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[/] [or1k/] [trunk/] [newlib-1.10.0/] [newlib/] [libm/] [math/] [ef_log10.c] - Blame information for rev 1773

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Line No. Rev Author Line
1 1010 ivang
/* ef_log10.c -- float version of e_log10.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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two25      =  3.3554432000e+07, /* 0x4c000000 */
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ivln10     =  4.3429449201e-01, /* 0x3ede5bd9 */
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log10_2hi  =  3.0102920532e-01, /* 0x3e9a2080 */
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log10_2lo  =  7.9034151668e-07; /* 0x355427db */
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#ifdef __STDC__
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static const float zero   =  0.0;
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#else
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static float zero   =  0.0;
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#endif
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#ifdef __STDC__
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        float __ieee754_log10f(float x)
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#else
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        float __ieee754_log10f(x)
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        float x;
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#endif
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{
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        float y,z;
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        __int32_t i,k,hx;
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        GET_FLOAT_WORD(hx,x);
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        k=0;
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        if (FLT_UWORD_IS_ZERO(hx&0x7fffffff))
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            return -two25/zero;             /* log(+-0)=-inf */
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        if (hx<0) return (x-x)/zero;        /* log(-#) = NaN */
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        if (!FLT_UWORD_IS_FINITE(hx)) return x+x;
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        if (FLT_UWORD_IS_SUBNORMAL(hx)) {
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            k -= 25; x *= two25; /* subnormal number, scale up x */
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            GET_FLOAT_WORD(hx,x);
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        }
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        k += (hx>>23)-127;
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        i  = ((__uint32_t)k&0x80000000)>>31;
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        hx = (hx&0x007fffff)|((0x7f-i)<<23);
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        y  = (float)(k+i);
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        SET_FLOAT_WORD(x,hx);
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        z  = y*log10_2lo + ivln10*__ieee754_logf(x);
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        return  z+y*log10_2hi;
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}

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