diff options
| author | Lioncash <mathew1800@gmail.com> | 2021-01-21 03:48:32 -0500 |
|---|---|---|
| committer | Lioncash <mathew1800@gmail.com> | 2021-01-21 04:07:58 -0500 |
| commit | 6ff2db181f3dc8a9c95f6f9564c0bb1db7cae8e3 (patch) | |
| tree | d6e0ba300638e038f5f2b343f9a779abd5d4a198 /src/common/bit_util.h | |
| parent | e8401964b4cb617223554e147091f109dc870ba5 (diff) | |
bit_util: Unify implementations of MostSignificantBit32/MostSignificantBit64
We can use the standardized CLZ facilities to perform this. This also
allows us to make utilizing functions constexpr and eliminate the
inclusion of an intrinsics header.
Diffstat (limited to 'src/common/bit_util.h')
| -rw-r--r-- | src/common/bit_util.h | 48 |
1 files changed, 13 insertions, 35 deletions
diff --git a/src/common/bit_util.h b/src/common/bit_util.h index 685e7fc9be..69fb4e5e4e 100644 --- a/src/common/bit_util.h +++ b/src/common/bit_util.h @@ -7,10 +7,6 @@ #include <climits> #include <cstddef> -#ifdef _MSC_VER -#include <intrin.h> -#endif - #include "common/common_types.h" namespace Common { @@ -21,48 +17,30 @@ template <typename T> return sizeof(T) * CHAR_BIT; } -#ifdef _MSC_VER - -[[nodiscard]] inline u32 MostSignificantBit32(const u32 value) { - unsigned long result; - _BitScanReverse(&result, value); - return static_cast<u32>(result); -} - -[[nodiscard]] inline u32 MostSignificantBit64(const u64 value) { - unsigned long result; - _BitScanReverse64(&result, value); - return static_cast<u32>(result); -} - -#else - -[[nodiscard]] inline u32 MostSignificantBit32(const u32 value) { - return 31U - static_cast<u32>(__builtin_clz(value)); +[[nodiscard]] constexpr u32 MostSignificantBit32(const u32 value) { + return 31U - static_cast<u32>(std::countl_zero(value)); } -[[nodiscard]] inline u32 MostSignificantBit64(const u64 value) { - return 63U - static_cast<u32>(__builtin_clzll(value)); +[[nodiscard]] constexpr u32 MostSignificantBit64(const u64 value) { + return 63U - static_cast<u32>(std::countl_zero(value)); } -#endif - -[[nodiscard]] inline u32 Log2Floor32(const u32 value) { +[[nodiscard]] constexpr u32 Log2Floor32(const u32 value) { return MostSignificantBit32(value); } -[[nodiscard]] inline u32 Log2Ceil32(const u32 value) { - const u32 log2_f = Log2Floor32(value); - return log2_f + ((value ^ (1U << log2_f)) != 0U); +[[nodiscard]] constexpr u32 Log2Floor64(const u64 value) { + return MostSignificantBit64(value); } -[[nodiscard]] inline u32 Log2Floor64(const u64 value) { - return MostSignificantBit64(value); +[[nodiscard]] constexpr u32 Log2Ceil32(const u32 value) { + const u32 log2_f = Log2Floor32(value); + return log2_f + static_cast<u32>((value ^ (1U << log2_f)) != 0U); } -[[nodiscard]] inline u32 Log2Ceil64(const u64 value) { - const u64 log2_f = static_cast<u64>(Log2Floor64(value)); - return static_cast<u32>(log2_f + ((value ^ (1ULL << log2_f)) != 0ULL)); +[[nodiscard]] constexpr u32 Log2Ceil64(const u64 value) { + const u64 log2_f = Log2Floor64(value); + return static_cast<u32>(log2_f + static_cast<u64>((value ^ (1ULL << log2_f)) != 0ULL)); } } // namespace Common |