Chris Wilson | 9e55cca | 2017-04-25 15:12:50 +0100 | [diff] [blame] | 1 | #ifndef ILOG2_H |
| 2 | #define ILOG2_H |
| 3 | |
| 4 | #include <stdint.h> |
| 5 | |
| 6 | static inline int fls(int x) |
| 7 | { |
| 8 | int r = -1; |
| 9 | asm("bsrl %1,%0" : "=r" (r) : "rm" (x), "0" (-1)); |
| 10 | return r + 1; |
| 11 | } |
| 12 | |
| 13 | static inline int fls64(__u64 x) |
| 14 | { |
| 15 | int r = -1; |
| 16 | asm("bsrq %1,%q0" : "+r" (r) : "rm" (x)); |
| 17 | return r + 1; |
| 18 | } |
| 19 | |
| 20 | static inline __attribute__((const)) |
| 21 | int __ilog2_u32(uint32_t n) |
| 22 | { |
| 23 | return fls(n) - 1; |
| 24 | } |
| 25 | |
| 26 | static inline __attribute__((const)) |
| 27 | int __ilog2_u64(uint64_t n) |
| 28 | { |
| 29 | return fls64(n) - 1; |
| 30 | } |
| 31 | |
| 32 | #define ilog2(n) \ |
| 33 | ( \ |
| 34 | __builtin_constant_p(n) ? ( \ |
| 35 | (n) < 2 ? 0 : \ |
| 36 | (n) & (1ULL << 63) ? 63 : \ |
| 37 | (n) & (1ULL << 62) ? 62 : \ |
| 38 | (n) & (1ULL << 61) ? 61 : \ |
| 39 | (n) & (1ULL << 60) ? 60 : \ |
| 40 | (n) & (1ULL << 59) ? 59 : \ |
| 41 | (n) & (1ULL << 58) ? 58 : \ |
| 42 | (n) & (1ULL << 57) ? 57 : \ |
| 43 | (n) & (1ULL << 56) ? 56 : \ |
| 44 | (n) & (1ULL << 55) ? 55 : \ |
| 45 | (n) & (1ULL << 54) ? 54 : \ |
| 46 | (n) & (1ULL << 53) ? 53 : \ |
| 47 | (n) & (1ULL << 52) ? 52 : \ |
| 48 | (n) & (1ULL << 51) ? 51 : \ |
| 49 | (n) & (1ULL << 50) ? 50 : \ |
| 50 | (n) & (1ULL << 49) ? 49 : \ |
| 51 | (n) & (1ULL << 48) ? 48 : \ |
| 52 | (n) & (1ULL << 47) ? 47 : \ |
| 53 | (n) & (1ULL << 46) ? 46 : \ |
| 54 | (n) & (1ULL << 45) ? 45 : \ |
| 55 | (n) & (1ULL << 44) ? 44 : \ |
| 56 | (n) & (1ULL << 43) ? 43 : \ |
| 57 | (n) & (1ULL << 42) ? 42 : \ |
| 58 | (n) & (1ULL << 41) ? 41 : \ |
| 59 | (n) & (1ULL << 40) ? 40 : \ |
| 60 | (n) & (1ULL << 39) ? 39 : \ |
| 61 | (n) & (1ULL << 38) ? 38 : \ |
| 62 | (n) & (1ULL << 37) ? 37 : \ |
| 63 | (n) & (1ULL << 36) ? 36 : \ |
| 64 | (n) & (1ULL << 35) ? 35 : \ |
| 65 | (n) & (1ULL << 34) ? 34 : \ |
| 66 | (n) & (1ULL << 33) ? 33 : \ |
| 67 | (n) & (1ULL << 32) ? 32 : \ |
| 68 | (n) & (1ULL << 31) ? 31 : \ |
| 69 | (n) & (1ULL << 30) ? 30 : \ |
| 70 | (n) & (1ULL << 29) ? 29 : \ |
| 71 | (n) & (1ULL << 28) ? 28 : \ |
| 72 | (n) & (1ULL << 27) ? 27 : \ |
| 73 | (n) & (1ULL << 26) ? 26 : \ |
| 74 | (n) & (1ULL << 25) ? 25 : \ |
| 75 | (n) & (1ULL << 24) ? 24 : \ |
| 76 | (n) & (1ULL << 23) ? 23 : \ |
| 77 | (n) & (1ULL << 22) ? 22 : \ |
| 78 | (n) & (1ULL << 21) ? 21 : \ |
| 79 | (n) & (1ULL << 20) ? 20 : \ |
| 80 | (n) & (1ULL << 19) ? 19 : \ |
| 81 | (n) & (1ULL << 18) ? 18 : \ |
| 82 | (n) & (1ULL << 17) ? 17 : \ |
| 83 | (n) & (1ULL << 16) ? 16 : \ |
| 84 | (n) & (1ULL << 15) ? 15 : \ |
| 85 | (n) & (1ULL << 14) ? 14 : \ |
| 86 | (n) & (1ULL << 13) ? 13 : \ |
| 87 | (n) & (1ULL << 12) ? 12 : \ |
| 88 | (n) & (1ULL << 11) ? 11 : \ |
| 89 | (n) & (1ULL << 10) ? 10 : \ |
| 90 | (n) & (1ULL << 9) ? 9 : \ |
| 91 | (n) & (1ULL << 8) ? 8 : \ |
| 92 | (n) & (1ULL << 7) ? 7 : \ |
| 93 | (n) & (1ULL << 6) ? 6 : \ |
| 94 | (n) & (1ULL << 5) ? 5 : \ |
| 95 | (n) & (1ULL << 4) ? 4 : \ |
| 96 | (n) & (1ULL << 3) ? 3 : \ |
| 97 | (n) & (1ULL << 2) ? 2 : \ |
| 98 | 1 ) : \ |
| 99 | (sizeof(n) <= 4) ? \ |
| 100 | __ilog2_u32(n) : \ |
| 101 | __ilog2_u64(n) \ |
| 102 | ) |
| 103 | |
| 104 | #endif /* ILOG2_H */ |