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[glibc/history.git] / sysdeps / ieee754 / ldbl-96 / s_ilogbl.c
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1 /* s_ilogbl.c -- long double version of s_ilogb.c.
2 * Conversion to long double by Ulrich Drepper,
3 * Cygnus Support, drepper@cygnus.com.
4 */
6 /*
7 * ====================================================
8 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
10 * Developed at SunPro, a Sun Microsystems, Inc. business.
11 * Permission to use, copy, modify, and distribute this
12 * software is freely granted, provided that this notice
13 * is preserved.
14 * ====================================================
17 #if defined(LIBM_SCCS) && !defined(lint)
18 static char rcsid[] = "$NetBSD: $";
19 #endif
21 /* ilogbl(long double x)
22 * return the binary exponent of non-zero x
23 * ilogbl(0) = FP_ILOGB0
24 * ilogbl(NaN) = FP_ILOGBNAN (no signal is raised)
25 * ilogbl(+-Inf) = INT_MAX (no signal is raised)
28 #include <limits.h>
29 #include "math.h"
30 #include "math_private.h"
32 #ifdef __STDC__
33 int __ilogbl(long double x)
34 #else
35 int __ilogbl(x)
36 long double x;
37 #endif
39 int32_t es,hx,lx,ix;
41 GET_LDOUBLE_EXP(es,x);
42 es &= 0x7fff;
43 if(es==0) {
44 GET_LDOUBLE_WORDS(es,hx,lx,x);
45 if((hx|lx)==0)
46 return FP_ILOGB0; /* ilogbl(0) = FP_ILOGB0 */
47 else /* subnormal x */
48 if(hx==0) {
49 for (ix = -16415; lx>0; lx<<=1) ix -=1;
50 } else {
51 for (ix = -16383; hx>0; hx<<=1) ix -=1;
53 return ix;
55 else if (es<0x7fff) return es-0x3fff;
56 else if (FP_ILOGBNAN != INT_MAX)
58 GET_LDOUBLE_WORDS(es,hx,lx,x);
59 if (((hx & 0x7fffffff)|lx) == 0)
60 /* ISO C99 requires ilogbl(+-Inf) == INT_MAX. */
61 return INT_MAX;
63 return FP_ILOGBNAN;
65 weak_alias (__ilogbl, ilogbl)