1/*
2 * ====================================================
3 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
4 *
5 * Developed at SunPro, a Sun Microsystems, Inc. business.
6 * Permission to use, copy, modify, and distribute this
7 * software is freely granted, provided that this notice
8 * is preserved.
9 * ====================================================
10 */
11
12/* ilogb(double x)
13 * return the binary exponent of non-zero x
14 * ilogb(0) = FP_ILOGB0
15 * ilogb(NaN) = FP_ILOGBNAN (no signal is raised)
16 * ilogb(inf) = INT_MAX (no signal is raised)
17 */
18
19#include <limits.h>
20
21#include "math.h"
22#include "math_private.h"
23
24	int ilogb(double x)
25{
26	int32_t hx,lx,ix;
27
28	EXTRACT_WORDS(hx,lx,x);
29	hx &= 0x7fffffff;
30	if(hx<0x00100000) {
31	    if((hx|lx)==0)
32		return FP_ILOGB0;
33	    else			/* subnormal x */
34		if(hx==0) {
35		    for (ix = -1043; lx>0; lx<<=1) ix -=1;
36		} else {
37		    for (ix = -1022,hx<<=11; hx>0; hx<<=1) ix -=1;
38		}
39	    return ix;
40	}
41	else if (hx<0x7ff00000) return (hx>>20)-1023;
42	else if (hx>0x7ff00000 || lx!=0) return FP_ILOGBNAN;
43	else return INT_MAX;
44}
45