xref: /freebsd/lib/msun/src/e_asinf.c (revision e8d8bef961a50d4dc22501cde4fb9fb0be1b2532)
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("$FreeBSD$");
18 
19 #include "math.h"
20 #include "math_private.h"
21 
22 static const float
23 one =  1.0000000000e+00, /* 0x3F800000 */
24 huge =  1.000e+30,
25 	/* coefficient for R(x^2) */
26 pS0 =  1.6666586697e-01,
27 pS1 = -4.2743422091e-02,
28 pS2 = -8.6563630030e-03,
29 qS1 = -7.0662963390e-01;
30 
31 static const double
32 pio2 =  1.570796326794896558e+00;
33 
34 float
35 __ieee754_asinf(float x)
36 {
37 	double s;
38 	float t,w,p,q;
39 	int32_t hx,ix;
40 	GET_FLOAT_WORD(hx,x);
41 	ix = hx&0x7fffffff;
42 	if(ix>=0x3f800000) {		/* |x| >= 1 */
43 	    if(ix==0x3f800000)		/* |x| == 1 */
44 		return x*pio2;		/* asin(+-1) = +-pi/2 with inexact */
45 	    return (x-x)/(x-x);		/* asin(|x|>1) is NaN */
46 	} else if (ix<0x3f000000) {	/* |x|<0.5 */
47 	    if(ix<0x39800000) {		/* |x| < 2**-12 */
48 		if(huge+x>one) return x;/* return x with inexact if x!=0*/
49 	    }
50 	    t = x*x;
51 	    p = t*(pS0+t*(pS1+t*pS2));
52 	    q = one+t*qS1;
53 	    w = p/q;
54 	    return x+x*w;
55 	}
56 	/* 1> |x|>= 0.5 */
57 	w = one-fabsf(x);
58 	t = w*(float)0.5;
59 	p = t*(pS0+t*(pS1+t*pS2));
60 	q = one+t*qS1;
61 	s = sqrt(t);
62 	w = p/q;
63 	t = pio2-2.0*(s+s*w);
64 	if(hx>0) return t; else return -t;
65 }
66