log2.h revision 255932
1219820Sjeff/*- 2219820Sjeff * Copyright (c) 2010 Isilon Systems, Inc. 3219820Sjeff * Copyright (c) 2010 iX Systems, Inc. 4219820Sjeff * Copyright (c) 2010 Panasas, Inc. 5219820Sjeff * All rights reserved. 6219820Sjeff * 7219820Sjeff * Redistribution and use in source and binary forms, with or without 8219820Sjeff * modification, are permitted provided that the following conditions 9219820Sjeff * are met: 10219820Sjeff * 1. Redistributions of source code must retain the above copyright 11219820Sjeff * notice unmodified, this list of conditions, and the following 12219820Sjeff * disclaimer. 13219820Sjeff * 2. Redistributions in binary form must reproduce the above copyright 14219820Sjeff * notice, this list of conditions and the following disclaimer in the 15219820Sjeff * documentation and/or other materials provided with the distribution. 16219820Sjeff * 17219820Sjeff * THIS SOFTWARE IS PROVIDED BY THE AUTHOR ``AS IS'' AND ANY EXPRESS OR 18219820Sjeff * IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE IMPLIED WARRANTIES 19219820Sjeff * OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE ARE DISCLAIMED. 20219820Sjeff * IN NO EVENT SHALL THE AUTHOR BE LIABLE FOR ANY DIRECT, INDIRECT, 21219820Sjeff * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT 22219820Sjeff * NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, 23219820Sjeff * DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY 24219820Sjeff * THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT 25219820Sjeff * (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF 26219820Sjeff * THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE. 27219820Sjeff */ 28219820Sjeff 29219820Sjeff#ifndef _LINUX_LOG2_H_ 30219820Sjeff#define _LINUX_LOG2_H_ 31219820Sjeff 32219820Sjeff#include <linux/types.h> 33219820Sjeff 34219820Sjeff#include <sys/libkern.h> 35219820Sjeff 36219820Sjeffstatic inline unsigned long 37219820Sjeffroundup_pow_of_two(unsigned long x) 38219820Sjeff{ 39219820Sjeff return (1UL << flsl(x - 1)); 40219820Sjeff} 41219820Sjeff 42219820Sjeffstatic inline int 43219820Sjeffis_power_of_2(unsigned long n) 44219820Sjeff{ 45219820Sjeff return (n == roundup_pow_of_two(n)); 46219820Sjeff} 47219820Sjeff 48219820Sjeffstatic inline unsigned long 49219820Sjeffrounddown_pow_of_two(unsigned long x) 50219820Sjeff{ 51219820Sjeff return (1UL << (flsl(x) - 1)); 52219820Sjeff} 53219820Sjeff 54255932Salfred 55255932Salfred/* 56255932Salfred * deal with unrepresentable constant logarithms 57255932Salfred */ 58255932Salfredextern __attribute__((const, noreturn)) 59255932Salfredint ____ilog2_NaN(void); 60255932Salfred 61255932Salfred/* 62255932Salfred * non-constant log of base 2 calculators 63255932Salfred * - the arch may override these in asm/bitops.h if they can be implemented 64255932Salfred * more efficiently than using fls() and fls64() 65255932Salfred * - the arch is not required to handle n==0 if implementing the fallback 66255932Salfred */ 67255932Salfred#ifndef CONFIG_ARCH_HAS_ILOG2_U32 68255932Salfredstatic inline __attribute__((const)) 69255932Salfredint __ilog2_u32(u32 n) 70219820Sjeff{ 71255932Salfred return flsl(n) - 1; 72219820Sjeff} 73255932Salfred#endif 74219820Sjeff 75255932Salfred#ifndef CONFIG_ARCH_HAS_ILOG2_U64 76255932Salfredstatic inline __attribute__((const)) 77255932Salfredint __ilog2_u64(u64 n) 78255932Salfred{ 79255932Salfred return flsl(n) - 1; 80255932Salfred} 81255932Salfred#endif 82255932Salfred 83255932Salfred 84255932Salfred/** 85255932Salfred * ilog2 - log of base 2 of 32-bit or a 64-bit unsigned value 86255932Salfred * @n - parameter 87255932Salfred * 88255932Salfred * constant-capable log of base 2 calculation 89255932Salfred * - this can be used to initialise global variables from constant data, hence 90255932Salfred * the massive ternary operator construction 91255932Salfred * 92255932Salfred * selects the appropriately-sized optimised version depending on sizeof(n) 93255932Salfred */ 94255932Salfred#define ilog2(n) \ 95255932Salfred( \ 96255932Salfred __builtin_constant_p(n) ? ( \ 97255932Salfred (n) < 1 ? ____ilog2_NaN() : \ 98255932Salfred (n) & (1ULL << 63) ? 63 : \ 99255932Salfred (n) & (1ULL << 62) ? 62 : \ 100255932Salfred (n) & (1ULL << 61) ? 61 : \ 101255932Salfred (n) & (1ULL << 60) ? 60 : \ 102255932Salfred (n) & (1ULL << 59) ? 59 : \ 103255932Salfred (n) & (1ULL << 58) ? 58 : \ 104255932Salfred (n) & (1ULL << 57) ? 57 : \ 105255932Salfred (n) & (1ULL << 56) ? 56 : \ 106255932Salfred (n) & (1ULL << 55) ? 55 : \ 107255932Salfred (n) & (1ULL << 54) ? 54 : \ 108255932Salfred (n) & (1ULL << 53) ? 53 : \ 109255932Salfred (n) & (1ULL << 52) ? 52 : \ 110255932Salfred (n) & (1ULL << 51) ? 51 : \ 111255932Salfred (n) & (1ULL << 50) ? 50 : \ 112255932Salfred (n) & (1ULL << 49) ? 49 : \ 113255932Salfred (n) & (1ULL << 48) ? 48 : \ 114255932Salfred (n) & (1ULL << 47) ? 47 : \ 115255932Salfred (n) & (1ULL << 46) ? 46 : \ 116255932Salfred (n) & (1ULL << 45) ? 45 : \ 117255932Salfred (n) & (1ULL << 44) ? 44 : \ 118255932Salfred (n) & (1ULL << 43) ? 43 : \ 119255932Salfred (n) & (1ULL << 42) ? 42 : \ 120255932Salfred (n) & (1ULL << 41) ? 41 : \ 121255932Salfred (n) & (1ULL << 40) ? 40 : \ 122255932Salfred (n) & (1ULL << 39) ? 39 : \ 123255932Salfred (n) & (1ULL << 38) ? 38 : \ 124255932Salfred (n) & (1ULL << 37) ? 37 : \ 125255932Salfred (n) & (1ULL << 36) ? 36 : \ 126255932Salfred (n) & (1ULL << 35) ? 35 : \ 127255932Salfred (n) & (1ULL << 34) ? 34 : \ 128255932Salfred (n) & (1ULL << 33) ? 33 : \ 129255932Salfred (n) & (1ULL << 32) ? 32 : \ 130255932Salfred (n) & (1ULL << 31) ? 31 : \ 131255932Salfred (n) & (1ULL << 30) ? 30 : \ 132255932Salfred (n) & (1ULL << 29) ? 29 : \ 133255932Salfred (n) & (1ULL << 28) ? 28 : \ 134255932Salfred (n) & (1ULL << 27) ? 27 : \ 135255932Salfred (n) & (1ULL << 26) ? 26 : \ 136255932Salfred (n) & (1ULL << 25) ? 25 : \ 137255932Salfred (n) & (1ULL << 24) ? 24 : \ 138255932Salfred (n) & (1ULL << 23) ? 23 : \ 139255932Salfred (n) & (1ULL << 22) ? 22 : \ 140255932Salfred (n) & (1ULL << 21) ? 21 : \ 141255932Salfred (n) & (1ULL << 20) ? 20 : \ 142255932Salfred (n) & (1ULL << 19) ? 19 : \ 143255932Salfred (n) & (1ULL << 18) ? 18 : \ 144255932Salfred (n) & (1ULL << 17) ? 17 : \ 145255932Salfred (n) & (1ULL << 16) ? 16 : \ 146255932Salfred (n) & (1ULL << 15) ? 15 : \ 147255932Salfred (n) & (1ULL << 14) ? 14 : \ 148255932Salfred (n) & (1ULL << 13) ? 13 : \ 149255932Salfred (n) & (1ULL << 12) ? 12 : \ 150255932Salfred (n) & (1ULL << 11) ? 11 : \ 151255932Salfred (n) & (1ULL << 10) ? 10 : \ 152255932Salfred (n) & (1ULL << 9) ? 9 : \ 153255932Salfred (n) & (1ULL << 8) ? 8 : \ 154255932Salfred (n) & (1ULL << 7) ? 7 : \ 155255932Salfred (n) & (1ULL << 6) ? 6 : \ 156255932Salfred (n) & (1ULL << 5) ? 5 : \ 157255932Salfred (n) & (1ULL << 4) ? 4 : \ 158255932Salfred (n) & (1ULL << 3) ? 3 : \ 159255932Salfred (n) & (1ULL << 2) ? 2 : \ 160255932Salfred (n) & (1ULL << 1) ? 1 : \ 161255932Salfred (n) & (1ULL << 0) ? 0 : \ 162255932Salfred ____ilog2_NaN() \ 163255932Salfred ) : \ 164255932Salfred (sizeof(n) <= 4) ? \ 165255932Salfred __ilog2_u32(n) : \ 166255932Salfred __ilog2_u64(n) \ 167255932Salfred ) 168255932Salfred 169219820Sjeff#endif /* _LINUX_LOG2_H_ */ 170