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e_acosf.c (2558B)
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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 #ifndef lint
17 static char rcsid[] = "$FreeBSD: src/lib/msun/src/e_acosf.c,v 1.7 2002/05/28 17:03:12 alfred Exp $";
18 #endif
19
20 #include "math.h"
21 #include "math_private.h"
22
23 static const float
24 one = 1.0000000000e+00, /* 0x3F800000 */
25 pi = 3.1415925026e+00, /* 0x40490fda */
26 pio2_hi = 1.5707962513e+00, /* 0x3fc90fda */
27 pio2_lo = 7.5497894159e-08, /* 0x33a22168 */
28 pS0 = 1.6666667163e-01, /* 0x3e2aaaab */
29 pS1 = -3.2556581497e-01, /* 0xbea6b090 */
30 pS2 = 2.0121252537e-01, /* 0x3e4e0aa8 */
31 pS3 = -4.0055535734e-02, /* 0xbd241146 */
32 pS4 = 7.9153501429e-04, /* 0x3a4f7f04 */
33 pS5 = 3.4793309169e-05, /* 0x3811ef08 */
34 qS1 = -2.4033949375e+00, /* 0xc019d139 */
35 qS2 = 2.0209457874e+00, /* 0x4001572d */
36 qS3 = -6.8828397989e-01, /* 0xbf303361 */
37 qS4 = 7.7038154006e-02; /* 0x3d9dc62e */
38
39 float
40 __ieee754_acosf(float x)
41 {
42 float z,p,q,r,w,s,c,df;
43 int32_t hx,ix;
44 GET_FLOAT_WORD(hx,x);
45 ix = hx&0x7fffffff;
46 if(ix==0x3f800000) { /* |x|==1 */
47 if(hx>0) return 0.0; /* acos(1) = 0 */
48 else return pi+(float)2.0*pio2_lo; /* acos(-1)= pi */
49 } else if(ix>0x3f800000) { /* |x| >= 1 */
50 return (x-x)/(x-x); /* acos(|x|>1) is NaN */
51 }
52 if(ix<0x3f000000) { /* |x| < 0.5 */
53 if(ix<=0x23000000) return pio2_hi+pio2_lo;/*if|x|<2**-57*/
54 z = x*x;
55 p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
56 q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
57 r = p/q;
58 return pio2_hi - (x - (pio2_lo-x*r));
59 } else if (hx<0) { /* x < -0.5 */
60 z = (one+x)*(float)0.5;
61 p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
62 q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
63 s = __ieee754_sqrtf(z);
64 r = p/q;
65 w = r*s-pio2_lo;
66 return pi - (float)2.0*(s+w);
67 } else { /* x > 0.5 */
68 int32_t idf;
69 z = (one-x)*(float)0.5;
70 s = __ieee754_sqrtf(z);
71 df = s;
72 GET_FLOAT_WORD(idf,df);
73 SET_FLOAT_WORD(df,idf&0xfffff000);
74 c = (z-df*df)/(s+df);
75 p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
76 q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
77 r = p/q;
78 w = r*s+c;
79 return (float)2.0*(df+w);
80 }
81 }