diff options
Diffstat (limited to 'src')
| -rw-r--r-- | src/zencore/include/zencore/varint.h | 14 |
1 files changed, 12 insertions, 2 deletions
diff --git a/src/zencore/include/zencore/varint.h b/src/zencore/include/zencore/varint.h index ae9aceed6..9fe905f25 100644 --- a/src/zencore/include/zencore/varint.h +++ b/src/zencore/include/zencore/varint.h @@ -76,14 +76,24 @@ MeasureVarInt(const void* InData) inline uint32_t MeasureVarUInt(uint32_t InValue) { - return uint32_t(int32_t(FloorLog2(InValue)) / 7 + 1); + // return + // This branching implementation is faster than branchless alternatives in real-world benchmarks. + // Replaces: uint32_t(int32_t(FloorLog2(InValue)) / 7 + 1); + return (InValue < (uint32_t(1) << 28)) + ? ((InValue < (uint32_t(1) << 14)) ? ((InValue < (uint32_t(1) << 7)) ? 1 : 2) : ((InValue < (uint32_t(1) << 21)) ? 3 : 4)) + : 5; } /** Measure the number of bytes (1-9) required to encode the 64-bit input. */ inline uint32_t MeasureVarUInt(uint64_t InValue) { - return uint32_t(std::min(int32_t(FloorLog2_64(InValue)) / 7 + 1, 9)); + // This branching implementation is faster than branchless alternatives in real-world benchmarks. + // Replaces: uint32_t(std::min(int32_t(FloorLog2_64(InValue)) / 7 + 1, 9)); + return (InValue < (uint64_t(1) << 28)) + ? ((InValue < (uint64_t(1) << 14)) ? ((InValue < (uint64_t(1) << 7)) ? 1 : 2) : ((InValue < (uint64_t(1) << 21)) ? 3 : 4)) + : ((InValue < (uint64_t(1) << 42)) ? ((InValue < (uint64_t(1) << 35)) ? 5 : 6) + : ((InValue < (uint64_t(1) << 49)) ? 7 : ((InValue < (uint64_t(1) << 56)) ? 8 : 9))); } /** Measure the number of bytes (1-5) required to encode the 32-bit input. \see \ref MeasureVarUInt */ |