e_asinf.c revision 181100 
1/* e_asinf.c -- float version of e_asin.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_asinf.c 181100 2008-08-01 01:24:25Z das $");
18
19#include "math.h"
20#include "math_private.h"
21
22static const float
23one =  1.0000000000e+00, /* 0x3F800000 */
24huge =  1.000e+30,
25	/* coefficient for R(x^2) */
26pS0 =  1.6666586697e-01,
27pS1 = -4.2743422091e-02,
28pS2 = -8.6563630030e-03,
29qS1 = -7.0662963390e-01;
30
31static const double
32pio2 =  1.570796326794896558e+00;
33
34float
35__ieee754_asinf(float x)
36{
37	double s;
38	float t=0.0,w,p,q,c,r;
39	int32_t hx,ix;
40	GET_FLOAT_WORD(hx,x);
41	ix = hx&0x7fffffff;
42	if(ix==0x3f800000) {
43		/* asin(1)=+-pi/2 with inexact */
44	    return x*pio2;
45	} else if(ix> 0x3f800000) {	/* |x|>= 1 */
46	    return (x-x)/(x-x);		/* asin(|x|>1) is NaN */
47	} else if (ix<0x3f000000) {	/* |x|<0.5 */
48	    if(ix<0x39800000) {		/* if |x| < 2**-12 */
49		if(huge+x>one) return x;/* return x with inexact if x!=0*/
50	    } else
51		t = x*x;
52	        p = t*(pS0+t*(pS1+t*pS2));
53	        q = one+t*qS1;
54		w = p/q;
55		return x+x*w;
56	}
57	/* 1> |x|>= 0.5 */
58	w = one-fabsf(x);
59	t = w*(float)0.5;
60	p = t*(pS0+t*(pS1+t*pS2));
61	q = one+t*qS1;
62	s = __ieee754_sqrt(t);
63	w = p/q;
64	t = pio2-2.0*(s+s*w);
65	if(hx>0) return t; else return -t;
66}
67