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[/] [or1k/] [trunk/] [newlib-1.10.0/] [newlib/] [libm/] [math/] [ef_asin.c] - Blame information for rev 1780

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1 1010 ivang 
/* 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 = 1.57079637050628662109375f,
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pio2_lo = -4.37113900018624283e-8f,
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pio4_hi = 0.785398185253143310546875f,
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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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        }
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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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