xref: /minix3/lib/libm/src/s_ilogbf.c (revision 84d9c625bfea59e274550651111ae9edfdc40fbd)
1 /* s_ilogbf.c -- float version of s_ilogb.c.
2  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
3  */
4 
5 /*
6  * ====================================================
7  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8  *
9  * Developed at SunPro, a Sun Microsystems, Inc. business.
10  * Permission to use, copy, modify, and distribute this
11  * software is freely granted, provided that this notice
12  * is preserved.
13  * ====================================================
14  */
15 
16 #include <sys/cdefs.h>
17 #if defined(LIBM_SCCS) && !defined(lint)
18 __RCSID("$NetBSD: s_ilogbf.c,v 1.8 2013/02/09 22:56:00 matt Exp $");
19 #endif
20 
21 #include "math.h"
22 #include "math_private.h"
23 
24 int
ilogbf(float x)25 ilogbf(float x)
26 {
27 	int32_t hx,ix;
28 
29 	GET_FLOAT_WORD(hx,x);
30 	hx &= 0x7fffffff;
31 	if(hx<0x00800000) {
32 	    if(hx==0)
33 		return FP_ILOGB0;	/* ilogb(0) = 0x80000001 */
34 	    else			/* subnormal x */
35 	        for (ix = -126,hx<<=8; hx>0; hx<<=1) ix -=1;
36 	    return ix;
37 	}
38 	else if (hx<0x7f800000) return (hx>>23)-127;
39 	else return FP_ILOGBNAN;	/* inf too */
40 }
41