Simplify a variable type by using StringRef instead of CachedHashStringRef.

A variable `ComdatGroup` is not supposed to contain a large number of
items. Even when linking clang, it ends up having only 300K strings.
It doesn't make sense to use CachedHashStringRef for this hash table.
This patch has neutral or slightly positive impact on performance while
reducing code complexity.

llvm-svn: 303787

lld/ELF/InputFiles.cpp

@@ -192,7 +192,7 @@ ArrayRef<SymbolBody *> elf::ObjectFile<ELFT>::getSymbols() {
 }
 
 template <class ELFT>
-void elf::ObjectFile<ELFT>::parse(DenseSet<CachedHashStringRef> &ComdatGroups) {
+void elf::ObjectFile<ELFT>::parse(DenseSet<StringRef> &ComdatGroups) {
   // Read section and symbol tables.
   initializeSections(ComdatGroups);
   initializeSymbols();
@@ -280,7 +280,7 @@ bool elf::ObjectFile<ELFT>::shouldMerge(const Elf_Shdr &Sec) {
 
 template <class ELFT>
 void elf::ObjectFile<ELFT>::initializeSections(
-    DenseSet<CachedHashStringRef> &ComdatGroups) {
+    DenseSet<StringRef> &ComdatGroups) {
   ArrayRef<Elf_Shdr> ObjSections =
       check(this->getObj().sections(), toString(this));
   const ELFFile<ELFT> &Obj = this->getObj();
@@ -305,10 +305,7 @@ void elf::ObjectFile<ELFT>::initializeSections(
     switch (Sec.sh_type) {
     case SHT_GROUP:
       this->Sections[I] = &InputSection::Discarded;
-      if (ComdatGroups
-              .insert(
-                  CachedHashStringRef(getShtGroupSignature(ObjSections, Sec)))
-              .second)
+      if (ComdatGroups.insert(getShtGroupSignature(ObjSections, Sec)).second)
         continue;
       for (uint32_t SecIndex : getShtGroupEntries(Sec)) {
         if (SecIndex >= Size)
@@ -876,10 +873,10 @@ static Symbol *createBitcodeSymbol(const std::vector<bool> &KeptComdats,
 }
 
 template <class ELFT>
-void BitcodeFile::parse(DenseSet<CachedHashStringRef> &ComdatGroups) {
+void BitcodeFile::parse(DenseSet<StringRef> &ComdatGroups) {
   std::vector<bool> KeptComdats;
   for (StringRef S : Obj->getComdatTable())
-    KeptComdats.push_back(ComdatGroups.insert(CachedHashStringRef(S)).second);
+    KeptComdats.push_back(ComdatGroups.insert(StringRef(S)).second);
 
   for (const lto::InputFile::Symbol &ObjSym : Obj->symbols())
     Symbols.push_back(createBitcodeSymbol<ELFT>(KeptComdats, ObjSym, this));
@@ -1048,10 +1045,10 @@ template void ArchiveFile::parse<ELF32BE>();
 template void ArchiveFile::parse<ELF64LE>();
 template void ArchiveFile::parse<ELF64BE>();
 
-template void BitcodeFile::parse<ELF32LE>(DenseSet<CachedHashStringRef> &);
-template void BitcodeFile::parse<ELF32BE>(DenseSet<CachedHashStringRef> &);
-template void BitcodeFile::parse<ELF64LE>(DenseSet<CachedHashStringRef> &);
-template void BitcodeFile::parse<ELF64BE>(DenseSet<CachedHashStringRef> &);
+template void BitcodeFile::parse<ELF32LE>(DenseSet<StringRef> &);
+template void BitcodeFile::parse<ELF32BE>(DenseSet<StringRef> &);
+template void BitcodeFile::parse<ELF64LE>(DenseSet<StringRef> &);
+template void BitcodeFile::parse<ELF64BE>(DenseSet<StringRef> &);
 
 template void LazyObjectFile::parse<ELF32LE>();
 template void LazyObjectFile::parse<ELF32BE>();

lld/ELF/InputFiles.h

@@ -17,7 +17,6 @@
 
 #include "lld/Core/LLVM.h"
 #include "lld/Core/Reproduce.h"
-#include "llvm/ADT/CachedHashString.h"
 #include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/STLExtras.h"
 #include "llvm/IR/Comdat.h"
@@ -157,7 +156,7 @@ public:
   ArrayRef<SymbolBody *> getLocalSymbols();
 
   ObjectFile(MemoryBufferRef M, StringRef ArchiveName);
-  void parse(llvm::DenseSet<llvm::CachedHashStringRef> &ComdatGroups);
+  void parse(llvm::DenseSet<StringRef> &ComdatGroups);
 
   InputSectionBase *getSection(const Elf_Sym &Sym) const;
 
@@ -189,8 +188,7 @@ public:
   StringRef SourceFile;
 
 private:
-  void
-  initializeSections(llvm::DenseSet<llvm::CachedHashStringRef> &ComdatGroups);
+  void initializeSections(llvm::DenseSet<StringRef> &ComdatGroups);
   void initializeSymbols();
   void initializeDwarfLine();
   InputSectionBase *getRelocTarget(const Elf_Shdr &Sec);
@@ -265,8 +263,7 @@ public:
   BitcodeFile(MemoryBufferRef M, StringRef ArchiveName,
               uint64_t OffsetInArchive);
   static bool classof(const InputFile *F) { return F->kind() == BitcodeKind; }
-  template <class ELFT>
-  void parse(llvm::DenseSet<llvm::CachedHashStringRef> &ComdatGroups);
+  template <class ELFT> void parse(llvm::DenseSet<StringRef> &ComdatGroups);
   ArrayRef<Symbol *> getSymbols() { return Symbols; }
   std::unique_ptr<llvm::lto::InputFile> Obj;
 

lld/ELF/SymbolTable.cpp

@@ -122,7 +122,7 @@ template <class ELFT> void SymbolTable<ELFT>::addCombinedLTOObject() {
 
   for (InputFile *File : LTO->compile()) {
     ObjectFile<ELFT> *Obj = cast<ObjectFile<ELFT>>(File);
-    DenseSet<CachedHashStringRef> DummyGroups;
+    DenseSet<StringRef> DummyGroups;
     Obj->parse(DummyGroups);
     ObjectFiles.push_back(Obj);
   }

lld/ELF/SymbolTable.h

@@ -117,7 +117,7 @@ private:
   // Comdat groups define "link once" sections. If two comdat groups have the
   // same name, only one of them is linked, and the other is ignored. This set
   // is used to uniquify them.
-  llvm::DenseSet<llvm::CachedHashStringRef> ComdatGroups;
+  llvm::DenseSet<StringRef> ComdatGroups;
 
   std::vector<ObjectFile<ELFT> *> ObjectFiles;
   std::vector<SharedFile<ELFT> *> SharedFiles;