1 /*- 2 * Copyright (c) 2010 Isilon Systems, Inc. 3 * Copyright (c) 2010 iX Systems, Inc. 4 * Copyright (c) 2010 Panasas, Inc. 5 * Copyright (c) 2013, 2014 Mellanox Technologies, Ltd. 6 * All rights reserved. 7 * 8 * Redistribution and use in source and binary forms, with or without 9 * modification, are permitted provided that the following conditions 10 * are met: 11 * 1. Redistributions of source code must retain the above copyright 12 * notice unmodified, this list of conditions, and the following 13 * disclaimer. 14 * 2. Redistributions in binary form must reproduce the above copyright 15 * notice, this list of conditions and the following disclaimer in the 16 * documentation and/or other materials provided with the distribution. 17 * 18 * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 19 * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 20 * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 21 * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 22 * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 23 * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 24 * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 25 * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 26 * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 27 * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 28 */ 29 30 #ifndef _LINUX_LOG2_H_ 31 #define _LINUX_LOG2_H_ 32 33 #include <linux/types.h> 34 35 #include <sys/libkern.h> 36 37 static inline unsigned long 38 roundup_pow_of_two(unsigned long x) 39 { 40 return (1UL << flsl(x - 1)); 41 } 42 43 static inline int 44 is_power_of_2(unsigned long n) 45 { 46 return (n == roundup_pow_of_two(n)); 47 } 48 49 static inline unsigned long 50 rounddown_pow_of_two(unsigned long x) 51 { 52 return (1UL << (flsl(x) - 1)); 53 } 54 55 56 /* 57 * deal with unrepresentable constant logarithms 58 */ 59 extern __attribute__((const, noreturn)) 60 int ____ilog2_NaN(void); 61 62 /* 63 * non-constant log of base 2 calculators 64 * - the arch may override these in asm/bitops.h if they can be implemented 65 * more efficiently than using fls() and fls64() 66 * - the arch is not required to handle n==0 if implementing the fallback 67 */ 68 #ifndef CONFIG_ARCH_HAS_ILOG2_U32 69 static inline __attribute__((const)) 70 int __ilog2_u32(u32 n) 71 { 72 return flsl(n) - 1; 73 } 74 #endif 75 76 #ifndef CONFIG_ARCH_HAS_ILOG2_U64 77 static inline __attribute__((const)) 78 int __ilog2_u64(u64 n) 79 { 80 return flsl(n) - 1; 81 } 82 #endif 83 84 85 /** 86 * ilog2 - log of base 2 of 32-bit or a 64-bit unsigned value 87 * @n - parameter 88 * 89 * constant-capable log of base 2 calculation 90 * - this can be used to initialise global variables from constant data, hence 91 * the massive ternary operator construction 92 * 93 * selects the appropriately-sized optimised version depending on sizeof(n) 94 */ 95 #define ilog2(n) \ 96 ( \ 97 __builtin_constant_p(n) ? ( \ 98 (n) < 1 ? ____ilog2_NaN() : \ 99 (n) & (1ULL << 63) ? 63 : \ 100 (n) & (1ULL << 62) ? 62 : \ 101 (n) & (1ULL << 61) ? 61 : \ 102 (n) & (1ULL << 60) ? 60 : \ 103 (n) & (1ULL << 59) ? 59 : \ 104 (n) & (1ULL << 58) ? 58 : \ 105 (n) & (1ULL << 57) ? 57 : \ 106 (n) & (1ULL << 56) ? 56 : \ 107 (n) & (1ULL << 55) ? 55 : \ 108 (n) & (1ULL << 54) ? 54 : \ 109 (n) & (1ULL << 53) ? 53 : \ 110 (n) & (1ULL << 52) ? 52 : \ 111 (n) & (1ULL << 51) ? 51 : \ 112 (n) & (1ULL << 50) ? 50 : \ 113 (n) & (1ULL << 49) ? 49 : \ 114 (n) & (1ULL << 48) ? 48 : \ 115 (n) & (1ULL << 47) ? 47 : \ 116 (n) & (1ULL << 46) ? 46 : \ 117 (n) & (1ULL << 45) ? 45 : \ 118 (n) & (1ULL << 44) ? 44 : \ 119 (n) & (1ULL << 43) ? 43 : \ 120 (n) & (1ULL << 42) ? 42 : \ 121 (n) & (1ULL << 41) ? 41 : \ 122 (n) & (1ULL << 40) ? 40 : \ 123 (n) & (1ULL << 39) ? 39 : \ 124 (n) & (1ULL << 38) ? 38 : \ 125 (n) & (1ULL << 37) ? 37 : \ 126 (n) & (1ULL << 36) ? 36 : \ 127 (n) & (1ULL << 35) ? 35 : \ 128 (n) & (1ULL << 34) ? 34 : \ 129 (n) & (1ULL << 33) ? 33 : \ 130 (n) & (1ULL << 32) ? 32 : \ 131 (n) & (1ULL << 31) ? 31 : \ 132 (n) & (1ULL << 30) ? 30 : \ 133 (n) & (1ULL << 29) ? 29 : \ 134 (n) & (1ULL << 28) ? 28 : \ 135 (n) & (1ULL << 27) ? 27 : \ 136 (n) & (1ULL << 26) ? 26 : \ 137 (n) & (1ULL << 25) ? 25 : \ 138 (n) & (1ULL << 24) ? 24 : \ 139 (n) & (1ULL << 23) ? 23 : \ 140 (n) & (1ULL << 22) ? 22 : \ 141 (n) & (1ULL << 21) ? 21 : \ 142 (n) & (1ULL << 20) ? 20 : \ 143 (n) & (1ULL << 19) ? 19 : \ 144 (n) & (1ULL << 18) ? 18 : \ 145 (n) & (1ULL << 17) ? 17 : \ 146 (n) & (1ULL << 16) ? 16 : \ 147 (n) & (1ULL << 15) ? 15 : \ 148 (n) & (1ULL << 14) ? 14 : \ 149 (n) & (1ULL << 13) ? 13 : \ 150 (n) & (1ULL << 12) ? 12 : \ 151 (n) & (1ULL << 11) ? 11 : \ 152 (n) & (1ULL << 10) ? 10 : \ 153 (n) & (1ULL << 9) ? 9 : \ 154 (n) & (1ULL << 8) ? 8 : \ 155 (n) & (1ULL << 7) ? 7 : \ 156 (n) & (1ULL << 6) ? 6 : \ 157 (n) & (1ULL << 5) ? 5 : \ 158 (n) & (1ULL << 4) ? 4 : \ 159 (n) & (1ULL << 3) ? 3 : \ 160 (n) & (1ULL << 2) ? 2 : \ 161 (n) & (1ULL << 1) ? 1 : \ 162 (n) & (1ULL << 0) ? 0 : \ 163 ____ilog2_NaN() \ 164 ) : \ 165 (sizeof(n) <= 4) ? \ 166 __ilog2_u32(n) : \ 167 __ilog2_u64(n) \ 168 ) 169 170 #endif /* _LINUX_LOG2_H_ */ 171