Resolver: Use LLVM StringMap and DenseMap.

All defined symbols from all archive files are inserted to _archiveMap,
so performance of hash table matters here (I'm not trying to convert
all std::maps with DenseMaps). This change seems to make the linker
0.5% - 1% faster for my test case.

llvm-svn: 231584

lld/include/lld/Core/Resolver.h

@@ -100,8 +100,8 @@ private:
   size_t _fileIndex;
 
   // Preloading
-  std::map<StringRef, ArchiveLibraryFile *> _archiveMap;
-  std::unordered_set<ArchiveLibraryFile *> _archiveSeen;
+  llvm::StringMap<ArchiveLibraryFile *> _archiveMap;
+  llvm::DenseSet<ArchiveLibraryFile *> _archiveSeen;
 
   // List of undefined symbols.
   std::vector<StringRef> _undefines;