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lampret |
/* ef_asin.c -- float version of e_asin.c.
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* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
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*/
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/*
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* ====================================================
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* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
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*
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* Developed at SunPro, a Sun Microsystems, Inc. business.
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* Permission to use, copy, modify, and distribute this
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* software is freely granted, provided that this notice
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* is preserved.
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* ====================================================
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*/
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#include "fdlibm.h"
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#ifdef __STDC__
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static const float
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#else
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static float
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#endif
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one = 1.0000000000e+00, /* 0x3F800000 */
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huge = 1.000e+30,
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pio2_hi = 1.5707962513e+00, /* 0x3fc90fda */
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pio2_lo = 7.5497894159e-08, /* 0x33a22168 */
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pio4_hi = 7.8539818525e-01, /* 0x3f490fdb */
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/* coefficient for R(x^2) */
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pS0 = 1.6666667163e-01, /* 0x3e2aaaab */
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pS1 = -3.2556581497e-01, /* 0xbea6b090 */
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pS2 = 2.0121252537e-01, /* 0x3e4e0aa8 */
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pS3 = -4.0055535734e-02, /* 0xbd241146 */
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pS4 = 7.9153501429e-04, /* 0x3a4f7f04 */
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pS5 = 3.4793309169e-05, /* 0x3811ef08 */
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qS1 = -2.4033949375e+00, /* 0xc019d139 */
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qS2 = 2.0209457874e+00, /* 0x4001572d */
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qS3 = -6.8828397989e-01, /* 0xbf303361 */
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qS4 = 7.7038154006e-02; /* 0x3d9dc62e */
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#ifdef __STDC__
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float __ieee754_asinf(float x)
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#else
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float __ieee754_asinf(x)
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float x;
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#endif
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{
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float t,w,p,q,c,r,s;
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__int32_t hx,ix;
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GET_FLOAT_WORD(hx,x);
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ix = hx&0x7fffffff;
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if(ix==0x3f800000) {
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/* asin(1)=+-pi/2 with inexact */
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return x*pio2_hi+x*pio2_lo;
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} else if(ix> 0x3f800000) { /* |x|>= 1 */
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return (x-x)/(x-x); /* asin(|x|>1) is NaN */
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} else if (ix<0x3f000000) { /* |x|<0.5 */
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if(ix<0x32000000) { /* if |x| < 2**-27 */
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if(huge+x>one) return x;/* return x with inexact if x!=0*/
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} else
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t = x*x;
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p = t*(pS0+t*(pS1+t*(pS2+t*(pS3+t*(pS4+t*pS5)))));
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q = one+t*(qS1+t*(qS2+t*(qS3+t*qS4)));
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w = p/q;
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return x+x*w;
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}
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/* 1> |x|>= 0.5 */
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w = one-fabsf(x);
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t = w*(float)0.5;
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p = t*(pS0+t*(pS1+t*(pS2+t*(pS3+t*(pS4+t*pS5)))));
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q = one+t*(qS1+t*(qS2+t*(qS3+t*qS4)));
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s = __ieee754_sqrtf(t);
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if(ix>=0x3F79999A) { /* if |x| > 0.975 */
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w = p/q;
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t = pio2_hi-((float)2.0*(s+s*w)-pio2_lo);
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} else {
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__int32_t iw;
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w = s;
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GET_FLOAT_WORD(iw,w);
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SET_FLOAT_WORD(w,iw&0xfffff000);
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c = (t-w*w)/(s+w);
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r = p/q;
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p = (float)2.0*s*r-(pio2_lo-(float)2.0*c);
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q = pio4_hi-(float)2.0*w;
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t = pio4_hi-(p-q);
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}
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if(hx>0) return t; else return -t;
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}
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