1df930be7Sderaadt /* e_asinf.c -- float version of e_asin.c.
2df930be7Sderaadt * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
3df930be7Sderaadt */
4df930be7Sderaadt
5df930be7Sderaadt /*
6df930be7Sderaadt * ====================================================
7df930be7Sderaadt * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8df930be7Sderaadt *
9df930be7Sderaadt * Developed at SunPro, a Sun Microsystems, Inc. business.
10df930be7Sderaadt * Permission to use, copy, modify, and distribute this
11df930be7Sderaadt * software is freely granted, provided that this notice
12df930be7Sderaadt * is preserved.
13df930be7Sderaadt * ====================================================
14df930be7Sderaadt */
15df930be7Sderaadt
16df930be7Sderaadt #include "math.h"
17df930be7Sderaadt #include "math_private.h"
18df930be7Sderaadt
19df930be7Sderaadt static const float
20df930be7Sderaadt one = 1.0000000000e+00, /* 0x3F800000 */
21df930be7Sderaadt huge = 1.000e+30,
22df930be7Sderaadt pio2_hi = 1.5707962513e+00, /* 0x3fc90fda */
23df930be7Sderaadt pio2_lo = 7.5497894159e-08, /* 0x33a22168 */
24df930be7Sderaadt pio4_hi = 7.8539818525e-01, /* 0x3f490fdb */
25df930be7Sderaadt /* coefficient for R(x^2) */
26df930be7Sderaadt pS0 = 1.6666667163e-01, /* 0x3e2aaaab */
27df930be7Sderaadt pS1 = -3.2556581497e-01, /* 0xbea6b090 */
28df930be7Sderaadt pS2 = 2.0121252537e-01, /* 0x3e4e0aa8 */
29df930be7Sderaadt pS3 = -4.0055535734e-02, /* 0xbd241146 */
30df930be7Sderaadt pS4 = 7.9153501429e-04, /* 0x3a4f7f04 */
31df930be7Sderaadt pS5 = 3.4793309169e-05, /* 0x3811ef08 */
32df930be7Sderaadt qS1 = -2.4033949375e+00, /* 0xc019d139 */
33df930be7Sderaadt qS2 = 2.0209457874e+00, /* 0x4001572d */
34df930be7Sderaadt qS3 = -6.8828397989e-01, /* 0xbf303361 */
35df930be7Sderaadt qS4 = 7.7038154006e-02; /* 0x3d9dc62e */
36df930be7Sderaadt
37e7beb4a7Smillert float
asinf(float x)387b36286aSmartynas asinf(float x)
39df930be7Sderaadt {
40df930be7Sderaadt float t,w,p,q,c,r,s;
41df930be7Sderaadt int32_t hx,ix;
42df930be7Sderaadt GET_FLOAT_WORD(hx,x);
43df930be7Sderaadt ix = hx&0x7fffffff;
44df930be7Sderaadt if(ix==0x3f800000) {
45df930be7Sderaadt /* asin(1)=+-pi/2 with inexact */
46df930be7Sderaadt return x*pio2_hi+x*pio2_lo;
47df930be7Sderaadt } else if(ix> 0x3f800000) { /* |x|>= 1 */
48df930be7Sderaadt return (x-x)/(x-x); /* asin(|x|>1) is NaN */
49df930be7Sderaadt } else if (ix<0x3f000000) { /* |x|<0.5 */
50df930be7Sderaadt if(ix<0x32000000) { /* if |x| < 2**-27 */
51df930be7Sderaadt if(huge+x>one) return x;/* return x with inexact if x!=0*/
52d9116cffSmiod }
53df930be7Sderaadt t = x*x;
54df930be7Sderaadt p = t*(pS0+t*(pS1+t*(pS2+t*(pS3+t*(pS4+t*pS5)))));
55df930be7Sderaadt q = one+t*(qS1+t*(qS2+t*(qS3+t*qS4)));
56df930be7Sderaadt w = p/q;
57df930be7Sderaadt return x+x*w;
58df930be7Sderaadt }
59df930be7Sderaadt /* 1> |x|>= 0.5 */
60df930be7Sderaadt w = one-fabsf(x);
61df930be7Sderaadt t = w*(float)0.5;
62df930be7Sderaadt p = t*(pS0+t*(pS1+t*(pS2+t*(pS3+t*(pS4+t*pS5)))));
63df930be7Sderaadt q = one+t*(qS1+t*(qS2+t*(qS3+t*qS4)));
647b36286aSmartynas s = sqrtf(t);
65df930be7Sderaadt if(ix>=0x3F79999A) { /* if |x| > 0.975 */
66df930be7Sderaadt w = p/q;
67df930be7Sderaadt t = pio2_hi-((float)2.0*(s+s*w)-pio2_lo);
68df930be7Sderaadt } else {
69df930be7Sderaadt int32_t iw;
70df930be7Sderaadt w = s;
71df930be7Sderaadt GET_FLOAT_WORD(iw,w);
72df930be7Sderaadt SET_FLOAT_WORD(w,iw&0xfffff000);
73df930be7Sderaadt c = (t-w*w)/(s+w);
74df930be7Sderaadt r = p/q;
75df930be7Sderaadt p = (float)2.0*s*r-(pio2_lo-(float)2.0*c);
76df930be7Sderaadt q = pio4_hi-(float)2.0*w;
77df930be7Sderaadt t = pio4_hi-(p-q);
78df930be7Sderaadt }
79df930be7Sderaadt if(hx>0) return t; else return -t;
80df930be7Sderaadt }
81*2f2c0062Sguenther DEF_STD(asinf);
82