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Revision 1.13.2.1, Thu May 22 11:36:57 2014 UTC (9 years, 10 months ago) by yamt
Branch: yamt-pagecache
Changes since 1.13: +3 -3 lines

sync with head.

for a reference, the tree before this commit was tagged
as yamt-pagecache-tag8.

this commit was splitted into small chunks to avoid
a limitation of cvs.  ("Protocol error: too many arguments")

/* @(#)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 1.13.2.1 2014/05/22 11:36:57 yamt 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"
#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)
		return FP_ILOGB0;	/* ilogb(0) = 0x80000001 */
	    else			/* subnormal x */
		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;
	}
	else if (hx<0x7ff00000) return (hx>>20)-1023;
	else return FP_ILOGBNAN;	/* inf too */
}