xref: /minix3/lib/libm/src/s_logbf.c (revision 2fe8fb192fe7e8720e3e7a77f928da545e872a6a)
1*2fe8fb19SBen Gras /* s_logbf.c -- float version of s_logb.c.
2*2fe8fb19SBen Gras  * Conversion to float by Ian Lance Taylor, Cygnus Support, ian@cygnus.com.
3*2fe8fb19SBen Gras  */
4*2fe8fb19SBen Gras 
5*2fe8fb19SBen Gras /*
6*2fe8fb19SBen Gras  * ====================================================
7*2fe8fb19SBen Gras  * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
8*2fe8fb19SBen Gras  *
9*2fe8fb19SBen Gras  * Developed at SunPro, a Sun Microsystems, Inc. business.
10*2fe8fb19SBen Gras  * Permission to use, copy, modify, and distribute this
11*2fe8fb19SBen Gras  * software is freely granted, provided that this notice
12*2fe8fb19SBen Gras  * is preserved.
13*2fe8fb19SBen Gras  * ====================================================
14*2fe8fb19SBen Gras  */
15*2fe8fb19SBen Gras 
16*2fe8fb19SBen Gras #include <sys/cdefs.h>
17*2fe8fb19SBen Gras #if defined(LIBM_SCCS) && !defined(lint)
18*2fe8fb19SBen Gras __RCSID("$NetBSD: s_logbf.c,v 1.7 2002/05/26 22:01:57 wiz Exp $");
19*2fe8fb19SBen Gras #endif
20*2fe8fb19SBen Gras 
21*2fe8fb19SBen Gras #include "math.h"
22*2fe8fb19SBen Gras #include "math_private.h"
23*2fe8fb19SBen Gras 
24*2fe8fb19SBen Gras float
logbf(float x)25*2fe8fb19SBen Gras logbf(float x)
26*2fe8fb19SBen Gras {
27*2fe8fb19SBen Gras 	int32_t ix;
28*2fe8fb19SBen Gras 	GET_FLOAT_WORD(ix,x);
29*2fe8fb19SBen Gras 	ix &= 0x7fffffff;			/* high |x| */
30*2fe8fb19SBen Gras 	if(ix==0) return (float)-1.0/fabsf(x);
31*2fe8fb19SBen Gras 	if(ix>=0x7f800000) return x*x;
32*2fe8fb19SBen Gras 	if((ix>>=23)==0) 			/* IEEE 754 logb */
33*2fe8fb19SBen Gras 		return -126.0;
34*2fe8fb19SBen Gras 	else
35*2fe8fb19SBen Gras 		return (float) (ix-127);
36*2fe8fb19SBen Gras }
37