1 /* s_ilogbl.c -- long double version of s_ilogb.c.
2 */
3
4 /*
5 * ====================================================
6 * Copyright (C) 1993 by Sun Microsystems, Inc. All rights reserved.
7 *
8 * Developed at SunPro, a Sun Microsystems, Inc. business.
9 * Permission to use, copy, modify, and distribute this
10 * software is freely granted, provided that this notice
11 * is preserved.
12 * ====================================================
13 */
14
15 #if defined(LIBM_SCCS) && !defined(lint)
16 static char rcsid[] = "$NetBSD: $";
17 #endif
18
19 /* ilogbl(long double x)
20 * return the binary exponent of non-zero x
21 * ilogbl(0) = FP_ILOGB0
22 * ilogbl(NaN) = FP_ILOGBNAN (no signal is raised)
23 * ilogbl(+-Inf) = INT_MAX (no signal is raised)
24 */
25
26 #include <limits.h>
27 #include <math.h>
28 #include <math_private.h>
29
__ieee754_ilogbl(_Float128 x)30 int __ieee754_ilogbl (_Float128 x)
31 {
32 int64_t hx,lx;
33 int ix;
34
35 GET_LDOUBLE_WORDS64(hx,lx,x);
36 hx &= 0x7fffffffffffffffLL;
37 if(hx <= 0x0001000000000000LL) {
38 if((hx|lx)==0)
39 return FP_ILOGB0; /* ilogbl(0) = FP_ILOGB0 */
40 else /* subnormal x */
41 if(hx==0) {
42 for (ix = -16431; lx>0; lx<<=1) ix -=1;
43 } else {
44 for (ix = -16382, hx<<=15; hx>0; hx<<=1) ix -=1;
45 }
46 return ix;
47 }
48 else if (hx<0x7fff000000000000LL) return (hx>>48)-0x3fff;
49 else if (FP_ILOGBNAN != INT_MAX) {
50 /* ISO C99 requires ilogbl(+-Inf) == INT_MAX. */
51 if (((hx^0x7fff000000000000LL)|lx) == 0)
52 return INT_MAX;
53 }
54 return FP_ILOGBNAN;
55 }
56