blob: a2ee1a166f03a71c0063dd85bc18994cd6ef332e [file] [log] [blame]
Elliott Hughesa0ee0782013-01-30 19:06:37 -08001/* 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
Elliott Hughesa0ee0782013-01-30 19:06:37 -080016#include "math.h"
17#include "math_private.h"
18
19static const float
20one = 1.0000000000e+00, /* 0x3F800000 */
21huge = 1.000e+30,
22 /* coefficient for R(x^2) */
23pS0 = 1.6666586697e-01,
24pS1 = -4.2743422091e-02,
25pS2 = -8.6563630030e-03,
26qS1 = -7.0662963390e-01;
27
28static const double
29pio2 = 1.570796326794896558e+00;
30
31float
Elliott Hughes4088e3a2023-08-03 13:33:56 -070032asinf(float x)
Elliott Hughesa0ee0782013-01-30 19:06:37 -080033{
34 double s;
35 float t,w,p,q;
36 int32_t hx,ix;
37 GET_FLOAT_WORD(hx,x);
38 ix = hx&0x7fffffff;
39 if(ix>=0x3f800000) { /* |x| >= 1 */
40 if(ix==0x3f800000) /* |x| == 1 */
41 return x*pio2; /* asin(+-1) = +-pi/2 with inexact */
42 return (x-x)/(x-x); /* asin(|x|>1) is NaN */
43 } else if (ix<0x3f000000) { /* |x|<0.5 */
44 if(ix<0x39800000) { /* |x| < 2**-12 */
45 if(huge+x>one) return x;/* return x with inexact if x!=0*/
46 }
47 t = x*x;
48 p = t*(pS0+t*(pS1+t*pS2));
49 q = one+t*qS1;
50 w = p/q;
51 return x+x*w;
52 }
53 /* 1> |x|>= 0.5 */
54 w = one-fabsf(x);
55 t = w*(float)0.5;
56 p = t*(pS0+t*(pS1+t*pS2));
57 q = one+t*qS1;
58 s = sqrt(t);
59 w = p/q;
60 t = pio2-2.0*(s+s*w);
61 if(hx>0) return t; else return -t;
62}