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lampret |
/* ef_acos.c -- float version of e_acos.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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pi = 3.1415925026e+00, /* 0x40490fda */
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pio2_hi = 1.5707962513e+00, /* 0x3fc90fda */
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pio2_lo = 7.5497894159e-08, /* 0x33a22168 */
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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_acosf(float x)
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#else
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float __ieee754_acosf(x)
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float x;
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#endif
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{
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float z,p,q,r,w,s,c,df;
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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) { /* |x|==1 */
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if(hx>0) return 0.0; /* acos(1) = 0 */
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else return pi+(float)2.0*pio2_lo; /* acos(-1)= pi */
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} else if(ix>0x3f800000) { /* |x| >= 1 */
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return (x-x)/(x-x); /* acos(|x|>1) is NaN */
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}
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if(ix<0x3f000000) { /* |x| < 0.5 */
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if(ix<=0x23000000) return pio2_hi+pio2_lo;/*if|x|<2**-57*/
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z = x*x;
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p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
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q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
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r = p/q;
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return pio2_hi - (x - (pio2_lo-x*r));
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} else if (hx<0) { /* x < -0.5 */
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z = (one+x)*(float)0.5;
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p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
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q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
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s = __ieee754_sqrtf(z);
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r = p/q;
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w = r*s-pio2_lo;
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return pi - (float)2.0*(s+w);
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} else { /* x > 0.5 */
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__int32_t idf;
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z = (one-x)*(float)0.5;
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s = __ieee754_sqrtf(z);
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df = s;
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GET_FLOAT_WORD(idf,df);
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SET_FLOAT_WORD(df,idf&0xfffff000);
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c = (z-df*df)/(s+df);
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p = z*(pS0+z*(pS1+z*(pS2+z*(pS3+z*(pS4+z*pS5)))));
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q = one+z*(qS1+z*(qS2+z*(qS3+z*qS4)));
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r = p/q;
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w = r*s+c;
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return (float)2.0*(df+w);
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}
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}
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