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
__ieee754_acosf(float x)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 }
82