C++ GlobalVariable::eraseFromParent方法代码示例

void InstrProfiling::emitUses() {
  if (UsedVars.empty())
    return;

  GlobalVariable *LLVMUsed = M->getGlobalVariable("llvm.used");
  std::vector<Constant *> MergedVars;
  if (LLVMUsed) {
    // Collect the existing members of llvm.used.
    ConstantArray *Inits = cast<ConstantArray>(LLVMUsed->getInitializer());
    for (unsigned I = 0, E = Inits->getNumOperands(); I != E; ++I)
      MergedVars.push_back(Inits->getOperand(I));
    LLVMUsed->eraseFromParent();
  }

  Type *i8PTy = Type::getInt8PtrTy(M->getContext());
  // Add uses for our data.
  for (auto *Value : UsedVars)
    MergedVars.push_back(
        ConstantExpr::getBitCast(cast<Constant>(Value), i8PTy));

  // Recreate llvm.used.
  ArrayType *ATy = ArrayType::get(i8PTy, MergedVars.size());
  LLVMUsed =
      new GlobalVariable(*M, ATy, false, GlobalValue::AppendingLinkage,
                         ConstantArray::get(ATy, MergedVars), "llvm.used");

  LLVMUsed->setSection("llvm.metadata");
}

void LTOCodeGenerator::applyScopeRestrictions() {
  if (ScopeRestrictionsDone || !ShouldInternalize)
    return;
  Module *mergedModule = IRLinker.getModule();

  // Start off with a verification pass.
  legacy::PassManager passes;
  passes.add(createVerifierPass());

  // mark which symbols can not be internalized
  Mangler Mangler(TargetMach->getDataLayout());
  std::vector<const char*> MustPreserveList;
  SmallPtrSet<GlobalValue*, 8> AsmUsed;
  std::vector<StringRef> Libcalls;
  TargetLibraryInfoImpl TLII(Triple(TargetMach->getTargetTriple()));
  TargetLibraryInfo TLI(TLII);

  accumulateAndSortLibcalls(Libcalls, TLI, *mergedModule, *TargetMach);

  for (Module::iterator f = mergedModule->begin(),
         e = mergedModule->end(); f != e; ++f)
    applyRestriction(*f, Libcalls, MustPreserveList, AsmUsed, Mangler);
  for (Module::global_iterator v = mergedModule->global_begin(),
         e = mergedModule->global_end(); v !=  e; ++v)
    applyRestriction(*v, Libcalls, MustPreserveList, AsmUsed, Mangler);
  for (Module::alias_iterator a = mergedModule->alias_begin(),
         e = mergedModule->alias_end(); a != e; ++a)
    applyRestriction(*a, Libcalls, MustPreserveList, AsmUsed, Mangler);

  GlobalVariable *LLVMCompilerUsed =
    mergedModule->getGlobalVariable("llvm.compiler.used");
  findUsedValues(LLVMCompilerUsed, AsmUsed);
  if (LLVMCompilerUsed)
    LLVMCompilerUsed->eraseFromParent();

  if (!AsmUsed.empty()) {
    llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(Context);
    std::vector<Constant*> asmUsed2;
    for (auto *GV : AsmUsed) {
      Constant *c = ConstantExpr::getBitCast(GV, i8PTy);
      asmUsed2.push_back(c);
    }

    llvm::ArrayType *ATy = llvm::ArrayType::get(i8PTy, asmUsed2.size());
    LLVMCompilerUsed =
      new llvm::GlobalVariable(*mergedModule, ATy, false,
                               llvm::GlobalValue::AppendingLinkage,
                               llvm::ConstantArray::get(ATy, asmUsed2),
                               "llvm.compiler.used");

    LLVMCompilerUsed->setSection("llvm.metadata");
  }

  passes.add(createInternalizePass(MustPreserveList));

  // apply scope restrictions
  passes.run(*mergedModule);

  ScopeRestrictionsDone = true;
}

void LTOCodeGenerator::applyScopeRestrictions() {
  if (ScopeRestrictionsDone)
    return;
  Module *mergedModule = Linker.getModule();

  // Start off with a verification pass.
  PassManager passes;
  passes.add(createVerifierPass());

  // mark which symbols can not be internalized
  MCContext MContext(TargetMach->getMCAsmInfo(), TargetMach->getRegisterInfo(),
                     NULL);
  Mangler Mangler(MContext, TargetMach);
  std::vector<const char*> MustPreserveList;
  SmallPtrSet<GlobalValue*, 8> AsmUsed;

  for (Module::iterator f = mergedModule->begin(),
         e = mergedModule->end(); f != e; ++f)
    applyRestriction(*f, MustPreserveList, AsmUsed, Mangler);
  for (Module::global_iterator v = mergedModule->global_begin(),
         e = mergedModule->global_end(); v !=  e; ++v)
    applyRestriction(*v, MustPreserveList, AsmUsed, Mangler);
  for (Module::alias_iterator a = mergedModule->alias_begin(),
         e = mergedModule->alias_end(); a != e; ++a)
    applyRestriction(*a, MustPreserveList, AsmUsed, Mangler);

  GlobalVariable *LLVMCompilerUsed =
    mergedModule->getGlobalVariable("llvm.compiler.used");
  findUsedValues(LLVMCompilerUsed, AsmUsed);
  if (LLVMCompilerUsed)
    LLVMCompilerUsed->eraseFromParent();

  if (!AsmUsed.empty()) {
    llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(Context);
    std::vector<Constant*> asmUsed2;
    for (SmallPtrSet<GlobalValue*, 16>::const_iterator i = AsmUsed.begin(),
           e = AsmUsed.end(); i !=e; ++i) {
      GlobalValue *GV = *i;
      Constant *c = ConstantExpr::getBitCast(GV, i8PTy);
      asmUsed2.push_back(c);
    }

    llvm::ArrayType *ATy = llvm::ArrayType::get(i8PTy, asmUsed2.size());
    LLVMCompilerUsed =
      new llvm::GlobalVariable(*mergedModule, ATy, false,
                               llvm::GlobalValue::AppendingLinkage,
                               llvm::ConstantArray::get(ATy, asmUsed2),
                               "llvm.compiler.used");

    LLVMCompilerUsed->setSection("llvm.metadata");
  }

  passes.add(createInternalizePass(MustPreserveList));

  // apply scope restrictions
  passes.run(*mergedModule);

  ScopeRestrictionsDone = true;
}

void LTOCodeGenerator::applyScopeRestrictions() {
  if (_scopeRestrictionsDone) return;
  Module *mergedModule = _linker.getModule();

  // Start off with a verification pass.
  PassManager passes;
  passes.add(createVerifierPass());

  // mark which symbols can not be internalized
  MCContext Context(*_target->getMCAsmInfo(), *_target->getRegisterInfo(),NULL);
  Mangler mangler(Context, *_target->getTargetData());
  std::vector<const char*> mustPreserveList;
  SmallPtrSet<GlobalValue*, 8> asmUsed;

  for (Module::iterator f = mergedModule->begin(),
         e = mergedModule->end(); f != e; ++f)
    applyRestriction(*f, mustPreserveList, asmUsed, mangler);
  for (Module::global_iterator v = mergedModule->global_begin(),
         e = mergedModule->global_end(); v !=  e; ++v)
    applyRestriction(*v, mustPreserveList, asmUsed, mangler);
  for (Module::alias_iterator a = mergedModule->alias_begin(),
         e = mergedModule->alias_end(); a != e; ++a)
    applyRestriction(*a, mustPreserveList, asmUsed, mangler);

  GlobalVariable *LLVMCompilerUsed =
    mergedModule->getGlobalVariable("llvm.compiler.used");
  findUsedValues(LLVMCompilerUsed, asmUsed);
  if (LLVMCompilerUsed)
    LLVMCompilerUsed->eraseFromParent();

  llvm::Type *i8PTy = llvm::Type::getInt8PtrTy(_context);
  std::vector<Constant*> asmUsed2;
  for (SmallPtrSet<GlobalValue*, 16>::const_iterator i = asmUsed.begin(),
         e = asmUsed.end(); i !=e; ++i) {
    GlobalValue *GV = *i;
    Constant *c = ConstantExpr::getBitCast(GV, i8PTy);
    asmUsed2.push_back(c);
  }

  llvm::ArrayType *ATy = llvm::ArrayType::get(i8PTy, asmUsed2.size());
  LLVMCompilerUsed =
    new llvm::GlobalVariable(*mergedModule, ATy, false,
                             llvm::GlobalValue::AppendingLinkage,
                             llvm::ConstantArray::get(ATy, asmUsed2),
                             "llvm.compiler.used");

  LLVMCompilerUsed->setSection("llvm.metadata");

  // Add prerequisite passes needed by SAFECode
  PassManagerBuilder().populateLTOPassManager(passes, /*Internalize=*/ false,
                                              !DisableInline);

  passes.add(createInternalizePass(mustPreserveList));

  // apply scope restrictions
  passes.run(*mergedModule);

  _scopeRestrictionsDone = true;
}

static void setGlobalVariableValue(Module &M, const char *Name,
                                   Constant *Value) {
  GlobalVariable *Var = M.getNamedGlobal(Name);
  if (!Var) {
    // This warning can happen in a program that does not use a libc
    // and does not initialize TLS variables.  Such a program might be
    // linked with "-nostdlib".
    errs() << "Warning: Variable " << Name << " not referenced\n";
  } else {
    if (Var->hasInitializer()) {
      report_fatal_error(std::string("Variable ") + Name +
                         " already has an initializer");
    }
    Var->replaceAllUsesWith(ConstantExpr::getBitCast(Value, Var->getType()));
    Var->eraseFromParent();
  }
}

static void defineFuncArray(Module &M, const char *LlvmArrayName,
                            const char *StartSymbol,
                            const char *EndSymbol) {
  std::vector<Constant*> Funcs;

  GlobalVariable *Array = M.getNamedGlobal(LlvmArrayName);
  if (Array) {
    readFuncList(Array, &Funcs);
    // No code should be referencing global_ctors/global_dtors,
    // because this symbol is internal to LLVM.
    Array->eraseFromParent();
  }

  Type *FuncTy = FunctionType::get(Type::getVoidTy(M.getContext()), false);
  Type *FuncPtrTy = FuncTy->getPointerTo();
  ArrayType *ArrayTy = ArrayType::get(FuncPtrTy, Funcs.size());
  GlobalVariable *NewArray =
      new GlobalVariable(M, ArrayTy, /* isConstant= */ true,
                         GlobalValue::InternalLinkage,
                         ConstantArray::get(ArrayTy, Funcs));
  setGlobalVariableValue(M, StartSymbol, NewArray);
  // We do this last so that LLVM gives NewArray the name
  // "__{init,fini}_array_start" without adding any suffixes to
  // disambiguate from the original GlobalVariable's name.  This is
  // not essential -- it just makes the output easier to understand
  // when looking at symbols for debugging.
  NewArray->setName(StartSymbol);

  // We replace "__{init,fini}_array_end" with the address of the end
  // of NewArray.  This removes the name "__{init,fini}_array_end"
  // from the output, which is not ideal for debugging.  Ideally we
  // would convert "__{init,fini}_array_end" to being a GlobalAlias
  // that points to the end of the array.  However, unfortunately LLVM
  // does not generate correct code when a GlobalAlias contains a
  // GetElementPtr ConstantExpr.
  Constant *NewArrayEnd =
      ConstantExpr::getGetElementPtr(ArrayTy, NewArray,
                                     ConstantInt::get(M.getContext(),
                                                      APInt(32, 1)));
  setGlobalVariableValue(M, EndSymbol, NewArrayEnd);
}

void MemoryInstrumenter::lowerGlobalCtors(Module &M) {
  // Find llvm.global_ctors.
  GlobalVariable *GV = M.getNamedGlobal("llvm.global_ctors");
  if (!GV)
    return;
  assert(!GV->isDeclaration() && !GV->hasLocalLinkage());

  // Should be an array of '{ int, void ()* }' structs.  The first value is
  // the init priority, which must be 65535 if the bitcode is generated using
  // clang.
  if (ConstantArray *InitList = dyn_cast<ConstantArray>(GV->getInitializer())) {
    for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i) {
      ConstantStruct *CS =
        dyn_cast<ConstantStruct>(InitList->getOperand(i));
      assert(CS);
      assert(CS->getNumOperands() == 2);

      // Get the priority.
      ConstantInt *Priority = dyn_cast<ConstantInt>(CS->getOperand(0));
      assert(Priority);
      // TODO: For now, we assume all priorities must be 65535.
      assert(Priority->equalsInt(65535));

      // Get the constructor function.
      Constant *FP = CS->getOperand(1);
      if (FP->isNullValue())
        break;  // Found a null terminator, exit.

      // Explicitly call the constructor at the main entry.
      CallInst::Create(FP, "", Main->begin()->getFirstNonPHI());
    }
  }

  // Clear the global_ctors array.
  // Use eraseFromParent() instead of removeFromParent().
  GV->eraseFromParent();
}

void PerfMonitor::addToGlobalConstructors(Function *Fn) {
  const char *Name = "llvm.global_ctors";
  GlobalVariable *GV = M->getGlobalVariable(Name);
  std::vector<Constant *> V;

  if (GV) {
    Constant *Array = GV->getInitializer();
    for (Value *X : Array->operand_values())
      V.push_back(cast<Constant>(X));
    GV->eraseFromParent();
  }

  StructType *ST = StructType::get(Builder.getInt32Ty(), Fn->getType(),
                                   Builder.getInt8PtrTy());

  V.push_back(
      ConstantStruct::get(ST, Builder.getInt32(10), Fn,
                          ConstantPointerNull::get(Builder.getInt8PtrTy())));
  ArrayType *Ty = ArrayType::get(ST, V.size());

  GV = new GlobalVariable(*M, Ty, true, GlobalValue::AppendingLinkage,
                          ConstantArray::get(Ty, V), Name, nullptr,
                          GlobalVariable::NotThreadLocal);
}

void InitializeSoftBound:: constructCheckHandlers(Module & module){

  Type* void_ty = Type::getVoidTy(module.getContext());

  Type* void_ptr_ty = PointerType::getUnqual(Type::getInt8Ty(module.getContext()));
  Type* size_ty = Type::getInt64Ty(module.getContext());

  module.getOrInsertFunction("__softboundcets_spatial_load_dereference_check",
                             void_ty, void_ptr_ty, void_ptr_ty, 
                             void_ptr_ty, size_ty, NULL);

  module.getOrInsertFunction("__softboundcets_spatial_store_dereference_check", 
                             void_ty, void_ptr_ty, void_ptr_ty, 
                             void_ptr_ty, size_ty, NULL);

  module.getOrInsertFunction("__softboundcets_temporal_load_dereference_check", 
                             void_ty, void_ptr_ty, size_ty, 
                             void_ptr_ty, void_ptr_ty, NULL);

  module.getOrInsertFunction("__softboundcets_temporal_store_dereference_check", 
                             void_ty, void_ptr_ty, size_ty, 
                             void_ptr_ty, void_ptr_ty, NULL);


  Function* global_init = (Function *) module.getOrInsertFunction("__softboundcets_global_init", 
                                                                  void_ty, NULL);

  global_init->setDoesNotThrow();
  global_init->setLinkage(GlobalValue::InternalLinkage);

  BasicBlock* BB = BasicBlock::Create(module.getContext(), 
                                      "entry", global_init);
  
  Function* softboundcets_init = (Function*) module.getOrInsertFunction("__softboundcets_init", void_ty, Type::getInt32Ty(module.getContext()), NULL);

  
  SmallVector<Value*, 8> args;
  Constant * const_one = ConstantInt::get(Type::getInt32Ty(module.getContext()), 1);
  
  args.push_back(const_one);
  Instruction* ret = ReturnInst::Create(module.getContext(), BB);
  
  CallInst::Create(softboundcets_init, args, "", ret);



  Type * Int32Type = IntegerType::getInt32Ty(module.getContext());
  std::vector<Constant *> CtorInits;
  CtorInits.push_back(ConstantInt::get(Int32Type, 0));
  CtorInits.push_back(global_init);
  StructType * ST = ConstantStruct::getTypeForElements(CtorInits, false);
  Constant * RuntimeCtorInit = ConstantStruct::get(ST, CtorInits);

  //
  // Get the current set of static global constructors and add the new ctor
  // to the list.
  //
  std::vector<Constant *> CurrentCtors;
  GlobalVariable * GVCtor = module.getNamedGlobal ("llvm.global_ctors");
  if (GVCtor) {
    if (Constant * C = GVCtor->getInitializer()) {
      for (unsigned index = 0; index < C->getNumOperands(); ++index) {
        CurrentCtors.push_back (dyn_cast<Constant>(C->getOperand (index)));
      }
    }
  }
  CurrentCtors.push_back(RuntimeCtorInit);

  //
  // Create a new initializer.
  //
  ArrayType * AT = ArrayType::get (RuntimeCtorInit-> getType(),
                                   CurrentCtors.size());
  Constant * NewInit = ConstantArray::get (AT, CurrentCtors);

  //
  // Create the new llvm.global_ctors global variable and remove the old one
  // if it existed.
  //
  Value * newGVCtor = new GlobalVariable (module,
                                          NewInit->getType(),
                                          false,
                                          GlobalValue::AppendingLinkage,
                                          NewInit,
                                          "llvm.global_ctors");
  if (GVCtor) {
    newGVCtor->takeName (GVCtor);
    GVCtor->eraseFromParent ();
  }



}

bool ConstantMerge::runOnModule(Module &M) {
  TD = getAnalysisIfAvailable<TargetData>();

  // Find all the globals that are marked "used".  These cannot be merged.
  SmallPtrSet<const GlobalValue*, 8> UsedGlobals;
  FindUsedValues(M.getGlobalVariable("llvm.used"), UsedGlobals);
  FindUsedValues(M.getGlobalVariable("llvm.compiler.used"), UsedGlobals);
  
  // Map unique <constants, has-unknown-alignment> pairs to globals.  We don't
  // want to merge globals of unknown alignment with those of explicit
  // alignment.  If we have TargetData, we always know the alignment.
  DenseMap<PointerIntPair<Constant*, 1, bool>, GlobalVariable*> CMap;

  // Replacements - This vector contains a list of replacements to perform.
  SmallVector<std::pair<GlobalVariable*, GlobalVariable*>, 32> Replacements;

  bool MadeChange = false;

  // Iterate constant merging while we are still making progress.  Merging two
  // constants together may allow us to merge other constants together if the
  // second level constants have initializers which point to the globals that
  // were just merged.
  while (1) {

    // First: Find the canonical constants others will be merged with.
    for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
         GVI != E; ) {
      GlobalVariable *GV = GVI++;

      // If this GV is dead, remove it.
      GV->removeDeadConstantUsers();
      if (GV->use_empty() && GV->hasLocalLinkage()) {
        GV->eraseFromParent();
        continue;
      }

      // Only process constants with initializers in the default address space.
      if (!GV->isConstant() || !GV->hasDefinitiveInitializer() ||
          GV->getType()->getAddressSpace() != 0 || GV->hasSection() ||
          // Don't touch values marked with attribute(used).
          UsedGlobals.count(GV))
        continue;

      // This transformation is legal for weak ODR globals in the sense it
      // doesn't change semantics, but we really don't want to perform it
      // anyway; it's likely to pessimize code generation, and some tools
      // (like the Darwin linker in cases involving CFString) don't expect it.
      if (GV->isWeakForLinker())
        continue;

      Constant *Init = GV->getInitializer();

      // Check to see if the initializer is already known.
      PointerIntPair<Constant*, 1, bool> Pair(Init, hasKnownAlignment(GV));
      GlobalVariable *&Slot = CMap[Pair];

      // If this is the first constant we find or if the old one is local,
      // replace with the current one. If the current is externally visible
      // it cannot be replace, but can be the canonical constant we merge with.
      if (Slot == 0 || IsBetterCannonical(*GV, *Slot))
        Slot = GV;
    }

    // Second: identify all globals that can be merged together, filling in
    // the Replacements vector.  We cannot do the replacement in this pass
    // because doing so may cause initializers of other globals to be rewritten,
    // invalidating the Constant* pointers in CMap.
    for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
         GVI != E; ) {
      GlobalVariable *GV = GVI++;

      // Only process constants with initializers in the default address space.
      if (!GV->isConstant() || !GV->hasDefinitiveInitializer() ||
          GV->getType()->getAddressSpace() != 0 || GV->hasSection() ||
          // Don't touch values marked with attribute(used).
          UsedGlobals.count(GV))
        continue;

      // We can only replace constant with local linkage.
      if (!GV->hasLocalLinkage())
        continue;

      Constant *Init = GV->getInitializer();

      // Check to see if the initializer is already known.
      PointerIntPair<Constant*, 1, bool> Pair(Init, hasKnownAlignment(GV));
      GlobalVariable *Slot = CMap[Pair];

      if (!Slot || Slot == GV)
        continue;

      if (!Slot->hasUnnamedAddr() && !GV->hasUnnamedAddr())
        continue;

      if (!GV->hasUnnamedAddr())
        Slot->setUnnamedAddr(false);

      // Make all uses of the duplicate constant use the canonical version.
      Replacements.push_back(std::make_pair(GV, Slot));
    }
//.........这里部分代码省略.........

//.........这里部分代码省略.........
        continue;
      }
    }

    GlobalsToChange.push_back(G);
  }

  size_t n = GlobalsToChange.size();
  if (n == 0) return false;

  // A global is described by a structure
  //   size_t beg;
  //   size_t size;
  //   size_t size_with_redzone;
  //   const char *name;
  // We initialize an array of such structures and pass it to a run-time call.
  StructType *GlobalStructTy = StructType::get(IntptrTy, IntptrTy,
                                               IntptrTy, IntptrTy, NULL);
  SmallVector<Constant *, 16> Initializers(n);

  IRBuilder<> IRB(CtorInsertBefore);

  for (size_t i = 0; i < n; i++) {
    GlobalVariable *G = GlobalsToChange[i];
    PointerType *PtrTy = cast<PointerType>(G->getType());
    Type *Ty = PtrTy->getElementType();
    uint64_t SizeInBytes = TD->getTypeStoreSizeInBits(Ty) / 8;
    uint64_t RightRedzoneSize = RedzoneSize +
        (RedzoneSize - (SizeInBytes % RedzoneSize));
    Type *RightRedZoneTy = ArrayType::get(IRB.getInt8Ty(), RightRedzoneSize);

    StructType *NewTy = StructType::get(Ty, RightRedZoneTy, NULL);
    Constant *NewInitializer = ConstantStruct::get(
        NewTy, G->getInitializer(),
        Constant::getNullValue(RightRedZoneTy), NULL);

    SmallString<2048> DescriptionOfGlobal = G->getName();
    DescriptionOfGlobal += " (";
    DescriptionOfGlobal += M.getModuleIdentifier();
    DescriptionOfGlobal += ")";
    GlobalVariable *Name = createPrivateGlobalForString(M, DescriptionOfGlobal);

    // Create a new global variable with enough space for a redzone.
    GlobalVariable *NewGlobal = new GlobalVariable(
        M, NewTy, G->isConstant(), G->getLinkage(),
        NewInitializer, "", G, G->isThreadLocal());
    NewGlobal->copyAttributesFrom(G);
    NewGlobal->setAlignment(RedzoneSize);

    Value *Indices2[2];
    Indices2[0] = IRB.getInt32(0);
    Indices2[1] = IRB.getInt32(0);

    G->replaceAllUsesWith(
        ConstantExpr::getGetElementPtr(NewGlobal, Indices2, true));
    NewGlobal->takeName(G);
    G->eraseFromParent();

    Initializers[i] = ConstantStruct::get(
        GlobalStructTy,
        ConstantExpr::getPointerCast(NewGlobal, IntptrTy),
        ConstantInt::get(IntptrTy, SizeInBytes),
        ConstantInt::get(IntptrTy, SizeInBytes + RightRedzoneSize),
        ConstantExpr::getPointerCast(Name, IntptrTy),
        NULL);
    DEBUG(dbgs() << "NEW GLOBAL:\n" << *NewGlobal);
  }

  ArrayType *ArrayOfGlobalStructTy = ArrayType::get(GlobalStructTy, n);
  GlobalVariable *AllGlobals = new GlobalVariable(
      M, ArrayOfGlobalStructTy, false, GlobalVariable::PrivateLinkage,
      ConstantArray::get(ArrayOfGlobalStructTy, Initializers), "");

  Function *AsanRegisterGlobals = cast<Function>(M.getOrInsertFunction(
      kAsanRegisterGlobalsName, IRB.getVoidTy(), IntptrTy, IntptrTy, NULL));
  AsanRegisterGlobals->setLinkage(Function::ExternalLinkage);

  IRB.CreateCall2(AsanRegisterGlobals,
                  IRB.CreatePointerCast(AllGlobals, IntptrTy),
                  ConstantInt::get(IntptrTy, n));

  // We also need to unregister globals at the end, e.g. when a shared library
  // gets closed.
  Function *AsanDtorFunction = Function::Create(
      FunctionType::get(Type::getVoidTy(*C), false),
      GlobalValue::InternalLinkage, kAsanModuleDtorName, &M);
  BasicBlock *AsanDtorBB = BasicBlock::Create(*C, "", AsanDtorFunction);
  IRBuilder<> IRB_Dtor(ReturnInst::Create(*C, AsanDtorBB));
  Function *AsanUnregisterGlobals = cast<Function>(M.getOrInsertFunction(
      kAsanUnregisterGlobalsName, IRB.getVoidTy(), IntptrTy, IntptrTy, NULL));
  AsanUnregisterGlobals->setLinkage(Function::ExternalLinkage);

  IRB_Dtor.CreateCall2(AsanUnregisterGlobals,
                       IRB.CreatePointerCast(AllGlobals, IntptrTy),
                       ConstantInt::get(IntptrTy, n));
  appendToGlobalDtors(M, AsanDtorFunction, kAsanCtorAndCtorPriority);

  DEBUG(dbgs() << M);
  return true;
}

bool ConstantMerge::runOnModule(Module &M) {
  // Find all the globals that are marked "used".  These cannot be merged.
  SmallPtrSet<const GlobalValue*, 8> UsedGlobals;
  FindUsedValues(M.getGlobalVariable("llvm.used"), UsedGlobals);
  FindUsedValues(M.getGlobalVariable("llvm.compiler.used"), UsedGlobals);
  
  // Map unique constant/section pairs to globals.  We don't want to merge
  // globals in different sections.
  DenseMap<Constant*, GlobalVariable*> CMap;

  // Replacements - This vector contains a list of replacements to perform.
  SmallVector<std::pair<GlobalVariable*, GlobalVariable*>, 32> Replacements;

  bool MadeChange = false;

  // Iterate constant merging while we are still making progress.  Merging two
  // constants together may allow us to merge other constants together if the
  // second level constants have initializers which point to the globals that
  // were just merged.
  while (1) {
    // First pass: identify all globals that can be merged together, filling in
    // the Replacements vector.  We cannot do the replacement in this pass
    // because doing so may cause initializers of other globals to be rewritten,
    // invalidating the Constant* pointers in CMap.
    //
    for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
         GVI != E; ) {
      GlobalVariable *GV = GVI++;
      
      // If this GV is dead, remove it.
      GV->removeDeadConstantUsers();
      if (GV->use_empty() && GV->hasLocalLinkage()) {
        GV->eraseFromParent();
        continue;
      }
      
      // Only process constants with initializers in the default addres space.
      if (!GV->isConstant() ||!GV->hasDefinitiveInitializer() ||
          GV->getType()->getAddressSpace() != 0 || !GV->getSection().empty() ||
          // Don't touch values marked with attribute(used).
          UsedGlobals.count(GV))
        continue;
      
      
      
      Constant *Init = GV->getInitializer();

      // Check to see if the initializer is already known.
      GlobalVariable *&Slot = CMap[Init];

      if (Slot == 0) {    // Nope, add it to the map.
        Slot = GV;
      } else if (GV->hasLocalLinkage()) {    // Yup, this is a duplicate!
        // Make all uses of the duplicate constant use the canonical version.
        Replacements.push_back(std::make_pair(GV, Slot));
      }
    }

    if (Replacements.empty())
      return MadeChange;
    CMap.clear();

    // Now that we have figured out which replacements must be made, do them all
    // now.  This avoid invalidating the pointers in CMap, which are unneeded
    // now.
    for (unsigned i = 0, e = Replacements.size(); i != e; ++i) {
      // Eliminate any uses of the dead global.
      Replacements[i].first->replaceAllUsesWith(Replacements[i].second);

      // Delete the global value from the module.
      Replacements[i].first->eraseFromParent();
    }

    NumMerged += Replacements.size();
    Replacements.clear();
  }
}

bool AllocateDataSegment::runOnModule(Module &M) {
  DataLayout DL(&M);
  Type *I8 = Type::getInt8Ty(M.getContext());
  Type *I32 = Type::getInt32Ty(M.getContext());
  Type *IntPtrType = DL.getIntPtrType(M.getContext());

  // First, we do a pass over the global variables, in which we compute
  // the amount of required padding between them and consequently their
  // addresses relative to the memory base of the sandbox. References to each
  // global are then replaced with direct memory pointers.
  uint32_t VarOffset = 0;
  DenseMap<GlobalVariable*, uint32_t> VarPadding;
  for (Module::global_iterator GV = M.global_begin(), E = M.global_end();
       GV != E; ++GV) {
    assert(GV->hasInitializer());

    uint32_t Padding = getPadding(VarOffset, GV, DL);
    VarPadding[GV] = Padding;
    VarOffset += Padding;

    GV->replaceAllUsesWith(
        ConstantExpr::getIntToPtr(
            ConstantInt::get(IntPtrType,
                             DataSegmentBaseAddress + VarOffset),
            GV->getType()));

    VarOffset += DL.getTypeStoreSize(GV->getType()->getPointerElementType());
  }

  // Using the offsets computed above, we prepare the layout and the contents
  // of the desired data structure. After the type and initializer of each
  // global is copied, the global is not needed any more and it is erased.
  SmallVector<Type*, 10> TemplateLayout;
  SmallVector<Constant*, 10> TemplateData;
  for (Module::global_iterator It = M.global_begin(), E = M.global_end();
       It != E; ) {
    GlobalVariable *GV = It++;

    uint32_t Padding = VarPadding[GV];
    if (Padding > 0) {
      Type *PaddingType = ArrayType::get(I8, Padding);
      TemplateLayout.push_back(PaddingType);
      TemplateData.push_back(ConstantAggregateZero::get(PaddingType));
    }

    TemplateLayout.push_back(GV->getType()->getPointerElementType());
    TemplateData.push_back(GV->getInitializer());

    GV->eraseFromParent();
  }

  // Finally, we create the struct and size global variables.
  StructType *TemplateType =
      StructType::create(M.getContext(), ExternalSymName_DataSegment);
  TemplateType->setBody(TemplateLayout, /*isPacked=*/true);

  Constant *Template = ConstantStruct::get(TemplateType, TemplateData);
  new GlobalVariable(M, Template->getType(), /*isConstant=*/true,
                     GlobalVariable::ExternalLinkage, Template,
                     ExternalSymName_DataSegment);

  Constant *TemplateSize =
      ConstantInt::get(I32, DL.getTypeAllocSize(TemplateType));
  new GlobalVariable(M, TemplateSize->getType(), /*isConstant=*/true,
                     GlobalVariable::ExternalLinkage, TemplateSize,
                     ExternalSymName_DataSegmentSize);

  return true;
}

bool GenericToNVVM::runOnModule(Module &M) {
  // Create a clone of each global variable that has the default address space.
  // The clone is created with the global address space  specifier, and the pair
  // of original global variable and its clone is placed in the GVMap for later
  // use.

  for (Module::global_iterator I = M.global_begin(), E = M.global_end();
       I != E;) {
    GlobalVariable *GV = &*I++;
    if (GV->getType()->getAddressSpace() == llvm::ADDRESS_SPACE_GENERIC &&
        !llvm::isTexture(*GV) && !llvm::isSurface(*GV) &&
        !llvm::isSampler(*GV) && !GV->getName().startswith("llvm.")) {
      GlobalVariable *NewGV = new GlobalVariable(
          M, GV->getValueType(), GV->isConstant(),
          GV->getLinkage(),
          GV->hasInitializer() ? GV->getInitializer() : nullptr,
          "", GV, GV->getThreadLocalMode(), llvm::ADDRESS_SPACE_GLOBAL);
      NewGV->copyAttributesFrom(GV);
      GVMap[GV] = NewGV;
    }
  }

  // Return immediately, if every global variable has a specific address space
  // specifier.
  if (GVMap.empty()) {
    return false;
  }

  // Walk through the instructions in function defitinions, and replace any use
  // of original global variables in GVMap with a use of the corresponding
  // copies in GVMap.  If necessary, promote constants to instructions.
  for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I) {
    if (I->isDeclaration()) {
      continue;
    }
    IRBuilder<> Builder(I->getEntryBlock().getFirstNonPHIOrDbg());
    for (Function::iterator BBI = I->begin(), BBE = I->end(); BBI != BBE;
         ++BBI) {
      for (BasicBlock::iterator II = BBI->begin(), IE = BBI->end(); II != IE;
           ++II) {
        for (unsigned i = 0, e = II->getNumOperands(); i < e; ++i) {
          Value *Operand = II->getOperand(i);
          if (isa<Constant>(Operand)) {
            II->setOperand(
                i, remapConstant(&M, &*I, cast<Constant>(Operand), Builder));
          }
        }
      }
    }
    ConstantToValueMap.clear();
  }

  // Copy GVMap over to a standard value map.
  ValueToValueMapTy VM;
  for (auto I = GVMap.begin(), E = GVMap.end(); I != E; ++I)
    VM[I->first] = I->second;

  // Walk through the metadata section and update the debug information
  // associated with the global variables in the default address space.
  for (NamedMDNode &I : M.named_metadata()) {
    remapNamedMDNode(VM, &I);
  }

  // Walk through the global variable  initializers, and replace any use of
  // original global variables in GVMap with a use of the corresponding copies
  // in GVMap.  The copies need to be bitcast to the original global variable
  // types, as we cannot use cvta in global variable initializers.
  for (GVMapTy::iterator I = GVMap.begin(), E = GVMap.end(); I != E;) {
    GlobalVariable *GV = I->first;
    GlobalVariable *NewGV = I->second;

    // Remove GV from the map so that it can be RAUWed.  Note that
    // DenseMap::erase() won't invalidate any iterators but this one.
    auto Next = std::next(I);
    GVMap.erase(I);
    I = Next;

    Constant *BitCastNewGV = ConstantExpr::getPointerCast(NewGV, GV->getType());
    // At this point, the remaining uses of GV should be found only in global
    // variable initializers, as other uses have been already been removed
    // while walking through the instructions in function definitions.
    GV->replaceAllUsesWith(BitCastNewGV);
    std::string Name = GV->getName();
    GV->eraseFromParent();
    NewGV->setName(Name);
  }
  assert(GVMap.empty() && "Expected it to be empty by now");

  return true;
}

// With -fembed-bitcode, save a copy of the llvm IR as data in the
// __LLVM,__bitcode section.
void clang::EmbedBitcode(llvm::Module *M, const CodeGenOptions &CGOpts,
                         llvm::MemoryBufferRef Buf) {
  if (CGOpts.getEmbedBitcode() == CodeGenOptions::Embed_Off)
    return;

  // Save llvm.compiler.used and remote it.
  SmallVector<Constant*, 2> UsedArray;
  SmallSet<GlobalValue*, 4> UsedGlobals;
  Type *UsedElementType = Type::getInt8Ty(M->getContext())->getPointerTo(0);
  GlobalVariable *Used = collectUsedGlobalVariables(*M, UsedGlobals, true);
  for (auto *GV : UsedGlobals) {
    if (GV->getName() != "llvm.embedded.module" &&
        GV->getName() != "llvm.cmdline")
      UsedArray.push_back(
          ConstantExpr::getPointerBitCastOrAddrSpaceCast(GV, UsedElementType));
  }
  if (Used)
    Used->eraseFromParent();

  // Embed the bitcode for the llvm module.
  std::string Data;
  ArrayRef<uint8_t> ModuleData;
  Triple T(M->getTargetTriple());
  // Create a constant that contains the bitcode.
  // In case of embedding a marker, ignore the input Buf and use the empty
  // ArrayRef. It is also legal to create a bitcode marker even Buf is empty.
  if (CGOpts.getEmbedBitcode() != CodeGenOptions::Embed_Marker) {
    if (!isBitcode((const unsigned char *)Buf.getBufferStart(),
                   (const unsigned char *)Buf.getBufferEnd())) {
      // If the input is LLVM Assembly, bitcode is produced by serializing
      // the module. Use-lists order need to be perserved in this case.
      llvm::raw_string_ostream OS(Data);
      llvm::WriteBitcodeToFile(M, OS, /* ShouldPreserveUseListOrder */ true);
      ModuleData =
          ArrayRef<uint8_t>((const uint8_t *)OS.str().data(), OS.str().size());
    } else
      // If the input is LLVM bitcode, write the input byte stream directly.
      ModuleData = ArrayRef<uint8_t>((const uint8_t *)Buf.getBufferStart(),
                                     Buf.getBufferSize());
  }
  llvm::Constant *ModuleConstant =
      llvm::ConstantDataArray::get(M->getContext(), ModuleData);
  llvm::GlobalVariable *GV = new llvm::GlobalVariable(
      *M, ModuleConstant->getType(), true, llvm::GlobalValue::PrivateLinkage,
      ModuleConstant);
  GV->setSection(getSectionNameForBitcode(T));
  UsedArray.push_back(
      ConstantExpr::getPointerBitCastOrAddrSpaceCast(GV, UsedElementType));
  if (llvm::GlobalVariable *Old =
          M->getGlobalVariable("llvm.embedded.module", true)) {
    assert(Old->hasOneUse() &&
           "llvm.embedded.module can only be used once in llvm.compiler.used");
    GV->takeName(Old);
    Old->eraseFromParent();
  } else {
    GV->setName("llvm.embedded.module");
  }

  // Skip if only bitcode needs to be embedded.
  if (CGOpts.getEmbedBitcode() != CodeGenOptions::Embed_Bitcode) {
    // Embed command-line options.
    ArrayRef<uint8_t> CmdData(const_cast<uint8_t *>(CGOpts.CmdArgs.data()),
                              CGOpts.CmdArgs.size());
    llvm::Constant *CmdConstant =
      llvm::ConstantDataArray::get(M->getContext(), CmdData);
    GV = new llvm::GlobalVariable(*M, CmdConstant->getType(), true,
                                  llvm::GlobalValue::PrivateLinkage,
                                  CmdConstant);
    GV->setSection(getSectionNameForCommandline(T));
    UsedArray.push_back(
        ConstantExpr::getPointerBitCastOrAddrSpaceCast(GV, UsedElementType));
    if (llvm::GlobalVariable *Old =
            M->getGlobalVariable("llvm.cmdline", true)) {
      assert(Old->hasOneUse() &&
             "llvm.cmdline can only be used once in llvm.compiler.used");
      GV->takeName(Old);
      Old->eraseFromParent();
    } else {
      GV->setName("llvm.cmdline");
    }
  }

  if (UsedArray.empty())
    return;

  // Recreate llvm.compiler.used.
  ArrayType *ATy = ArrayType::get(UsedElementType, UsedArray.size());
  auto *NewUsed = new GlobalVariable(
      *M, ATy, false, llvm::GlobalValue::AppendingLinkage,
      llvm::ConstantArray::get(ATy, UsedArray), "llvm.compiler.used");
  NewUsed->setSection("llvm.metadata");
}