1/* origin: FreeBSD /usr/src/lib/msun/src/e_asinf.c */
2/*
3 * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
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#include "libm.h"
16
17static const double
18pio2 = 1.570796326794896558e+00;
19
20static const float
21/* coefficients for R(x^2) */
22pS0 = 1.6666586697e-01,
23pS1 = -4.2743422091e-02,
24pS2 = -8.6563630030e-03,
25qS1 = -7.0662963390e-01;
26
27static float R(float z)
28{
29 float_t p, q;
30 p = z*(pS0+z*(pS1+z*pS2));
31 q = 1.0f+z*qS1;
32 return p/q;
33}
34
35float asinf(float x)
36{
37 double s;
38 float z;
39 uint32_t hx,ix;
40
41 GET_FLOAT_WORD(hx, x);
42 ix = hx & 0x7fffffff;
43 if (ix >= 0x3f800000) { /* |x| >= 1 */
44 if (ix == 0x3f800000) /* |x| == 1 */
45 return x*pio2 + 0x1p-120f; /* asin(+-1) = +-pi/2 with inexact */
46 return 0/(x-x); /* asin(|x|>1) is NaN */
47 }
48 if (ix < 0x3f000000) { /* |x| < 0.5 */
49 /* if 0x1p-126 <= |x| < 0x1p-12, avoid raising underflow */
50 if (ix < 0x39800000 && ix >= 0x00800000)
51 return x;
52 return x + x*R(x*x);
53 }
54 /* 1 > |x| >= 0.5 */
55 z = (1 - fabsf(x))*0.5f;
56 s = sqrt(z);
57 x = pio2 - 2*(s+s*R(z));
58 if (hx >> 31)
59 return -x;
60 return x;
61}