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1/*
2 * ilogb.h
3 * cLibm
4 *
5 * Created by Ian Ollmann on 6/13/07.
6 * Copyright 2007 Apple Inc. All rights reserved.
7 *
8 */
9
10#include <math.h>
11#include <stdint.h>
12#include <limits.h>
13
14#ifdef ARMLIBM_SET_FLAGS
15#include "required_arithmetic.h"
16
17int ilogb( double x )
18{
19 union{ double d; uint64_t u;}u = {x};
20
21 u.u &= 0x7fffffffffffffffULL;
22 int32_t exp = (int32_t) (u.u >> 52);
23
24 if( __builtin_expect( (uint32_t) exp - 1U >= 2046, 0 ) )
25 { // +-0, +-denorm, +-inf, NaN
26 if( 0.0 == x )
27 {
28 required_multiply_double( x, __builtin_inf() ); //set invalid
29 return FP_ILOGB0;
30 }
31
32 if( x != x )
33 {
34 required_multiply_double( 0.0, __builtin_inf() ); //set invalid
35 return FP_ILOGBNAN;
36 }
37
38 if( u.u == 0x7ff0000000000000ULL )
39 {
40 required_multiply_double( 0.0, x ); //set invalid
41 return INT_MAX;
42 }
43
44 u.u |= 0x3ff0000000000000ULL;
45 u.d -= 1.0;
46 exp = (int32_t) (u.u >> 52);
47
48 return exp - (1023+1022);
49 }
50
51 return exp - 1023;
52}
53
54#else
55
56int ilogb( double x )
57{
58 union{ double d; uint64_t u;}u = {x};
59
60 u.u &= 0x7fffffffffffffffULL;
61 int32_t exp = (int32_t) (u.u >> 52);
62
63 if( __builtin_expect( (uint32_t) exp - 1U >= 2046, 0 ) )
64 { // +-0, +-denorm, +-inf, NaN
65 if( 0.0 == x )
66 {
67 return FP_ILOGB0;
68 }
69
70 if( x != x )
71 {
72 return FP_ILOGBNAN;
73 }
74
75 if( u.u == 0x7ff0000000000000ULL )
76 {
77 return INT_MAX;
78 }
79
80 u.u |= 0x3ff0000000000000ULL;
81 u.d -= 1.0;
82 exp = (int32_t) (u.u >> 52);
83
84 return exp - (1023+1022);
85 }
86
87 return exp - 1023;
88}
89
90#endif // ARMLIBM_SET_FLAGS
91