<=2**-26*/ |
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 | libm_alias_finite (__ieee754_acosf, __acosf) |
79 | |