1 /* SPDX-License-Identifier: MIT */
2 /*
3 * Helper functions for manipulation & testing of integer values
4 * like zero or sign-extensions.
5 *
6 * Copyright (C) 2017 Luc Van Oostenryck
7 *
8 */
9
10 #ifndef BITS_H
11 #define BITS_H
12
sign_bit(unsigned size)13 static inline unsigned long long sign_bit(unsigned size)
14 {
15 return 1ULL << (size - 1);
16 }
17
sign_mask(unsigned size)18 static inline unsigned long long sign_mask(unsigned size)
19 {
20 unsigned long long sbit = sign_bit(size);
21 return sbit - 1;
22 }
23
bits_mask(unsigned size)24 static inline unsigned long long bits_mask(unsigned size)
25 {
26 unsigned long long sbit = sign_bit(size);
27 return sbit | (sbit - 1);
28 }
29
30
zero_extend(long long val,unsigned size)31 static inline long long zero_extend(long long val, unsigned size)
32 {
33 return val & bits_mask(size);
34 }
35
sign_extend(long long val,unsigned size)36 static inline long long sign_extend(long long val, unsigned size)
37 {
38 if (val & sign_bit(size))
39 val |= ~sign_mask(size);
40 return val;
41 }
42
43 ///
44 // sign extend @val but only if exactly representable
sign_extend_safe(long long val,unsigned size)45 static inline long long sign_extend_safe(long long val, unsigned size)
46 {
47 unsigned long long mask = bits_mask(size);
48 if (!(val & ~mask))
49 val = sign_extend(val, size);
50 return val;
51 }
52
bits_extend(long long val,unsigned size,int is_signed)53 static inline long long bits_extend(long long val, unsigned size, int is_signed)
54 {
55 val = zero_extend(val, size);
56 if (is_signed)
57 val = sign_extend(val, size);
58 return val;
59 }
60
is_power_of_2(long long val)61 static inline int is_power_of_2(long long val)
62 {
63 return val && !(val & (val - 1));
64 }
65
66 ///
67 // log base 2 of an exact power-of-2
log2_exact(unsigned long long val)68 static inline int log2_exact(unsigned long long val)
69 {
70 return 8 * sizeof(val) - __builtin_clzl(val) - 1;
71 }
72
73 #endif
74