text: //===-- ExecutionEngine.cpp - Common Implementation shared by EEs ---------===//
  //
  //                     The LLVM Compiler Infrastructure
  //
  // This file is distributed under the University of Illinois Open Source
  // License. See LICENSE.TXT for details.
  //
  //===----------------------------------------------------------------------===//
  //
  // This file defines the common interface used by the various execution engine
  // subclasses.
  //
  //===----------------------------------------------------------------------===//
  
  #include "llvm/ExecutionEngine/ExecutionEngine.h"
  #include "llvm/ADT/STLExtras.h"
  #include "llvm/ADT/SmallString.h"
  #include "llvm/ADT/Statistic.h"
  #include "llvm/ExecutionEngine/GenericValue.h"
  #include "llvm/ExecutionEngine/JITEventListener.h"
  #include "llvm/ExecutionEngine/RTDyldMemoryManager.h"
  #include "llvm/IR/Constants.h"
  #include "llvm/IR/DataLayout.h"
  #include "llvm/IR/DerivedTypes.h"
  #include "llvm/IR/Mangler.h"
  #include "llvm/IR/Module.h"
  #include "llvm/IR/Operator.h"
  #include "llvm/IR/ValueHandle.h"
  #include "llvm/Object/Archive.h"
  #include "llvm/Object/ObjectFile.h"
  #include "llvm/Support/Debug.h"
  #include "llvm/Support/DynamicLibrary.h"
  #include "llvm/Support/ErrorHandling.h"
  #include "llvm/Support/Host.h"
  #include "llvm/Support/MutexGuard.h"
  #include "llvm/Support/TargetRegistry.h"
  #include "llvm/Support/raw_ostream.h"
  #include "llvm/Target/TargetMachine.h"
  #include <cmath>
  #include <cstring>
  using namespace llvm;
  
  #define DEBUG_TYPE "jit"
  
  STATISTIC(NumInitBytes, "Number of bytes of global vars initialized");
  STATISTIC(NumGlobals  , "Number of global vars initialized");
  
  ExecutionEngine *(*ExecutionEngine::MCJITCtor)(
      std::unique_ptr<Module> M, std::string *ErrorStr,
      std::shared_ptr<MCJITMemoryManager> MemMgr,
      std::shared_ptr<RuntimeDyld::SymbolResolver> Resolver,
      std::unique_ptr<TargetMachine> TM) = nullptr;
  
  ExecutionEngine *(*ExecutionEngine::OrcMCJITReplacementCtor)(
    std::string *ErrorStr, std::shared_ptr<MCJITMemoryManager> MemMgr,
    std::shared_ptr<RuntimeDyld::SymbolResolver> Resolver,
    std::unique_ptr<TargetMachine> TM) = nullptr;
  
  ExecutionEngine *(*ExecutionEngine::InterpCtor)(std::unique_ptr<Module> M,
                                                  std::string *ErrorStr) =nullptr;
  
  void JITEventListener::anchor() {}
  
  void ExecutionEngine::Init(std::unique_ptr<Module> M) {
    CompilingLazily         = false;
    GVCompilationDisabled   = false;
    SymbolSearchingDisabled = false;
  
    // IR module verification is enabled by default in debug builds, and disabled
    // by default in release builds.
  #ifndef NDEBUG
    VerifyModules = true;
  #else
    VerifyModules = false;
  #endif
  
    assert(M && "Module is null?");
    Modules.push_back(std::move(M));
  }
  
  ExecutionEngine::ExecutionEngine(std::unique_ptr<Module> M)
      : DL(M->getDataLayout()), LazyFunctionCreator(nullptr) {
    Init(std::move(M));
  }
  
  ExecutionEngine::ExecutionEngine(DataLayout DL, std::unique_ptr<Module> M)
      : DL(std::move(DL)), LazyFunctionCreator(nullptr) {
    Init(std::move(M));
  }
  
  ExecutionEngine::~ExecutionEngine() {
    clearAllGlobalMappings();
  }
  
  namespace {
  /// \brief Helper class which uses a value handler to automatically deletes the
  /// memory block when the GlobalVariable is destroyed.
  class GVMemoryBlock final : public CallbackVH {
    GVMemoryBlock(const GlobalVariable *GV)
      : CallbackVH(const_cast<GlobalVariable*>(GV)) {}
  
  public:
    /// \brief Returns the address the GlobalVariable should be written into.  The
    /// GVMemoryBlock object prefixes that.
    static char *Create(const GlobalVariable *GV, const DataLayout& TD) {
      Type *ElTy = GV->getType()->getElementType();
      size_t GVSize = (size_t)TD.getTypeAllocSize(ElTy);
      void *RawMemory = ::operator new(
        RoundUpToAlignment(sizeof(GVMemoryBlock),
                           TD.getPreferredAlignment(GV))
        + GVSize);
      new(RawMemory) GVMemoryBlock(GV);
      return static_cast<char*>(RawMemory) + sizeof(GVMemoryBlock);
    }
  
    void deleted() override {
      // We allocated with operator new and with some extra memory hanging off the
      // end, so don't just delete this.  I'm not sure if this is actually
      // required.
      this->~GVMemoryBlock();
      ::operator delete(this);
    }
  };
  }  // anonymous namespace
  
  char *ExecutionEngine::getMemoryForGV(const GlobalVariable *GV) {
    return GVMemoryBlock::Create(GV, getDataLayout());
  }
  
  void ExecutionEngine::addObjectFile(std::unique_ptr<object::ObjectFile> O) {
    llvm_unreachable("ExecutionEngine subclass doesn't implement addObjectFile.");
  }
  
  void
  ExecutionEngine::addObjectFile(object::OwningBinary<object::ObjectFile> O) {
    llvm_unreachable("ExecutionEngine subclass doesn't implement addObjectFile.");
  }
  
  void ExecutionEngine::addArchive(object::OwningBinary<object::Archive> A) {
    llvm_unreachable("ExecutionEngine subclass doesn't implement addArchive.");
  }
  
  bool ExecutionEngine::removeModule(Module *M) {
    for (auto I = Modules.begin(), E = Modules.end(); I != E; ++I) {
      Module *Found = I->get();
      if (Found == M) {
        I->release();
        Modules.erase(I);
        clearGlobalMappingsFromModule(M);
        return true;
      }
    }
    return false;
  }
  
  Function *ExecutionEngine::FindFunctionNamed(const char *FnName) {
    for (unsigned i = 0, e = Modules.size(); i != e; ++i) {
      Function *F = Modules[i]->getFunction(FnName);
      if (F && !F->isDeclaration())
        return F;
    }
    return nullptr;
  }
  
  GlobalVariable *ExecutionEngine::FindGlobalVariableNamed(const char *Name, bool AllowInternal) {
    for (unsigned i = 0, e = Modules.size(); i != e; ++i) {
      GlobalVariable *GV = Modules[i]->getGlobalVariable(Name,AllowInternal);
      if (GV && !GV->isDeclaration())
        return GV;
    }
    return nullptr;
  }
  
  uint64_t ExecutionEngineState::RemoveMapping(StringRef Name) {
    GlobalAddressMapTy::iterator I = GlobalAddressMap.find(Name);
    uint64_t OldVal;
  
    // FIXME: This is silly, we shouldn't end up with a mapping -> 0 in the
    // GlobalAddressMap.
    if (I == GlobalAddressMap.end())
      OldVal = 0;
    else {
      GlobalAddressReverseMap.erase(I->second);
      OldVal = I->second;
      GlobalAddressMap.erase(I);
    }
  
    return OldVal;
  }
  
  std::string ExecutionEngine::getMangledName(const GlobalValue *GV) {
    assert(GV->hasName() && "Global must have name.");
  
    MutexGuard locked(lock);
    SmallString<128> FullName;
  
    const DataLayout &DL =
      GV->getParent()->getDataLayout().isDefault()
        ? getDataLayout()
        : GV->getParent()->getDataLayout();
  
    Mangler::getNameWithPrefix(FullName, GV->getName(), DL);
    return FullName.str();
  }
  
  void ExecutionEngine::addGlobalMapping(const GlobalValue *GV, void *Addr) {
    MutexGuard locked(lock);
    addGlobalMapping(getMangledName(GV), (uint64_t) Addr);
  }
  
  void ExecutionEngine::addGlobalMapping(StringRef Name, uint64_t Addr) {
    MutexGuard locked(lock);
  
    assert(!Name.empty() && "Empty GlobalMapping symbol name!");
  
    DEBUG(dbgs() << "JIT: Map \'" << Name  << "\' to [" << Addr << "]\n";);
    uint64_t &CurVal = EEState.getGlobalAddressMap()[Name];
    assert((!CurVal || !Addr) && "GlobalMapping already established!");
    CurVal = Addr;
  
    // If we are using the reverse mapping, add it too.
    if (!EEState.getGlobalAddressReverseMap().empty()) {
      std::string &V = EEState.getGlobalAddressReverseMap()[CurVal];
      assert((!V.empty() || !Name.empty()) &&
             "GlobalMapping already established!");
      V = Name;
    }
  }
  
  void ExecutionEngine::clearAllGlobalMappings() {
    MutexGuard locked(lock);
  
    EEState.getGlobalAddressMap().clear();
    EEState.getGlobalAddressReverseMap().clear();
  }
  
  void ExecutionEngine::clearGlobalMappingsFromModule(Module *M) {
    MutexGuard locked(lock);
  
    for (Function &FI : *M)
      EEState.RemoveMapping(getMangledName(&FI));
    for (GlobalVariable &GI : M->globals())
      EEState.RemoveMapping(getMangledName(&GI));
  }
  
  uint64_t ExecutionEngine::updateGlobalMapping(const GlobalValue *GV,
                                                void *Addr) {
    MutexGuard locked(lock);
    return updateGlobalMapping(getMangledName(GV), (uint64_t) Addr);
  }
  
  uint64_t ExecutionEngine::updateGlobalMapping(StringRef Name, uint64_t Addr) {
    MutexGuard locked(lock);
  
    ExecutionEngineState::GlobalAddressMapTy &Map =
      EEState.getGlobalAddressMap();
  
    // Deleting from the mapping?
    if (!Addr)
      return EEState.RemoveMapping(Name);
  
    uint64_t &CurVal = Map[Name];
    uint64_t OldVal = CurVal;
  
    if (CurVal && !EEState.getGlobalAddressReverseMap().empty())
      EEState.getGlobalAddressReverseMap().erase(CurVal);
    CurVal = Addr;
  
    // If we are using the reverse mapping, add it too.
    if (!EEState.getGlobalAddressReverseMap().empty()) {
      std::string &V = EEState.getGlobalAddressReverseMap()[CurVal];
      assert((!V.empty() || !Name.empty()) &&
             "GlobalMapping already established!");
      V = Name;
    }
    return OldVal;
  }
  
  uint64_t ExecutionEngine::getAddressToGlobalIfAvailable(StringRef S) {
    MutexGuard locked(lock);
    uint64_t Address = 0;
    ExecutionEngineState::GlobalAddressMapTy::iterator I =
      EEState.getGlobalAddressMap().find(S);
    if (I != EEState.getGlobalAddressMap().end())
      Address = I->second;
    return Address;
  }
  
  
  void *ExecutionEngine::getPointerToGlobalIfAvailable(StringRef S) {
    MutexGuard locked(lock);
    if (void* Address = (void *) getAddressToGlobalIfAvailable(S))
      return Address;
    return nullptr;
  }
  
  void *ExecutionEngine::getPointerToGlobalIfAvailable(const GlobalValue *GV) {
    MutexGuard locked(lock);
    return getPointerToGlobalIfAvailable(getMangledName(GV));
  }
  
  const GlobalValue *ExecutionEngine::getGlobalValueAtAddress(void *Addr) {
    MutexGuard locked(lock);
  
    // If we haven't computed the reverse mapping yet, do so first.
    if (EEState.getGlobalAddressReverseMap().empty()) {
      for (ExecutionEngineState::GlobalAddressMapTy::iterator
             I = EEState.getGlobalAddressMap().begin(),
             E = EEState.getGlobalAddressMap().end(); I != E; ++I) {
        StringRef Name = I->first();
        uint64_t Addr = I->second;
        EEState.getGlobalAddressReverseMap().insert(std::make_pair(
                                                            Addr, Name));
      }
    }
  
    std::map<uint64_t, std::string>::iterator I =
      EEState.getGlobalAddressReverseMap().find((uint64_t) Addr);
  
    if (I != EEState.getGlobalAddressReverseMap().end()) {
      StringRef Name = I->second;
      for (unsigned i = 0, e = Modules.size(); i != e; ++i)
        if (GlobalValue *GV = Modules[i]->getNamedValue(Name))
          return GV;
    }
    return nullptr;
  }
  
  namespace {
  class ArgvArray {
    std::unique_ptr<char[]> Array;
    std::vector<std::unique_ptr<char[]>> Values;
  public:
    /// Turn a vector of strings into a nice argv style array of pointers to null
    /// terminated strings.
    void *reset(LLVMContext &C, ExecutionEngine *EE,
                const std::vector<std::string> &InputArgv);
  };
  }  // anonymous namespace
  void *ArgvArray::reset(LLVMContext &C, ExecutionEngine *EE,
                         const std::vector<std::string> &InputArgv) {
    Values.clear();  // Free the old contents.
    Values.reserve(InputArgv.size());
    unsigned PtrSize = EE->getDataLayout().getPointerSize();
    Array = make_unique<char[]>((InputArgv.size()+1)*PtrSize);
  
    DEBUG(dbgs() << "JIT: ARGV = " << (void*)Array.get() << "\n");
    Type *SBytePtr = Type::getInt8PtrTy(C);
  
    for (unsigned i = 0; i != InputArgv.size(); ++i) {
      unsigned Size = InputArgv[i].size()+1;
      auto Dest = make_unique<char[]>(Size);
      DEBUG(dbgs() << "JIT: ARGV[" << i << "] = " << (void*)Dest.get() << "\n");
  
      std::copy(InputArgv[i].begin(), InputArgv[i].end(), Dest.get());
      Dest[Size-1] = 0;
  
      // Endian safe: Array[i] = (PointerTy)Dest;
      EE->StoreValueToMemory(PTOGV(Dest.get()),
                             (GenericValue*)(&Array[i*PtrSize]), SBytePtr);
      Values.push_back(std::move(Dest));
    }
  
    // Null terminate it
    EE->StoreValueToMemory(PTOGV(nullptr),
                           (GenericValue*)(&Array[InputArgv.size()*PtrSize]),
                           SBytePtr);
    return Array.get();
  }
  
  void ExecutionEngine::runStaticConstructorsDestructors(Module &module,
                                                         bool isDtors) {
    const char *Name = isDtors ? "llvm.global_dtors" : "llvm.global_ctors";
    GlobalVariable *GV = module.getNamedGlobal(Name);
  
    // If this global has internal linkage, or if it has a use, then it must be
    // an old-style (llvmgcc3) static ctor with __main linked in and in use.  If
    // this is the case, don't execute any of the global ctors, __main will do
    // it.
    if (!GV || GV->isDeclaration() || GV->hasLocalLinkage()) return;
  
    // Should be an array of '{ i32, void ()* }' structs.  The first value is
    // the init priority, which we ignore.
    ConstantArray *InitList = dyn_cast<ConstantArray>(GV->getInitializer());
    if (!InitList)
      return;
    for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i) {
      ConstantStruct *CS = dyn_cast<ConstantStruct>(InitList->getOperand(i));
      if (!CS) continue;
  
      Constant *FP = CS->getOperand(1);
      if (FP->isNullValue())
        continue;  // Found a sentinal value, ignore.
  
      // Strip off constant expression casts.
      if (ConstantExpr *CE = dyn_cast<ConstantExpr>(FP))
        if (CE->isCast())
          FP = CE->getOperand(0);
  
      // Execute the ctor/dtor function!
      if (Function *F = dyn_cast<Function>(FP))
        runFunction(F, None);
  
      // FIXME: It is marginally lame that we just do nothing here if we see an
      // entry we don't recognize. It might not be unreasonable for the verifier
      // to not even allow this and just assert here.
    }
  }
  
  void ExecutionEngine::runStaticConstructorsDestructors(bool isDtors) {
    // Execute global ctors/dtors for each module in the program.
    for (std::unique_ptr<Module> &M : Modules)
      runStaticConstructorsDestructors(*M, isDtors);
  }
  
  #ifndef NDEBUG
  /// isTargetNullPtr - Return whether the target pointer stored at Loc is null.
  static bool isTargetNullPtr(ExecutionEngine *EE, void *Loc) {
    unsigned PtrSize = EE->getDataLayout().getPointerSize();
    for (unsigned i = 0; i < PtrSize; ++i)
      if (*(i + (uint8_t*)Loc))
        return false;
    return true;
  }
  #endif
  
  int ExecutionEngine::runFunctionAsMain(Function *Fn,
                                         const std::vector<std::string> &argv,
                                         const char * const * envp) {
    std::vector<GenericValue> GVArgs;
    GenericValue GVArgc;
    GVArgc.IntVal = APInt(32, argv.size());
  
    // Check main() type
    unsigned NumArgs = Fn->getFunctionType()->getNumParams();
    FunctionType *FTy = Fn->getFunctionType();
    Type* PPInt8Ty = Type::getInt8PtrTy(Fn->getContext())->getPointerTo();
  
    // Check the argument types.
    if (NumArgs > 3)
      report_fatal_error("Invalid number of arguments of main() supplied");
    if (NumArgs >= 3 && FTy->getParamType(2) != PPInt8Ty)
      report_fatal_error("Invalid type for third argument of main() supplied");
    if (NumArgs >= 2 && FTy->getParamType(1) != PPInt8Ty)
      report_fatal_error("Invalid type for second argument of main() supplied");
    if (NumArgs >= 1 && !FTy->getParamType(0)->isIntegerTy(32))
      report_fatal_error("Invalid type for first argument of main() supplied");
    if (!FTy->getReturnType()->isIntegerTy() &&
        !FTy->getReturnType()->isVoidTy())
      report_fatal_error("Invalid return type of main() supplied");
  
    ArgvArray CArgv;
    ArgvArray CEnv;
    if (NumArgs) {
      GVArgs.push_back(GVArgc); // Arg #0 = argc.
      if (NumArgs > 1) {
        // Arg #1 = argv.
        GVArgs.push_back(PTOGV(CArgv.reset(Fn->getContext(), this, argv)));
        assert(!isTargetNullPtr(this, GVTOP(GVArgs[1])) &&
               "argv[0] was null after CreateArgv");
        if (NumArgs > 2) {
          std::vector<std::string> EnvVars;
          for (unsigned i = 0; envp[i]; ++i)
            EnvVars.emplace_back(envp[i]);
          // Arg #2 = envp.
          GVArgs.push_back(PTOGV(CEnv.reset(Fn->getContext(), this, EnvVars)));
        }
      }
    }
  
    return runFunction(Fn, GVArgs).IntVal.getZExtValue();
  }
  
  EngineBuilder::EngineBuilder() : EngineBuilder(nullptr) {}
  
  EngineBuilder::EngineBuilder(std::unique_ptr<Module> M)
      : M(std::move(M)), WhichEngine(EngineKind::Either), ErrorStr(nullptr),
        OptLevel(CodeGenOpt::Default), MemMgr(nullptr), Resolver(nullptr),
        RelocModel(Reloc::Default), CMModel(CodeModel::JITDefault),
        UseOrcMCJITReplacement(false) {
  // IR module verification is enabled by default in debug builds, and disabled
  // by default in release builds.
  #ifndef NDEBUG
    VerifyModules = true;
  #else
    VerifyModules = false;
  #endif
  }
  
  EngineBuilder::~EngineBuilder() = default;
  
  EngineBuilder &EngineBuilder::setMCJITMemoryManager(
                                     std::unique_ptr<RTDyldMemoryManager> mcjmm) {
    auto SharedMM = std::shared_ptr<RTDyldMemoryManager>(std::move(mcjmm));
    MemMgr = SharedMM;
    Resolver = SharedMM;
    return *this;
  }
  
  EngineBuilder&
  EngineBuilder::setMemoryManager(std::unique_ptr<MCJITMemoryManager> MM) {
    MemMgr = std::shared_ptr<MCJITMemoryManager>(std::move(MM));
    return *this;
  }
  
  EngineBuilder&
  EngineBuilder::setSymbolResolver(std::unique_ptr<RuntimeDyld::SymbolResolver> SR) {
    Resolver = std::shared_ptr<RuntimeDyld::SymbolResolver>(std::move(SR));
    return *this;
  }
  
  ExecutionEngine *EngineBuilder::create(TargetMachine *TM) {
    std::unique_ptr<TargetMachine> TheTM(TM); // Take ownership.
  
    // Make sure we can resolve symbols in the program as well. The zero arg
    // to the function tells DynamicLibrary to load the program, not a library.
    if (sys::DynamicLibrary::LoadLibraryPermanently(nullptr, ErrorStr))
      return nullptr;
    
    // If the user specified a memory manager but didn't specify which engine to
    // create, we assume they only want the JIT, and we fail if they only want
    // the interpreter.
    if (MemMgr) {
      if (WhichEngine & EngineKind::JIT)
        WhichEngine = EngineKind::JIT;
      else {
        if (ErrorStr)
          *ErrorStr = "Cannot create an interpreter with a memory manager.";
        return nullptr;
      }
    }
  
    // Unless the interpreter was explicitly selected or the JIT is not linked,
    // try making a JIT.
    if ((WhichEngine & EngineKind::JIT) && TheTM) {
      Triple TT(M->getTargetTriple());
      if (!TM->getTarget().hasJIT()) {
        errs() << "WARNING: This target JIT is not designed for the host"
               << " you are running.  If bad things happen, please choose"
               << " a different -march switch.\n";
      }
  
      ExecutionEngine *EE = nullptr;
      if (ExecutionEngine::OrcMCJITReplacementCtor && UseOrcMCJITReplacement) {
        EE = ExecutionEngine::OrcMCJITReplacementCtor(ErrorStr, std::move(MemMgr),
                                                      std::move(Resolver),
                                                      std::move(TheTM));
        EE->addModule(std::move(M));
      } else if (ExecutionEngine::MCJITCtor)
        EE = ExecutionEngine::MCJITCtor(std::move(M), ErrorStr, std::move(MemMgr),
                                        std::move(Resolver), std::move(TheTM));
  
      if (EE) {
        EE->setVerifyModules(VerifyModules);
        return EE;
      }
    }
  
    // If we can't make a JIT and we didn't request one specifically, try making
    // an interpreter instead.
    if (WhichEngine & EngineKind::Interpreter) {
      if (ExecutionEngine::InterpCtor)
        return ExecutionEngine::InterpCtor(std::move(M), ErrorStr);
      if (ErrorStr)
        *ErrorStr = "Interpreter has not been linked in.";
      return nullptr;
    }
  
    if ((WhichEngine & EngineKind::JIT) && !ExecutionEngine::MCJITCtor) {
      if (ErrorStr)
        *ErrorStr = "JIT has not been linked in.";
    }
  
    return nullptr;
  }
  
  void *ExecutionEngine::getPointerToGlobal(const GlobalValue *GV) {
    if (Function *F = const_cast<Function*>(dyn_cast<Function>(GV)))
      return getPointerToFunction(F);
  
    MutexGuard locked(lock);
    if (void* P = getPointerToGlobalIfAvailable(GV))
      return P;
  
    // Global variable might have been added since interpreter started.
    if (GlobalVariable *GVar =
            const_cast<GlobalVariable *>(dyn_cast<GlobalVariable>(GV)))
      EmitGlobalVariable(GVar);
    else
      llvm_unreachable("Global hasn't had an address allocated yet!");
  
    return getPointerToGlobalIfAvailable(GV);
  }
  
  /// \brief Converts a Constant* into a GenericValue, including handling of
  /// ConstantExpr values.
  GenericValue ExecutionEngine::getConstantValue(const Constant *C) {
    // If its undefined, return the garbage.
    if (isa<UndefValue>(C)) {
      GenericValue Result;
      switch (C->getType()->getTypeID()) {
      default:
        break;
      case Type::IntegerTyID:
      case Type::X86_FP80TyID:
      case Type::FP128TyID:
      case Type::PPC_FP128TyID:
        // Although the value is undefined, we still have to construct an APInt
        // with the correct bit width.
        Result.IntVal = APInt(C->getType()->getPrimitiveSizeInBits(), 0);
        break;
      case Type::StructTyID: {
        // if the whole struct is 'undef' just reserve memory for the value.
        if(StructType *STy = dyn_cast<StructType>(C->getType())) {
          unsigned int elemNum = STy->getNumElements();
          Result.AggregateVal.resize(elemNum);
          for (unsigned int i = 0; i < elemNum; ++i) {
            Type *ElemTy = STy->getElementType(i);
            if (ElemTy->isIntegerTy())
              Result.AggregateVal[i].IntVal = 
                APInt(ElemTy->getPrimitiveSizeInBits(), 0);
            else if (ElemTy->isAggregateType()) {
                const Constant *ElemUndef = UndefValue::get(ElemTy);
                Result.AggregateVal[i] = getConstantValue(ElemUndef);
              }
            }
          }
        }
        break;
      case Type::VectorTyID:
        // if the whole vector is 'undef' just reserve memory for the value.
        auto* VTy = dyn_cast<VectorType>(C->getType());
        Type *ElemTy = VTy->getElementType();
        unsigned int elemNum = VTy->getNumElements();
        Result.AggregateVal.resize(elemNum);
        if (ElemTy->isIntegerTy())
          for (unsigned int i = 0; i < elemNum; ++i)
            Result.AggregateVal[i].IntVal =
              APInt(ElemTy->getPrimitiveSizeInBits(), 0);
        break;
      }
      return Result;
    }
  
    // Otherwise, if the value is a ConstantExpr...
    if (const ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
      Constant *Op0 = CE->getOperand(0);
      switch (CE->getOpcode()) {
      case Instruction::GetElementPtr: {
        // Compute the index
        GenericValue Result = getConstantValue(Op0);
        APInt Offset(DL.getPointerSizeInBits(), 0);
        cast<GEPOperator>(CE)->accumulateConstantOffset(DL, Offset);
  
        char* tmp = (char*) Result.PointerVal;
        Result = PTOGV(tmp + Offset.getSExtValue());
        return Result;
      }
      case Instruction::Trunc: {
        GenericValue GV = getConstantValue(Op0);
        uint32_t BitWidth = cast<IntegerType>(CE->getType())->getBitWidth();
        GV.IntVal = GV.IntVal.trunc(BitWidth);
        return GV;
      }
      case Instruction::ZExt: {
        GenericValue GV = getConstantValue(Op0);
        uint32_t BitWidth = cast<IntegerType>(CE->getType())->getBitWidth();
        GV.IntVal = GV.IntVal.zext(BitWidth);
        return GV;
      }
      case Instruction::SExt: {
        GenericValue GV = getConstantValue(Op0);
        uint32_t BitWidth = cast<IntegerType>(CE->getType())->getBitWidth();
        GV.IntVal = GV.IntVal.sext(BitWidth);
        return GV;
      }
      case Instruction::FPTrunc: {
        // FIXME long double
        GenericValue GV = getConstantValue(Op0);
        GV.FloatVal = float(GV.DoubleVal);
        return GV;
      }
      case Instruction::FPExt:{
        // FIXME long double
        GenericValue GV = getConstantValue(Op0);
        GV.DoubleVal = double(GV.FloatVal);
        return GV;
      }
      case Instruction::UIToFP: {
        GenericValue GV = getConstantValue(Op0);
        if (CE->getType()->isFloatTy())
          GV.FloatVal = float(GV.IntVal.roundToDouble());
        else if (CE->getType()->isDoubleTy())
          GV.DoubleVal = GV.IntVal.roundToDouble();
        else if (CE->getType()->isX86_FP80Ty()) {
          APFloat apf = APFloat::getZero(APFloat::x87DoubleExtended);
          (void)apf.convertFromAPInt(GV.IntVal,
                                     false,
                                     APFloat::rmNearestTiesToEven);
          GV.IntVal = apf.bitcastToAPInt();
        }
        return GV;
      }
      case Instruction::SIToFP: {
        GenericValue GV = getConstantValue(Op0);
        if (CE->getType()->isFloatTy())
          GV.FloatVal = float(GV.IntVal.signedRoundToDouble());
        else if (CE->getType()->isDoubleTy())
          GV.DoubleVal = GV.IntVal.signedRoundToDouble();
        else if (CE->getType()->isX86_FP80Ty()) {
          APFloat apf = APFloat::getZero(APFloat::x87DoubleExtended);
          (void)apf.convertFromAPInt(GV.IntVal,
                                     true,
                                     APFloat::rmNearestTiesToEven);
          GV.IntVal = apf.bitcastToAPInt();
        }
        return GV;
      }
      case Instruction::FPToUI: // double->APInt conversion handles sign
      case Instruction::FPToSI: {
        GenericValue GV = getConstantValue(Op0);
        uint32_t BitWidth = cast<IntegerType>(CE->getType())->getBitWidth();
        if (Op0->getType()->isFloatTy())
          GV.IntVal = APIntOps::RoundFloatToAPInt(GV.FloatVal, BitWidth);
        else if (Op0->getType()->isDoubleTy())
          GV.IntVal = APIntOps::RoundDoubleToAPInt(GV.DoubleVal, BitWidth);
        else if (Op0->getType()->isX86_FP80Ty()) {
          APFloat apf = APFloat(APFloat::x87DoubleExtended, GV.IntVal);
          uint64_t v;
          bool ignored;
          (void)apf.convertToInteger(&v, BitWidth,
                                     CE->getOpcode()==Instruction::FPToSI,
                                     APFloat::rmTowardZero, &ignored);
          GV.IntVal = v; // endian?
        }
        return GV;
      }
      case Instruction::PtrToInt: {
        GenericValue GV = getConstantValue(Op0);
        uint32_t PtrWidth = DL.getTypeSizeInBits(Op0->getType());
        assert(PtrWidth <= 64 && "Bad pointer width");
        GV.IntVal = APInt(PtrWidth, uintptr_t(GV.PointerVal));
        uint32_t IntWidth = DL.getTypeSizeInBits(CE->getType());
        GV.IntVal = GV.IntVal.zextOrTrunc(IntWidth);
        return GV;
      }
      case Instruction::IntToPtr: {
        GenericValue GV = getConstantValue(Op0);
        uint32_t PtrWidth = DL.getTypeSizeInBits(CE->getType());
        GV.IntVal = GV.IntVal.zextOrTrunc(PtrWidth);
        assert(GV.IntVal.getBitWidth() <= 64 && "Bad pointer width");
        GV.PointerVal = PointerTy(uintptr_t(GV.IntVal.getZExtValue()));
        return GV;
      }
      case Instruction::BitCast: {
        GenericValue GV = getConstantValue(Op0);
        Type* DestTy = CE->getType();
        switch (Op0->getType()->getTypeID()) {
          default: llvm_unreachable("Invalid bitcast operand");
          case Type::IntegerTyID:
            assert(DestTy->isFloatingPointTy() && "invalid bitcast");
            if (DestTy->isFloatTy())
              GV.FloatVal = GV.IntVal.bitsToFloat();
            else if (DestTy->isDoubleTy())
              GV.DoubleVal = GV.IntVal.bitsToDouble();
            break;
          case Type::FloatTyID:
            assert(DestTy->isIntegerTy(32) && "Invalid bitcast");
            GV.IntVal = APInt::floatToBits(GV.FloatVal);
            break;
          case Type::DoubleTyID:
            assert(DestTy->isIntegerTy(64) && "Invalid bitcast");
            GV.IntVal = APInt::doubleToBits(GV.DoubleVal);
            break;
          case Type::PointerTyID:
            assert(DestTy->isPointerTy() && "Invalid bitcast");
            break; // getConstantValue(Op0)  above already converted it
        }
        return GV;
      }
      case Instruction::Add:
      case Instruction::FAdd:
      case Instruction::Sub:
      case Instruction::FSub:
      case Instruction::Mul:
      case Instruction::FMul:
      case Instruction::UDiv:
      case Instruction::SDiv:
      case Instruction::URem:
      case Instruction::SRem:
      case Instruction::And:
      case Instruction::Or:
      case Instruction::Xor: {
        GenericValue LHS = getConstantValue(Op0);
        GenericValue RHS = getConstantValue(CE->getOperand(1));
        GenericValue GV;
        switch (CE->getOperand(0)->getType()->getTypeID()) {
        default: llvm_unreachable("Bad add type!");
        case Type::IntegerTyID:
          switch (CE->getOpcode()) {
            default: llvm_unreachable("Invalid integer opcode");
            case Instruction::Add: GV.IntVal = LHS.IntVal + RHS.IntVal; break;
            case Instruction::Sub: GV.IntVal = LHS.IntVal - RHS.IntVal; break;
            case Instruction::Mul: GV.IntVal = LHS.IntVal * RHS.IntVal; break;
            case Instruction::UDiv:GV.IntVal = LHS.IntVal.udiv(RHS.IntVal); break;
            case Instruction::SDiv:GV.IntVal = LHS.IntVal.sdiv(RHS.IntVal); break;
            case Instruction::URem:GV.IntVal = LHS.IntVal.urem(RHS.IntVal); break;
            case Instruction::SRem:GV.IntVal = LHS.IntVal.srem(RHS.IntVal); break;
            case Instruction::And: GV.IntVal = LHS.IntVal & RHS.IntVal; break;
            case Instruction::Or:  GV.IntVal = LHS.IntVal | RHS.IntVal; break;
            case Instruction::Xor: GV.IntVal = LHS.IntVal ^ RHS.IntVal; break;
          }
          break;
        case Type::FloatTyID:
          switch (CE->getOpcode()) {
            default: llvm_unreachable("Invalid float opcode");
            case Instruction::FAdd:
              GV.FloatVal = LHS.FloatVal + RHS.FloatVal; break;
            case Instruction::FSub:
              GV.FloatVal = LHS.FloatVal - RHS.FloatVal; break;
            case Instruction::FMul:
              GV.FloatVal = LHS.FloatVal * RHS.FloatVal; break;
            case Instruction::FDiv:
              GV.FloatVal = LHS.FloatVal / RHS.FloatVal; break;
            case Instruction::FRem:
              GV.FloatVal = std::fmod(LHS.FloatVal,RHS.FloatVal); break;
          }
          break;
        case Type::DoubleTyID:
          switch (CE->getOpcode()) {
            default: llvm_unreachable("Invalid double opcode");
            case Instruction::FAdd:
              GV.DoubleVal = LHS.DoubleVal + RHS.DoubleVal; break;
            case Instruction::FSub:
              GV.DoubleVal = LHS.DoubleVal - RHS.DoubleVal; break;
            case Instruction::FMul:
              GV.DoubleVal = LHS.DoubleVal * RHS.DoubleVal; break;
            case Instruction::FDiv:
              GV.DoubleVal = LHS.DoubleVal / RHS.DoubleVal; break;
            case Instruction::FRem:
              GV.DoubleVal = std::fmod(LHS.DoubleVal,RHS.DoubleVal); break;
          }
          break;
        case Type::X86_FP80TyID:
        case Type::PPC_FP128TyID:
        case Type::FP128TyID: {
          const fltSemantics &Sem = CE->getOperand(0)->getType()->getFltSemantics();
          APFloat apfLHS = APFloat(Sem, LHS.IntVal);
          switch (CE->getOpcode()) {
            default: llvm_unreachable("Invalid long double opcode");
            case Instruction::FAdd:
              apfLHS.add(APFloat(Sem, RHS.IntVal), APFloat::rmNearestTiesToEven);
              GV.IntVal = apfLHS.bitcastToAPInt();
              break;
            case Instruction::FSub:
              apfLHS.subtract(APFloat(Sem, RHS.IntVal),
                              APFloat::rmNearestTiesToEven);
              GV.IntVal = apfLHS.bitcastToAPInt();
              break;
            case Instruction::FMul:
              apfLHS.multiply(APFloat(Sem, RHS.IntVal),
                              APFloat::rmNearestTiesToEven);
              GV.IntVal = apfLHS.bitcastToAPInt();
              break;
            case Instruction::FDiv:
              apfLHS.divide(APFloat(Sem, RHS.IntVal),
                            APFloat::rmNearestTiesToEven);
              GV.IntVal = apfLHS.bitcastToAPInt();
              break;
            case Instruction::FRem:
              apfLHS.mod(APFloat(Sem, RHS.IntVal));
              GV.IntVal = apfLHS.bitcastToAPInt();
              break;
            }
          }
          break;
        }
        return GV;
      }
      default:
        break;
      }
  
      SmallString<256> Msg;
      raw_svector_ostream OS(Msg);
      OS << "ConstantExpr not handled: " << *CE;
      report_fatal_error(OS.str());
    }
  
    // Otherwise, we have a simple constant.
    GenericValue Result;
    switch (C->getType()->getTypeID()) {
    case Type::FloatTyID:
      Result.FloatVal = cast<ConstantFP>(C)->getValueAPF().convertToFloat();
      break;
    case Type::DoubleTyID:
      Result.DoubleVal = cast<ConstantFP>(C)->getValueAPF().convertToDouble();
      break;
    case Type::X86_FP80TyID:
    case Type::FP128TyID:
    case Type::PPC_FP128TyID:
      Result.IntVal = cast <ConstantFP>(C)->getValueAPF().bitcastToAPInt();
      break;
    case Type::IntegerTyID:
      Result.IntVal = cast<ConstantInt>(C)->getValue();
      break;
    case Type::PointerTyID:
      if (isa<ConstantPointerNull>(C))
        Result.PointerVal = nullptr;
      else if (const Function *F = dyn_cast<Function>(C))
        Result = PTOGV(getPointerToFunctionOrStub(const_cast<Function*>(F)));
      else if (const GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
        Result = PTOGV(getOrEmitGlobalVariable(const_cast<GlobalVariable*>(GV)));
      else
        llvm_unreachable("Unknown constant pointer type!");
      break;
    case Type::VectorTyID: {
      unsigned elemNum;
      Type* ElemTy;
      const ConstantDataVector *CDV = dyn_cast<ConstantDataVector>(C);
      const ConstantVector *CV = dyn_cast<ConstantVector>(C);
      const ConstantAggregateZero *CAZ = dyn_cast<ConstantAggregateZero>(C);
  
      if (CDV) {
          elemNum = CDV->getNumElements();
          ElemTy = CDV->getElementType();
      } else if (CV || CAZ) {
          VectorType* VTy = dyn_cast<VectorType>(C->getType());
          elemNum = VTy->getNumElements();
          ElemTy = VTy->getElementType();
      } else {
          llvm_unreachable("Unknown constant vector type!");
      }
  
      Result.AggregateVal.resize(elemNum);
      // Check if vector holds floats.
      if(ElemTy->isFloatTy()) {
        if (CAZ) {
          GenericValue floatZero;
          floatZero.FloatVal = 0.f;
          std::fill(Result.AggregateVal.begin(), Result.AggregateVal.end(),
                    floatZero);
          break;
        }
        if(CV) {
          for (unsigned i = 0; i < elemNum; ++i)
            if (!isa<UndefValue>(CV->getOperand(i)))
              Result.AggregateVal[i].FloatVal = cast<ConstantFP>(
                CV->getOperand(i))->getValueAPF().convertToFloat();
          break;
        }
        if(CDV)
          for (unsigned i = 0; i < elemNum; ++i)
            Result.AggregateVal[i].FloatVal = CDV->getElementAsFloat(i);
  
        break;
      }
      // Check if vector holds doubles.
      if (ElemTy->isDoubleTy()) {
        if (CAZ) {
          GenericValue doubleZero;
          doubleZero.DoubleVal = 0.0;
          std::fill(Result.AggregateVal.begin(), Result.AggregateVal.end(),
                    doubleZero);
          break;
        }
        if(CV) {
          for (unsigned i = 0; i < elemNum; ++i)
            if (!isa<UndefValue>(CV->getOperand(i)))
              Result.AggregateVal[i].DoubleVal = cast<ConstantFP>(
                CV->getOperand(i))->getValueAPF().convertToDouble();
          break;
        }
        if(CDV)
          for (unsigned i = 0; i < elemNum; ++i)
            Result.AggregateVal[i].DoubleVal = CDV->getElementAsDouble(i);
  
        break;
      }
      // Check if vector holds integers.
      if (ElemTy->isIntegerTy()) {
        if (CAZ) {
          GenericValue intZero;     
          intZero.IntVal = APInt(ElemTy->getScalarSizeInBits(), 0ull);
          std::fill(Result.AggregateVal.begin(), Result.AggregateVal.end(),
                    intZero);
          break;
        }
        if(CV) {
          for (unsigned i = 0; i < elemNum; ++i)
            if (!isa<UndefValue>(CV->getOperand(i)))
              Result.AggregateVal[i].IntVal = cast<ConstantInt>(
                                              CV->getOperand(i))->getValue();
            else {
              Result.AggregateVal[i].IntVal =
                APInt(CV->getOperand(i)->getType()->getPrimitiveSizeInBits(), 0);
            }
          break;
        }
        if(CDV)
          for (unsigned i = 0; i < elemNum; ++i)
            Result.AggregateVal[i].IntVal = APInt(
              CDV->getElementType()->getPrimitiveSizeInBits(),
              CDV->getElementAsInteger(i));
  
        break;
      }
      llvm_unreachable("Unknown constant pointer type!");
    }
    break;
  
    default:
      SmallString<256> Msg;
      raw_svector_ostream OS(Msg);
      OS << "ERROR: Constant unimplemented for type: " << *C->getType();
      report_fatal_error(OS.str());
    }
  
    return Result;
  }
  
  /// StoreIntToMemory - Fills the StoreBytes bytes of memory starting from Dst
  /// with the integer held in IntVal.
  static void StoreIntToMemory(const APInt &IntVal, uint8_t *Dst,
                               unsigned StoreBytes) {
    assert((IntVal.getBitWidth()+7)/8 >= StoreBytes && "Integer too small!");
    const uint8_t *Src = (const uint8_t *)IntVal.getRawData();
  
    if (sys::IsLittleEndianHost) {
      // Little-endian host - the source is ordered from LSB to MSB.  Order the
      // destination from LSB to MSB: Do a straight copy.
      memcpy(Dst, Src, StoreBytes);
    } else {
      // Big-endian host - the source is an array of 64 bit words ordered from
      // LSW to MSW.  Each word is ordered from MSB to LSB.  Order the destination
      // from MSB to LSB: Reverse the word order, but not the bytes in a word.
      while (StoreBytes > sizeof(uint64_t)) {
        StoreBytes -= sizeof(uint64_t);
        // May not be aligned so use memcpy.
        memcpy(Dst + StoreBytes, Src, sizeof(uint64_t));
        Src += sizeof(uint64_t);
      }
  
      memcpy(Dst, Src + sizeof(uint64_t) - StoreBytes, StoreBytes);
    }
  }
  
  void ExecutionEngine::StoreValueToMemory(const GenericValue &Val,
                                           GenericValue *Ptr, Type *Ty) {
    const unsigned StoreBytes = getDataLayout().getTypeStoreSize(Ty);
  
    switch (Ty->getTypeID()) {
    default:
      dbgs() << "Cannot store value of type " << *Ty << "!\n";
      break;
    case Type::IntegerTyID:
      StoreIntToMemory(Val.IntVal, (uint8_t*)Ptr, StoreBytes);
      break;
    case Type::FloatTyID:
      *((float*)Ptr) = Val.FloatVal;
      break;
    case Type::DoubleTyID:
      *((double*)Ptr) = Val.DoubleVal;
      break;
    case Type::X86_FP80TyID:
      memcpy(Ptr, Val.IntVal.getRawData(), 10);
      break;
    case Type::PointerTyID:
      // Ensure 64 bit target pointers are fully initialized on 32 bit hosts.
      if (StoreBytes != sizeof(PointerTy))
        memset(&(Ptr->PointerVal), 0, StoreBytes);
  
      *((PointerTy*)Ptr) = Val.PointerVal;
      break;
    case Type::VectorTyID:
      for (unsigned i = 0; i < Val.AggregateVal.size(); ++i) {
        if (cast<VectorType>(Ty)->getElementType()->isDoubleTy())
          *(((double*)Ptr)+i) = Val.AggregateVal[i].DoubleVal;
        if (cast<VectorType>(Ty)->getElementType()->isFloatTy())
          *(((float*)Ptr)+i) = Val.AggregateVal[i].FloatVal;
        if (cast<VectorType>(Ty)->getElementType()->isIntegerTy()) {
          unsigned numOfBytes =(Val.AggregateVal[i].IntVal.getBitWidth()+7)/8;
          StoreIntToMemory(Val.AggregateVal[i].IntVal, 
            (uint8_t*)Ptr + numOfBytes*i, numOfBytes);
        }
      }
      break;
    }
  
    if (sys::IsLittleEndianHost != getDataLayout().isLittleEndian())
      // Host and target are different endian - reverse the stored bytes.
      std::reverse((uint8_t*)Ptr, StoreBytes + (uint8_t*)Ptr);
  }
  
  /// LoadIntFromMemory - Loads the integer stored in the LoadBytes bytes starting
  /// from Src into IntVal, which is assumed to be wide enough and to hold zero.
  static void LoadIntFromMemory(APInt &IntVal, uint8_t *Src, unsigned LoadBytes) {
    assert((IntVal.getBitWidth()+7)/8 >= LoadBytes && "Integer too small!");
    uint8_t *Dst = reinterpret_cast<uint8_t *>(
                     const_cast<uint64_t *>(IntVal.getRawData()));
  
    if (sys::IsLittleEndianHost)
      // Little-endian host - the destination must be ordered from LSB to MSB.
      // The source is ordered from LSB to MSB: Do a straight copy.
      memcpy(Dst, Src, LoadBytes);
    else {
      // Big-endian - the destination is an array of 64 bit words ordered from
      // LSW to MSW.  Each word must be ordered from MSB to LSB.  The source is
      // ordered from MSB to LSB: Reverse the word order, but not the bytes in
      // a word.
      while (LoadBytes > sizeof(uint64_t)) {
        LoadBytes -= sizeof(uint64_t);
        // May not be aligned so use memcpy.
        memcpy(Dst, Src + LoadBytes, sizeof(uint64_t));
        Dst += sizeof(uint64_t);
      }
  
      memcpy(Dst + sizeof(uint64_t) - LoadBytes, Src, LoadBytes);
    }
  }
  
  /// FIXME: document
  ///
  void ExecutionEngine::LoadValueFromMemory(GenericValue &Result,
                                            GenericValue *Ptr,
                                            Type *Ty) {
    const unsigned LoadBytes = getDataLayout().getTypeStoreSize(Ty);
  
    switch (Ty->getTypeID()) {
    case Type::IntegerTyID:
      // An APInt with all words initially zero.
      Result.IntVal = APInt(cast<IntegerType>(Ty)->getBitWidth(), 0);
      LoadIntFromMemory(Result.IntVal, (uint8_t*)Ptr, LoadBytes);
      break;
    case Type::FloatTyID:
      Result.FloatVal = *((float*)Ptr);
      break;
    case Type::DoubleTyID:
      Result.DoubleVal = *((double*)Ptr);
      break;
    case Type::PointerTyID:
      Result.PointerVal = *((PointerTy*)Ptr);
      break;
    case Type::X86_FP80TyID: {
      // This is endian dependent, but it will only work on x86 anyway.
      // FIXME: Will not trap if loading a signaling NaN.
      uint64_t y[2];
      memcpy(y, Ptr, 10);
      Result.IntVal = APInt(80, y);
      break;
    }
    case Type::VectorTyID: {
      auto *VT = cast<VectorType>(Ty);
      Type *ElemT = VT->getElementType();
      const unsigned numElems = VT->getNumElements();
      if (ElemT->isFloatTy()) {
        Result.AggregateVal.resize(numElems);
        for (unsigned i = 0; i < numElems; ++i)
          Result.AggregateVal[i].FloatVal = *((float*)Ptr+i);
      }
      if (ElemT->isDoubleTy()) {
        Result.AggregateVal.resize(numElems);
        for (unsigned i = 0; i < numElems; ++i)
          Result.AggregateVal[i].DoubleVal = *((double*)Ptr+i);
      }
      if (ElemT->isIntegerTy()) {
        GenericValue intZero;
        const unsigned elemBitWidth = cast<IntegerType>(ElemT)->getBitWidth();
        intZero.IntVal = APInt(elemBitWidth, 0);
        Result.AggregateVal.resize(numElems, intZero);
        for (unsigned i = 0; i < numElems; ++i)
          LoadIntFromMemory(Result.AggregateVal[i].IntVal,
            (uint8_t*)Ptr+((elemBitWidth+7)/8)*i, (elemBitWidth+7)/8);
      }
    break;
    }
    default:
      SmallString<256> Msg;
      raw_svector_ostream OS(Msg);
      OS << "Cannot load value of type " << *Ty << "!";
      report_fatal_error(OS.str());
    }
  }
  
  void ExecutionEngine::InitializeMemory(const Constant *Init, void *Addr) {
    DEBUG(dbgs() << "JIT: Initializing " << Addr << " ");
    DEBUG(Init->dump());
    if (isa<UndefValue>(Init))
      return;
    
    if (const ConstantVector *CP = dyn_cast<ConstantVector>(Init)) {
      unsigned ElementSize =
          getDataLayout().getTypeAllocSize(CP->getType()->getElementType());
      for (unsigned i = 0, e = CP->getNumOperands(); i != e; ++i)
        InitializeMemory(CP->getOperand(i), (char*)Addr+i*ElementSize);
      return;
    }
    
    if (isa<ConstantAggregateZero>(Init)) {
      memset(Addr, 0, (size_t)getDataLayout().getTypeAllocSize(Init->getType()));
      return;
    }
    
    if (const ConstantArray *CPA = dyn_cast<ConstantArray>(Init)) {
      unsigned ElementSize =
          getDataLayout().getTypeAllocSize(CPA->getType()->getElementType());
      for (unsigned i = 0, e = CPA->getNumOperands(); i != e; ++i)
        InitializeMemory(CPA->getOperand(i), (char*)Addr+i*ElementSize);
      return;
    }
    
    if (const ConstantStruct *CPS = dyn_cast<ConstantStruct>(Init)) {
      const StructLayout *SL =
          getDataLayout().getStructLayout(cast<StructType>(CPS->getType()));
      for (unsigned i = 0, e = CPS->getNumOperands(); i != e; ++i)
        InitializeMemory(CPS->getOperand(i), (char*)Addr+SL->getElementOffset(i));
      return;
    }
  
    if (const ConstantDataSequential *CDS =
                 dyn_cast<ConstantDataSequential>(Init)) {
      // CDS is already laid out in host memory order.
      StringRef Data = CDS->getRawDataValues();
      memcpy(Addr, Data.data(), Data.size());
      return;
    }
  
    if (Init->getType()->isFirstClassType()) {
      GenericValue Val = getConstantValue(Init);
      StoreValueToMemory(Val, (GenericValue*)Addr, Init->getType());
      return;
    }
  
    DEBUG(dbgs() << "Bad Type: " << *Init->getType() << "\n");
    llvm_unreachable("Unknown constant type to initialize memory with!");
  }
  
  /// EmitGlobals - Emit all of the global variables to memory, storing their
  /// addresses into GlobalAddress.  This must make sure to copy the contents of
  /// their initializers into the memory.
  void ExecutionEngine::emitGlobals() {
    // Loop over all of the global variables in the program, allocating the memory
    // to hold them.  If there is more than one module, do a prepass over globals
    // to figure out how the different modules should link together.
    std::map<std::pair<std::string, Type*>,
             const GlobalValue*> LinkedGlobalsMap;
  
    if (Modules.size() != 1) {
      for (unsigned m = 0, e = Modules.size(); m != e; ++m) {
        Module &M = *Modules[m];
        for (const auto &GV : M.globals()) {
          if (GV.hasLocalLinkage() || GV.isDeclaration() ||
              GV.hasAppendingLinkage() || !GV.hasName())
            continue;// Ignore external globals and globals with internal linkage.
  
          const GlobalValue *&GVEntry =
            LinkedGlobalsMap[std::make_pair(GV.getName(), GV.getType())];
  
          // If this is the first time we've seen this global, it is the canonical
          // version.
          if (!GVEntry) {
            GVEntry = &GV;
            continue;
          }
  
          // If the existing global is strong, never replace it.
          if (GVEntry->hasExternalLinkage())
            continue;
  
          // Otherwise, we know it's linkonce/weak, replace it if this is a strong
          // symbol.  FIXME is this right for common?
          if (GV.hasExternalLinkage() || GVEntry->hasExternalWeakLinkage())
            GVEntry = &GV;
        }
      }
    }
  
    std::vector<const GlobalValue*> NonCanonicalGlobals;
    for (unsigned m = 0, e = Modules.size(); m != e; ++m) {
      Module &M = *Modules[m];
      for (const auto &GV : M.globals()) {
        // In the multi-module case, see what this global maps to.
        if (!LinkedGlobalsMap.empty()) {
          if (const GlobalValue *GVEntry =
                LinkedGlobalsMap[std::make_pair(GV.getName(), GV.getType())]) {
            // If something else is the canonical global, ignore this one.
            if (GVEntry != &GV) {
              NonCanonicalGlobals.push_back(&GV);
              continue;
            }
          }
        }
  
        if (!GV.isDeclaration()) {
          addGlobalMapping(&GV, getMemoryForGV(&GV));
        } else {
          // External variable reference. Try to use the dynamic loader to
          // get a pointer to it.
          if (void *SymAddr =
              sys::DynamicLibrary::SearchForAddressOfSymbol(GV.getName()))
            addGlobalMapping(&GV, SymAddr);
          else {
            report_fatal_error("Could not resolve external global address: "
                              +GV.getName());
          }
        }
      }
  
      // If there are multiple modules, map the non-canonical globals to their
      // canonical location.
      if (!NonCanonicalGlobals.empty()) {
        for (unsigned i = 0, e = NonCanonicalGlobals.size(); i != e; ++i) {
          const GlobalValue *GV = NonCanonicalGlobals[i];
          const GlobalValue *CGV =
            LinkedGlobalsMap[std::make_pair(GV->getName(), GV->getType())];
          void *Ptr = getPointerToGlobalIfAvailable(CGV);
          assert(Ptr && "Canonical global wasn't codegen'd!");
          addGlobalMapping(GV, Ptr);
        }
      }
  
      // Now that all of the globals are set up in memory, loop through them all
      // and initialize their contents.
      for (const auto &GV : M.globals()) {
        if (!GV.isDeclaration()) {
          if (!LinkedGlobalsMap.empty()) {
            if (const GlobalValue *GVEntry =
                  LinkedGlobalsMap[std::make_pair(GV.getName(), GV.getType())])
              if (GVEntry != &GV)  // Not the canonical variable.
                continue;
          }
          EmitGlobalVariable(&GV);
        }
      }
    }
  }
  
  // EmitGlobalVariable - This method emits the specified global variable to the
  // address specified in GlobalAddresses, or allocates new memory if it's not
  // already in the map.
  void ExecutionEngine::EmitGlobalVariable(const GlobalVariable *GV) {
    void *GA = getPointerToGlobalIfAvailable(GV);
  
    if (!GA) {
      // If it's not already specified, allocate memory for the global.
      GA = getMemoryForGV(GV);
  
      // If we failed to allocate memory for this global, return.
      if (!GA) return;
  
      addGlobalMapping(GV, GA);
    }
  
    // Don't initialize if it's thread local, let the client do it.
    if (!GV->isThreadLocal())
      InitializeMemory(GV->getInitializer(), GA);
  
    Type *ElTy = GV->getType()->getElementType();
    size_t GVSize = (size_t)getDataLayout().getTypeAllocSize(ElTy);
    NumInitBytes += (unsigned)GVSize;
    ++NumGlobals;
  }
  