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Encoding improvements * New hash table implementation --- Move away from 16-bit hashes since we need more than 64k buckets to hold 2M entries efficiently --- Change to CityHash64, which is faster and stronger --- Remove hardcoded max limit * NAME_INDEX changed from contigouos int to monotonically increasing int --- Opens up for future deduplication schemes that are better than number suffix dedup. --- Saves some memory since we don't need to maintain a contiguous array --- Typed up to cause compile errors when used as integer directly * Avoid touching data repeatedly, normal path only does single hash of data * New constructor that allows supplying string length up front * Avoid dynamic allocations in string conversions >= 128 characters * Avoid extra copying when splitting numbers * More efficient IsPureAnsi check * Only do one global lazy initialization call instead of multiple * Switch to faster RW locks * Switch from single lock to sharded hash map with separate locks * Memory optimizations that reduces per entry overhead: 4 bytes slots, 2 byte headers and don't store null terminator Improved API & documentation * Document that IsValid() rarely makes sense * Hide global state such as GetNames() * Reduce amount of implementation details visible in header * NameTypes.h size down by ~1/3 while adding documentation, stronger type safety and new APIs Future possibilities * Memory savings: Removing public NAME_INDEX and global FName array allows using the 32-bit FNameEntryId for arbitrary deduplication schemes. This can save both actual stored strings memory by deduplication and half the size of FName instances from 8B to 4B in shipping / test configs by removing the number part. * Implementation can be tweaked further, for instance could persist 32-bit slot index hash inside slot to increase encoding performance in development / debug at the cost of memory. Perf & mem results for internal project: * Editor startup wall time: 12% speedup, 22.0s -> 19.5s --- Warm disk and asset registry cache --- Some gains from nametable serialization improvements --- Some of these gains might be from orthogonal asset discovery optimizations * Win64 Test Client memory usage with ~400k names: 30.3Mb -> 22.2Mb #rb steve.robb, pj.kack #jira UE-59973 [CL 5774657 by Johan Torp in Dev-Core branch]