mirror of
https://github.com/autc04/Retro68.git
synced 2024-12-01 11:52:47 +00:00
63 lines
1.6 KiB
C
63 lines
1.6 KiB
C
|
/* 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;
|
||
|
|
}
|