From 466c82b74f72c6b122e97a3a4c903c173045ef08 Mon Sep 17 00:00:00 2001
From: Rui Ueyama <ruiu@google.com>
Date: Wed, 24 May 2017 18:22:27 +0000
Subject: [PATCH] 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  | 21 +++++++++------------
 lld/ELF/InputFiles.h    |  9 +++------
 lld/ELF/SymbolTable.cpp |  2 +-
 lld/ELF/SymbolTable.h   |  2 +-
 4 files changed, 14 insertions(+), 20 deletions(-)

diff --git a/lld/ELF/InputFiles.cpp b/lld/ELF/InputFiles.cpp
index fe036a644f41..05140d49d270 100644
--- a/lld/ELF/InputFiles.cpp
+++ b/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>();
diff --git a/lld/ELF/InputFiles.h b/lld/ELF/InputFiles.h
index 6daf26649859..8b0e2e3f0bcd 100644
--- a/lld/ELF/InputFiles.h
+++ b/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;
 
diff --git a/lld/ELF/SymbolTable.cpp b/lld/ELF/SymbolTable.cpp
index ed8a790c9599..dae294fca6ee 100644
--- a/lld/ELF/SymbolTable.cpp
+++ b/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);
   }
diff --git a/lld/ELF/SymbolTable.h b/lld/ELF/SymbolTable.h
index 1a745f9deea5..2f39e98e4a68 100644
--- a/lld/ELF/SymbolTable.h
+++ b/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;