[DWARFLinkerParallel] Switch to xxh3_64bits

[MaskRay]

Summary

xxh3 is substantially faster than xxh64.
For lld .debug_str there is substantial speedup (D154813).

@avl reports that it is around 1-2% improvement for different number of input sets and for different threads configuration.

[avl]

I checked the performance impact on x86_64 ubuntu using utility from D132548 - it looks like, it is around 1-2% improvement for different number of input sets and for different threads configuration.

[avl]

LGTM

[MaskRay]

In D155675#4515178, @avl wrote:

I checked the performance impact on x86_64 ubuntu using utility from D132548 - it looks like, it is around 1-2% improvement for different number of input sets and for different threads configuration.

Thank you for checking!

llvm/include/llvm/ADT/ConcurrentHashtable.h

 /// ConcurrentHashTableByPtr uses an external thread-safe allocator to allocate
 /// KeyDataTy items.
 
 template <typename KeyTy, typename KeyDataTy, typename AllocatorTy>
 class ConcurrentHashTableInfoByPtr {
 public:
   /// \returns Hash value for the specified \p Key.
   static inline uint64_t getHashValue(const KeyTy &Key) {
-    return xxHash64(Key);
+    return xxh3_64bits(Key);
   }
 
   /// \returns true if both \p LHS and \p RHS are equal.
   static inline bool isEqual(const KeyTy &LHS, const KeyTy &RHS) {
     return LHS == RHS;
   }
 
   /// \returns key for the specified \p KeyData.

llvm/include/llvm/DWARFLinkerParallel/StringPool.h

 /// StringEntry keeps data of the string: the length, external offset
 /// and a string body which is placed right after StringEntry.
 using StringEntry = StringMapEntry<DwarfStringPoolEntry *>;
 
 class StringPoolEntryInfo {
 public:
   /// \returns Hash value for the specified \p Key.
   static inline uint64_t getHashValue(const StringRef &Key) {
-    return xxHash64(Key);
+    return xxh3_64bits(Key);
   }
 
   /// \returns true if both \p LHS and \p RHS are equal.
   static inline bool isEqual(const StringRef &LHS, const StringRef &RHS) {
     return LHS == RHS;
   }
 
   /// \returns key for the specified \p KeyData.