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 | |
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 | |