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 #include <math_ldbl_opt.h>
30
__ieee754_ilogbl(long double x)31 int __ieee754_ilogbl(long double x)
32 {
33 int64_t hx, hxs;
34 int ix;
35 double xhi, xlo;
36
37 ldbl_unpack (x, &xhi, &xlo);
38 EXTRACT_WORDS64 (hx, xhi);
39 hxs = hx;
40 hx &= 0x7fffffffffffffffLL;
41 if(hx <= 0x0010000000000000LL) {
42 if(hx==0)
43 return FP_ILOGB0; /* ilogbl(0) = FP_ILOGB0 */
44 else /* subnormal x */
45 for (ix = -1022, hx<<=11; hx>0; hx<<=1) ix -=1;
46 return ix;
47 }
48 else if (hx < 0x7ff0000000000000LL)
49 {
50 int hexp = (hx >> 52) - 0x3ff;
51 /* If the high part is a power of 2, and the low part is
52 nonzero with the opposite sign, the low part affects
53 the exponent. */
54 if ((hx & 0x000fffffffffffffLL) == 0)
55 {
56 int64_t lx;
57 EXTRACT_WORDS64 (lx, xlo);
58 if ((hxs ^ lx) < 0 && (lx & 0x7fffffffffffffffLL) != 0)
59 hexp--;
60 }
61 return hexp;
62 }
63 else if (FP_ILOGBNAN != INT_MAX) {
64 /* ISO C99 requires ilogbl(+-Inf) == INT_MAX. */
65 if (hx==0x7ff0000000000000LL)
66 return INT_MAX;
67 }
68 return FP_ILOGBNAN;
69 }
70