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/* @(#)s_ilogb.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.
* ====================================================
*/
#include <sys/cdefs.h>
#if defined(LIBM_SCCS) && !defined(lint)
__RCSID("$NetBSD: s_ilogb.c,v 1.16 2016/08/26 08:20:31 christos Exp $");
#endif
/* ilogb(double x)
* return the binary exponent of non-zero x
* ilogb(0) = 0x80000001
* ilogb(inf/NaN) = 0x7fffffff (no signal is raised)
*/
#include <math.h>
#define __TEST_FENV
#include <fenv.h>
#ifndef __HAVE_FENV
#define feraiseexcept(a)
#endif
#include "math_private.h"
#ifndef __HAVE_LONG_DOUBLE
__strong_alias(ilogbl,ilogb)
#endif
int
ilogb(double x)
{
int32_t hx, lx, ix;
GET_HIGH_WORD(hx, x);
hx &= 0x7fffffff;
if (hx < 0x00100000) {
GET_LOW_WORD(lx, x);
if ((hx | lx) == 0) {
feraiseexcept(FE_INVALID);
return FP_ILOGB0; /* ilogb(0) = 0x80000001 */
}
if (hx == 0) {
for (ix = -1043; lx > 0; lx <<= 1) ix -= 1;
} else {
for (ix = -1022, hx <<= 11; hx > 0; hx <<= 1) ix -= 1;
}
return ix;
}
if (hx < 0x7ff00000) {
return (hx >> 20) - 1023;
}
feraiseexcept(FE_INVALID);
return isnan(x) ? FP_ILOGBNAN : INT_MAX;
}
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