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
__ieee754_asinf(float x)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