e_acosf.c revision 181062 
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__FBSDID("$FreeBSD: head/lib/msun/src/e_acosf.c 181062 2008-07-31 19:57:50Z das $");
18
19#include "math.h"
20#include "math_private.h"
21
22static const float
23one =  1.0000000000e+00, /* 0x3F800000 */
24pi =  3.1415925026e+00, /* 0x40490fda */
25pio2_hi =  1.5707962513e+00; /* 0x3fc90fda */
26static volatile float
27pio2_lo =  7.5497894159e-08; /* 0x33a22168 */
28static const float
29pS0 =  1.6666667163e-01, /* 0x3e2aaaab */
30pS1 = -3.2556581497e-01, /* 0xbea6b090 */
31pS2 =  2.0121252537e-01, /* 0x3e4e0aa8 */
32pS3 = -4.0055535734e-02, /* 0xbd241146 */
33pS4 =  7.9153501429e-04, /* 0x3a4f7f04 */
34pS5 =  3.4793309169e-05, /* 0x3811ef08 */
35qS1 = -2.4033949375e+00, /* 0xc019d139 */
36qS2 =  2.0209457874e+00, /* 0x4001572d */
37qS3 = -6.8828397989e-01, /* 0xbf303361 */
38qS4 =  7.7038154006e-02; /* 0x3d9dc62e */
39
40float
41__ieee754_acosf(float x)
42{
43	float z,p,q,r,w,s,c,df;
44	int32_t hx,ix;
45	GET_FLOAT_WORD(hx,x);
46	ix = hx&0x7fffffff;
47	if(ix==0x3f800000) {		/* |x|==1 */
48	    if(hx>0) return 0.0;	/* acos(1) = 0  */
49	    else return pi+(float)2.0*pio2_lo;	/* acos(-1)= pi */
50	} else if(ix>0x3f800000) {	/* |x| >= 1 */
51	    return (x-x)/(x-x);		/* acos(|x|>1) is NaN */
52	}
53	if(ix<0x3f000000) {	/* |x| < 0.5 */
54	    if(ix<=0x23000000) return pio2_hi+pio2_lo;/*if|x|<2**-57*/
55	    z = x*x;
56	    p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
57	    q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
58	    r = p/q;
59	    return pio2_hi - (x - (pio2_lo-x*r));
60	} else  if (hx<0) {		/* x < -0.5 */
61	    z = (one+x)*(float)0.5;
62	    p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
63	    q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
64	    s = __ieee754_sqrtf(z);
65	    r = p/q;
66	    w = r*s-pio2_lo;
67	    return pi - (float)2.0*(s+w);
68	} else {			/* x > 0.5 */
69	    int32_t idf;
70	    z = (one-x)*(float)0.5;
71	    s = __ieee754_sqrtf(z);
72	    df = s;
73	    GET_FLOAT_WORD(idf,df);
74	    SET_FLOAT_WORD(df,idf&0xfffff000);
75	    c  = (z-df*df)/(s+df);
76	    p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
77	    q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
78	    r = p/q;
79	    w = r*s+c;
80	    return (float)2.0*(df+w);
81	}
82}
83