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/* @(#)s_logb.c 5.1 93/09/24 */
/*
* ====================================================
* 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.
* ====================================================
*/
/*
* double logb(x)
* IEEE 754 logb. Included to pass IEEE test suite. Not recommend.
* Use ilogb instead.
*/
#include <math.h>
#include <math_private.h>
#include <libm-alias-double.h>
#include <fix-int-fp-convert-zero.h>
double
__logb (double x)
{
int32_t lx, ix, rix;
EXTRACT_WORDS (ix, lx, x);
ix &= 0x7fffffff; /* high |x| */
if ((ix | lx) == 0)
return -1.0 / fabs (x);
if (ix >= 0x7ff00000)
return x * x;
if (__glibc_unlikely ((rix = ix >> 20) == 0))
{
/* POSIX specifies that denormal number is treated as
though it were normalized. */
int ma;
if (ix == 0)
ma = __builtin_clz (lx) + 32;
else
ma = __builtin_clz (ix);
rix -= ma - 12;
}
if (FIX_INT_FP_CONVERT_ZERO && rix == 1023)
return 0.0;
return (double) (rix - 1023);
}
#ifndef __logb
libm_alias_double (__logb, logb)
#endif
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