e_asinf.c revision 97407 
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
17static char rcsid[] = "$FreeBSD: head/lib/msun/src/e_asinf.c 97407 2002-05-28 17:03:12Z alfred $";
18#endif
19
20#include "math.h"
21#include "math_private.h"
22
23static const float
24one =  1.0000000000e+00, /* 0x3F800000 */
25huge =  1.000e+30,
26pio2_hi =  1.5707962513e+00, /* 0x3fc90fda */
27pio2_lo =  7.5497894159e-08, /* 0x33a22168 */
28pio4_hi =  7.8539818525e-01, /* 0x3f490fdb */
29	/* coefficient for R(x^2) */
30pS0 =  1.6666667163e-01, /* 0x3e2aaaab */
31pS1 = -3.2556581497e-01, /* 0xbea6b090 */
32pS2 =  2.0121252537e-01, /* 0x3e4e0aa8 */
33pS3 = -4.0055535734e-02, /* 0xbd241146 */
34pS4 =  7.9153501429e-04, /* 0x3a4f7f04 */
35pS5 =  3.4793309169e-05, /* 0x3811ef08 */
36qS1 = -2.4033949375e+00, /* 0xc019d139 */
37qS2 =  2.0209457874e+00, /* 0x4001572d */
38qS3 = -6.8828397989e-01, /* 0xbf303361 */
39qS4 =  7.7038154006e-02; /* 0x3d9dc62e */
40
41float
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}
85