Subzero. Allocate global initializers from a dedicated arena.

src/IceCfg.cpp

@@ -122,46 +122,43 @@ bool Cfg::hasComputedFrame() const { return getTarget()->hasComputedFrame(); }
 namespace {
 constexpr char BlockNameGlobalPrefix[] = ".L$profiler$block_name$";
 constexpr char BlockStatsGlobalPrefix[] = ".L$profiler$block_info$";
+} // end of anonymous namespace
 
-VariableDeclaration *nodeNameDeclaration(GlobalContext *Ctx,
-                                         const IceString &NodeAsmName) {
-  auto *Var = VariableDeclaration::create(Ctx);
+void Cfg::createNodeNameDeclaration(const IceString &NodeAsmName) {
+  auto *Var = VariableDeclaration::create(GlobalInits.get());
   Var->setName(BlockNameGlobalPrefix + NodeAsmName);
   Var->setIsConstant(true);
   Var->addInitializer(VariableDeclaration::DataInitializer::create(
-      NodeAsmName.data(), NodeAsmName.size() + 1));
+      GlobalInits.get(), NodeAsmName.data(), NodeAsmName.size() + 1));
   const SizeT Int64ByteSize = typeWidthInBytes(IceType_i64);
   Var->setAlignment(Int64ByteSize); // Wasteful, 32-bit could use 4 bytes.
-  return Var;
+  GlobalInits->push_back(Var);
 }
 
-VariableDeclaration *
-blockProfilingInfoDeclaration(GlobalContext *Ctx, const IceString &NodeAsmName,
-                              VariableDeclaration *NodeNameDeclaration) {
-  auto *Var = VariableDeclaration::create(Ctx);
+void Cfg::createBlockProfilingInfoDeclaration(
+    const IceString &NodeAsmName, VariableDeclaration *NodeNameDeclaration) {
+  auto *Var = VariableDeclaration::create(GlobalInits.get());
   Var->setName(BlockStatsGlobalPrefix + NodeAsmName);
   const SizeT Int64ByteSize = typeWidthInBytes(IceType_i64);
-  Var->addInitializer(
-      VariableDeclaration::ZeroInitializer::create(Int64ByteSize));
+  Var->addInitializer(VariableDeclaration::ZeroInitializer::create(
+      GlobalInits.get(), Int64ByteSize));
 
   const RelocOffsetT NodeNameDeclarationOffset = 0;
   Var->addInitializer(VariableDeclaration::RelocInitializer::create(
-      NodeNameDeclaration,
+      GlobalInits.get(), NodeNameDeclaration,
       {RelocOffset::create(Ctx, NodeNameDeclarationOffset)}));
   Var->setAlignment(Int64ByteSize);
-  return Var;
+  GlobalInits->push_back(Var);
 }
-} // end of anonymous namespace
 
 void Cfg::profileBlocks() {
   if (GlobalInits == nullptr)
     GlobalInits.reset(new VariableDeclarationList());
 
   for (CfgNode *Node : Nodes) {
-    IceString NodeAsmName = Node->getAsmName();
-    GlobalInits->push_back(nodeNameDeclaration(Ctx, NodeAsmName));
-    GlobalInits->push_back(
-        blockProfilingInfoDeclaration(Ctx, NodeAsmName, GlobalInits->back()));
+    const IceString NodeAsmName = Node->getAsmName();
+    createNodeNameDeclaration(NodeAsmName);
+    createBlockProfilingInfoDeclaration(NodeAsmName, GlobalInits->back());
     Node->profileExecutionCount(GlobalInits->back());
   }
 }

src/IceCfg.h

@@ -158,6 +158,12 @@ public:
     }
     GlobalInits->push_back(Global);
   }
+  VariableDeclarationList *getGlobalPool() {
+    if (GlobalInits == nullptr) {
+      GlobalInits.reset(new VariableDeclarationList);
+    }
+    return GlobalInits.get();
+  }
   /// @}
 
   /// \name Miscellaneous accessors.
@@ -269,6 +275,11 @@ private:
   /// code needs to be defined.
   void profileBlocks();
 
+  void createNodeNameDeclaration(const IceString &NodeAsmName);
+  void
+  createBlockProfilingInfoDeclaration(const IceString &NodeAsmName,
+                                      VariableDeclaration *NodeNameDeclaration);
+
   /// Delete registered jump table placeholder instructions. This should only be
   /// called once all repointing has taken place.
   void deleteJumpTableInsts();

src/IceCompiler.cpp

@@ -93,6 +93,9 @@ void Compiler::run(const Ice::ClFlagsExtra &ExtraFlags, GlobalContext &Ctx,
       Ctx.getErrorStatus()->assign(EC_Args);
       return;
     }
+    // Globals must be kept alive after lowering when converting from LLVM to
+    // Ice.
+    Ctx.setDisposeGlobalVariablesAfterLowering(false);
     // Parse the input LLVM IR file into a module.
     llvm::SMDiagnostic Err;
     TimerMarker T1(Ice::TimerStack::TT_parse, &Ctx);

src/IceConverter.cpp

@@ -659,13 +659,13 @@ class LLVM2ICEGlobalsConverter : public LLVM2ICEConverter {
   operator=(const LLVM2ICEGlobalsConverter &) = delete;
 
 public:
-  explicit LLVM2ICEGlobalsConverter(Ice::Converter &Converter)
-      : LLVM2ICEConverter(Converter) {}
+  explicit LLVM2ICEGlobalsConverter(Ice::Converter &Converter,
+                                    Ice::VariableDeclarationList *G)
+      : LLVM2ICEConverter(Converter), GlobalPool(G) {}
 
   /// Converts global variables, and their initializers into ICE global variable
   /// declarations, for module Mod. Returns the set of converted declarations.
-  std::unique_ptr<Ice::VariableDeclarationList>
-  convertGlobalsToIce(Module *Mod);
+  void convertGlobalsToIce(Module *Mod);
 
 private:
   // Adds the Initializer to the list of initializers for the Global variable
@@ -697,12 +697,11 @@ private:
     report_fatal_error(StrBuf.str());
     return 0;
   }
+
+  Ice::VariableDeclarationList *GlobalPool;
 };
 
-std::unique_ptr<Ice::VariableDeclarationList>
-LLVM2ICEGlobalsConverter::convertGlobalsToIce(Module *Mod) {
-  std::unique_ptr<Ice::VariableDeclarationList> VariableDeclarations(
-      new Ice::VariableDeclarationList);
+void LLVM2ICEGlobalsConverter::convertGlobalsToIce(Module *Mod) {
   for (Module::const_global_iterator I = Mod->global_begin(),
                                      E = Mod->global_end();
        I != E; ++I) {
@@ -711,7 +710,7 @@ LLVM2ICEGlobalsConverter::convertGlobalsToIce(Module *Mod) {
 
     Ice::GlobalDeclaration *Var = getConverter().getGlobalDeclaration(GV);
     auto *VarDecl = cast<Ice::VariableDeclaration>(Var);
-    VariableDeclarations->push_back(VarDecl);
+    GlobalPool->push_back(VarDecl);
 
     if (!GV->hasInternalLinkage() && GV->hasInitializer()) {
       std::string Buffer;
@@ -744,7 +743,6 @@ LLVM2ICEGlobalsConverter::convertGlobalsToIce(Module *Mod) {
       addGlobalInitializer(*VarDecl, Initializer);
     }
   }
-  return VariableDeclarations;
 }
 
 void LLVM2ICEGlobalsConverter::addGlobalInitializer(
@@ -757,7 +755,7 @@ void LLVM2ICEGlobalsConverter::addGlobalInitializer(
     assert(!HasOffset && isa<IntegerType>(CDA->getElementType()) &&
            (cast<IntegerType>(CDA->getElementType())->getBitWidth() == 8));
     Global.addInitializer(Ice::VariableDeclaration::DataInitializer::create(
-        CDA->getRawDataValues().data(), CDA->getNumElements()));
+        GlobalPool, CDA->getRawDataValues().data(), CDA->getNumElements()));
     return;
   }
 
@@ -766,7 +764,7 @@ void LLVM2ICEGlobalsConverter::addGlobalInitializer(
       assert(!HasOffset && isa<IntegerType>(AT->getElementType()) &&
              (cast<IntegerType>(AT->getElementType())->getBitWidth() == 8));
       Global.addInitializer(Ice::VariableDeclaration::ZeroInitializer::create(
-          AT->getNumElements()));
+          GlobalPool, AT->getNumElements()));
     } else {
       llvm_unreachable("Unhandled constant aggregate zero type");
     }
@@ -788,7 +786,7 @@ void LLVM2ICEGlobalsConverter::addGlobalInitializer(
       const Ice::GlobalDeclaration *Addr =
           getConverter().getGlobalDeclaration(GV);
       Global.addInitializer(Ice::VariableDeclaration::RelocInitializer::create(
-          Addr, {Ice::RelocOffset::create(Ctx, Offset)}));
+          GlobalPool, Addr, {Ice::RelocOffset::create(Ctx, Offset)}));
       return;
     }
     default:
@@ -890,8 +888,8 @@ void Converter::installGlobalDeclarations(Module *Mod) {
        I != E; ++I) {
     const GlobalVariable *GV = I;
     constexpr bool NoSuppressMangling = false;
-    auto *Var =
-        VariableDeclaration::create(Ctx, NoSuppressMangling, GV->getLinkage());
+    auto *Var = VariableDeclaration::create(
+        GlobalDeclarationsPool.get(), NoSuppressMangling, GV->getLinkage());
     Var->setAlignment(GV->getAlignment());
     Var->setIsConstant(GV->isConstant());
     Var->setName(GV->getName());
@@ -909,7 +907,9 @@ void Converter::installGlobalDeclarations(Module *Mod) {
 }
 
 void Converter::convertGlobals(Module *Mod) {
-  lowerGlobals(LLVM2ICEGlobalsConverter(*this).convertGlobalsToIce(Mod));
+  LLVM2ICEGlobalsConverter(*this, GlobalDeclarationsPool.get())
+      .convertGlobalsToIce(Mod);
+  lowerGlobals(std::move(GlobalDeclarationsPool));
 }
 
 void Converter::convertFunctions() {

src/IceConverter.h

@@ -32,7 +32,8 @@ class Converter : public Translator {
 
 public:
   Converter(llvm::Module *Mod, GlobalContext *Ctx)
-      : Translator(Ctx), Mod(Mod) {}
+      : Translator(Ctx), Mod(Mod),
+        GlobalDeclarationsPool(new VariableDeclarationList()) {}
 
   ~Converter() override = default;
 
@@ -52,6 +53,8 @@ private:
       std::map<const llvm::GlobalValue *, GlobalDeclaration *>;
   GlobalDeclarationMapType GlobalDeclarationMap;
 
+  std::unique_ptr<VariableDeclarationList> GlobalDeclarationsPool;
+
   /// Walks module and generates names for unnamed globals using prefix
   /// getFlags().DefaultGlobalPrefix, if the prefix is non-empty.
   void nameUnnamedGlobalVariables(llvm::Module *Mod);

src/IceDefs.h

@@ -73,6 +73,11 @@ class Variable;
 class VariableDeclaration;
 class VariablesMetadata;
 
+/// SizeT is for holding small-ish limits like number of source operands in an
+/// instruction. It is used instead of size_t (which may be 64-bits wide) when
+/// we want to save space.
+using SizeT = uint32_t;
+
 constexpr char GlobalOffsetTable[] = "_GLOBAL_OFFSET_TABLE_";
 // makeUnique should be used when memory is expected to be allocated from the
 // heap (as opposed to allocated from some Allocator.) It is intended to be
@@ -139,12 +144,127 @@ using NodeList = CfgVector<CfgNode *>;
 // Containers that use the default (global) allocator.
 using ConstantList = std::vector<Constant *>;
 using FunctionDeclarationList = std::vector<FunctionDeclaration *>;
-using VariableDeclarationList = std::vector<VariableDeclaration *>;
 
-/// SizeT is for holding small-ish limits like number of source operands in an
-/// instruction. It is used instead of size_t (which may be 64-bits wide) when
-/// we want to save space.
-using SizeT = uint32_t;
+/// VariableDeclarationList is a container for holding VariableDeclarations --
+/// i.e., Global Variables. It is also used to create said variables, and their
+/// initializers in an arena.
+class VariableDeclarationList {
+  VariableDeclarationList(const VariableDeclarationList &) = delete;
+  VariableDeclarationList &operator=(const VariableDeclarationList &) = delete;
+  VariableDeclarationList(VariableDeclarationList &&) = delete;
+  VariableDeclarationList &operator=(VariableDeclarationList &&) = delete;
+
+public:
+  using VariableDeclarationArray = std::vector<VariableDeclaration *>;
+
+  VariableDeclarationList() : Arena(new ArenaAllocator()) {}
+
+  ~VariableDeclarationList() { clearAndPurge(); }
+
+  template <typename T> T *allocate_initializer(SizeT Count = 1) {
+    static_assert(
+        std::is_trivially_destructible<T>::value,
+        "allocate_initializer can only allocate trivially destructible types.");
+    return Arena->Allocate<T>(Count);
+  }
+
+  template <typename T> T *allocate_variable_declaration() {
+    static_assert(!std::is_trivially_destructible<T>::value,
+                  "allocate_variable_declaration expects non-trivially "
+                  "destructible types.");
+    T *Ret = Arena->Allocate<T>();
+    Dtors.emplace_back([Ret]() { Ret->~T(); });
+    return Ret;
+  }
+
+  // This do nothing method is invoked when a global variable is created, but it
+  // will not be emitted. If we ever need to track the created variabled, having
+  // this hook is handy.
+  void willNotBeEmitted(VariableDeclaration *) {}
+
+  /// Merges Other with this, effectively resetting Other to an empty state.
+  void merge(VariableDeclarationList *Other) {
+    assert(Other != nullptr);
+    addArena(std::move(Other->Arena));
+    for (std::size_t i = 0; i < Other->MergedArenas.size(); ++i) {
+      addArena(std::move(Other->MergedArenas[i]));
+    }
+    Other->MergedArenas.clear();
+
+    Dtors.insert(Dtors.end(), Other->Dtors.begin(), Other->Dtors.end());
+    Other->Dtors.clear();
+
+    Globals.insert(Globals.end(), Other->Globals.begin(), Other->Globals.end());
+    Other->Globals.clear();
+  }
+
+  /// Destroys all GlobalVariables and initializers that this knows about
+  /// (including those merged with it), and releases memory.
+  void clearAndPurge() {
+    if (Arena == nullptr) {
+      // Arena is only null if this was merged, so we ensure there's no state
+      // being held by this.
+      assert(Dtors.empty());
+      assert(Globals.empty());
+      assert(MergedArenas.empty());
+      return;
+    }
+    // Invokes destructors in reverse creation order.
+    for (auto Dtor = Dtors.rbegin(); Dtor != Dtors.rend(); ++Dtor) {
+      (*Dtor)();
+    }
+    Dtors.clear();
+    Globals.clear();
+    MergedArenas.clear();
+    Arena->Reset();
+  }
+
+  /// Adapt the relevant parts of the std::vector<VariableDeclaration *>
+  /// interface.
+  /// @{
+  VariableDeclarationArray::iterator begin() { return Globals.begin(); }
+
+  VariableDeclarationArray::iterator end() { return Globals.end(); }
+
+  VariableDeclarationArray::const_iterator begin() const {
+    return Globals.begin();
+  }
+
+  VariableDeclarationArray::const_iterator end() const { return Globals.end(); }
+
+  bool empty() const { return Globals.empty(); }
+
+  VariableDeclarationArray::size_type size() const { return Globals.size(); }
+
+  VariableDeclarationArray::reference
+  at(VariableDeclarationArray::size_type Pos) {
+    return Globals.at(Pos);
+  }
+
+  void push_back(VariableDeclaration *Global) { Globals.push_back(Global); }
+
+  void reserve(VariableDeclarationArray::size_type Capacity) {
+    Globals.reserve(Capacity);
+  }
+
+  void clear() { Globals.clear(); }
+
+  VariableDeclarationArray::reference back() { return Globals.back(); }
+  /// @}
+
+private:
+  using ArenaPtr = std::unique_ptr<ArenaAllocator>;
+  using DestructorsArray = std::vector<std::function<void()>>;
+
+  void addArena(ArenaPtr NewArena) {
+    MergedArenas.emplace_back(std::move(NewArena));
+  }
+
+  ArenaPtr Arena;
+  VariableDeclarationArray Globals;
+  DestructorsArray Dtors;
+  std::vector<ArenaPtr> MergedArenas;
+};
 
 /// InstNumberT is for holding an instruction number. Instruction numbers are
 /// used for representing Variable live ranges.

src/IceELFObjectWriter.cpp

@@ -288,7 +288,7 @@ classifyGlobalSection(const VariableDeclaration *Var) {
 // Partition the Vars list by SectionType into VarsBySection. If TranslateOnly
 // is non-empty, then only the TranslateOnly variable is kept for emission.
 void partitionGlobalsBySection(const VariableDeclarationList &Vars,
-                               VariableDeclarationList VarsBySection[],
+                               VariableDeclarationPartition VarsBySection[],
                                const IceString &TranslateOnly) {
   for (VariableDeclaration *Var : Vars) {
     if (GlobalContext::matchSymbolName(Var->getName(), TranslateOnly)) {
@@ -307,7 +307,7 @@ void ELFObjectWriter::writeDataSection(const VariableDeclarationList &Vars,
                                        bool IsPIC) {
   TimerMarker Timer(TimerStack::TT_writeELF, &Ctx);
   assert(!SectionNumbersAssigned);
-  VariableDeclarationList VarsBySection[ELFObjectWriter::NumSectionTypes];
+  VariableDeclarationPartition VarsBySection[ELFObjectWriter::NumSectionTypes];
   for (auto &SectionList : VarsBySection)
     SectionList.reserve(Vars.size());
   partitionGlobalsBySection(Vars, VarsBySection,
@@ -329,7 +329,7 @@ IceString MangleSectionName(const char Base[], const IceString &Suffix) {
 
 // TODO(jvoung): Handle fdata-sections.
 void ELFObjectWriter::writeDataOfType(SectionType ST,
-                                      const VariableDeclarationList &Vars,
+                                      const VariableDeclarationPartition &Vars,
                                       FixupKind RelocationKind,
                                       const IceString &SectionSuffix,
                                       bool IsPIC) {
@@ -407,12 +407,11 @@ void ELFObjectWriter::writeDataOfType(SectionType ST,
         Section->setSize(Section->getCurrentSize() + SymbolSize);
     } else {
       assert(ST != BSS);
-      for (const std::unique_ptr<VariableDeclaration::Initializer> &Init :
-           Var->getInitializers()) {
+      for (const auto *Init : Var->getInitializers()) {
         switch (Init->getKind()) {
         case VariableDeclaration::Initializer::DataInitializerKind: {
           const auto &Data =
-              llvm::cast<VariableDeclaration::DataInitializer>(Init.get())
+              llvm::cast<VariableDeclaration::DataInitializer>(Init)
                   ->getContents();
           Section->appendData(Str, llvm::StringRef(Data.data(), Data.size()));
           break;
@@ -422,7 +421,7 @@ void ELFObjectWriter::writeDataOfType(SectionType ST,
           break;
         case VariableDeclaration::Initializer::RelocInitializerKind: {
           const auto *Reloc =
-              llvm::cast<VariableDeclaration::RelocInitializer>(Init.get());
+              llvm::cast<VariableDeclaration::RelocInitializer>(Init);
           AssemblerFixup NewFixup;
           NewFixup.set_position(Section->getCurrentSize());
           NewFixup.set_kind(Reloc->hasFixup() ? Reloc->getFixup()

src/IceELFObjectWriter.h

@@ -24,6 +24,8 @@ using namespace llvm::ELF;
 
 namespace Ice {
 
+using VariableDeclarationPartition = std::vector<VariableDeclaration *>;
+
 /// Higher level ELF object writer. Manages section information and writes the
 /// final ELF object. The object writer will write to file the code and data as
 /// it is being defined (rather than keep a copy). After all definitions are
@@ -153,7 +155,7 @@ private:
   /// SectionType, given the global variables Vars belonging to that
   /// SectionType.
   void writeDataOfType(SectionType SectionType,
-                       const VariableDeclarationList &Vars,
+                       const VariableDeclarationPartition &Vars,
                        FixupKind RelocationKind, const IceString &SectionSuffix,
                        bool IsPIC);
 

src/IceGlobalContext.cpp

@@ -292,17 +292,6 @@ GlobalContext::GlobalContext(Ostream *OsDump, Ostream *OsEmit, Ostream *OsError,
     break;
   }
 
-  // ProfileBlockInfoVarDecl is initialized here because it takes this as a
-  // parameter -- we want to
-  // ensure that at least this' member variables are initialized.
-  ProfileBlockInfoVarDecl = VariableDeclaration::createExternal(this);
-  ProfileBlockInfoVarDecl->setAlignment(typeWidthInBytes(IceType_i64));
-  ProfileBlockInfoVarDecl->setIsConstant(true);
-
-  // Note: if you change this symbol, make sure to update
-  // runtime/szrt_profiler.c as well.
-  ProfileBlockInfoVarDecl->setName("__Sz_block_profile_info");
-
   TargetLowering::staticInit(this);
 }
 
@@ -397,14 +386,10 @@ void GlobalContext::lowerConstants() { DataLowering->lowerConstants(); }
 
 void GlobalContext::lowerJumpTables() { DataLowering->lowerJumpTables(); }
 
-void GlobalContext::addBlockInfoPtrs(VariableDeclaration *ProfileBlockInfo) {
-  for (const VariableDeclaration *Global : Globals) {
+void GlobalContext::saveBlockInfoPtrs() {
+  for (VariableDeclaration *Global : Globals) {
     if (Cfg::isProfileGlobal(*Global)) {
-      constexpr RelocOffsetT BlockExecutionCounterOffset = 0;
-      ProfileBlockInfo->addInitializer(
-          VariableDeclaration::RelocInitializer::create(
-              Global,
-              {RelocOffset::create(this, BlockExecutionCounterOffset)}));
+      ProfileBlockInfos.push_back(Global);
     }
   }
 }
@@ -424,7 +409,7 @@ void GlobalContext::lowerGlobals(const IceString &SectionSuffix) {
   if (Flags.getDisableTranslation())
     return;
 
-  addBlockInfoPtrs(ProfileBlockInfoVarDecl);
+  saveBlockInfoPtrs();
   // If we need to shuffle the layout of global variables, shuffle them now.
   if (getFlags().shouldReorderGlobalVariables()) {
     // Create a random number generator for global variable reordering.
@@ -434,26 +419,48 @@ void GlobalContext::lowerGlobals(const IceString &SectionSuffix) {
                   [&RNG](int N) { return (uint32_t)RNG.next(N); });
   }
   DataLowering->lowerGlobals(Globals, SectionSuffix);
-  for (VariableDeclaration *Var : Globals) {
-    Var->discardInitializers();
-  }
+  if (ProfileBlockInfos.empty() && DisposeGlobalVariablesAfterLowering) {
+    Globals.clearAndPurge();
+  } else {
     Globals.clear();
+  }
 }
 
 void GlobalContext::lowerProfileData() {
   // ProfileBlockInfoVarDecl is initialized in the constructor, and will only
   // ever be nullptr after this method completes. This assertion is a convoluted
   // way of ensuring lowerProfileData is invoked a single time.
-  assert(ProfileBlockInfoVarDecl != nullptr);
+  assert(ProfileBlockInfoVarDecl == nullptr);
+
+  auto GlobalVariablePool = getInitializerAllocator();
+  ProfileBlockInfoVarDecl =
+      VariableDeclaration::createExternal(GlobalVariablePool.get());
+  ProfileBlockInfoVarDecl->setAlignment(typeWidthInBytes(IceType_i64));
+  ProfileBlockInfoVarDecl->setIsConstant(true);
+
+  // Note: if you change this symbol, make sure to update
+  // runtime/szrt_profiler.c as well.
+  ProfileBlockInfoVarDecl->setName("__Sz_block_profile_info");
+
+  for (const VariableDeclaration *PBI : ProfileBlockInfos) {
+    if (Cfg::isProfileGlobal(*PBI)) {
+      constexpr RelocOffsetT BlockExecutionCounterOffset = 0;
+      ProfileBlockInfoVarDecl->addInitializer(
+          VariableDeclaration::RelocInitializer::create(
+              GlobalVariablePool.get(), PBI,
+              {RelocOffset::create(this, BlockExecutionCounterOffset)}));
+    }
+  }
+
   // This adds a 64-bit sentinel entry to the end of our array. For 32-bit
   // architectures this will waste 4 bytes.
   const SizeT Sizeof64BitNullPtr = typeWidthInBytes(IceType_i64);
   ProfileBlockInfoVarDecl->addInitializer(
-      VariableDeclaration::ZeroInitializer::create(Sizeof64BitNullPtr));
+      VariableDeclaration::ZeroInitializer::create(GlobalVariablePool.get(),
+                                                   Sizeof64BitNullPtr));
   Globals.push_back(ProfileBlockInfoVarDecl);
   constexpr char ProfileDataSection[] = "$sz_profiler$";
   lowerGlobals(ProfileDataSection);
-  ProfileBlockInfoVarDecl = nullptr;
 }
 
 void GlobalContext::emitItems() {

src/IceGlobalContext.h

@@ -57,6 +57,7 @@ public:
   ~LockedPtr() { Lock->unlock(); }
   T *operator->() const { return Value; }
   T &operator*() const { return *Value; }
+  T *get() { return Value; }
 
 private:
   T *Value;
@@ -435,6 +436,18 @@ public:
   static ClFlags Flags;
   static ClFlagsExtra ExtraFlags;
 
+  /// DisposeGlobalVariablesAfterLowering controls whether the memory used by
+  /// GlobaleVariables can be reclaimed right after they have been lowered.
+  /// @{
+  bool getDisposeGlobalVariablesAfterLowering() const {
+    return DisposeGlobalVariablesAfterLowering;
+  }
+
+  void setDisposeGlobalVariablesAfterLowering(bool Value) {
+    DisposeGlobalVariablesAfterLowering = Value;
+  }
+  /// @}
+
 private:
   // Try to ensure mutexes are allocated on separate cache lines.
 
@@ -445,6 +458,11 @@ private:
   ArenaAllocator Allocator;
 
   ICE_CACHELINE_BOUNDARY;
+  // Managed by getInitializerAllocator()
+  GlobalLockType InitAllocLock;
+  VariableDeclarationList Globals;
+
+  ICE_CACHELINE_BOUNDARY;
   // Managed by getDestructors()
   using DestructorArray = std::vector<std::function<void()>>;
   GlobalLockType DestructorsLock;
@@ -499,13 +517,18 @@ private:
   // TODO(jpp): move to EmitterContext.
   bool HasSeenCode = false;
   // TODO(jpp): move to EmitterContext.
-  VariableDeclarationList Globals;
-  // TODO(jpp): move to EmitterContext.
-  VariableDeclaration *ProfileBlockInfoVarDecl;
+  VariableDeclaration *ProfileBlockInfoVarDecl = nullptr;
+  std::vector<VariableDeclaration *> ProfileBlockInfos;
+  /// Indicates if global variable declarations can be disposed of right after
+  /// lowering.
+  bool DisposeGlobalVariablesAfterLowering = true;
 
   LockedPtr<ArenaAllocator> getAllocator() {
     return LockedPtr<ArenaAllocator>(&Allocator, &AllocLock);
   }
+  LockedPtr<VariableDeclarationList> getInitializerAllocator() {
+    return LockedPtr<VariableDeclarationList>(&Globals, &InitAllocLock);
+  }
   LockedPtr<ConstantPool> getConstPool() {
     return LockedPtr<ConstantPool>(ConstPool.get(), &ConstPoolLock);
   }
@@ -523,8 +546,10 @@ private:
   }
 
   void accumulateGlobals(std::unique_ptr<VariableDeclarationList> Globls) {
-    if (Globls != nullptr)
-      Globals.insert(Globals.end(), Globls->begin(), Globls->end());
+    LockedPtr<VariableDeclarationList> _(&Globals, &InitAllocLock);
+    if (Globls != nullptr) {
+      Globals.merge(Globls.get());
+    }
   }
 
   void lowerGlobalsIfNoCodeHasBeenSeen() {
@@ -535,7 +560,7 @@ private:
     HasSeenCode = true;
   }
 
-  void addBlockInfoPtrs(VariableDeclaration *ProfileBlockInfo);
+  void saveBlockInfoPtrs();
 
   llvm::SmallVector<ThreadContext *, 128> AllThreadContexts;
   llvm::SmallVector<std::thread, 128> TranslationThreads;

src/IceGlobalInits.cpp

@@ -138,12 +138,12 @@ void FunctionDeclaration::dump(Ostream &Stream) const {
 void VariableDeclaration::dumpType(Ostream &Stream) const {
   if (!Ice::BuildDefs::dump())
     return;
-  if (Initializers->size() == 1) {
-    Initializers->front()->dumpType(Stream);
+  if (Initializers.size() == 1) {
+    Initializers.front()->dumpType(Stream);
   } else {
     Stream << "<{ ";
     bool IsFirst = true;
-    for (const std::unique_ptr<Initializer> &Init : *Initializers) {
+    for (const auto *Init : Initializers) {
       if (IsFirst) {
         IsFirst = false;
       } else {
@@ -163,13 +163,13 @@ void VariableDeclaration::dump(Ostream &Stream) const {
   Stream << " " << (IsConstant ? "constant" : "global") << " ";
 
   // Add initializer.
-  if (Initializers->size() == 1) {
-    Initializers->front()->dump(Stream);
+  if (Initializers.size() == 1) {
+    Initializers.front()->dump(Stream);
   } else {
     dumpType(Stream);
     Stream << " <{ ";
     bool IsFirst = true;
-    for (const std::unique_ptr<Initializer> &Init : *Initializers) {
+    for (const auto *Init : Initializers) {
       if (IsFirst) {
         IsFirst = false;
       } else {
@@ -199,7 +199,8 @@ void VariableDeclaration::DataInitializer::dump(Ostream &Stream) const {
   Stream << " c\"";
   // Code taken from PrintEscapedString() in AsmWriter.cpp. Keep the strings in
   // the same format as the .ll file for practical diffing.
-  for (uint8_t C : Contents) {
+  for (SizeT i = 0; i < ContentsSize; ++i) {
+    uint8_t C = Contents[i];
     if (isprint(C) && C != '\\' && C != '"')
       Stream << C;
     else

src/IceTargetLowering.cpp

@@ -826,12 +826,11 @@ void TargetDataLowering::emitGlobal(const VariableDeclaration &Var,
   Str << Name << ":\n";
 
   if (HasNonzeroInitializer) {
-    for (const std::unique_ptr<VariableDeclaration::Initializer> &Init :
-         Var.getInitializers()) {
+    for (const auto *Init : Var.getInitializers()) {
       switch (Init->getKind()) {
       case VariableDeclaration::Initializer::DataInitializerKind: {
         const auto &Data =
-            llvm::cast<VariableDeclaration::DataInitializer>(Init.get())
+            llvm::cast<VariableDeclaration::DataInitializer>(Init)
                 ->getContents();
         for (SizeT i = 0; i < Init->getNumBytes(); ++i) {
           Str << "\t.byte\t" << (((unsigned)Data[i]) & 0xff) << "\n";
@@ -843,7 +842,7 @@ void TargetDataLowering::emitGlobal(const VariableDeclaration &Var,
         break;
       case VariableDeclaration::Initializer::RelocInitializerKind: {
         const auto *Reloc =
-            llvm::cast<VariableDeclaration::RelocInitializer>(Init.get());
+            llvm::cast<VariableDeclaration::RelocInitializer>(Init);
         Str << "\t" << getEmit32Directive() << "\t";
         Str << Reloc->getDeclaration()->getName();
         if (Reloc->hasFixup()) {

src/IceTargetLoweringARM32.cpp

@@ -908,15 +908,19 @@ IceString TargetARM32::createGotoffRelocation(const ConstantRelocatable *CR) {
       "GOTOFF$" + Func->getFunctionName() + "$" + CRName;
   if (KnownGotoffs.count(CRGotoffName) == 0) {
     constexpr bool SuppressMangling = true;
-    auto *Global = VariableDeclaration::create(Ctx, SuppressMangling);
+    auto *Global =
+        VariableDeclaration::create(Func->getGlobalPool(), SuppressMangling);
     Global->setIsConstant(true);
     Global->setName(CRName);
+    Func->getGlobalPool()->willNotBeEmitted(Global);
 
-    auto *Gotoff = VariableDeclaration::create(Ctx, SuppressMangling);
+    auto *Gotoff =
+        VariableDeclaration::create(Func->getGlobalPool(), SuppressMangling);
     constexpr auto GotFixup = R_ARM_GOTOFF32;
     Gotoff->setIsConstant(true);
     Gotoff->addInitializer(VariableDeclaration::RelocInitializer::create(
-        Global, {RelocOffset::create(Ctx, 0)}, GotFixup));
+        Func->getGlobalPool(), Global, {RelocOffset::create(Ctx, 0)},
+        GotFixup));
     Gotoff->setName(CRGotoffName);
     Func->addGlobal(Gotoff);
     KnownGotoffs.emplace(CRGotoffName);

src/PNaClTranslator.cpp

@@ -257,6 +257,11 @@ public:
 
   size_t getNumTypeIDValues() const { return TypeIDValues.size(); }
 
+  /// Returns a pointer to the pool where globals are allocated.
+  Ice::VariableDeclarationList *getGlobalVariablesPool() {
+    return VariableDeclarations.get();
+  }
+
   /// Returns the undefined type associated with type ID. Note: Returns extended
   /// type ready to be defined.
   ExtendedType *getTypeByIDForDefining(NaClBcIndexSize_t ID) {
@@ -1021,9 +1026,11 @@ public:
       : BlockParserBaseClass(BlockID, EnclosingParser),
         Timer(Ice::TimerStack::TT_parseGlobals, getTranslator().getContext()),
         NumFunctionIDs(Context->getNumFunctionIDs()),
-        DummyGlobalVar(
-            Ice::VariableDeclaration::create(getTranslator().getContext())),
-        CurGlobalVar(DummyGlobalVar) {}
+        DummyGlobalVar(Ice::VariableDeclaration::create(
+            Context->getGlobalVariablesPool())),
+        CurGlobalVar(DummyGlobalVar) {
+    Context->getGlobalVariablesPool()->willNotBeEmitted(DummyGlobalVar);
+  }
 
   ~GlobalsParser() final = default;
 
@@ -1063,7 +1070,8 @@ private:
   Ice::VariableDeclaration *getGlobalVarByID(NaClBcIndexSize_t Index) {
     Ice::VariableDeclaration *&Decl = GlobalVarsMap[Index];
     if (Decl == nullptr)
-      Decl = Ice::VariableDeclaration::create(getTranslator().getContext());
+      Decl =
+          Ice::VariableDeclaration::create(Context->getGlobalVariablesPool());
     return Decl;
   }
 
@@ -1173,16 +1181,18 @@ void GlobalsParser::ProcessRecord() {
     // ZEROFILL: [size]
     if (!isValidRecordSize(1, "zerofill"))
       return;
+    auto *Pool = Context->getGlobalVariablesPool();
     CurGlobalVar->addInitializer(
-        Ice::VariableDeclaration::ZeroInitializer::create(Values[0]));
+        Ice::VariableDeclaration::ZeroInitializer::create(Pool, Values[0]));
     return;
   }
   case naclbitc::GLOBALVAR_DATA: {
     // DATA: [b0, b1, ...]
     if (!isValidRecordSizeAtLeast(1, "data"))
       return;
+    auto *Pool = Context->getGlobalVariablesPool();
     CurGlobalVar->addInitializer(
-        Ice::VariableDeclaration::DataInitializer::create(Values));
+        Ice::VariableDeclaration::DataInitializer::create(Pool, Values));
     return;
   }
   case naclbitc::GLOBALVAR_RELOC: {
@@ -1208,10 +1218,12 @@ void GlobalsParser::ProcessRecord() {
         Error(StrBuf.str());
       }
     }
+    auto *Pool = Context->getGlobalVariablesPool();
     Ice::GlobalContext *Ctx = getTranslator().getContext();
     CurGlobalVar->addInitializer(
         Ice::VariableDeclaration::RelocInitializer::create(
-            getGlobalDeclByID(Index), {Ice::RelocOffset::create(Ctx, Offset)}));
+            Pool, getGlobalDeclByID(Index),
+            {Ice::RelocOffset::create(Ctx, Offset)}));
     return;
   }
   default: