12fe8fb19SBen Gras /* @(#)s_ilogb.c 5.1 93/09/24 */
22fe8fb19SBen Gras /*
32fe8fb19SBen Gras * ====================================================
42fe8fb19SBen Gras * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
52fe8fb19SBen Gras *
62fe8fb19SBen Gras * Developed at SunPro, a Sun Microsystems, Inc. business.
72fe8fb19SBen Gras * Permission to use, copy, modify, and distribute this
82fe8fb19SBen Gras * software is freely granted, provided that this notice
92fe8fb19SBen Gras * is preserved.
102fe8fb19SBen Gras * ====================================================
112fe8fb19SBen Gras */
122fe8fb19SBen Gras
132fe8fb19SBen Gras #include <sys/cdefs.h>
142fe8fb19SBen Gras #if defined(LIBM_SCCS) && !defined(lint)
15*84d9c625SLionel Sambuc __RCSID("$NetBSD: s_ilogb.c,v 1.14 2013/02/09 22:56:00 matt Exp $");
162fe8fb19SBen Gras #endif
172fe8fb19SBen Gras
182fe8fb19SBen Gras /* ilogb(double x)
192fe8fb19SBen Gras * return the binary exponent of non-zero x
202fe8fb19SBen Gras * ilogb(0) = 0x80000001
212fe8fb19SBen Gras * ilogb(inf/NaN) = 0x7fffffff (no signal is raised)
222fe8fb19SBen Gras */
232fe8fb19SBen Gras
242fe8fb19SBen Gras #include "math.h"
252fe8fb19SBen Gras #include "math_private.h"
262fe8fb19SBen Gras
27*84d9c625SLionel Sambuc #ifndef __HAVE_LONG_DOUBLE
__strong_alias(ilogbl,ilogb)28*84d9c625SLionel Sambuc __strong_alias(ilogbl,ilogb)
29*84d9c625SLionel Sambuc #endif
30*84d9c625SLionel Sambuc
312fe8fb19SBen Gras int
322fe8fb19SBen Gras ilogb(double x)
332fe8fb19SBen Gras {
342fe8fb19SBen Gras int32_t hx,lx,ix;
352fe8fb19SBen Gras
362fe8fb19SBen Gras GET_HIGH_WORD(hx,x);
372fe8fb19SBen Gras hx &= 0x7fffffff;
382fe8fb19SBen Gras if(hx<0x00100000) {
392fe8fb19SBen Gras GET_LOW_WORD(lx,x);
402fe8fb19SBen Gras if((hx|lx)==0)
41*84d9c625SLionel Sambuc return FP_ILOGB0; /* ilogb(0) = 0x80000001 */
422fe8fb19SBen Gras else /* subnormal x */
432fe8fb19SBen Gras if(hx==0) {
442fe8fb19SBen Gras for (ix = -1043; lx>0; lx<<=1) ix -=1;
452fe8fb19SBen Gras } else {
462fe8fb19SBen Gras for (ix = -1022,hx<<=11; hx>0; hx<<=1) ix -=1;
472fe8fb19SBen Gras }
482fe8fb19SBen Gras return ix;
492fe8fb19SBen Gras }
502fe8fb19SBen Gras else if (hx<0x7ff00000) return (hx>>20)-1023;
51*84d9c625SLionel Sambuc else return FP_ILOGBNAN; /* inf too */
522fe8fb19SBen Gras }
53