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[/] [openrisc/] [trunk/] [gnu-stable/] [newlib-1.18.0/] [newlib/] [libm/] [math/] [ef_log10.c] - Rev 829
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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; }