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 "math.h"
17#include "math_private.h"
18
19static const float
20one =  1.0000000000e+00, /* 0x3F800000 */
21pi =  3.1415925026e+00, /* 0x40490fda */
22pio2_hi =  1.5707962513e+00; /* 0x3fc90fda */
23static volatile float
24pio2_lo =  7.5497894159e-08; /* 0x33a22168 */
25static const float
26pS0 =  1.6666586697e-01,
27pS1 = -4.2743422091e-02,
28pS2 = -8.6563630030e-03,
29qS1 = -7.0662963390e-01;
30
31float
32acosf(float x)
33{
34	float z,p,q,r,w,s,c,df;
35	int32_t hx,ix;
36	GET_FLOAT_WORD(hx,x);
37	ix = hx&0x7fffffff;
38	if(ix>=0x3f800000) {		/* |x| >= 1 */
39	    if(ix==0x3f800000) {	/* |x| == 1 */
40		if(hx>0) return 0.0;	/* acos(1) = 0 */
41		else return pi+(float)2.0*pio2_lo;	/* acos(-1)= pi */
42	    }
43	    return (x-x)/(x-x);		/* acos(|x|>1) is NaN */
44	}
45	if(ix<0x3f000000) {	/* |x| < 0.5 */
46	    if(ix<=0x32800000) return pio2_hi+pio2_lo;/*if|x|<2**-26*/
47	    z = x*x;
48	    p = z*(pS0+z*(pS1+z*pS2));
49	    q = one+z*qS1;
50	    r = p/q;
51	    return pio2_hi - (x - (pio2_lo-x*r));
52	} else  if (hx<0) {		/* x < -0.5 */
53	    z = (one+x)*(float)0.5;
54	    p = z*(pS0+z*(pS1+z*pS2));
55	    q = one+z*qS1;
56	    s = sqrtf(z);
57	    r = p/q;
58	    w = r*s-pio2_lo;
59	    return pi - (float)2.0*(s+w);
60	} else {			/* x > 0.5 */
61	    int32_t idf;
62	    z = (one-x)*(float)0.5;
63	    s = sqrtf(z);
64	    df = s;
65	    GET_FLOAT_WORD(idf,df);
66	    SET_FLOAT_WORD(df,idf&0xfffff000);
67	    c  = (z-df*df)/(s+df);
68	    p = z*(pS0+z*(pS1+z*pS2));
69	    q = one+z*qS1;
70	    r = p/q;
71	    w = r*s+c;
72	    return (float)2.0*(df+w);
73	}
74}
75