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e_asinf.c (2516B)
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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 #ifndef lint
17 static char rcsid[] = "$FreeBSD: src/lib/msun/src/e_asinf.c,v 1.8 2002/05/28 17:03:12 alfred Exp $";
18 #endif
19
20 #include "math.h"
21 #include "math_private.h"
22
23 static const float
24 one = 1.0000000000e+00, /* 0x3F800000 */
25 huge = 1.000e+30,
26 pio2_hi = 1.5707962513e+00, /* 0x3fc90fda */
27 pio2_lo = 7.5497894159e-08, /* 0x33a22168 */
28 pio4_hi = 7.8539818525e-01, /* 0x3f490fdb */
29 /* coefficient for R(x^2) */
30 pS0 = 1.6666667163e-01, /* 0x3e2aaaab */
31 pS1 = -3.2556581497e-01, /* 0xbea6b090 */
32 pS2 = 2.0121252537e-01, /* 0x3e4e0aa8 */
33 pS3 = -4.0055535734e-02, /* 0xbd241146 */
34 pS4 = 7.9153501429e-04, /* 0x3a4f7f04 */
35 pS5 = 3.4793309169e-05, /* 0x3811ef08 */
36 qS1 = -2.4033949375e+00, /* 0xc019d139 */
37 qS2 = 2.0209457874e+00, /* 0x4001572d */
38 qS3 = -6.8828397989e-01, /* 0xbf303361 */
39 qS4 = 7.7038154006e-02; /* 0x3d9dc62e */
40
41 float
42 __ieee754_asinf(float x)
43 {
44 float t=0.0,w,p,q,c,r,s;
45 int32_t hx,ix;
46 GET_FLOAT_WORD(hx,x);
47 ix = hx&0x7fffffff;
48 if(ix==0x3f800000) {
49 /* asin(1)=+-pi/2 with inexact */
50 return x*pio2_hi+x*pio2_lo;
51 } else if(ix> 0x3f800000) { /* |x|>= 1 */
52 return (x-x)/(x-x); /* asin(|x|>1) is NaN */
53 } else if (ix<0x3f000000) { /* |x|<0.5 */
54 if(ix<0x32000000) { /* if |x| < 2**-27 */
55 if(huge+x>one) return x;/* return x with inexact if x!=0*/
56 } else
57 t = x*x;
58 p = t*(pS0+t*(pS1+t*(pS2+t*(pS3+t*(pS4+t*pS5)))));
59 q = one+t*(qS1+t*(qS2+t*(qS3+t*qS4)));
60 w = p/q;
61 return x+x*w;
62 }
63 /* 1> |x|>= 0.5 */
64 w = one-fabsf(x);
65 t = w*(float)0.5;
66 p = t*(pS0+t*(pS1+t*(pS2+t*(pS3+t*(pS4+t*pS5)))));
67 q = one+t*(qS1+t*(qS2+t*(qS3+t*qS4)));
68 s = __ieee754_sqrtf(t);
69 if(ix>=0x3F79999A) { /* if |x| > 0.975 */
70 w = p/q;
71 t = pio2_hi-((float)2.0*(s+s*w)-pio2_lo);
72 } else {
73 int32_t iw;
74 w = s;
75 GET_FLOAT_WORD(iw,w);
76 SET_FLOAT_WORD(w,iw&0xfffff000);
77 c = (t-w*w)/(s+w);
78 r = p/q;
79 p = (float)2.0*s*r-(pio2_lo-(float)2.0*c);
80 q = pio4_hi-(float)2.0*w;
81 t = pio4_hi-(p-q);
82 }
83 if(hx>0) return t; else return -t;
84 }