12874c5fdSThomas Gleixner /* SPDX-License-Identifier: GPL-2.0-or-later */ 2f0d1b0b3SDavid Howells /* Integer base 2 logarithm calculation 3f0d1b0b3SDavid Howells * 4f0d1b0b3SDavid Howells * Copyright (C) 2006 Red Hat, Inc. All Rights Reserved. 5f0d1b0b3SDavid Howells * Written by David Howells (dhowells@redhat.com) 6f0d1b0b3SDavid Howells */ 7f0d1b0b3SDavid Howells 8f0d1b0b3SDavid Howells #ifndef _LINUX_LOG2_H 9f0d1b0b3SDavid Howells #define _LINUX_LOG2_H 10f0d1b0b3SDavid Howells 11f0d1b0b3SDavid Howells #include <linux/types.h> 12f0d1b0b3SDavid Howells #include <linux/bitops.h> 13f0d1b0b3SDavid Howells 14f0d1b0b3SDavid Howells /* 15f0d1b0b3SDavid Howells * non-constant log of base 2 calculators 16f0d1b0b3SDavid Howells * - the arch may override these in asm/bitops.h if they can be implemented 17f0d1b0b3SDavid Howells * more efficiently than using fls() and fls64() 18f0d1b0b3SDavid Howells * - the arch is not required to handle n==0 if implementing the fallback 19f0d1b0b3SDavid Howells */ 20f0d1b0b3SDavid Howells #ifndef CONFIG_ARCH_HAS_ILOG2_U32 21*f334f566SChristophe Leroy static __always_inline __attribute__((const)) __ilog2_u32(u32 n)22f0d1b0b3SDavid Howellsint __ilog2_u32(u32 n) 23f0d1b0b3SDavid Howells { 24f0d1b0b3SDavid Howells return fls(n) - 1; 25f0d1b0b3SDavid Howells } 26f0d1b0b3SDavid Howells #endif 27f0d1b0b3SDavid Howells 28f0d1b0b3SDavid Howells #ifndef CONFIG_ARCH_HAS_ILOG2_U64 29*f334f566SChristophe Leroy static __always_inline __attribute__((const)) __ilog2_u64(u64 n)30f0d1b0b3SDavid Howellsint __ilog2_u64(u64 n) 31f0d1b0b3SDavid Howells { 32f0d1b0b3SDavid Howells return fls64(n) - 1; 33f0d1b0b3SDavid Howells } 34f0d1b0b3SDavid Howells #endif 35f0d1b0b3SDavid Howells 36a1c4d24eSRandy Dunlap /** 37a1c4d24eSRandy Dunlap * is_power_of_2() - check if a value is a power of two 38a1c4d24eSRandy Dunlap * @n: the value to check 39a1c4d24eSRandy Dunlap * 4063c2f782SRobert P. J. Day * Determine whether some value is a power of two, where zero is 4163c2f782SRobert P. J. Day * *not* considered a power of two. 42a1c4d24eSRandy Dunlap * Return: true if @n is a power of 2, otherwise false. 4363c2f782SRobert P. J. Day */ 4463c2f782SRobert P. J. Day static inline __attribute__((const)) is_power_of_2(unsigned long n)4563c2f782SRobert P. J. Daybool is_power_of_2(unsigned long n) 4663c2f782SRobert P. J. Day { 4763c2f782SRobert P. J. Day return (n != 0 && ((n & (n - 1)) == 0)); 4863c2f782SRobert P. J. Day } 4963c2f782SRobert P. J. Day 50a1c4d24eSRandy Dunlap /** 51a1c4d24eSRandy Dunlap * __roundup_pow_of_two() - round up to nearest power of two 52a1c4d24eSRandy Dunlap * @n: value to round up 53312a0c17SDavid Howells */ 54312a0c17SDavid Howells static inline __attribute__((const)) __roundup_pow_of_two(unsigned long n)55312a0c17SDavid Howellsunsigned long __roundup_pow_of_two(unsigned long n) 56312a0c17SDavid Howells { 57312a0c17SDavid Howells return 1UL << fls_long(n - 1); 58312a0c17SDavid Howells } 59312a0c17SDavid Howells 60a1c4d24eSRandy Dunlap /** 61a1c4d24eSRandy Dunlap * __rounddown_pow_of_two() - round down to nearest power of two 62a1c4d24eSRandy Dunlap * @n: value to round down 63b311e921SRobert P. J. Day */ 64b311e921SRobert P. J. Day static inline __attribute__((const)) __rounddown_pow_of_two(unsigned long n)65b311e921SRobert P. J. Dayunsigned long __rounddown_pow_of_two(unsigned long n) 66b311e921SRobert P. J. Day { 67b311e921SRobert P. J. Day return 1UL << (fls_long(n) - 1); 68b311e921SRobert P. J. Day } 69b311e921SRobert P. J. Day 70f0d1b0b3SDavid Howells /** 71dbef91ecSMartin Wilck * const_ilog2 - log base 2 of 32-bit or a 64-bit constant unsigned value 72a1c4d24eSRandy Dunlap * @n: parameter 73f0d1b0b3SDavid Howells * 74dbef91ecSMartin Wilck * Use this where sparse expects a true constant expression, e.g. for array 75dbef91ecSMartin Wilck * indices. 76f0d1b0b3SDavid Howells */ 77dbef91ecSMartin Wilck #define const_ilog2(n) \ 78f0d1b0b3SDavid Howells ( \ 79f0d1b0b3SDavid Howells __builtin_constant_p(n) ? ( \ 80474c9015SLinus Torvalds (n) < 2 ? 0 : \ 81f0d1b0b3SDavid Howells (n) & (1ULL << 63) ? 63 : \ 82f0d1b0b3SDavid Howells (n) & (1ULL << 62) ? 62 : \ 83f0d1b0b3SDavid Howells (n) & (1ULL << 61) ? 61 : \ 84f0d1b0b3SDavid Howells (n) & (1ULL << 60) ? 60 : \ 85f0d1b0b3SDavid Howells (n) & (1ULL << 59) ? 59 : \ 86f0d1b0b3SDavid Howells (n) & (1ULL << 58) ? 58 : \ 87f0d1b0b3SDavid Howells (n) & (1ULL << 57) ? 57 : \ 88f0d1b0b3SDavid Howells (n) & (1ULL << 56) ? 56 : \ 89f0d1b0b3SDavid Howells (n) & (1ULL << 55) ? 55 : \ 90f0d1b0b3SDavid Howells (n) & (1ULL << 54) ? 54 : \ 91f0d1b0b3SDavid Howells (n) & (1ULL << 53) ? 53 : \ 92f0d1b0b3SDavid Howells (n) & (1ULL << 52) ? 52 : \ 93f0d1b0b3SDavid Howells (n) & (1ULL << 51) ? 51 : \ 94f0d1b0b3SDavid Howells (n) & (1ULL << 50) ? 50 : \ 95f0d1b0b3SDavid Howells (n) & (1ULL << 49) ? 49 : \ 96f0d1b0b3SDavid Howells (n) & (1ULL << 48) ? 48 : \ 97f0d1b0b3SDavid Howells (n) & (1ULL << 47) ? 47 : \ 98f0d1b0b3SDavid Howells (n) & (1ULL << 46) ? 46 : \ 99f0d1b0b3SDavid Howells (n) & (1ULL << 45) ? 45 : \ 100f0d1b0b3SDavid Howells (n) & (1ULL << 44) ? 44 : \ 101f0d1b0b3SDavid Howells (n) & (1ULL << 43) ? 43 : \ 102f0d1b0b3SDavid Howells (n) & (1ULL << 42) ? 42 : \ 103f0d1b0b3SDavid Howells (n) & (1ULL << 41) ? 41 : \ 104f0d1b0b3SDavid Howells (n) & (1ULL << 40) ? 40 : \ 105f0d1b0b3SDavid Howells (n) & (1ULL << 39) ? 39 : \ 106f0d1b0b3SDavid Howells (n) & (1ULL << 38) ? 38 : \ 107f0d1b0b3SDavid Howells (n) & (1ULL << 37) ? 37 : \ 108f0d1b0b3SDavid Howells (n) & (1ULL << 36) ? 36 : \ 109f0d1b0b3SDavid Howells (n) & (1ULL << 35) ? 35 : \ 110f0d1b0b3SDavid Howells (n) & (1ULL << 34) ? 34 : \ 111f0d1b0b3SDavid Howells (n) & (1ULL << 33) ? 33 : \ 112f0d1b0b3SDavid Howells (n) & (1ULL << 32) ? 32 : \ 113f0d1b0b3SDavid Howells (n) & (1ULL << 31) ? 31 : \ 114f0d1b0b3SDavid Howells (n) & (1ULL << 30) ? 30 : \ 115f0d1b0b3SDavid Howells (n) & (1ULL << 29) ? 29 : \ 116f0d1b0b3SDavid Howells (n) & (1ULL << 28) ? 28 : \ 117f0d1b0b3SDavid Howells (n) & (1ULL << 27) ? 27 : \ 118f0d1b0b3SDavid Howells (n) & (1ULL << 26) ? 26 : \ 119f0d1b0b3SDavid Howells (n) & (1ULL << 25) ? 25 : \ 120f0d1b0b3SDavid Howells (n) & (1ULL << 24) ? 24 : \ 121f0d1b0b3SDavid Howells (n) & (1ULL << 23) ? 23 : \ 122f0d1b0b3SDavid Howells (n) & (1ULL << 22) ? 22 : \ 123f0d1b0b3SDavid Howells (n) & (1ULL << 21) ? 21 : \ 124f0d1b0b3SDavid Howells (n) & (1ULL << 20) ? 20 : \ 125f0d1b0b3SDavid Howells (n) & (1ULL << 19) ? 19 : \ 126f0d1b0b3SDavid Howells (n) & (1ULL << 18) ? 18 : \ 127f0d1b0b3SDavid Howells (n) & (1ULL << 17) ? 17 : \ 128f0d1b0b3SDavid Howells (n) & (1ULL << 16) ? 16 : \ 129f0d1b0b3SDavid Howells (n) & (1ULL << 15) ? 15 : \ 130f0d1b0b3SDavid Howells (n) & (1ULL << 14) ? 14 : \ 131f0d1b0b3SDavid Howells (n) & (1ULL << 13) ? 13 : \ 132f0d1b0b3SDavid Howells (n) & (1ULL << 12) ? 12 : \ 133f0d1b0b3SDavid Howells (n) & (1ULL << 11) ? 11 : \ 134f0d1b0b3SDavid Howells (n) & (1ULL << 10) ? 10 : \ 135f0d1b0b3SDavid Howells (n) & (1ULL << 9) ? 9 : \ 136f0d1b0b3SDavid Howells (n) & (1ULL << 8) ? 8 : \ 137f0d1b0b3SDavid Howells (n) & (1ULL << 7) ? 7 : \ 138f0d1b0b3SDavid Howells (n) & (1ULL << 6) ? 6 : \ 139f0d1b0b3SDavid Howells (n) & (1ULL << 5) ? 5 : \ 140f0d1b0b3SDavid Howells (n) & (1ULL << 4) ? 4 : \ 141f0d1b0b3SDavid Howells (n) & (1ULL << 3) ? 3 : \ 142f0d1b0b3SDavid Howells (n) & (1ULL << 2) ? 2 : \ 143474c9015SLinus Torvalds 1) : \ 144dbef91ecSMartin Wilck -1) 145dbef91ecSMartin Wilck 146dbef91ecSMartin Wilck /** 147dbef91ecSMartin Wilck * ilog2 - log base 2 of 32-bit or a 64-bit unsigned value 148dbef91ecSMartin Wilck * @n: parameter 149dbef91ecSMartin Wilck * 150dbef91ecSMartin Wilck * constant-capable log of base 2 calculation 151dbef91ecSMartin Wilck * - this can be used to initialise global variables from constant data, hence 152dbef91ecSMartin Wilck * the massive ternary operator construction 153dbef91ecSMartin Wilck * 154dbef91ecSMartin Wilck * selects the appropriately-sized optimised version depending on sizeof(n) 155dbef91ecSMartin Wilck */ 156dbef91ecSMartin Wilck #define ilog2(n) \ 157dbef91ecSMartin Wilck ( \ 158dbef91ecSMartin Wilck __builtin_constant_p(n) ? \ 1592f78788bSJakub Jelinek ((n) < 2 ? 0 : \ 1602f78788bSJakub Jelinek 63 - __builtin_clzll(n)) : \ 161f0d1b0b3SDavid Howells (sizeof(n) <= 4) ? \ 162f0d1b0b3SDavid Howells __ilog2_u32(n) : \ 163f0d1b0b3SDavid Howells __ilog2_u64(n) \ 164f0d1b0b3SDavid Howells ) 165f0d1b0b3SDavid Howells 166312a0c17SDavid Howells /** 167312a0c17SDavid Howells * roundup_pow_of_two - round the given value up to nearest power of two 168a1c4d24eSRandy Dunlap * @n: parameter 169312a0c17SDavid Howells * 1706fb189c2SRobert P. J. Day * round the given value up to the nearest power of two 171312a0c17SDavid Howells * - the result is undefined when n == 0 172312a0c17SDavid Howells * - this can be used to initialise global variables from constant data 173312a0c17SDavid Howells */ 174312a0c17SDavid Howells #define roundup_pow_of_two(n) \ 175312a0c17SDavid Howells ( \ 176312a0c17SDavid Howells __builtin_constant_p(n) ? ( \ 177428fc0afSJason Gunthorpe ((n) == 1) ? 1 : \ 178312a0c17SDavid Howells (1UL << (ilog2((n) - 1) + 1)) \ 179312a0c17SDavid Howells ) : \ 180312a0c17SDavid Howells __roundup_pow_of_two(n) \ 181312a0c17SDavid Howells ) 182312a0c17SDavid Howells 183b311e921SRobert P. J. Day /** 184b311e921SRobert P. J. Day * rounddown_pow_of_two - round the given value down to nearest power of two 185a1c4d24eSRandy Dunlap * @n: parameter 186b311e921SRobert P. J. Day * 187b311e921SRobert P. J. Day * round the given value down to the nearest power of two 188b311e921SRobert P. J. Day * - the result is undefined when n == 0 189b311e921SRobert P. J. Day * - this can be used to initialise global variables from constant data 190b311e921SRobert P. J. Day */ 191b311e921SRobert P. J. Day #define rounddown_pow_of_two(n) \ 192b311e921SRobert P. J. Day ( \ 193b311e921SRobert P. J. Day __builtin_constant_p(n) ? ( \ 194b311e921SRobert P. J. Day (1UL << ilog2(n))) : \ 195b311e921SRobert P. J. Day __rounddown_pow_of_two(n) \ 196b311e921SRobert P. J. Day ) 197b311e921SRobert P. J. Day 198a1c4d24eSRandy Dunlap static inline __attribute_const__ __order_base_2(unsigned long n)199a1c4d24eSRandy Dunlapint __order_base_2(unsigned long n) 200a1c4d24eSRandy Dunlap { 201a1c4d24eSRandy Dunlap return n > 1 ? ilog2(n - 1) + 1 : 0; 202a1c4d24eSRandy Dunlap } 203a1c4d24eSRandy Dunlap 204de9330d1SRobert P. J. Day /** 205de9330d1SRobert P. J. Day * order_base_2 - calculate the (rounded up) base 2 order of the argument 206de9330d1SRobert P. J. Day * @n: parameter 207de9330d1SRobert P. J. Day * 208de9330d1SRobert P. J. Day * The first few values calculated by this routine: 209de9330d1SRobert P. J. Day * ob2(0) = 0 210de9330d1SRobert P. J. Day * ob2(1) = 0 211de9330d1SRobert P. J. Day * ob2(2) = 1 212de9330d1SRobert P. J. Day * ob2(3) = 2 213de9330d1SRobert P. J. Day * ob2(4) = 2 214de9330d1SRobert P. J. Day * ob2(5) = 3 215de9330d1SRobert P. J. Day * ... and so on. 216de9330d1SRobert P. J. Day */ 21729905b52SArd Biesheuvel #define order_base_2(n) \ 21829905b52SArd Biesheuvel ( \ 21929905b52SArd Biesheuvel __builtin_constant_p(n) ? ( \ 22029905b52SArd Biesheuvel ((n) == 0 || (n) == 1) ? 0 : \ 22129905b52SArd Biesheuvel ilog2((n) - 1) + 1) : \ 22229905b52SArd Biesheuvel __order_base_2(n) \ 22329905b52SArd Biesheuvel ) 22469842cbaSPatrick Bellasi 22569842cbaSPatrick Bellasi static inline __attribute__((const)) __bits_per(unsigned long n)22669842cbaSPatrick Bellasiint __bits_per(unsigned long n) 22769842cbaSPatrick Bellasi { 22869842cbaSPatrick Bellasi if (n < 2) 22969842cbaSPatrick Bellasi return 1; 23069842cbaSPatrick Bellasi if (is_power_of_2(n)) 23169842cbaSPatrick Bellasi return order_base_2(n) + 1; 23269842cbaSPatrick Bellasi return order_base_2(n); 23369842cbaSPatrick Bellasi } 23469842cbaSPatrick Bellasi 23569842cbaSPatrick Bellasi /** 23669842cbaSPatrick Bellasi * bits_per - calculate the number of bits required for the argument 23769842cbaSPatrick Bellasi * @n: parameter 23869842cbaSPatrick Bellasi * 23969842cbaSPatrick Bellasi * This is constant-capable and can be used for compile time 24069842cbaSPatrick Bellasi * initializations, e.g bitfields. 24169842cbaSPatrick Bellasi * 24269842cbaSPatrick Bellasi * The first few values calculated by this routine: 24369842cbaSPatrick Bellasi * bf(0) = 1 24469842cbaSPatrick Bellasi * bf(1) = 1 24569842cbaSPatrick Bellasi * bf(2) = 2 24669842cbaSPatrick Bellasi * bf(3) = 2 24769842cbaSPatrick Bellasi * bf(4) = 3 24869842cbaSPatrick Bellasi * ... and so on. 24969842cbaSPatrick Bellasi */ 25069842cbaSPatrick Bellasi #define bits_per(n) \ 25169842cbaSPatrick Bellasi ( \ 25269842cbaSPatrick Bellasi __builtin_constant_p(n) ? ( \ 25369842cbaSPatrick Bellasi ((n) == 0 || (n) == 1) \ 25469842cbaSPatrick Bellasi ? 1 : ilog2(n) + 1 \ 25569842cbaSPatrick Bellasi ) : \ 25669842cbaSPatrick Bellasi __bits_per(n) \ 25769842cbaSPatrick Bellasi ) 258f0d1b0b3SDavid Howells #endif /* _LINUX_LOG2_H */ 259