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/* ef_log10.c -- float version of e_log10.c.
* Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
*/
/*
* ====================================================
* Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
*
* Developed at SunPro, a Sun Microsystems, Inc. business.
* Permission to use, copy, modify, and distribute this
* software is freely granted, provided that this notice
* is preserved.
* ====================================================
*/
#include "fdlibm.h"
#ifdef __STDC__
static const float
#else
static float
#endif
two25 = 3.3554432000e+07, /* 0x4c000000 */
ivln10 = 4.3429449201e-01, /* 0x3ede5bd9 */
log10_2hi = 3.0102920532e-01, /* 0x3e9a2080 */
log10_2lo = 7.9034151668e-07; /* 0x355427db */
#ifdef __STDC__
static const float zero = 0.0;
#else
static float zero = 0.0;
#endif
#ifdef __STDC__
float __ieee754_log10f(float x)
#else
float __ieee754_log10f(x)
float x;
#endif
{
float y,z;
__int32_t i,k,hx;
GET_FLOAT_WORD(hx,x);
k=0;
if (FLT_UWORD_IS_ZERO(hx&0x7fffffff))
return -two25/zero; /* log(+-0)=-inf */
if (hx<0) return (x-x)/zero; /* log(-#) = NaN */
if (!FLT_UWORD_IS_FINITE(hx)) return x+x;
if (FLT_UWORD_IS_SUBNORMAL(hx)) {
k -= 25; x *= two25; /* subnormal number, scale up x */
GET_FLOAT_WORD(hx,x);
}
k += (hx>>23)-127;
i = ((__uint32_t)k&0x80000000)>>31;
hx = (hx&0x007fffff)|((0x7f-i)<<23);
y = (float)(k+i);
SET_FLOAT_WORD(x,hx);
z = y*log10_2lo + ivln10*__ieee754_logf(x);
return z+y*log10_2hi;
}
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