| Line | Branch | Exec | Source |
|---|---|---|---|
| 1 | #ifndef UTIL_BIT_H | ||
| 2 | #define UTIL_BIT_H | ||
| 3 | |||
| 4 | #include <stdint.h> | ||
| 5 | #include "debug.h" | ||
| 6 | #include "macros.h" | ||
| 7 | |||
| 8 | /* | ||
| 9 | * The default C compiler on FreeBSD 14.1 (Clang 18.1.5) accepts the | ||
| 10 | * -std=gnu23 command-line option and then defines __STDC_VERSION__ as | ||
| 11 | * 202311L, while not actually providing a C23 conforming libc (the | ||
| 12 | * <stdbit.h> header is missing). This guard condition originally used | ||
| 13 | * `||` instead of `&&`, but it was changed so as to work around this | ||
| 14 | * disregard for standards. Fortunately this doesn't really have any | ||
| 15 | * downsides for other platforms, since __has_include() is also part | ||
| 16 | * of C23. | ||
| 17 | */ | ||
| 18 | #if __STDC_VERSION__ >= 202311L && HAS_INCLUDE(<stdbit.h>) | ||
| 19 | #include <stdbit.h> | ||
| 20 | #define USE_STDBIT(fn, arg) return fn(arg) | ||
| 21 | #else | ||
| 22 | #define USE_STDBIT(fn, arg) | ||
| 23 | #endif | ||
| 24 | |||
| 25 | #define U64(x) (UINT64_C(x)) | ||
| 26 | #define U32(x) (UINT32_C(x)) | ||
| 27 | |||
| 28 | #ifdef HAS_BUILTIN_TYPES_COMPATIBLE_P | ||
| 29 | #define HAS_COMPATIBLE_BUILTIN(arg, type, fn) \ | ||
| 30 | (GNUC_AT_LEAST(3, 4) || HAS_BUILTIN(__builtin_ ## fn)) \ | ||
| 31 | && __builtin_types_compatible_p(__typeof__(arg), type) | ||
| 32 | |||
| 33 | // If there's an appropriate built-in function for `arg`, emit | ||
| 34 | // a call to it (and eliminate everything below it as dead code) | ||
| 35 | #define USE_BUILTIN(fn, arg) \ | ||
| 36 | if (HAS_COMPATIBLE_BUILTIN(arg, unsigned long long, fn ## ll)) { \ | ||
| 37 | return __builtin_ ## fn ## ll(arg); \ | ||
| 38 | } else if (HAS_COMPATIBLE_BUILTIN(arg, unsigned long, fn ## l)) { \ | ||
| 39 | return __builtin_ ## fn ## l(arg); \ | ||
| 40 | } else if (HAS_COMPATIBLE_BUILTIN(arg, unsigned int, fn)) { \ | ||
| 41 | return __builtin_ ## fn(arg); \ | ||
| 42 | } | ||
| 43 | #else | ||
| 44 | #define USE_BUILTIN(fn, arg) | ||
| 45 | #endif | ||
| 46 | |||
| 47 | // Population count (cardinality) of set bits | ||
| 48 | 344 | static inline unsigned int u64_popcount(uint64_t n) | |
| 49 | { | ||
| 50 | 344 | USE_STDBIT(stdc_count_ones, n); | |
| 51 | 344 | USE_BUILTIN(popcount, n); | |
| 52 | n -= ((n >> 1) & U64(0x5555555555555555)); | ||
| 53 | n = (n & U64(0x3333333333333333)) + ((n >> 2) & U64(0x3333333333333333)); | ||
| 54 | n = (n + (n >> 4)) & U64(0x0F0F0F0F0F0F0F0F); | ||
| 55 | return (n * U64(0x0101010101010101)) >> 56; | ||
| 56 | } | ||
| 57 | |||
| 58 | 104 | static inline unsigned int u32_popcount(uint32_t n) | |
| 59 | { | ||
| 60 | 104 | USE_STDBIT(stdc_count_ones, n); | |
| 61 | 104 | USE_BUILTIN(popcount, n); | |
| 62 | n -= ((n >> 1) & U32(0x55555555)); | ||
| 63 | n = (n & U32(0x33333333)) + ((n >> 2) & U32(0x33333333)); | ||
| 64 | n = (n + (n >> 4)) & U32(0x0F0F0F0F); | ||
| 65 | return (n * U32(0x01010101)) >> 24; | ||
| 66 | } | ||
| 67 | |||
| 68 | // Count trailing zeros | ||
| 69 | 168 | static inline unsigned int u32_ctz(uint32_t n) | |
| 70 | { | ||
| 71 | 168 | BUG_ON(n == 0); | |
| 72 | 168 | USE_STDBIT(stdc_trailing_zeros, n); | |
| 73 | 168 | USE_BUILTIN(ctz, n); | |
| 74 | return u32_popcount(~n & (n - 1)); | ||
| 75 | } | ||
| 76 | |||
| 77 | // Find position of first (least significant) set bit (starting at 1) | ||
| 78 | 94 | static inline unsigned int u32_ffs(uint32_t n) | |
| 79 | { | ||
| 80 | 94 | USE_BUILTIN(ffs, n); | |
| 81 | return n ? u32_ctz(n) + 1 : 0; | ||
| 82 | } | ||
| 83 | |||
| 84 | // Extract (isolate) least significant set bit | ||
| 85 | 83 | static inline uint32_t u32_lsbit(uint32_t x) | |
| 86 | { | ||
| 87 |
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83 | return x ? 1u << (u32_ffs(x) - 1) : 0; |
| 88 | } | ||
| 89 | |||
| 90 | #endif | ||
| 91 |