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log2.h (219820) log2.h (255932)
1/*-
2 * Copyright (c) 2010 Isilon Systems, Inc.
3 * Copyright (c) 2010 iX Systems, Inc.
4 * Copyright (c) 2010 Panasas, Inc.
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions

--- 37 unchanged lines hidden (view full) ---

46}
47
48static inline unsigned long
49rounddown_pow_of_two(unsigned long x)
50{
51 return (1UL << (flsl(x) - 1));
52}
53
1/*-
2 * Copyright (c) 2010 Isilon Systems, Inc.
3 * Copyright (c) 2010 iX Systems, Inc.
4 * Copyright (c) 2010 Panasas, Inc.
5 * All rights reserved.
6 *
7 * Redistribution and use in source and binary forms, with or without
8 * modification, are permitted provided that the following conditions

--- 37 unchanged lines hidden (view full) ---

46}
47
48static inline unsigned long
49rounddown_pow_of_two(unsigned long x)
50{
51 return (1UL << (flsl(x) - 1));
52}
53
54static inline unsigned long
55ilog2(unsigned long x)
54
55/*
56 * deal with unrepresentable constant logarithms
57 */
58extern __attribute__((const, noreturn))
59int ____ilog2_NaN(void);
60
61/*
62 * non-constant log of base 2 calculators
63 * - the arch may override these in asm/bitops.h if they can be implemented
64 * more efficiently than using fls() and fls64()
65 * - the arch is not required to handle n==0 if implementing the fallback
66 */
67#ifndef CONFIG_ARCH_HAS_ILOG2_U32
68static inline __attribute__((const))
69int __ilog2_u32(u32 n)
56{
70{
57 return (flsl(x) - 1);
71 return flsl(n) - 1;
58}
72}
73#endif
59
74
75#ifndef CONFIG_ARCH_HAS_ILOG2_U64
76static inline __attribute__((const))
77int __ilog2_u64(u64 n)
78{
79 return flsl(n) - 1;
80}
81#endif
82
83
84/**
85 * ilog2 - log of base 2 of 32-bit or a 64-bit unsigned value
86 * @n - parameter
87 *
88 * constant-capable log of base 2 calculation
89 * - this can be used to initialise global variables from constant data, hence
90 * the massive ternary operator construction
91 *
92 * selects the appropriately-sized optimised version depending on sizeof(n)
93 */
94#define ilog2(n) \
95( \
96 __builtin_constant_p(n) ? ( \
97 (n) < 1 ? ____ilog2_NaN() : \
98 (n) & (1ULL << 63) ? 63 : \
99 (n) & (1ULL << 62) ? 62 : \
100 (n) & (1ULL << 61) ? 61 : \
101 (n) & (1ULL << 60) ? 60 : \
102 (n) & (1ULL << 59) ? 59 : \
103 (n) & (1ULL << 58) ? 58 : \
104 (n) & (1ULL << 57) ? 57 : \
105 (n) & (1ULL << 56) ? 56 : \
106 (n) & (1ULL << 55) ? 55 : \
107 (n) & (1ULL << 54) ? 54 : \
108 (n) & (1ULL << 53) ? 53 : \
109 (n) & (1ULL << 52) ? 52 : \
110 (n) & (1ULL << 51) ? 51 : \
111 (n) & (1ULL << 50) ? 50 : \
112 (n) & (1ULL << 49) ? 49 : \
113 (n) & (1ULL << 48) ? 48 : \
114 (n) & (1ULL << 47) ? 47 : \
115 (n) & (1ULL << 46) ? 46 : \
116 (n) & (1ULL << 45) ? 45 : \
117 (n) & (1ULL << 44) ? 44 : \
118 (n) & (1ULL << 43) ? 43 : \
119 (n) & (1ULL << 42) ? 42 : \
120 (n) & (1ULL << 41) ? 41 : \
121 (n) & (1ULL << 40) ? 40 : \
122 (n) & (1ULL << 39) ? 39 : \
123 (n) & (1ULL << 38) ? 38 : \
124 (n) & (1ULL << 37) ? 37 : \
125 (n) & (1ULL << 36) ? 36 : \
126 (n) & (1ULL << 35) ? 35 : \
127 (n) & (1ULL << 34) ? 34 : \
128 (n) & (1ULL << 33) ? 33 : \
129 (n) & (1ULL << 32) ? 32 : \
130 (n) & (1ULL << 31) ? 31 : \
131 (n) & (1ULL << 30) ? 30 : \
132 (n) & (1ULL << 29) ? 29 : \
133 (n) & (1ULL << 28) ? 28 : \
134 (n) & (1ULL << 27) ? 27 : \
135 (n) & (1ULL << 26) ? 26 : \
136 (n) & (1ULL << 25) ? 25 : \
137 (n) & (1ULL << 24) ? 24 : \
138 (n) & (1ULL << 23) ? 23 : \
139 (n) & (1ULL << 22) ? 22 : \
140 (n) & (1ULL << 21) ? 21 : \
141 (n) & (1ULL << 20) ? 20 : \
142 (n) & (1ULL << 19) ? 19 : \
143 (n) & (1ULL << 18) ? 18 : \
144 (n) & (1ULL << 17) ? 17 : \
145 (n) & (1ULL << 16) ? 16 : \
146 (n) & (1ULL << 15) ? 15 : \
147 (n) & (1ULL << 14) ? 14 : \
148 (n) & (1ULL << 13) ? 13 : \
149 (n) & (1ULL << 12) ? 12 : \
150 (n) & (1ULL << 11) ? 11 : \
151 (n) & (1ULL << 10) ? 10 : \
152 (n) & (1ULL << 9) ? 9 : \
153 (n) & (1ULL << 8) ? 8 : \
154 (n) & (1ULL << 7) ? 7 : \
155 (n) & (1ULL << 6) ? 6 : \
156 (n) & (1ULL << 5) ? 5 : \
157 (n) & (1ULL << 4) ? 4 : \
158 (n) & (1ULL << 3) ? 3 : \
159 (n) & (1ULL << 2) ? 2 : \
160 (n) & (1ULL << 1) ? 1 : \
161 (n) & (1ULL << 0) ? 0 : \
162 ____ilog2_NaN() \
163 ) : \
164 (sizeof(n) <= 4) ? \
165 __ilog2_u32(n) : \
166 __ilog2_u64(n) \
167 )
168
60#endif /* _LINUX_LOG2_H_ */
169#endif /* _LINUX_LOG2_H_ */