1 /* @(#)s_ilogb.c 5.1 93/09/24 */
3 * ====================================================
4 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
6 * Developed at SunPro, a Sun Microsystems, Inc. business.
7 * Permission to use, copy, modify, and distribute this
8 * software is freely granted, provided that this notice
10 * ====================================================
12 * $NetBSD: s_ilogb.c,v 1.12 2002/05/26 22:01:56 wiz Exp $
13 * $DragonFly: src/lib/libm/src/s_ilogb.c,v 1.1 2005/07/26 21:15:20 joerg Exp $
17 * return the binary exponent of non-zero x
18 * ilogb(0) = 0x80000001
19 * ilogb(inf/NaN) = 0x7fffffff (no signal is raised)
23 #include "math_private.h"
35 return 0x80000001; /* ilogb(0) = 0x80000001 */
36 else /* subnormal x */
38 for (ix = -1043; lx>0; lx<<=1) ix -=1;
40 for (ix = -1022,hx<<=11; hx>0; hx<<=1) ix -=1;
44 else if (hx<0x7ff00000) return (hx>>20)-1023;
45 else return 0x7fffffff;