xref: /minix3/lib/libm/src/e_asinf.c (revision 2fe8fb192fe7e8720e3e7a77f928da545e872a6a)
1*2fe8fb19SBen Gras /* e_asinf.c -- float version of e_asin.c.
2*2fe8fb19SBen Gras  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
3*2fe8fb19SBen Gras  */
4*2fe8fb19SBen Gras 
5*2fe8fb19SBen Gras /*
6*2fe8fb19SBen Gras  * ====================================================
7*2fe8fb19SBen Gras  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8*2fe8fb19SBen Gras  *
9*2fe8fb19SBen Gras  * Developed at SunPro, a Sun Microsystems, Inc. business.
10*2fe8fb19SBen Gras  * Permission to use, copy, modify, and distribute this
11*2fe8fb19SBen Gras  * software is freely granted, provided that this notice
12*2fe8fb19SBen Gras  * is preserved.
13*2fe8fb19SBen Gras  * ====================================================
14*2fe8fb19SBen Gras  */
15*2fe8fb19SBen Gras 
16*2fe8fb19SBen Gras #include <sys/cdefs.h>
17*2fe8fb19SBen Gras #if defined(LIBM_SCCS) && !defined(lint)
18*2fe8fb19SBen Gras __RCSID("$NetBSD: e_asinf.c,v 1.8 2002/05/26 22:01:48 wiz Exp $");
19*2fe8fb19SBen Gras #endif
20*2fe8fb19SBen Gras 
21*2fe8fb19SBen Gras #include "math.h"
22*2fe8fb19SBen Gras #include "math_private.h"
23*2fe8fb19SBen Gras 
24*2fe8fb19SBen Gras static const float
25*2fe8fb19SBen Gras one =  1.0000000000e+00, /* 0x3F800000 */
26*2fe8fb19SBen Gras huge =  1.000e+30,
27*2fe8fb19SBen Gras pio2_hi =  1.5707962513e+00, /* 0x3fc90fda */
28*2fe8fb19SBen Gras pio2_lo =  7.5497894159e-08, /* 0x33a22168 */
29*2fe8fb19SBen Gras pio4_hi =  7.8539818525e-01, /* 0x3f490fdb */
30*2fe8fb19SBen Gras 	/* coefficient for R(x^2) */
31*2fe8fb19SBen Gras pS0 =  1.6666667163e-01, /* 0x3e2aaaab */
32*2fe8fb19SBen Gras pS1 = -3.2556581497e-01, /* 0xbea6b090 */
33*2fe8fb19SBen Gras pS2 =  2.0121252537e-01, /* 0x3e4e0aa8 */
34*2fe8fb19SBen Gras pS3 = -4.0055535734e-02, /* 0xbd241146 */
35*2fe8fb19SBen Gras pS4 =  7.9153501429e-04, /* 0x3a4f7f04 */
36*2fe8fb19SBen Gras pS5 =  3.4793309169e-05, /* 0x3811ef08 */
37*2fe8fb19SBen Gras qS1 = -2.4033949375e+00, /* 0xc019d139 */
38*2fe8fb19SBen Gras qS2 =  2.0209457874e+00, /* 0x4001572d */
39*2fe8fb19SBen Gras qS3 = -6.8828397989e-01, /* 0xbf303361 */
40*2fe8fb19SBen Gras qS4 =  7.7038154006e-02; /* 0x3d9dc62e */
41*2fe8fb19SBen Gras 
42*2fe8fb19SBen Gras float
__ieee754_asinf(float x)43*2fe8fb19SBen Gras __ieee754_asinf(float x)
44*2fe8fb19SBen Gras {
45*2fe8fb19SBen Gras 	float t,w,p,q,c,r,s;
46*2fe8fb19SBen Gras 	int32_t hx,ix;
47*2fe8fb19SBen Gras 
48*2fe8fb19SBen Gras 	t = 0;
49*2fe8fb19SBen Gras 	GET_FLOAT_WORD(hx,x);
50*2fe8fb19SBen Gras 	ix = hx&0x7fffffff;
51*2fe8fb19SBen Gras 	if(ix==0x3f800000) {
52*2fe8fb19SBen Gras 		/* asin(1)=+-pi/2 with inexact */
53*2fe8fb19SBen Gras 	    return x*pio2_hi+x*pio2_lo;
54*2fe8fb19SBen Gras 	} else if(ix> 0x3f800000) {	/* |x|>= 1 */
55*2fe8fb19SBen Gras 	    return (x-x)/(x-x);		/* asin(|x|>1) is NaN */
56*2fe8fb19SBen Gras 	} else if (ix<0x3f000000) {	/* |x|<0.5 */
57*2fe8fb19SBen Gras 	    if(ix<0x32000000) {		/* if |x| < 2**-27 */
58*2fe8fb19SBen Gras 		if(huge+x>one) return x;/* return x with inexact if x!=0*/
59*2fe8fb19SBen Gras 	    } else
60*2fe8fb19SBen Gras 		t = x*x;
61*2fe8fb19SBen Gras 		p = t*(pS0+t*(pS1+t*(pS2+t*(pS3+t*(pS4+t*pS5)))));
62*2fe8fb19SBen Gras 		q = one+t*(qS1+t*(qS2+t*(qS3+t*qS4)));
63*2fe8fb19SBen Gras 		w = p/q;
64*2fe8fb19SBen Gras 		return x+x*w;
65*2fe8fb19SBen Gras 	}
66*2fe8fb19SBen Gras 	/* 1> |x|>= 0.5 */
67*2fe8fb19SBen Gras 	w = one-fabsf(x);
68*2fe8fb19SBen Gras 	t = w*(float)0.5;
69*2fe8fb19SBen Gras 	p = t*(pS0+t*(pS1+t*(pS2+t*(pS3+t*(pS4+t*pS5)))));
70*2fe8fb19SBen Gras 	q = one+t*(qS1+t*(qS2+t*(qS3+t*qS4)));
71*2fe8fb19SBen Gras 	s = __ieee754_sqrtf(t);
72*2fe8fb19SBen Gras 	if(ix>=0x3F79999A) { 	/* if |x| > 0.975 */
73*2fe8fb19SBen Gras 	    w = p/q;
74*2fe8fb19SBen Gras 	    t = pio2_hi-((float)2.0*(s+s*w)-pio2_lo);
75*2fe8fb19SBen Gras 	} else {
76*2fe8fb19SBen Gras 	    int32_t iw;
77*2fe8fb19SBen Gras 	    w  = s;
78*2fe8fb19SBen Gras 	    GET_FLOAT_WORD(iw,w);
79*2fe8fb19SBen Gras 	    SET_FLOAT_WORD(w,iw&0xfffff000);
80*2fe8fb19SBen Gras 	    c  = (t-w*w)/(s+w);
81*2fe8fb19SBen Gras 	    r  = p/q;
82*2fe8fb19SBen Gras 	    p  = (float)2.0*s*r-(pio2_lo-(float)2.0*c);
83*2fe8fb19SBen Gras 	    q  = pio4_hi-(float)2.0*w;
84*2fe8fb19SBen Gras 	    t  = pio4_hi-(p-q);
85*2fe8fb19SBen Gras 	}
86*2fe8fb19SBen Gras 	if(hx>0) return t; else return -t;
87*2fe8fb19SBen Gras }
88