63 lines
1.6 KiB
C
63 lines
1.6 KiB
C
/* s_logbl.c -- long double version of s_logb.c.
|
|
*/
|
|
|
|
/*
|
|
* ====================================================
|
|
* 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.
|
|
* ====================================================
|
|
*/
|
|
|
|
/*
|
|
* long double logbl(x)
|
|
* IEEE 754 logb. Included to pass IEEE test suite. Not recommend.
|
|
* Use ilogb instead.
|
|
*/
|
|
|
|
#include <math.h>
|
|
#include <math_private.h>
|
|
#include <math_ldbl_opt.h>
|
|
#include <fix-int-fp-convert-zero.h>
|
|
|
|
long double
|
|
__logbl (long double x)
|
|
{
|
|
int64_t hx, hxs, rhx;
|
|
double xhi, xlo;
|
|
|
|
ldbl_unpack (x, &xhi, &xlo);
|
|
EXTRACT_WORDS64 (hx, xhi);
|
|
hxs = hx;
|
|
hx &= 0x7fffffffffffffffLL; /* high |x| */
|
|
if (hx == 0)
|
|
return -1.0 / fabs (x);
|
|
if (hx >= 0x7ff0000000000000LL)
|
|
return x * x;
|
|
if (__glibc_unlikely ((rhx = hx >> 52) == 0))
|
|
{
|
|
/* POSIX specifies that denormal number is treated as
|
|
though it were normalized. */
|
|
rhx -= __builtin_clzll (hx) - 12;
|
|
}
|
|
else if ((hx & 0x000fffffffffffffLL) == 0)
|
|
{
|
|
/* If the high part is a power of 2, and the low part is nonzero
|
|
with the opposite sign, the low part affects the
|
|
exponent. */
|
|
int64_t lx;
|
|
EXTRACT_WORDS64 (lx, xlo);
|
|
if ((hxs ^ lx) < 0 && (lx & 0x7fffffffffffffffLL) != 0)
|
|
rhx--;
|
|
}
|
|
if (FIX_INT_FP_CONVERT_ZERO && rhx == 1023)
|
|
return 0.0L;
|
|
return (long double) (rhx - 1023);
|
|
}
|
|
#ifndef __logbl
|
|
long_double_symbol (libm, __logbl, logbl);
|
|
#endif
|