mirror of
https://sourceware.org/git/glibc.git
synced 2024-11-30 00:31:08 +00:00
50 lines
1.2 KiB
C
50 lines
1.2 KiB
C
/* @(#)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>
|
|
|
|
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 (__builtin_expect ((rix = ix >> 20) == 0, 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;
|
|
}
|
|
return (double) (rix - 1023);
|
|
}
|
|
weak_alias (__logb, logb)
|
|
#ifdef NO_LONG_DOUBLE
|
|
strong_alias (__logb, __logbl) weak_alias (__logb, logbl)
|
|
#endif
|