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[/] [openrisc/] [trunk/] [gnu-src/] [newlib-1.17.0/] [newlib/] [libm/] [math/] [ef_acos.c] - Blame information for rev 148

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1 148 jeremybenn 
/* 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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