Use CachedHashStringRef instead of CachedHash<StringRef>.

[jlebar]

Summary

This uses one less word on 64-bit platforms, so should be a strict
improvement. This change also lets us get rid of llvm::CachedHash.

lld/ELF/SymbolTable.h

 //===- SymbolTable.h --------------------------------------------*- C++ -*-===//
 //
 //                             The LLVM Linker
 //
 // This file is distributed under the University of Illinois Open Source
 // License. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
 
 #ifndef LLD_ELF_SYMBOL_TABLE_H
 #define LLD_ELF_SYMBOL_TABLE_H
 
 #include "InputFiles.h"
 #include "LTO.h"
+#include "llvm/ADT/CachedHashString.h"
 #include "llvm/ADT/DenseMap.h"
 #include "llvm/Support/Regex.h"
 
 namespace lld {
 namespace elf {
 class Lazy;
 template <class ELFT> class OutputSectionBase;
 struct Symbol;
 
-typedef llvm::CachedHash<StringRef> SymName;
+typedef llvm::CachedHashStringRef SymName;
 
 // SymbolTable is a bucket of all known symbols, including defined,
 // undefined, or lazy symbols (the last one is symbols in archive
 // files whose archive members are not yet loaded).
 //
 // We put all symbols of all files to a SymbolTable, and the
 // SymbolTable selects the "best" symbols if there are name
 // conflicts. For example, obviously, a defined symbol is better than

lld/ELF/SymbolTable.cpp

DefinedRegular<ELFT> *SymbolTable<ELFT>::addIgnored(StringRef Name,
   if (!find(Name))
     return nullptr;
   return addAbsolute(Name, Visibility);
 }
 
 // Set a flag for --trace-symbol so that we can print out a log message
 // if a new symbol with the same name is inserted into the symbol table.
 template <class ELFT> void SymbolTable<ELFT>::trace(StringRef Name) {
-  Symtab.insert({Name, {-1, true}});
+  Symtab.insert({CachedHashStringRef(Name), {-1, true}});
 }
 
 // Rename SYM as __wrap_SYM. The original symbol is preserved as __real_SYM.
 // Used to implement --wrap.
 template <class ELFT> void SymbolTable<ELFT>::wrap(StringRef Name) {
   SymbolBody *B = find(Name);
   if (!B)
     return;
static std::pair<StringRef, uint16_t> getSymbolVersion(StringRef S) {
   // It is an error if the specified version was not defined.
   error("symbol " + S + " has undefined version " + Verstr);
   return {S, Config->DefaultSymbolVersion};
 }
 
 // Find an existing symbol or create and insert a new one.
 template <class ELFT>
 std::pair<Symbol *, bool> SymbolTable<ELFT>::insert(StringRef &Name) {
-  auto P = Symtab.insert({Name, SymIndex((int)SymVector.size(), false)});
+  auto P = Symtab.insert(
+      {CachedHashStringRef(Name), SymIndex((int)SymVector.size(), false)});
   SymIndex &V = P.first->second;
   bool IsNew = P.second;
 
   if (V.Idx == -1) {
     IsNew = true;
     V = SymIndex((int)SymVector.size(), true);
   }
 
Symbol *SymbolTable<ELFT>::addBitcode(StringRef Name, uint8_t Binding,
   if (Cmp > 0)
     replaceBody<DefinedRegular<ELFT>>(S, Name, StOther, Type, F);
   else if (Cmp == 0)
     reportDuplicate(S->body(), F);
   return S;
 }
 
 template <class ELFT> SymbolBody *SymbolTable<ELFT>::find(StringRef Name) {
-  auto It = Symtab.find(Name);
+  auto It = Symtab.find(CachedHashStringRef(Name));
   if (It == Symtab.end())
     return nullptr;
   SymIndex V = It->second;
   if (V.Idx == -1)
     return nullptr;
   return SymVector[V.Idx]->body();
 }