| 1 | /* e_asinf.c -- float version of e_asin.c.
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| 2 | * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
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| 3 | */
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| 4 |
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| 5 | /*
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| 6 | * ====================================================
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| 7 | * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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| 8 | *
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| 9 | * Developed at SunPro, a Sun Microsystems, Inc. business.
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| 10 | * Permission to use, copy, modify, and distribute this
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| 11 | * software is freely granted, provided that this notice
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| 12 | * is preserved.
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| 13 | * ====================================================
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| 14 | */
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| 15 |
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| 16 | #ifndef lint
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| 17 | static char rcsid[] = "$FreeBSD: src/lib/msun/src/e_asinf.c,v 1.8 2002/05/28 17:03:12 alfred Exp $";
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| 18 | #endif
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| 19 |
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| 20 | #include "math.h"
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| 21 | #include "math_private.h"
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| 22 |
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| 23 | static const float
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| 24 | one = 1.0000000000e+00, /* 0x3F800000 */
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| 25 | huge = 1.000e+30,
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| 26 | pio2_hi = 1.5707962513e+00, /* 0x3fc90fda */
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| 27 | pio2_lo = 7.5497894159e-08, /* 0x33a22168 */
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| 28 | pio4_hi = 7.8539818525e-01, /* 0x3f490fdb */
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| 29 | /* coefficient for R(x^2) */
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| 30 | pS0 = 1.6666667163e-01, /* 0x3e2aaaab */
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| 31 | pS1 = -3.2556581497e-01, /* 0xbea6b090 */
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| 32 | pS2 = 2.0121252537e-01, /* 0x3e4e0aa8 */
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| 33 | pS3 = -4.0055535734e-02, /* 0xbd241146 */
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| 34 | pS4 = 7.9153501429e-04, /* 0x3a4f7f04 */
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| 35 | pS5 = 3.4793309169e-05, /* 0x3811ef08 */
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| 36 | qS1 = -2.4033949375e+00, /* 0xc019d139 */
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| 37 | qS2 = 2.0209457874e+00, /* 0x4001572d */
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| 38 | qS3 = -6.8828397989e-01, /* 0xbf303361 */
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| 39 | qS4 = 7.7038154006e-02; /* 0x3d9dc62e */
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| 40 |
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| 41 | float
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| 42 | __ieee754_asinf(float x)
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| 43 | {
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| 44 | float t=0.0,w,p,q,c,r,s;
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| 45 | int32_t hx,ix;
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| 46 | GET_FLOAT_WORD(hx,x);
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| 47 | ix = hx&0x7fffffff;
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| 48 | if(ix==0x3f800000) {
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| 49 | /* asin(1)=+-pi/2 with inexact */
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| 50 | return x*pio2_hi+x*pio2_lo;
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| 51 | } else if(ix> 0x3f800000) { /* |x|>= 1 */
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| 52 | return (x-x)/(x-x); /* asin(|x|>1) is NaN */
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| 53 | } else if (ix<0x3f000000) { /* |x|<0.5 */
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| 54 | if(ix<0x32000000) { /* if |x| < 2**-27 */
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| 55 | if(huge+x>one) return x;/* return x with inexact if x!=0*/
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| 56 | } else
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| 57 | t = x*x;
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| 58 | p = t*(pS0+t*(pS1+t*(pS2+t*(pS3+t*(pS4+t*pS5)))));
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| 59 | q = one+t*(qS1+t*(qS2+t*(qS3+t*qS4)));
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| 60 | w = p/q;
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| 61 | return x+x*w;
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| 62 | }
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| 63 | /* 1> |x|>= 0.5 */
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| 64 | w = one-fabsf(x);
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| 65 | t = w*(float)0.5;
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| 66 | p = t*(pS0+t*(pS1+t*(pS2+t*(pS3+t*(pS4+t*pS5)))));
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| 67 | q = one+t*(qS1+t*(qS2+t*(qS3+t*qS4)));
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| 68 | s = __ieee754_sqrtf(t);
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| 69 | if(ix>=0x3F79999A) { /* if |x| > 0.975 */
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| 70 | w = p/q;
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| 71 | t = pio2_hi-((float)2.0*(s+s*w)-pio2_lo);
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| 72 | } else {
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| 73 | int32_t iw;
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| 74 | w = s;
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| 75 | GET_FLOAT_WORD(iw,w);
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| 76 | SET_FLOAT_WORD(w,iw&0xfffff000);
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| 77 | c = (t-w*w)/(s+w);
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| 78 | r = p/q;
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| 79 | p = (float)2.0*s*r-(pio2_lo-(float)2.0*c);
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| 80 | q = pio4_hi-(float)2.0*w;
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| 81 | t = pio4_hi-(p-q);
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| 82 | }
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| 83 | if(hx>0) return t; else return -t;
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| 84 | }
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