xref: /netbsd-src/lib/libm/src/e_acosf.c (revision 2a399c6883d870daece976daec6ffa7bb7f934ce)
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 <sys/cdefs.h>
17 #if defined(LIBM_SCCS) && !defined(lint)
18 __RCSID("$NetBSD: e_acosf.c,v 1.6 1997/10/09 11:28:26 lukem Exp $");
19 #endif
20 
21 #include "math.h"
22 #include "math_private.h"
23 
24 #ifdef __STDC__
25 static const float
26 #else
27 static float
28 #endif
29 one =  1.0000000000e+00, /* 0x3F800000 */
30 pi =  3.1415925026e+00, /* 0x40490fda */
31 pio2_hi =  1.5707962513e+00, /* 0x3fc90fda */
32 pio2_lo =  7.5497894159e-08, /* 0x33a22168 */
33 pS0 =  1.6666667163e-01, /* 0x3e2aaaab */
34 pS1 = -3.2556581497e-01, /* 0xbea6b090 */
35 pS2 =  2.0121252537e-01, /* 0x3e4e0aa8 */
36 pS3 = -4.0055535734e-02, /* 0xbd241146 */
37 pS4 =  7.9153501429e-04, /* 0x3a4f7f04 */
38 pS5 =  3.4793309169e-05, /* 0x3811ef08 */
39 qS1 = -2.4033949375e+00, /* 0xc019d139 */
40 qS2 =  2.0209457874e+00, /* 0x4001572d */
41 qS3 = -6.8828397989e-01, /* 0xbf303361 */
42 qS4 =  7.7038154006e-02; /* 0x3d9dc62e */
43 
44 #ifdef __STDC__
45 	float __ieee754_acosf(float x)
46 #else
47 	float __ieee754_acosf(x)
48 	float x;
49 #endif
50 {
51 	float z,p,q,r,w,s,c,df;
52 	int32_t hx,ix;
53 	GET_FLOAT_WORD(hx,x);
54 	ix = hx&0x7fffffff;
55 	if(ix==0x3f800000) {		/* |x|==1 */
56 	    if(hx>0) return 0.0;	/* acos(1) = 0  */
57 	    else return pi+(float)2.0*pio2_lo;	/* acos(-1)= pi */
58 	} else if(ix>0x3f800000) {	/* |x| >= 1 */
59 	    return (x-x)/(x-x);		/* acos(|x|>1) is NaN */
60 	}
61 	if(ix<0x3f000000) {	/* |x| < 0.5 */
62 	    if(ix<=0x23000000) return pio2_hi+pio2_lo;/*if|x|<2**-57*/
63 	    z = x*x;
64 	    p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
65 	    q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
66 	    r = p/q;
67 	    return pio2_hi - (x - (pio2_lo-x*r));
68 	} else  if (hx<0) {		/* x < -0.5 */
69 	    z = (one+x)*(float)0.5;
70 	    p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
71 	    q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
72 	    s = __ieee754_sqrtf(z);
73 	    r = p/q;
74 	    w = r*s-pio2_lo;
75 	    return pi - (float)2.0*(s+w);
76 	} else {			/* x > 0.5 */
77 	    int32_t idf;
78 	    z = (one-x)*(float)0.5;
79 	    s = __ieee754_sqrtf(z);
80 	    df = s;
81 	    GET_FLOAT_WORD(idf,df);
82 	    SET_FLOAT_WORD(df,idf&0xfffff000);
83 	    c  = (z-df*df)/(s+df);
84 	    p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
85 	    q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
86 	    r = p/q;
87 	    w = r*s+c;
88 	    return (float)2.0*(df+w);
89 	}
90 }
91