xref: /freebsd/lib/msun/src/s_logbf.c (revision 1e413cf93298b5b97441a21d9a50fdcd0ee9945e)
1 /* s_logbf.c -- float version of s_logb.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 #ifndef lint
17 static char rcsid[] = "$FreeBSD$";
18 #endif
19 
20 #include "math.h"
21 #include "math_private.h"
22 
23 static const float
24 two25 = 3.355443200e+07;		/* 0x4c000000 */
25 
26 float
27 logbf(float x)
28 {
29 	int32_t ix;
30 	GET_FLOAT_WORD(ix,x);
31 	ix &= 0x7fffffff;			/* high |x| */
32 	if(ix==0) return (float)-1.0/fabsf(x);
33 	if(ix>=0x7f800000) return x*x;
34 	if(ix<0x00800000) {
35 		x *= two25;		 /* convert subnormal x to normal */
36 		GET_FLOAT_WORD(ix,x);
37 		ix &= 0x7fffffff;
38 		return (float) ((ix>>23)-127-25);
39 	} else
40 		return (float) ((ix>>23)-127);
41 }
42