POK
e_asinf.c
1 /*
2  * POK header
3  *
4  * The following file is a part of the POK project. Any modification should
5  * made according to the POK licence. You CANNOT use this file or a part of
6  * this file is this part of a file for your own project
7  *
8  * For more information on the POK licence, please see our LICENCE FILE
9  *
10  * Please follow the coding guidelines described in doc/CODING_GUIDELINES
11  *
12  * Copyright (c) 2007-2009 POK team
13  *
14  * Created by julien on Fri Jan 30 14:41:34 2009
15  */
16 
17 /* e_asinf.c -- float version of e_asin.c.
18  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
19  */
20 
21 /*
22  * ====================================================
23  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
24  *
25  * Developed at SunPro, a Sun Microsystems, Inc. business.
26  * Permission to use, copy, modify, and distribute this
27  * software is freely granted, provided that this notice
28  * is preserved.
29  * ====================================================
30  */
31 
32 #ifdef POK_NEEDS_LIBMATH
33 #include <libm.h>
34 #include "math_private.h"
35 
36 static const float
37 one = 1.0000000000e+00, /* 0x3F800000 */
38 huge = 1.000e+30,
39 pio2_hi = 1.5707962513e+00, /* 0x3fc90fda */
40 pio2_lo = 7.5497894159e-08, /* 0x33a22168 */
41 pio4_hi = 7.8539818525e-01, /* 0x3f490fdb */
42  /* coefficient for R(x^2) */
43 pS0 = 1.6666667163e-01, /* 0x3e2aaaab */
44 pS1 = -3.2556581497e-01, /* 0xbea6b090 */
45 pS2 = 2.0121252537e-01, /* 0x3e4e0aa8 */
46 pS3 = -4.0055535734e-02, /* 0xbd241146 */
47 pS4 = 7.9153501429e-04, /* 0x3a4f7f04 */
48 pS5 = 3.4793309169e-05, /* 0x3811ef08 */
49 qS1 = -2.4033949375e+00, /* 0xc019d139 */
50 qS2 = 2.0209457874e+00, /* 0x4001572d */
51 qS3 = -6.8828397989e-01, /* 0xbf303361 */
52 qS4 = 7.7038154006e-02; /* 0x3d9dc62e */
53 
54 float
55 __ieee754_asinf(float x)
56 {
57  float t,w,p,q,c,r,s;
58  int32_t hx,ix;
59 
60  t = 0;
61  GET_FLOAT_WORD(hx,x);
62  ix = hx&0x7fffffff;
63  if(ix==0x3f800000) {
64  /* asin(1)=+-pi/2 with inexact */
65  return x*pio2_hi+x*pio2_lo;
66  } else if(ix> 0x3f800000) { /* |x|>= 1 */
67  return (x-x)/(x-x); /* asin(|x|>1) is NaN */
68  } else if (ix<0x3f000000) { /* |x|<0.5 */
69  if(ix<0x32000000) { /* if |x| < 2**-27 */
70  if(huge+x>one) return x;/* return x with inexact if x!=0*/
71  } else
72  t = x*x;
73  p = t*(pS0+t*(pS1+t*(pS2+t*(pS3+t*(pS4+t*pS5)))));
74  q = one+t*(qS1+t*(qS2+t*(qS3+t*qS4)));
75  w = p/q;
76  return x+x*w;
77  }
78  /* 1> |x|>= 0.5 */
79  w = one-fabsf(x);
80  t = w*(float)0.5;
81  p = t*(pS0+t*(pS1+t*(pS2+t*(pS3+t*(pS4+t*pS5)))));
82  q = one+t*(qS1+t*(qS2+t*(qS3+t*qS4)));
83  s = __ieee754_sqrtf(t);
84  if(ix>=0x3F79999A) { /* if |x| > 0.975 */
85  w = p/q;
86  t = pio2_hi-((float)2.0*(s+s*w)-pio2_lo);
87  } else {
88  int32_t iw;
89  w = s;
90  GET_FLOAT_WORD(iw,w);
91  SET_FLOAT_WORD(w,iw&0xfffff000);
92  c = (t-w*w)/(s+w);
93  r = p/q;
94  p = (float)2.0*s*r-(pio2_lo-(float)2.0*c);
95  q = pio4_hi-(float)2.0*w;
96  t = pio4_hi-(p-q);
97  }
98  if(hx>0) return t; else return -t;
99 }
100 #endif