xref: /freebsd/lib/msun/src/s_logbf.c (revision d8a0fe102c0cfdfcd5b818f850eff09d8536c9bc)
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 #include <sys/cdefs.h>
17 __FBSDID("$FreeBSD$");
18 
19 #include "math.h"
20 #include "math_private.h"
21 
22 static const float
23 two25 = 3.355443200e+07;		/* 0x4c000000 */
24 
25 float
26 logbf(float x)
27 {
28 	int32_t ix;
29 	GET_FLOAT_WORD(ix,x);
30 	ix &= 0x7fffffff;			/* high |x| */
31 	if(ix==0) return (float)-1.0/fabsf(x);
32 	if(ix>=0x7f800000) return x*x;
33 	if(ix<0x00800000) {
34 		x *= two25;		 /* convert subnormal x to normal */
35 		GET_FLOAT_WORD(ix,x);
36 		ix &= 0x7fffffff;
37 		return (float) ((ix>>23)-127-25);
38 	} else
39 		return (float) ((ix>>23)-127);
40 }
41