It's not necessary to do rounding for alloca operations when the requested

alignment is equal to the stack alignment.


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@40004 91177308-0d34-0410-b5e6-96231b3b80d8

1 files changed, 809 insertions, 0 deletions

diff --git a/lib/ExecutionEngine/ExecutionEngine.cpp b/lib/ExecutionEngine/ExecutionEngine.cpp
new file mode 100644
index 0000000000..bbddb95ec3
--- /dev/null
+++ b/lib/ExecutionEngine/ExecutionEngine.cpp
@@ -0,0 +1,809 @@
+//===-- ExecutionEngine.cpp - Common Implementation shared by EEs ---------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file was developed by the LLVM research group and 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.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "jit"
+#include "llvm/Constants.h"
+#include "llvm/DerivedTypes.h"
+#include "llvm/Module.h"
+#include "llvm/ModuleProvider.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/ExecutionEngine/ExecutionEngine.h"
+#include "llvm/ExecutionEngine/GenericValue.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/MutexGuard.h"
+#include "llvm/System/DynamicLibrary.h"
+#include "llvm/Target/TargetData.h"
+#include <math.h>
+using namespace llvm;
+
+STATISTIC(NumInitBytes, "Number of bytes of global vars initialized");
+STATISTIC(NumGlobals  , "Number of global vars initialized");
+
+ExecutionEngine::EECtorFn ExecutionEngine::JITCtor = 0;
+ExecutionEngine::EECtorFn ExecutionEngine::InterpCtor = 0;
+
+ExecutionEngine::ExecutionEngine(ModuleProvider *P) {
+  LazyCompilationDisabled = false;
+  Modules.push_back(P);
+  assert(P && "ModuleProvider is null?");
+}
+
+ExecutionEngine::ExecutionEngine(Module *M) {
+  LazyCompilationDisabled = false;
+  assert(M && "Module is null?");
+  Modules.push_back(new ExistingModuleProvider(M));
+}
+
+ExecutionEngine::~ExecutionEngine() {
+  clearAllGlobalMappings();
+  for (unsigned i = 0, e = Modules.size(); i != e; ++i)
+    delete Modules[i];
+}
+
+/// FindFunctionNamed - Search all of the active modules to find the one that
+/// defines FnName.  This is very slow operation and shouldn't be used for
+/// general code.
+Function *ExecutionEngine::FindFunctionNamed(const char *FnName) {
+  for (unsigned i = 0, e = Modules.size(); i != e; ++i) {
+    if (Function *F = Modules[i]->getModule()->getFunction(FnName))
+      return F;
+  }
+  return 0;
+}
+
+
+/// addGlobalMapping - Tell the execution engine that the specified global is
+/// at the specified location.  This is used internally as functions are JIT'd
+/// and as global variables are laid out in memory.  It can and should also be
+/// used by clients of the EE that want to have an LLVM global overlay
+/// existing data in memory.
+void ExecutionEngine::addGlobalMapping(const GlobalValue *GV, void *Addr) {
+  MutexGuard locked(lock);
+  
+  void *&CurVal = state.getGlobalAddressMap(locked)[GV];
+  assert((CurVal == 0 || Addr == 0) && "GlobalMapping already established!");
+  CurVal = Addr;
+  
+  // If we are using the reverse mapping, add it too
+  if (!state.getGlobalAddressReverseMap(locked).empty()) {
+    const GlobalValue *&V = state.getGlobalAddressReverseMap(locked)[Addr];
+    assert((V == 0 || GV == 0) && "GlobalMapping already established!");
+    V = GV;
+  }
+}
+
+/// clearAllGlobalMappings - Clear all global mappings and start over again
+/// use in dynamic compilation scenarios when you want to move globals
+void ExecutionEngine::clearAllGlobalMappings() {
+  MutexGuard locked(lock);
+  
+  state.getGlobalAddressMap(locked).clear();
+  state.getGlobalAddressReverseMap(locked).clear();
+}
+
+/// updateGlobalMapping - Replace an existing mapping for GV with a new
+/// address.  This updates both maps as required.  If "Addr" is null, the
+/// entry for the global is removed from the mappings.
+void ExecutionEngine::updateGlobalMapping(const GlobalValue *GV, void *Addr) {
+  MutexGuard locked(lock);
+  
+  // Deleting from the mapping?
+  if (Addr == 0) {
+    state.getGlobalAddressMap(locked).erase(GV);
+    if (!state.getGlobalAddressReverseMap(locked).empty())
+      state.getGlobalAddressReverseMap(locked).erase(Addr);
+    return;
+  }
+  
+  void *&CurVal = state.getGlobalAddressMap(locked)[GV];
+  if (CurVal && !state.getGlobalAddressReverseMap(locked).empty())
+    state.getGlobalAddressReverseMap(locked).erase(CurVal);
+  CurVal = Addr;
+  
+  // If we are using the reverse mapping, add it too
+  if (!state.getGlobalAddressReverseMap(locked).empty()) {
+    const GlobalValue *&V = state.getGlobalAddressReverseMap(locked)[Addr];
+    assert((V == 0 || GV == 0) && "GlobalMapping already established!");
+    V = GV;
+  }
+}
+
+/// getPointerToGlobalIfAvailable - This returns the address of the specified
+/// global value if it is has already been codegen'd, otherwise it returns null.
+///
+void *ExecutionEngine::getPointerToGlobalIfAvailable(const GlobalValue *GV) {
+  MutexGuard locked(lock);
+  
+  std::map<const GlobalValue*, void*>::iterator I =
+  state.getGlobalAddressMap(locked).find(GV);
+  return I != state.getGlobalAddressMap(locked).end() ? I->second : 0;
+}
+
+/// getGlobalValueAtAddress - Return the LLVM global value object that starts
+/// at the specified address.
+///
+const GlobalValue *ExecutionEngine::getGlobalValueAtAddress(void *Addr) {
+  MutexGuard locked(lock);
+
+  // If we haven't computed the reverse mapping yet, do so first.
+  if (state.getGlobalAddressReverseMap(locked).empty()) {
+    for (std::map<const GlobalValue*, void *>::iterator
+         I = state.getGlobalAddressMap(locked).begin(),
+         E = state.getGlobalAddressMap(locked).end(); I != E; ++I)
+      state.getGlobalAddressReverseMap(locked).insert(std::make_pair(I->second,
+                                                                     I->first));
+  }
+
+  std::map<void *, const GlobalValue*>::iterator I =
+    state.getGlobalAddressReverseMap(locked).find(Addr);
+  return I != state.getGlobalAddressReverseMap(locked).end() ? I->second : 0;
+}
+
+// CreateArgv - Turn a vector of strings into a nice argv style array of
+// pointers to null terminated strings.
+//
+static void *CreateArgv(ExecutionEngine *EE,
+                        const std::vector<std::string> &InputArgv) {
+  unsigned PtrSize = EE->getTargetData()->getPointerSize();
+  char *Result = new char[(InputArgv.size()+1)*PtrSize];
+
+  DOUT << "ARGV = " << (void*)Result << "\n";
+  const Type *SBytePtr = PointerType::get(Type::Int8Ty);
+
+  for (unsigned i = 0; i != InputArgv.size(); ++i) {
+    unsigned Size = InputArgv[i].size()+1;
+    char *Dest = new char[Size];
+    DOUT << "ARGV[" << i << "] = " << (void*)Dest << "\n";
+
+    std::copy(InputArgv[i].begin(), InputArgv[i].end(), Dest);
+    Dest[Size-1] = 0;
+
+    // Endian safe: Result[i] = (PointerTy)Dest;
+    EE->StoreValueToMemory(PTOGV(Dest), (GenericValue*)(Result+i*PtrSize),
+                           SBytePtr);
+  }
+
+  // Null terminate it
+  EE->StoreValueToMemory(PTOGV(0),
+                         (GenericValue*)(Result+InputArgv.size()*PtrSize),
+                         SBytePtr);
+  return Result;
+}
+
+
+/// runStaticConstructorsDestructors - This method is used to execute all of
+/// the static constructors or destructors for a program, depending on the
+/// value of isDtors.
+void ExecutionEngine::runStaticConstructorsDestructors(bool isDtors) {
+  const char *Name = isDtors ? "llvm.global_dtors" : "llvm.global_ctors";
+  
+  // Execute global ctors/dtors for each module in the program.
+  for (unsigned m = 0, e = Modules.size(); m != e; ++m) {
+    GlobalVariable *GV = Modules[m]->getModule()->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->hasInternalLinkage()) continue;
+  
+    // Should be an array of '{ int, void ()* }' structs.  The first value is
+    // the init priority, which we ignore.
+    ConstantArray *InitList = dyn_cast<ConstantArray>(GV->getInitializer());
+    if (!InitList) continue;
+    for (unsigned i = 0, e = InitList->getNumOperands(); i != e; ++i)
+      if (ConstantStruct *CS = 
+          dyn_cast<ConstantStruct>(InitList->getOperand(i))) {
+        if (CS->getNumOperands() != 2) break; // Not array of 2-element structs.
+      
+        Constant *FP = CS->getOperand(1);
+        if (FP->isNullValue())
+          break;  // Found a null terminator, exit.
+      
+        if (ConstantExpr *CE = dyn_cast<ConstantExpr>(FP))
+          if (CE->isCast())
+            FP = CE->getOperand(0);
+        if (Function *F = dyn_cast<Function>(FP)) {
+          // Execute the ctor/dtor function!
+          runFunction(F, std::vector<GenericValue>());
+        }
+      }
+  }
+}
+
+/// runFunctionAsMain - This is a helper function which wraps runFunction to
+/// handle the common task of starting up main with the specified argc, argv,
+/// and envp parameters.
+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();
+  const FunctionType *FTy = Fn->getFunctionType();
+  const Type* PPInt8Ty = PointerType::get(PointerType::get(Type::Int8Ty));
+  switch (NumArgs) {
+  case 3:
+   if (FTy->getParamType(2) != PPInt8Ty) {
+     cerr << "Invalid type for third argument of main() supplied\n";
+     abort();
+   }
+   // FALLS THROUGH
+  case 2:
+   if (FTy->getParamType(1) != PPInt8Ty) {
+     cerr << "Invalid type for second argument of main() supplied\n";
+     abort();
+   }
+   // FALLS THROUGH
+  case 1:
+   if (FTy->getParamType(0) != Type::Int32Ty) {
+     cerr << "Invalid type for first argument of main() supplied\n";
+     abort();
+   }
+   // FALLS THROUGH
+  case 0:
+   if (FTy->getReturnType() != Type::Int32Ty &&
+       FTy->getReturnType() != Type::VoidTy) {
+     cerr << "Invalid return type of main() supplied\n";
+     abort();
+   }
+   break;
+  default:
+   cerr << "Invalid number of arguments of main() supplied\n";
+   abort();
+  }
+  
+  if (NumArgs) {
+    GVArgs.push_back(GVArgc); // Arg #0 = argc.
+    if (NumArgs > 1) {
+      GVArgs.push_back(PTOGV(CreateArgv(this, argv))); // Arg #1 = argv.
+      assert(((char **)GVTOP(GVArgs[1]))[0] &&
+             "argv[0] was null after CreateArgv");
+      if (NumArgs > 2) {
+        std::vector<std::string> EnvVars;
+        for (unsigned i = 0; envp[i]; ++i)
+          EnvVars.push_back(envp[i]);
+        GVArgs.push_back(PTOGV(CreateArgv(this, EnvVars))); // Arg #2 = envp.
+      }
+    }
+  }
+  return runFunction(Fn, GVArgs).IntVal.getZExtValue();
+}
+
+/// If possible, create a JIT, unless the caller specifically requests an
+/// Interpreter or there's an error. If even an Interpreter cannot be created,
+/// NULL is returned.
+///
+ExecutionEngine *ExecutionEngine::create(ModuleProvider *MP,
+                                         bool ForceInterpreter,
+                                         std::string *ErrorStr) {
+  ExecutionEngine *EE = 0;
+
+  // Unless the interpreter was explicitly selected, try making a JIT.
+  if (!ForceInterpreter && JITCtor)
+    EE = JITCtor(MP, ErrorStr);
+
+  // If we can't make a JIT, make an interpreter instead.
+  if (EE == 0 && InterpCtor)
+    EE = InterpCtor(MP, ErrorStr);
+
+  if (EE) {
+    // 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.
+    try {
+      sys::DynamicLibrary::LoadLibraryPermanently(0);
+    } catch (...) {
+    }
+  }
+
+  return EE;
+}
+
+/// getPointerToGlobal - This returns the address of the specified global
+/// value.  This may involve code generation if it's a function.
+///
+void *ExecutionEngine::getPointerToGlobal(const GlobalValue *GV) {
+  if (Function *F = const_cast<Function*>(dyn_cast<Function>(GV)))
+    return getPointerToFunction(F);
+
+  MutexGuard locked(lock);
+  void *p = state.getGlobalAddressMap(locked)[GV];
+  if (p)
+    return p;
+
+  // Global variable might have been added since interpreter started.
+  if (GlobalVariable *GVar =
+          const_cast<GlobalVariable *>(dyn_cast<GlobalVariable>(GV)))
+    EmitGlobalVariable(GVar);
+  else
+    assert(0 && "Global hasn't had an address allocated yet!");
+  return state.getGlobalAddressMap(locked)[GV];
+}
+
+/// This function converts a Constant* into a GenericValue. The interesting 
+/// part is if C is a ConstantExpr.
+/// @brief Get a GenericValue for a Constnat*
+GenericValue ExecutionEngine::getConstantValue(const Constant *C) {
+  // If its undefined, return the garbage.
+  if (isa<UndefValue>(C)) 
+    return GenericValue();
+
+  // 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);
+      SmallVector<Value*, 8> Indices(CE->op_begin()+1, CE->op_end());
+      uint64_t Offset =
+        TD->getIndexedOffset(Op0->getType(), &Indices[0], Indices.size());
+
+      char* tmp = (char*) Result.PointerVal;
+      Result = PTOGV(tmp + Offset);
+      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: {
+      GenericValue GV = getConstantValue(Op0);
+      GV.FloatVal = float(GV.DoubleVal);
+      return GV;
+    }
+    case Instruction::FPExt:{
+      GenericValue GV = getConstantValue(Op0);
+      GV.DoubleVal = double(GV.FloatVal);
+      return GV;
+    }
+    case Instruction::UIToFP: {
+      GenericValue GV = getConstantValue(Op0);
+      if (CE->getType() == Type::FloatTy)
+        GV.FloatVal = float(GV.IntVal.roundToDouble());
+      else
+        GV.DoubleVal = GV.IntVal.roundToDouble();
+      return GV;
+    }
+    case Instruction::SIToFP: {
+      GenericValue GV = getConstantValue(Op0);
+      if (CE->getType() == Type::FloatTy)
+        GV.FloatVal = float(GV.IntVal.signedRoundToDouble());
+      else
+        GV.DoubleVal = GV.IntVal.signedRoundToDouble();
+      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() == Type::FloatTy)
+        GV.IntVal = APIntOps::RoundFloatToAPInt(GV.FloatVal, BitWidth);
+      else
+        GV.IntVal = APIntOps::RoundDoubleToAPInt(GV.DoubleVal, BitWidth);
+      return GV;
+    }
+    case Instruction::PtrToInt: {
+      GenericValue GV = getConstantValue(Op0);
+      uint32_t PtrWidth = TD->getPointerSizeInBits();
+      GV.IntVal = APInt(PtrWidth, uintptr_t(GV.PointerVal));
+      return GV;
+    }
+    case Instruction::IntToPtr: {
+      GenericValue GV = getConstantValue(Op0);
+      uint32_t PtrWidth = TD->getPointerSizeInBits();
+      if (PtrWidth != GV.IntVal.getBitWidth())
+        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);
+      const Type* DestTy = CE->getType();
+      switch (Op0->getType()->getTypeID()) {
+        default: assert(0 && "Invalid bitcast operand");
+        case Type::IntegerTyID:
+          assert(DestTy->isFloatingPoint() && "invalid bitcast");
+          if (DestTy == Type::FloatTy)
+            GV.FloatVal = GV.IntVal.bitsToFloat();
+          else if (DestTy == Type::DoubleTy)
+            GV.DoubleVal = GV.IntVal.bitsToDouble();
+          break;
+        case Type::FloatTyID: 
+          assert(DestTy == Type::Int32Ty && "Invalid bitcast");
+          GV.IntVal.floatToBits(GV.FloatVal);
+          break;
+        case Type::DoubleTyID:
+          assert(DestTy == Type::Int64Ty && "Invalid bitcast");
+          GV.IntVal.doubleToBits(GV.DoubleVal);
+          break;
+        case Type::PointerTyID:
+          assert(isa<PointerType>(DestTy) && "Invalid bitcast");
+          break; // getConstantValue(Op0)  above already converted it
+      }
+      return GV;
+    }
+    case Instruction::Add:
+    case Instruction::Sub:
+    case Instruction::Mul:
+    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: assert(0 && "Bad add type!"); abort();
+      case Type::IntegerTyID:
+        switch (CE->getOpcode()) {
+          default: assert(0 && "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: assert(0 && "Invalid float opcode"); abort();
+          case Instruction::Add:  
+            GV.FloatVal = LHS.FloatVal + RHS.FloatVal; break;
+          case Instruction::Sub:  
+            GV.FloatVal = LHS.FloatVal - RHS.FloatVal; break;
+          case Instruction::Mul:  
+            GV.FloatVal = LHS.FloatVal * RHS.FloatVal; break;
+          case Instruction::FDiv: 
+            GV.FloatVal = LHS.FloatVal / RHS.FloatVal; break;
+          case Instruction::FRem: 
+            GV.FloatVal = ::fmodf(LHS.FloatVal,RHS.FloatVal); break;
+        }
+        break;
+      case Type::DoubleTyID:
+        switch (CE->getOpcode()) {
+          default: assert(0 && "Invalid double opcode"); abort();
+          case Instruction::Add:  
+            GV.DoubleVal = LHS.DoubleVal + RHS.DoubleVal; break;
+          case Instruction::Sub:  
+            GV.DoubleVal = LHS.DoubleVal - RHS.DoubleVal; break;
+          case Instruction::Mul:  
+            GV.DoubleVal = LHS.DoubleVal * RHS.DoubleVal; break;
+          case Instruction::FDiv: 
+            GV.DoubleVal = LHS.DoubleVal / RHS.DoubleVal; break;
+          case Instruction::FRem: 
+            GV.DoubleVal = ::fmod(LHS.DoubleVal,RHS.DoubleVal); break;
+        }
+        break;
+      }
+      return GV;
+    }
+    default:
+      break;
+    }
+    cerr << "ConstantExpr not handled: " << *CE << "\n";
+    abort();
+  }
+
+  GenericValue Result;
+  switch (C->getType()->getTypeID()) {
+  case Type::FloatTyID: 
+    Result.FloatVal = (float)cast<ConstantFP>(C)->getValue(); 
+    break;
+  case Type::DoubleTyID:
+    Result.DoubleVal = (double)cast<ConstantFP>(C)->getValue(); 
+    break;
+  case Type::IntegerTyID:
+    Result.IntVal = cast<ConstantInt>(C)->getValue();
+    break;
+  case Type::PointerTyID:
+    if (isa<ConstantPointerNull>(C))
+      Result.PointerVal = 0;
+    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
+      assert(0 && "Unknown constant pointer type!");
+    break;
+  default:
+    cerr << "ERROR: Constant unimplemented for type: " << *C->getType() << "\n";
+    abort();
+  }
+  return Result;
+}
+
+/// StoreValueToMemory - Stores the data in Val of type Ty at address Ptr.  Ptr
+/// is the address of the memory at which to store Val, cast to GenericValue *.
+/// It is not a pointer to a GenericValue containing the address at which to
+/// store Val.
+///
+void ExecutionEngine::StoreValueToMemory(const GenericValue &Val, GenericValue *Ptr,
+                                         const Type *Ty) {
+  switch (Ty->getTypeID()) {
+  case Type::IntegerTyID: {
+    unsigned BitWidth = cast<IntegerType>(Ty)->getBitWidth();
+    GenericValue TmpVal = Val;
+    if (BitWidth <= 8)
+      *((uint8_t*)Ptr) = uint8_t(Val.IntVal.getZExtValue());
+    else if (BitWidth <= 16) {
+      *((uint16_t*)Ptr) = uint16_t(Val.IntVal.getZExtValue());
+    } else if (BitWidth <= 32) {
+      *((uint32_t*)Ptr) = uint32_t(Val.IntVal.getZExtValue());
+    } else if (BitWidth <= 64) {
+      *((uint64_t*)Ptr) = uint64_t(Val.IntVal.getZExtValue());
+    } else {
+      uint64_t *Dest = (uint64_t*)Ptr;
+      const uint64_t *Src = Val.IntVal.getRawData();
+      for (uint32_t i = 0; i < Val.IntVal.getNumWords(); ++i)
+        Dest[i] = Src[i];
+    }
+    break;
+  }
+  case Type::FloatTyID:
+    *((float*)Ptr) = Val.FloatVal;
+    break;
+  case Type::DoubleTyID:
+    *((double*)Ptr) = Val.DoubleVal;
+    break;
+  case Type::PointerTyID: 
+    *((PointerTy*)Ptr) = Val.PointerVal;
+    break;
+  default:
+    cerr << "Cannot store value of type " << *Ty << "!\n";
+  }
+}
+
+/// FIXME: document
+///
+void ExecutionEngine::LoadValueFromMemory(GenericValue &Result, 
+                                                  GenericValue *Ptr,
+                                                  const Type *Ty) {
+  switch (Ty->getTypeID()) {
+  case Type::IntegerTyID: {
+    unsigned BitWidth = cast<IntegerType>(Ty)->getBitWidth();
+    if (BitWidth <= 8)
+      Result.IntVal = APInt(BitWidth, *((uint8_t*)Ptr));
+    else if (BitWidth <= 16) {
+      Result.IntVal = APInt(BitWidth, *((uint16_t*)Ptr));
+    } else if (BitWidth <= 32) {
+      Result.IntVal = APInt(BitWidth, *((uint32_t*)Ptr));
+    } else if (BitWidth <= 64) {
+      Result.IntVal = APInt(BitWidth, *((uint64_t*)Ptr));
+    } else
+      Result.IntVal = APInt(BitWidth, (BitWidth+63)/64, (uint64_t*)Ptr);
+    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;
+  default:
+    cerr << "Cannot load value of type " << *Ty << "!\n";
+    abort();
+  }
+}
+
+// InitializeMemory - Recursive function to apply a Constant value into the
+// specified memory location...
+//
+void ExecutionEngine::InitializeMemory(const Constant *Init, void *Addr) {
+  if (isa<UndefValue>(Init)) {
+    return;
+  } else if (const ConstantVector *CP = dyn_cast<ConstantVector>(Init)) {
+    unsigned ElementSize =
+      getTargetData()->getTypeSize(CP->getType()->getElementType());
+    for (unsigned i = 0, e = CP->getNumOperands(); i != e; ++i)
+      InitializeMemory(CP->getOperand(i), (char*)Addr+i*ElementSize);
+    return;
+  } else if (Init->getType()->isFirstClassType()) {
+    GenericValue Val = getConstantValue(Init);
+    StoreValueToMemory(Val, (GenericValue*)Addr, Init->getType());
+    return;
+  } else if (isa<ConstantAggregateZero>(Init)) {
+    memset(Addr, 0, (size_t)getTargetData()->getTypeSize(Init->getType()));
+    return;
+  }
+
+  switch (Init->getType()->getTypeID()) {
+  case Type::ArrayTyID: {
+    const ConstantArray *CPA = cast<ConstantArray>(Init);
+    unsigned ElementSize =
+      getTargetData()->getTypeSize(CPA->getType()->getElementType());
+    for (unsigned i = 0, e = CPA->getNumOperands(); i != e; ++i)
+      InitializeMemory(CPA->getOperand(i), (char*)Addr+i*ElementSize);
+    return;
+  }
+
+  case Type::StructTyID: {
+    const ConstantStruct *CPS = cast<ConstantStruct>(Init);
+    const StructLayout *SL =
+      getTargetData()->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;
+  }
+
+  default:
+    cerr << "Bad Type: " << *Init->getType() << "\n";
+    assert(0 && "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() {
+  const TargetData *TD = getTargetData();
+
+  // 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, const Type*>,
+           const GlobalValue*> LinkedGlobalsMap;
+
+  if (Modules.size() != 1) {
+    for (unsigned m = 0, e = Modules.size(); m != e; ++m) {
+      Module &M = *Modules[m]->getModule();
+      for (Module::const_global_iterator I = M.global_begin(),
+           E = M.global_end(); I != E; ++I) {
+        const GlobalValue *GV = I;
+        if (GV->hasInternalLinkage() || 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() ||
+            GVEntry->hasDLLImportLinkage() ||
+            GVEntry->hasDLLExportLinkage())
+          continue;
+        
+        // Otherwise, we know it's linkonce/weak, replace it if this is a strong
+        // symbol.
+        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]->getModule();
+    for (Module::const_global_iterator I = M.global_begin(), E = M.global_end();
+         I != E; ++I) {
+      // In the multi-module case, see what this global maps to.
+      if (!LinkedGlobalsMap.empty()) {
+        if (const GlobalValue *GVEntry = 
+              LinkedGlobalsMap[std::make_pair(I->getName(), I->getType())]) {
+          // If something else is the canonical global, ignore this one.
+          if (GVEntry != &*I) {
+            NonCanonicalGlobals.push_back(I);
+            continue;
+          }
+        }
+      }
+      
+      if (!I->isDeclaration()) {
+        // Get the type of the global.
+        const Type *Ty = I->getType()->getElementType();
+
+        // Allocate some memory for it!
+        unsigned Size = TD->getTypeSize(Ty);
+        addGlobalMapping(I, new char[Size]);
+      } else {
+        // External variable reference. Try to use the dynamic loader to
+        // get a pointer to it.
+        if (void *SymAddr =
+            sys::DynamicLibrary::SearchForAddressOfSymbol(I->getName().c_str()))
+          addGlobalMapping(I, SymAddr);
+        else {
+          cerr << "Could not resolve external global address: "
+               << I->getName() << "\n";
+          abort();
+        }
+      }
+    }
+    
+    // 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, getPointerToGlobalIfAvailable(CGV));
+      }
+    }
+    
+    // Now that all of the globals are set up in memory, loop through them all 
+    // and initialize their contents.
+    for (Module::const_global_iterator I = M.global_begin(), E = M.global_end();
+         I != E; ++I) {
+      if (!I->isDeclaration()) {
+        if (!LinkedGlobalsMap.empty()) {
+          if (const GlobalValue *GVEntry = 
+                LinkedGlobalsMap[std::make_pair(I->getName(), I->getType())])
+            if (GVEntry != &*I)  // Not the canonical variable.
+              continue;
+        }
+        EmitGlobalVariable(I);
+      }
+    }
+  }
+}
+
+// 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);
+  DOUT << "Global '" << GV->getName() << "' -> " << GA << "\n";
+
+  const Type *ElTy = GV->getType()->getElementType();
+  size_t GVSize = (size_t)getTargetData()->getTypeSize(ElTy);
+  if (GA == 0) {
+    // If it's not already specified, allocate memory for the global.
+    GA = new char[GVSize];
+    addGlobalMapping(GV, GA);
+  }
+
+  InitializeMemory(GV->getInitializer(), GA);
+  NumInitBytes += (unsigned)GVSize;
+  ++NumGlobals;
+}