--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/lib/Transforms/IPO/GlobalOpt.cpp	Thu Dec 12 13:56:28 2013 +0900
@@ -0,0 +1,3185 @@
+//===- GlobalOpt.cpp - Optimize Global Variables --------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass transforms simple global variables that never have their address
+// taken.  If obviously true, it marks read/write globals as constant, deletes
+// variables only stored to, etc.
+//
+//===----------------------------------------------------------------------===//
+
+#define DEBUG_TYPE "globalopt"
+#include "llvm/Transforms/IPO.h"
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/STLExtras.h"
+#include "llvm/ADT/SmallPtrSet.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/Statistic.h"
+#include "llvm/Analysis/ConstantFolding.h"
+#include "llvm/Analysis/MemoryBuiltins.h"
+#include "llvm/IR/CallingConv.h"
+#include "llvm/IR/Constants.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/Operator.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/CallSite.h"
+#include "llvm/Support/Debug.h"
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/GetElementPtrTypeIterator.h"
+#include "llvm/Support/MathExtras.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Target/TargetLibraryInfo.h"
+#include "llvm/Transforms/Utils/GlobalStatus.h"
+#include "llvm/Transforms/Utils/ModuleUtils.h"
+#include <algorithm>
+using namespace llvm;
+
+STATISTIC(NumMarked    , "Number of globals marked constant");
+STATISTIC(NumUnnamed   , "Number of globals marked unnamed_addr");
+STATISTIC(NumSRA       , "Number of aggregate globals broken into scalars");
+STATISTIC(NumHeapSRA   , "Number of heap objects SRA'd");
+STATISTIC(NumSubstitute,"Number of globals with initializers stored into them");
+STATISTIC(NumDeleted   , "Number of globals deleted");
+STATISTIC(NumFnDeleted , "Number of functions deleted");
+STATISTIC(NumGlobUses  , "Number of global uses devirtualized");
+STATISTIC(NumLocalized , "Number of globals localized");
+STATISTIC(NumShrunkToBool  , "Number of global vars shrunk to booleans");
+STATISTIC(NumFastCallFns   , "Number of functions converted to fastcc");
+STATISTIC(NumCtorsEvaluated, "Number of static ctors evaluated");
+STATISTIC(NumNestRemoved   , "Number of nest attributes removed");
+STATISTIC(NumAliasesResolved, "Number of global aliases resolved");
+STATISTIC(NumAliasesRemoved, "Number of global aliases eliminated");
+STATISTIC(NumCXXDtorsRemoved, "Number of global C++ destructors removed");
+
+namespace {
+  struct GlobalOpt : public ModulePass {
+    virtual void getAnalysisUsage(AnalysisUsage &AU) const {
+      AU.addRequired<TargetLibraryInfo>();
+    }
+    static char ID; // Pass identification, replacement for typeid
+    GlobalOpt() : ModulePass(ID) {
+      initializeGlobalOptPass(*PassRegistry::getPassRegistry());
+    }
+
+    bool runOnModule(Module &M);
+
+  private:
+    GlobalVariable *FindGlobalCtors(Module &M);
+    bool OptimizeFunctions(Module &M);
+    bool OptimizeGlobalVars(Module &M);
+    bool OptimizeGlobalAliases(Module &M);
+    bool OptimizeGlobalCtorsList(GlobalVariable *&GCL);
+    bool ProcessGlobal(GlobalVariable *GV,Module::global_iterator &GVI);
+    bool ProcessInternalGlobal(GlobalVariable *GV,Module::global_iterator &GVI,
+                               const GlobalStatus &GS);
+    bool OptimizeEmptyGlobalCXXDtors(Function *CXAAtExitFn);
+
+    DataLayout *TD;
+    TargetLibraryInfo *TLI;
+  };
+}
+
+char GlobalOpt::ID = 0;
+INITIALIZE_PASS_BEGIN(GlobalOpt, "globalopt",
+                "Global Variable Optimizer", false, false)
+INITIALIZE_PASS_DEPENDENCY(TargetLibraryInfo)
+INITIALIZE_PASS_END(GlobalOpt, "globalopt",
+                "Global Variable Optimizer", false, false)
+
+ModulePass *llvm::createGlobalOptimizerPass() { return new GlobalOpt(); }
+
+/// isLeakCheckerRoot - Is this global variable possibly used by a leak checker
+/// as a root?  If so, we might not really want to eliminate the stores to it.
+static bool isLeakCheckerRoot(GlobalVariable *GV) {
+  // A global variable is a root if it is a pointer, or could plausibly contain
+  // a pointer.  There are two challenges; one is that we could have a struct
+  // the has an inner member which is a pointer.  We recurse through the type to
+  // detect these (up to a point).  The other is that we may actually be a union
+  // of a pointer and another type, and so our LLVM type is an integer which
+  // gets converted into a pointer, or our type is an [i8 x #] with a pointer
+  // potentially contained here.
+
+  if (GV->hasPrivateLinkage())
+    return false;
+
+  SmallVector<Type *, 4> Types;
+  Types.push_back(cast<PointerType>(GV->getType())->getElementType());
+
+  unsigned Limit = 20;
+  do {
+    Type *Ty = Types.pop_back_val();
+    switch (Ty->getTypeID()) {
+      default: break;
+      case Type::PointerTyID: return true;
+      case Type::ArrayTyID:
+      case Type::VectorTyID: {
+        SequentialType *STy = cast<SequentialType>(Ty);
+        Types.push_back(STy->getElementType());
+        break;
+      }
+      case Type::StructTyID: {
+        StructType *STy = cast<StructType>(Ty);
+        if (STy->isOpaque()) return true;
+        for (StructType::element_iterator I = STy->element_begin(),
+                 E = STy->element_end(); I != E; ++I) {
+          Type *InnerTy = *I;
+          if (isa<PointerType>(InnerTy)) return true;
+          if (isa<CompositeType>(InnerTy))
+            Types.push_back(InnerTy);
+        }
+        break;
+      }
+    }
+    if (--Limit == 0) return true;
+  } while (!Types.empty());
+  return false;
+}
+
+/// Given a value that is stored to a global but never read, determine whether
+/// it's safe to remove the store and the chain of computation that feeds the
+/// store.
+static bool IsSafeComputationToRemove(Value *V, const TargetLibraryInfo *TLI) {
+  do {
+    if (isa<Constant>(V))
+      return true;
+    if (!V->hasOneUse())
+      return false;
+    if (isa<LoadInst>(V) || isa<InvokeInst>(V) || isa<Argument>(V) ||
+        isa<GlobalValue>(V))
+      return false;
+    if (isAllocationFn(V, TLI))
+      return true;
+
+    Instruction *I = cast<Instruction>(V);
+    if (I->mayHaveSideEffects())
+      return false;
+    if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(I)) {
+      if (!GEP->hasAllConstantIndices())
+        return false;
+    } else if (I->getNumOperands() != 1) {
+      return false;
+    }
+
+    V = I->getOperand(0);
+  } while (1);
+}
+
+/// CleanupPointerRootUsers - This GV is a pointer root.  Loop over all users
+/// of the global and clean up any that obviously don't assign the global a
+/// value that isn't dynamically allocated.
+///
+static bool CleanupPointerRootUsers(GlobalVariable *GV,
+                                    const TargetLibraryInfo *TLI) {
+  // A brief explanation of leak checkers.  The goal is to find bugs where
+  // pointers are forgotten, causing an accumulating growth in memory
+  // usage over time.  The common strategy for leak checkers is to whitelist the
+  // memory pointed to by globals at exit.  This is popular because it also
+  // solves another problem where the main thread of a C++ program may shut down
+  // before other threads that are still expecting to use those globals.  To
+  // handle that case, we expect the program may create a singleton and never
+  // destroy it.
+
+  bool Changed = false;
+
+  // If Dead[n].first is the only use of a malloc result, we can delete its
+  // chain of computation and the store to the global in Dead[n].second.
+  SmallVector<std::pair<Instruction *, Instruction *>, 32> Dead;
+
+  // Constants can't be pointers to dynamically allocated memory.
+  for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end();
+       UI != E;) {
+    User *U = *UI++;
+    if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
+      Value *V = SI->getValueOperand();
+      if (isa<Constant>(V)) {
+        Changed = true;
+        SI->eraseFromParent();
+      } else if (Instruction *I = dyn_cast<Instruction>(V)) {
+        if (I->hasOneUse())
+          Dead.push_back(std::make_pair(I, SI));
+      }
+    } else if (MemSetInst *MSI = dyn_cast<MemSetInst>(U)) {
+      if (isa<Constant>(MSI->getValue())) {
+        Changed = true;
+        MSI->eraseFromParent();
+      } else if (Instruction *I = dyn_cast<Instruction>(MSI->getValue())) {
+        if (I->hasOneUse())
+          Dead.push_back(std::make_pair(I, MSI));
+      }
+    } else if (MemTransferInst *MTI = dyn_cast<MemTransferInst>(U)) {
+      GlobalVariable *MemSrc = dyn_cast<GlobalVariable>(MTI->getSource());
+      if (MemSrc && MemSrc->isConstant()) {
+        Changed = true;
+        MTI->eraseFromParent();
+      } else if (Instruction *I = dyn_cast<Instruction>(MemSrc)) {
+        if (I->hasOneUse())
+          Dead.push_back(std::make_pair(I, MTI));
+      }
+    } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
+      if (CE->use_empty()) {
+        CE->destroyConstant();
+        Changed = true;
+      }
+    } else if (Constant *C = dyn_cast<Constant>(U)) {
+      if (isSafeToDestroyConstant(C)) {
+        C->destroyConstant();
+        // This could have invalidated UI, start over from scratch.
+        Dead.clear();
+        CleanupPointerRootUsers(GV, TLI);
+        return true;
+      }
+    }
+  }
+
+  for (int i = 0, e = Dead.size(); i != e; ++i) {
+    if (IsSafeComputationToRemove(Dead[i].first, TLI)) {
+      Dead[i].second->eraseFromParent();
+      Instruction *I = Dead[i].first;
+      do {
+        if (isAllocationFn(I, TLI))
+          break;
+        Instruction *J = dyn_cast<Instruction>(I->getOperand(0));
+        if (!J)
+          break;
+        I->eraseFromParent();
+        I = J;
+      } while (1);
+      I->eraseFromParent();
+    }
+  }
+
+  return Changed;
+}
+
+/// CleanupConstantGlobalUsers - We just marked GV constant.  Loop over all
+/// users of the global, cleaning up the obvious ones.  This is largely just a
+/// quick scan over the use list to clean up the easy and obvious cruft.  This
+/// returns true if it made a change.
+static bool CleanupConstantGlobalUsers(Value *V, Constant *Init,
+                                       DataLayout *TD, TargetLibraryInfo *TLI) {
+  bool Changed = false;
+  SmallVector<User*, 8> WorkList(V->use_begin(), V->use_end());
+  while (!WorkList.empty()) {
+    User *U = WorkList.pop_back_val();
+
+    if (LoadInst *LI = dyn_cast<LoadInst>(U)) {
+      if (Init) {
+        // Replace the load with the initializer.
+        LI->replaceAllUsesWith(Init);
+        LI->eraseFromParent();
+        Changed = true;
+      }
+    } else if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
+      // Store must be unreachable or storing Init into the global.
+      SI->eraseFromParent();
+      Changed = true;
+    } else if (ConstantExpr *CE = dyn_cast<ConstantExpr>(U)) {
+      if (CE->getOpcode() == Instruction::GetElementPtr) {
+        Constant *SubInit = 0;
+        if (Init)
+          SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
+        Changed |= CleanupConstantGlobalUsers(CE, SubInit, TD, TLI);
+      } else if (CE->getOpcode() == Instruction::BitCast &&
+                 CE->getType()->isPointerTy()) {
+        // Pointer cast, delete any stores and memsets to the global.
+        Changed |= CleanupConstantGlobalUsers(CE, 0, TD, TLI);
+      }
+
+      if (CE->use_empty()) {
+        CE->destroyConstant();
+        Changed = true;
+      }
+    } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(U)) {
+      // Do not transform "gepinst (gep constexpr (GV))" here, because forming
+      // "gepconstexpr (gep constexpr (GV))" will cause the two gep's to fold
+      // and will invalidate our notion of what Init is.
+      Constant *SubInit = 0;
+      if (!isa<ConstantExpr>(GEP->getOperand(0))) {
+        ConstantExpr *CE =
+          dyn_cast_or_null<ConstantExpr>(ConstantFoldInstruction(GEP, TD, TLI));
+        if (Init && CE && CE->getOpcode() == Instruction::GetElementPtr)
+          SubInit = ConstantFoldLoadThroughGEPConstantExpr(Init, CE);
+
+        // If the initializer is an all-null value and we have an inbounds GEP,
+        // we already know what the result of any load from that GEP is.
+        // TODO: Handle splats.
+        if (Init && isa<ConstantAggregateZero>(Init) && GEP->isInBounds())
+          SubInit = Constant::getNullValue(GEP->getType()->getElementType());
+      }
+      Changed |= CleanupConstantGlobalUsers(GEP, SubInit, TD, TLI);
+
+      if (GEP->use_empty()) {
+        GEP->eraseFromParent();
+        Changed = true;
+      }
+    } else if (MemIntrinsic *MI = dyn_cast<MemIntrinsic>(U)) { // memset/cpy/mv
+      if (MI->getRawDest() == V) {
+        MI->eraseFromParent();
+        Changed = true;
+      }
+
+    } else if (Constant *C = dyn_cast<Constant>(U)) {
+      // If we have a chain of dead constantexprs or other things dangling from
+      // us, and if they are all dead, nuke them without remorse.
+      if (isSafeToDestroyConstant(C)) {
+        C->destroyConstant();
+        CleanupConstantGlobalUsers(V, Init, TD, TLI);
+        return true;
+      }
+    }
+  }
+  return Changed;
+}
+
+/// isSafeSROAElementUse - Return true if the specified instruction is a safe
+/// user of a derived expression from a global that we want to SROA.
+static bool isSafeSROAElementUse(Value *V) {
+  // We might have a dead and dangling constant hanging off of here.
+  if (Constant *C = dyn_cast<Constant>(V))
+    return isSafeToDestroyConstant(C);
+
+  Instruction *I = dyn_cast<Instruction>(V);
+  if (!I) return false;
+
+  // Loads are ok.
+  if (isa<LoadInst>(I)) return true;
+
+  // Stores *to* the pointer are ok.
+  if (StoreInst *SI = dyn_cast<StoreInst>(I))
+    return SI->getOperand(0) != V;
+
+  // Otherwise, it must be a GEP.
+  GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I);
+  if (GEPI == 0) return false;
+
+  if (GEPI->getNumOperands() < 3 || !isa<Constant>(GEPI->getOperand(1)) ||
+      !cast<Constant>(GEPI->getOperand(1))->isNullValue())
+    return false;
+
+  for (Value::use_iterator I = GEPI->use_begin(), E = GEPI->use_end();
+       I != E; ++I)
+    if (!isSafeSROAElementUse(*I))
+      return false;
+  return true;
+}
+
+
+/// IsUserOfGlobalSafeForSRA - U is a direct user of the specified global value.
+/// Look at it and its uses and decide whether it is safe to SROA this global.
+///
+static bool IsUserOfGlobalSafeForSRA(User *U, GlobalValue *GV) {
+  // The user of the global must be a GEP Inst or a ConstantExpr GEP.
+  if (!isa<GetElementPtrInst>(U) &&
+      (!isa<ConstantExpr>(U) ||
+       cast<ConstantExpr>(U)->getOpcode() != Instruction::GetElementPtr))
+    return false;
+
+  // Check to see if this ConstantExpr GEP is SRA'able.  In particular, we
+  // don't like < 3 operand CE's, and we don't like non-constant integer
+  // indices.  This enforces that all uses are 'gep GV, 0, C, ...' for some
+  // value of C.
+  if (U->getNumOperands() < 3 || !isa<Constant>(U->getOperand(1)) ||
+      !cast<Constant>(U->getOperand(1))->isNullValue() ||
+      !isa<ConstantInt>(U->getOperand(2)))
+    return false;
+
+  gep_type_iterator GEPI = gep_type_begin(U), E = gep_type_end(U);
+  ++GEPI;  // Skip over the pointer index.
+
+  // If this is a use of an array allocation, do a bit more checking for sanity.
+  if (ArrayType *AT = dyn_cast<ArrayType>(*GEPI)) {
+    uint64_t NumElements = AT->getNumElements();
+    ConstantInt *Idx = cast<ConstantInt>(U->getOperand(2));
+
+    // Check to make sure that index falls within the array.  If not,
+    // something funny is going on, so we won't do the optimization.
+    //
+    if (Idx->getZExtValue() >= NumElements)
+      return false;
+
+    // We cannot scalar repl this level of the array unless any array
+    // sub-indices are in-range constants.  In particular, consider:
+    // A[0][i].  We cannot know that the user isn't doing invalid things like
+    // allowing i to index an out-of-range subscript that accesses A[1].
+    //
+    // Scalar replacing *just* the outer index of the array is probably not
+    // going to be a win anyway, so just give up.
+    for (++GEPI; // Skip array index.
+         GEPI != E;
+         ++GEPI) {
+      uint64_t NumElements;
+      if (ArrayType *SubArrayTy = dyn_cast<ArrayType>(*GEPI))
+        NumElements = SubArrayTy->getNumElements();
+      else if (VectorType *SubVectorTy = dyn_cast<VectorType>(*GEPI))
+        NumElements = SubVectorTy->getNumElements();
+      else {
+        assert((*GEPI)->isStructTy() &&
+               "Indexed GEP type is not array, vector, or struct!");
+        continue;
+      }
+
+      ConstantInt *IdxVal = dyn_cast<ConstantInt>(GEPI.getOperand());
+      if (!IdxVal || IdxVal->getZExtValue() >= NumElements)
+        return false;
+    }
+  }
+
+  for (Value::use_iterator I = U->use_begin(), E = U->use_end(); I != E; ++I)
+    if (!isSafeSROAElementUse(*I))
+      return false;
+  return true;
+}
+
+/// GlobalUsersSafeToSRA - Look at all uses of the global and decide whether it
+/// is safe for us to perform this transformation.
+///
+static bool GlobalUsersSafeToSRA(GlobalValue *GV) {
+  for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end();
+       UI != E; ++UI) {
+    if (!IsUserOfGlobalSafeForSRA(*UI, GV))
+      return false;
+  }
+  return true;
+}
+
+
+/// SRAGlobal - Perform scalar replacement of aggregates on the specified global
+/// variable.  This opens the door for other optimizations by exposing the
+/// behavior of the program in a more fine-grained way.  We have determined that
+/// this transformation is safe already.  We return the first global variable we
+/// insert so that the caller can reprocess it.
+static GlobalVariable *SRAGlobal(GlobalVariable *GV, const DataLayout &TD) {
+  // Make sure this global only has simple uses that we can SRA.
+  if (!GlobalUsersSafeToSRA(GV))
+    return 0;
+
+  assert(GV->hasLocalLinkage() && !GV->isConstant());
+  Constant *Init = GV->getInitializer();
+  Type *Ty = Init->getType();
+
+  std::vector<GlobalVariable*> NewGlobals;
+  Module::GlobalListType &Globals = GV->getParent()->getGlobalList();
+
+  // Get the alignment of the global, either explicit or target-specific.
+  unsigned StartAlignment = GV->getAlignment();
+  if (StartAlignment == 0)
+    StartAlignment = TD.getABITypeAlignment(GV->getType());
+
+  if (StructType *STy = dyn_cast<StructType>(Ty)) {
+    NewGlobals.reserve(STy->getNumElements());
+    const StructLayout &Layout = *TD.getStructLayout(STy);
+    for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i) {
+      Constant *In = Init->getAggregateElement(i);
+      assert(In && "Couldn't get element of initializer?");
+      GlobalVariable *NGV = new GlobalVariable(STy->getElementType(i), false,
+                                               GlobalVariable::InternalLinkage,
+                                               In, GV->getName()+"."+Twine(i),
+                                               GV->getThreadLocalMode(),
+                                              GV->getType()->getAddressSpace());
+      Globals.insert(GV, NGV);
+      NewGlobals.push_back(NGV);
+
+      // Calculate the known alignment of the field.  If the original aggregate
+      // had 256 byte alignment for example, something might depend on that:
+      // propagate info to each field.
+      uint64_t FieldOffset = Layout.getElementOffset(i);
+      unsigned NewAlign = (unsigned)MinAlign(StartAlignment, FieldOffset);
+      if (NewAlign > TD.getABITypeAlignment(STy->getElementType(i)))
+        NGV->setAlignment(NewAlign);
+    }
+  } else if (SequentialType *STy = dyn_cast<SequentialType>(Ty)) {
+    unsigned NumElements = 0;
+    if (ArrayType *ATy = dyn_cast<ArrayType>(STy))
+      NumElements = ATy->getNumElements();
+    else
+      NumElements = cast<VectorType>(STy)->getNumElements();
+
+    if (NumElements > 16 && GV->hasNUsesOrMore(16))
+      return 0; // It's not worth it.
+    NewGlobals.reserve(NumElements);
+
+    uint64_t EltSize = TD.getTypeAllocSize(STy->getElementType());
+    unsigned EltAlign = TD.getABITypeAlignment(STy->getElementType());
+    for (unsigned i = 0, e = NumElements; i != e; ++i) {
+      Constant *In = Init->getAggregateElement(i);
+      assert(In && "Couldn't get element of initializer?");
+
+      GlobalVariable *NGV = new GlobalVariable(STy->getElementType(), false,
+                                               GlobalVariable::InternalLinkage,
+                                               In, GV->getName()+"."+Twine(i),
+                                               GV->getThreadLocalMode(),
+                                              GV->getType()->getAddressSpace());
+      Globals.insert(GV, NGV);
+      NewGlobals.push_back(NGV);
+
+      // Calculate the known alignment of the field.  If the original aggregate
+      // had 256 byte alignment for example, something might depend on that:
+      // propagate info to each field.
+      unsigned NewAlign = (unsigned)MinAlign(StartAlignment, EltSize*i);
+      if (NewAlign > EltAlign)
+        NGV->setAlignment(NewAlign);
+    }
+  }
+
+  if (NewGlobals.empty())
+    return 0;
+
+  DEBUG(dbgs() << "PERFORMING GLOBAL SRA ON: " << *GV);
+
+  Constant *NullInt =Constant::getNullValue(Type::getInt32Ty(GV->getContext()));
+
+  // Loop over all of the uses of the global, replacing the constantexpr geps,
+  // with smaller constantexpr geps or direct references.
+  while (!GV->use_empty()) {
+    User *GEP = GV->use_back();
+    assert(((isa<ConstantExpr>(GEP) &&
+             cast<ConstantExpr>(GEP)->getOpcode()==Instruction::GetElementPtr)||
+            isa<GetElementPtrInst>(GEP)) && "NonGEP CE's are not SRAable!");
+
+    // Ignore the 1th operand, which has to be zero or else the program is quite
+    // broken (undefined).  Get the 2nd operand, which is the structure or array
+    // index.
+    unsigned Val = cast<ConstantInt>(GEP->getOperand(2))->getZExtValue();
+    if (Val >= NewGlobals.size()) Val = 0; // Out of bound array access.
+
+    Value *NewPtr = NewGlobals[Val];
+
+    // Form a shorter GEP if needed.
+    if (GEP->getNumOperands() > 3) {
+      if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GEP)) {
+        SmallVector<Constant*, 8> Idxs;
+        Idxs.push_back(NullInt);
+        for (unsigned i = 3, e = CE->getNumOperands(); i != e; ++i)
+          Idxs.push_back(CE->getOperand(i));
+        NewPtr = ConstantExpr::getGetElementPtr(cast<Constant>(NewPtr), Idxs);
+      } else {
+        GetElementPtrInst *GEPI = cast<GetElementPtrInst>(GEP);
+        SmallVector<Value*, 8> Idxs;
+        Idxs.push_back(NullInt);
+        for (unsigned i = 3, e = GEPI->getNumOperands(); i != e; ++i)
+          Idxs.push_back(GEPI->getOperand(i));
+        NewPtr = GetElementPtrInst::Create(NewPtr, Idxs,
+                                           GEPI->getName()+"."+Twine(Val),GEPI);
+      }
+    }
+    GEP->replaceAllUsesWith(NewPtr);
+
+    if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(GEP))
+      GEPI->eraseFromParent();
+    else
+      cast<ConstantExpr>(GEP)->destroyConstant();
+  }
+
+  // Delete the old global, now that it is dead.
+  Globals.erase(GV);
+  ++NumSRA;
+
+  // Loop over the new globals array deleting any globals that are obviously
+  // dead.  This can arise due to scalarization of a structure or an array that
+  // has elements that are dead.
+  unsigned FirstGlobal = 0;
+  for (unsigned i = 0, e = NewGlobals.size(); i != e; ++i)
+    if (NewGlobals[i]->use_empty()) {
+      Globals.erase(NewGlobals[i]);
+      if (FirstGlobal == i) ++FirstGlobal;
+    }
+
+  return FirstGlobal != NewGlobals.size() ? NewGlobals[FirstGlobal] : 0;
+}
+
+/// AllUsesOfValueWillTrapIfNull - Return true if all users of the specified
+/// value will trap if the value is dynamically null.  PHIs keeps track of any
+/// phi nodes we've seen to avoid reprocessing them.
+static bool AllUsesOfValueWillTrapIfNull(const Value *V,
+                                         SmallPtrSet<const PHINode*, 8> &PHIs) {
+  for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;
+       ++UI) {
+    const User *U = *UI;
+
+    if (isa<LoadInst>(U)) {
+      // Will trap.
+    } else if (const StoreInst *SI = dyn_cast<StoreInst>(U)) {
+      if (SI->getOperand(0) == V) {
+        //cerr << "NONTRAPPING USE: " << *U;
+        return false;  // Storing the value.
+      }
+    } else if (const CallInst *CI = dyn_cast<CallInst>(U)) {
+      if (CI->getCalledValue() != V) {
+        //cerr << "NONTRAPPING USE: " << *U;
+        return false;  // Not calling the ptr
+      }
+    } else if (const InvokeInst *II = dyn_cast<InvokeInst>(U)) {
+      if (II->getCalledValue() != V) {
+        //cerr << "NONTRAPPING USE: " << *U;
+        return false;  // Not calling the ptr
+      }
+    } else if (const BitCastInst *CI = dyn_cast<BitCastInst>(U)) {
+      if (!AllUsesOfValueWillTrapIfNull(CI, PHIs)) return false;
+    } else if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) {
+      if (!AllUsesOfValueWillTrapIfNull(GEPI, PHIs)) return false;
+    } else if (const PHINode *PN = dyn_cast<PHINode>(U)) {
+      // If we've already seen this phi node, ignore it, it has already been
+      // checked.
+      if (PHIs.insert(PN) && !AllUsesOfValueWillTrapIfNull(PN, PHIs))
+        return false;
+    } else if (isa<ICmpInst>(U) &&
+               isa<ConstantPointerNull>(UI->getOperand(1))) {
+      // Ignore icmp X, null
+    } else {
+      //cerr << "NONTRAPPING USE: " << *U;
+      return false;
+    }
+  }
+  return true;
+}
+
+/// AllUsesOfLoadedValueWillTrapIfNull - Return true if all uses of any loads
+/// from GV will trap if the loaded value is null.  Note that this also permits
+/// comparisons of the loaded value against null, as a special case.
+static bool AllUsesOfLoadedValueWillTrapIfNull(const GlobalVariable *GV) {
+  for (Value::const_use_iterator UI = GV->use_begin(), E = GV->use_end();
+       UI != E; ++UI) {
+    const User *U = *UI;
+
+    if (const LoadInst *LI = dyn_cast<LoadInst>(U)) {
+      SmallPtrSet<const PHINode*, 8> PHIs;
+      if (!AllUsesOfValueWillTrapIfNull(LI, PHIs))
+        return false;
+    } else if (isa<StoreInst>(U)) {
+      // Ignore stores to the global.
+    } else {
+      // We don't know or understand this user, bail out.
+      //cerr << "UNKNOWN USER OF GLOBAL!: " << *U;
+      return false;
+    }
+  }
+  return true;
+}
+
+static bool OptimizeAwayTrappingUsesOfValue(Value *V, Constant *NewV) {
+  bool Changed = false;
+  for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; ) {
+    Instruction *I = cast<Instruction>(*UI++);
+    if (LoadInst *LI = dyn_cast<LoadInst>(I)) {
+      LI->setOperand(0, NewV);
+      Changed = true;
+    } else if (StoreInst *SI = dyn_cast<StoreInst>(I)) {
+      if (SI->getOperand(1) == V) {
+        SI->setOperand(1, NewV);
+        Changed = true;
+      }
+    } else if (isa<CallInst>(I) || isa<InvokeInst>(I)) {
+      CallSite CS(I);
+      if (CS.getCalledValue() == V) {
+        // Calling through the pointer!  Turn into a direct call, but be careful
+        // that the pointer is not also being passed as an argument.
+        CS.setCalledFunction(NewV);
+        Changed = true;
+        bool PassedAsArg = false;
+        for (unsigned i = 0, e = CS.arg_size(); i != e; ++i)
+          if (CS.getArgument(i) == V) {
+            PassedAsArg = true;
+            CS.setArgument(i, NewV);
+          }
+
+        if (PassedAsArg) {
+          // Being passed as an argument also.  Be careful to not invalidate UI!
+          UI = V->use_begin();
+        }
+      }
+    } else if (CastInst *CI = dyn_cast<CastInst>(I)) {
+      Changed |= OptimizeAwayTrappingUsesOfValue(CI,
+                                ConstantExpr::getCast(CI->getOpcode(),
+                                                      NewV, CI->getType()));
+      if (CI->use_empty()) {
+        Changed = true;
+        CI->eraseFromParent();
+      }
+    } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(I)) {
+      // Should handle GEP here.
+      SmallVector<Constant*, 8> Idxs;
+      Idxs.reserve(GEPI->getNumOperands()-1);
+      for (User::op_iterator i = GEPI->op_begin() + 1, e = GEPI->op_end();
+           i != e; ++i)
+        if (Constant *C = dyn_cast<Constant>(*i))
+          Idxs.push_back(C);
+        else
+          break;
+      if (Idxs.size() == GEPI->getNumOperands()-1)
+        Changed |= OptimizeAwayTrappingUsesOfValue(GEPI,
+                          ConstantExpr::getGetElementPtr(NewV, Idxs));
+      if (GEPI->use_empty()) {
+        Changed = true;
+        GEPI->eraseFromParent();
+      }
+    }
+  }
+
+  return Changed;
+}
+
+
+/// OptimizeAwayTrappingUsesOfLoads - The specified global has only one non-null
+/// value stored into it.  If there are uses of the loaded value that would trap
+/// if the loaded value is dynamically null, then we know that they cannot be
+/// reachable with a null optimize away the load.
+static bool OptimizeAwayTrappingUsesOfLoads(GlobalVariable *GV, Constant *LV,
+                                            DataLayout *TD,
+                                            TargetLibraryInfo *TLI) {
+  bool Changed = false;
+
+  // Keep track of whether we are able to remove all the uses of the global
+  // other than the store that defines it.
+  bool AllNonStoreUsesGone = true;
+
+  // Replace all uses of loads with uses of uses of the stored value.
+  for (Value::use_iterator GUI = GV->use_begin(), E = GV->use_end(); GUI != E;){
+    User *GlobalUser = *GUI++;
+    if (LoadInst *LI = dyn_cast<LoadInst>(GlobalUser)) {
+      Changed |= OptimizeAwayTrappingUsesOfValue(LI, LV);
+      // If we were able to delete all uses of the loads
+      if (LI->use_empty()) {
+        LI->eraseFromParent();
+        Changed = true;
+      } else {
+        AllNonStoreUsesGone = false;
+      }
+    } else if (isa<StoreInst>(GlobalUser)) {
+      // Ignore the store that stores "LV" to the global.
+      assert(GlobalUser->getOperand(1) == GV &&
+             "Must be storing *to* the global");
+    } else {
+      AllNonStoreUsesGone = false;
+
+      // If we get here we could have other crazy uses that are transitively
+      // loaded.
+      assert((isa<PHINode>(GlobalUser) || isa<SelectInst>(GlobalUser) ||
+              isa<ConstantExpr>(GlobalUser) || isa<CmpInst>(GlobalUser) ||
+              isa<BitCastInst>(GlobalUser) ||
+              isa<GetElementPtrInst>(GlobalUser)) &&
+             "Only expect load and stores!");
+    }
+  }
+
+  if (Changed) {
+    DEBUG(dbgs() << "OPTIMIZED LOADS FROM STORED ONCE POINTER: " << *GV);
+    ++NumGlobUses;
+  }
+
+  // If we nuked all of the loads, then none of the stores are needed either,
+  // nor is the global.
+  if (AllNonStoreUsesGone) {
+    if (isLeakCheckerRoot(GV)) {
+      Changed |= CleanupPointerRootUsers(GV, TLI);
+    } else {
+      Changed = true;
+      CleanupConstantGlobalUsers(GV, 0, TD, TLI);
+    }
+    if (GV->use_empty()) {
+      DEBUG(dbgs() << "  *** GLOBAL NOW DEAD!\n");
+      Changed = true;
+      GV->eraseFromParent();
+      ++NumDeleted;
+    }
+  }
+  return Changed;
+}
+
+/// ConstantPropUsersOf - Walk the use list of V, constant folding all of the
+/// instructions that are foldable.
+static void ConstantPropUsersOf(Value *V,
+                                DataLayout *TD, TargetLibraryInfo *TLI) {
+  for (Value::use_iterator UI = V->use_begin(), E = V->use_end(); UI != E; )
+    if (Instruction *I = dyn_cast<Instruction>(*UI++))
+      if (Constant *NewC = ConstantFoldInstruction(I, TD, TLI)) {
+        I->replaceAllUsesWith(NewC);
+
+        // Advance UI to the next non-I use to avoid invalidating it!
+        // Instructions could multiply use V.
+        while (UI != E && *UI == I)
+          ++UI;
+        I->eraseFromParent();
+      }
+}
+
+/// OptimizeGlobalAddressOfMalloc - This function takes the specified global
+/// variable, and transforms the program as if it always contained the result of
+/// the specified malloc.  Because it is always the result of the specified
+/// malloc, there is no reason to actually DO the malloc.  Instead, turn the
+/// malloc into a global, and any loads of GV as uses of the new global.
+static GlobalVariable *OptimizeGlobalAddressOfMalloc(GlobalVariable *GV,
+                                                     CallInst *CI,
+                                                     Type *AllocTy,
+                                                     ConstantInt *NElements,
+                                                     DataLayout *TD,
+                                                     TargetLibraryInfo *TLI) {
+  DEBUG(errs() << "PROMOTING GLOBAL: " << *GV << "  CALL = " << *CI << '\n');
+
+  Type *GlobalType;
+  if (NElements->getZExtValue() == 1)
+    GlobalType = AllocTy;
+  else
+    // If we have an array allocation, the global variable is of an array.
+    GlobalType = ArrayType::get(AllocTy, NElements->getZExtValue());
+
+  // Create the new global variable.  The contents of the malloc'd memory is
+  // undefined, so initialize with an undef value.
+  GlobalVariable *NewGV = new GlobalVariable(*GV->getParent(),
+                                             GlobalType, false,
+                                             GlobalValue::InternalLinkage,
+                                             UndefValue::get(GlobalType),
+                                             GV->getName()+".body",
+                                             GV,
+                                             GV->getThreadLocalMode());
+
+  // If there are bitcast users of the malloc (which is typical, usually we have
+  // a malloc + bitcast) then replace them with uses of the new global.  Update
+  // other users to use the global as well.
+  BitCastInst *TheBC = 0;
+  while (!CI->use_empty()) {
+    Instruction *User = cast<Instruction>(CI->use_back());
+    if (BitCastInst *BCI = dyn_cast<BitCastInst>(User)) {
+      if (BCI->getType() == NewGV->getType()) {
+        BCI->replaceAllUsesWith(NewGV);
+        BCI->eraseFromParent();
+      } else {
+        BCI->setOperand(0, NewGV);
+      }
+    } else {
+      if (TheBC == 0)
+        TheBC = new BitCastInst(NewGV, CI->getType(), "newgv", CI);
+      User->replaceUsesOfWith(CI, TheBC);
+    }
+  }
+
+  Constant *RepValue = NewGV;
+  if (NewGV->getType() != GV->getType()->getElementType())
+    RepValue = ConstantExpr::getBitCast(RepValue,
+                                        GV->getType()->getElementType());
+
+  // If there is a comparison against null, we will insert a global bool to
+  // keep track of whether the global was initialized yet or not.
+  GlobalVariable *InitBool =
+    new GlobalVariable(Type::getInt1Ty(GV->getContext()), false,
+                       GlobalValue::InternalLinkage,
+                       ConstantInt::getFalse(GV->getContext()),
+                       GV->getName()+".init", GV->getThreadLocalMode());
+  bool InitBoolUsed = false;
+
+  // Loop over all uses of GV, processing them in turn.
+  while (!GV->use_empty()) {
+    if (StoreInst *SI = dyn_cast<StoreInst>(GV->use_back())) {
+      // The global is initialized when the store to it occurs.
+      new StoreInst(ConstantInt::getTrue(GV->getContext()), InitBool, false, 0,
+                    SI->getOrdering(), SI->getSynchScope(), SI);
+      SI->eraseFromParent();
+      continue;
+    }
+
+    LoadInst *LI = cast<LoadInst>(GV->use_back());
+    while (!LI->use_empty()) {
+      Use &LoadUse = LI->use_begin().getUse();
+      if (!isa<ICmpInst>(LoadUse.getUser())) {
+        LoadUse = RepValue;
+        continue;
+      }
+
+      ICmpInst *ICI = cast<ICmpInst>(LoadUse.getUser());
+      // Replace the cmp X, 0 with a use of the bool value.
+      // Sink the load to where the compare was, if atomic rules allow us to.
+      Value *LV = new LoadInst(InitBool, InitBool->getName()+".val", false, 0,
+                               LI->getOrdering(), LI->getSynchScope(),
+                               LI->isUnordered() ? (Instruction*)ICI : LI);
+      InitBoolUsed = true;
+      switch (ICI->getPredicate()) {
+      default: llvm_unreachable("Unknown ICmp Predicate!");
+      case ICmpInst::ICMP_ULT:
+      case ICmpInst::ICMP_SLT:   // X < null -> always false
+        LV = ConstantInt::getFalse(GV->getContext());
+        break;
+      case ICmpInst::ICMP_ULE:
+      case ICmpInst::ICMP_SLE:
+      case ICmpInst::ICMP_EQ:
+        LV = BinaryOperator::CreateNot(LV, "notinit", ICI);
+        break;
+      case ICmpInst::ICMP_NE:
+      case ICmpInst::ICMP_UGE:
+      case ICmpInst::ICMP_SGE:
+      case ICmpInst::ICMP_UGT:
+      case ICmpInst::ICMP_SGT:
+        break;  // no change.
+      }
+      ICI->replaceAllUsesWith(LV);
+      ICI->eraseFromParent();
+    }
+    LI->eraseFromParent();
+  }
+
+  // If the initialization boolean was used, insert it, otherwise delete it.
+  if (!InitBoolUsed) {
+    while (!InitBool->use_empty())  // Delete initializations
+      cast<StoreInst>(InitBool->use_back())->eraseFromParent();
+    delete InitBool;
+  } else
+    GV->getParent()->getGlobalList().insert(GV, InitBool);
+
+  // Now the GV is dead, nuke it and the malloc..
+  GV->eraseFromParent();
+  CI->eraseFromParent();
+
+  // To further other optimizations, loop over all users of NewGV and try to
+  // constant prop them.  This will promote GEP instructions with constant
+  // indices into GEP constant-exprs, which will allow global-opt to hack on it.
+  ConstantPropUsersOf(NewGV, TD, TLI);
+  if (RepValue != NewGV)
+    ConstantPropUsersOf(RepValue, TD, TLI);
+
+  return NewGV;
+}
+
+/// ValueIsOnlyUsedLocallyOrStoredToOneGlobal - Scan the use-list of V checking
+/// to make sure that there are no complex uses of V.  We permit simple things
+/// like dereferencing the pointer, but not storing through the address, unless
+/// it is to the specified global.
+static bool ValueIsOnlyUsedLocallyOrStoredToOneGlobal(const Instruction *V,
+                                                      const GlobalVariable *GV,
+                                         SmallPtrSet<const PHINode*, 8> &PHIs) {
+  for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end();
+       UI != E; ++UI) {
+    const Instruction *Inst = cast<Instruction>(*UI);
+
+    if (isa<LoadInst>(Inst) || isa<CmpInst>(Inst)) {
+      continue; // Fine, ignore.
+    }
+
+    if (const StoreInst *SI = dyn_cast<StoreInst>(Inst)) {
+      if (SI->getOperand(0) == V && SI->getOperand(1) != GV)
+        return false;  // Storing the pointer itself... bad.
+      continue; // Otherwise, storing through it, or storing into GV... fine.
+    }
+
+    // Must index into the array and into the struct.
+    if (isa<GetElementPtrInst>(Inst) && Inst->getNumOperands() >= 3) {
+      if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(Inst, GV, PHIs))
+        return false;
+      continue;
+    }
+
+    if (const PHINode *PN = dyn_cast<PHINode>(Inst)) {
+      // PHIs are ok if all uses are ok.  Don't infinitely recurse through PHI
+      // cycles.
+      if (PHIs.insert(PN))
+        if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(PN, GV, PHIs))
+          return false;
+      continue;
+    }
+
+    if (const BitCastInst *BCI = dyn_cast<BitCastInst>(Inst)) {
+      if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(BCI, GV, PHIs))
+        return false;
+      continue;
+    }
+
+    return false;
+  }
+  return true;
+}
+
+/// ReplaceUsesOfMallocWithGlobal - The Alloc pointer is stored into GV
+/// somewhere.  Transform all uses of the allocation into loads from the
+/// global and uses of the resultant pointer.  Further, delete the store into
+/// GV.  This assumes that these value pass the
+/// 'ValueIsOnlyUsedLocallyOrStoredToOneGlobal' predicate.
+static void ReplaceUsesOfMallocWithGlobal(Instruction *Alloc,
+                                          GlobalVariable *GV) {
+  while (!Alloc->use_empty()) {
+    Instruction *U = cast<Instruction>(*Alloc->use_begin());
+    Instruction *InsertPt = U;
+    if (StoreInst *SI = dyn_cast<StoreInst>(U)) {
+      // If this is the store of the allocation into the global, remove it.
+      if (SI->getOperand(1) == GV) {
+        SI->eraseFromParent();
+        continue;
+      }
+    } else if (PHINode *PN = dyn_cast<PHINode>(U)) {
+      // Insert the load in the corresponding predecessor, not right before the
+      // PHI.
+      InsertPt = PN->getIncomingBlock(Alloc->use_begin())->getTerminator();
+    } else if (isa<BitCastInst>(U)) {
+      // Must be bitcast between the malloc and store to initialize the global.
+      ReplaceUsesOfMallocWithGlobal(U, GV);
+      U->eraseFromParent();
+      continue;
+    } else if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(U)) {
+      // If this is a "GEP bitcast" and the user is a store to the global, then
+      // just process it as a bitcast.
+      if (GEPI->hasAllZeroIndices() && GEPI->hasOneUse())
+        if (StoreInst *SI = dyn_cast<StoreInst>(GEPI->use_back()))
+          if (SI->getOperand(1) == GV) {
+            // Must be bitcast GEP between the malloc and store to initialize
+            // the global.
+            ReplaceUsesOfMallocWithGlobal(GEPI, GV);
+            GEPI->eraseFromParent();
+            continue;
+          }
+    }
+
+    // Insert a load from the global, and use it instead of the malloc.
+    Value *NL = new LoadInst(GV, GV->getName()+".val", InsertPt);
+    U->replaceUsesOfWith(Alloc, NL);
+  }
+}
+
+/// LoadUsesSimpleEnoughForHeapSRA - Verify that all uses of V (a load, or a phi
+/// of a load) are simple enough to perform heap SRA on.  This permits GEP's
+/// that index through the array and struct field, icmps of null, and PHIs.
+static bool LoadUsesSimpleEnoughForHeapSRA(const Value *V,
+                        SmallPtrSet<const PHINode*, 32> &LoadUsingPHIs,
+                        SmallPtrSet<const PHINode*, 32> &LoadUsingPHIsPerLoad) {
+  // We permit two users of the load: setcc comparing against the null
+  // pointer, and a getelementptr of a specific form.
+  for (Value::const_use_iterator UI = V->use_begin(), E = V->use_end(); UI != E;
+       ++UI) {
+    const Instruction *User = cast<Instruction>(*UI);
+
+    // Comparison against null is ok.
+    if (const ICmpInst *ICI = dyn_cast<ICmpInst>(User)) {
+      if (!isa<ConstantPointerNull>(ICI->getOperand(1)))
+        return false;
+      continue;
+    }
+
+    // getelementptr is also ok, but only a simple form.
+    if (const GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(User)) {
+      // Must index into the array and into the struct.
+      if (GEPI->getNumOperands() < 3)
+        return false;
+
+      // Otherwise the GEP is ok.
+      continue;
+    }
+
+    if (const PHINode *PN = dyn_cast<PHINode>(User)) {
+      if (!LoadUsingPHIsPerLoad.insert(PN))
+        // This means some phi nodes are dependent on each other.
+        // Avoid infinite looping!
+        return false;
+      if (!LoadUsingPHIs.insert(PN))
+        // If we have already analyzed this PHI, then it is safe.
+        continue;
+
+      // Make sure all uses of the PHI are simple enough to transform.
+      if (!LoadUsesSimpleEnoughForHeapSRA(PN,
+                                          LoadUsingPHIs, LoadUsingPHIsPerLoad))
+        return false;
+
+      continue;
+    }
+
+    // Otherwise we don't know what this is, not ok.
+    return false;
+  }
+
+  return true;
+}
+
+
+/// AllGlobalLoadUsesSimpleEnoughForHeapSRA - If all users of values loaded from
+/// GV are simple enough to perform HeapSRA, return true.
+static bool AllGlobalLoadUsesSimpleEnoughForHeapSRA(const GlobalVariable *GV,
+                                                    Instruction *StoredVal) {
+  SmallPtrSet<const PHINode*, 32> LoadUsingPHIs;
+  SmallPtrSet<const PHINode*, 32> LoadUsingPHIsPerLoad;
+  for (Value::const_use_iterator UI = GV->use_begin(), E = GV->use_end();
+       UI != E; ++UI)
+    if (const LoadInst *LI = dyn_cast<LoadInst>(*UI)) {
+      if (!LoadUsesSimpleEnoughForHeapSRA(LI, LoadUsingPHIs,
+                                          LoadUsingPHIsPerLoad))
+        return false;
+      LoadUsingPHIsPerLoad.clear();
+    }
+
+  // If we reach here, we know that all uses of the loads and transitive uses
+  // (through PHI nodes) are simple enough to transform.  However, we don't know
+  // that all inputs the to the PHI nodes are in the same equivalence sets.
+  // Check to verify that all operands of the PHIs are either PHIS that can be
+  // transformed, loads from GV, or MI itself.
+  for (SmallPtrSet<const PHINode*, 32>::const_iterator I = LoadUsingPHIs.begin()
+       , E = LoadUsingPHIs.end(); I != E; ++I) {
+    const PHINode *PN = *I;
+    for (unsigned op = 0, e = PN->getNumIncomingValues(); op != e; ++op) {
+      Value *InVal = PN->getIncomingValue(op);
+
+      // PHI of the stored value itself is ok.
+      if (InVal == StoredVal) continue;
+
+      if (const PHINode *InPN = dyn_cast<PHINode>(InVal)) {
+        // One of the PHIs in our set is (optimistically) ok.
+        if (LoadUsingPHIs.count(InPN))
+          continue;
+        return false;
+      }
+
+      // Load from GV is ok.
+      if (const LoadInst *LI = dyn_cast<LoadInst>(InVal))
+        if (LI->getOperand(0) == GV)
+          continue;
+
+      // UNDEF? NULL?
+
+      // Anything else is rejected.
+      return false;
+    }
+  }
+
+  return true;
+}
+
+static Value *GetHeapSROAValue(Value *V, unsigned FieldNo,
+               DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
+                   std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
+  std::vector<Value*> &FieldVals = InsertedScalarizedValues[V];
+
+  if (FieldNo >= FieldVals.size())
+    FieldVals.resize(FieldNo+1);
+
+  // If we already have this value, just reuse the previously scalarized
+  // version.
+  if (Value *FieldVal = FieldVals[FieldNo])
+    return FieldVal;
+
+  // Depending on what instruction this is, we have several cases.
+  Value *Result;
+  if (LoadInst *LI = dyn_cast<LoadInst>(V)) {
+    // This is a scalarized version of the load from the global.  Just create
+    // a new Load of the scalarized global.
+    Result = new LoadInst(GetHeapSROAValue(LI->getOperand(0), FieldNo,
+                                           InsertedScalarizedValues,
+                                           PHIsToRewrite),
+                          LI->getName()+".f"+Twine(FieldNo), LI);
+  } else if (PHINode *PN = dyn_cast<PHINode>(V)) {
+    // PN's type is pointer to struct.  Make a new PHI of pointer to struct
+    // field.
+    StructType *ST = cast<StructType>(PN->getType()->getPointerElementType());
+
+    PHINode *NewPN =
+     PHINode::Create(PointerType::getUnqual(ST->getElementType(FieldNo)),
+                     PN->getNumIncomingValues(),
+                     PN->getName()+".f"+Twine(FieldNo), PN);
+    Result = NewPN;
+    PHIsToRewrite.push_back(std::make_pair(PN, FieldNo));
+  } else {
+    llvm_unreachable("Unknown usable value");
+  }
+
+  return FieldVals[FieldNo] = Result;
+}
+
+/// RewriteHeapSROALoadUser - Given a load instruction and a value derived from
+/// the load, rewrite the derived value to use the HeapSRoA'd load.
+static void RewriteHeapSROALoadUser(Instruction *LoadUser,
+             DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
+                   std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
+  // If this is a comparison against null, handle it.
+  if (ICmpInst *SCI = dyn_cast<ICmpInst>(LoadUser)) {
+    assert(isa<ConstantPointerNull>(SCI->getOperand(1)));
+    // If we have a setcc of the loaded pointer, we can use a setcc of any
+    // field.
+    Value *NPtr = GetHeapSROAValue(SCI->getOperand(0), 0,
+                                   InsertedScalarizedValues, PHIsToRewrite);
+
+    Value *New = new ICmpInst(SCI, SCI->getPredicate(), NPtr,
+                              Constant::getNullValue(NPtr->getType()),
+                              SCI->getName());
+    SCI->replaceAllUsesWith(New);
+    SCI->eraseFromParent();
+    return;
+  }
+
+  // Handle 'getelementptr Ptr, Idx, i32 FieldNo ...'
+  if (GetElementPtrInst *GEPI = dyn_cast<GetElementPtrInst>(LoadUser)) {
+    assert(GEPI->getNumOperands() >= 3 && isa<ConstantInt>(GEPI->getOperand(2))
+           && "Unexpected GEPI!");
+
+    // Load the pointer for this field.
+    unsigned FieldNo = cast<ConstantInt>(GEPI->getOperand(2))->getZExtValue();
+    Value *NewPtr = GetHeapSROAValue(GEPI->getOperand(0), FieldNo,
+                                     InsertedScalarizedValues, PHIsToRewrite);
+
+    // Create the new GEP idx vector.
+    SmallVector<Value*, 8> GEPIdx;
+    GEPIdx.push_back(GEPI->getOperand(1));
+    GEPIdx.append(GEPI->op_begin()+3, GEPI->op_end());
+
+    Value *NGEPI = GetElementPtrInst::Create(NewPtr, GEPIdx,
+                                             GEPI->getName(), GEPI);
+    GEPI->replaceAllUsesWith(NGEPI);
+    GEPI->eraseFromParent();
+    return;
+  }
+
+  // Recursively transform the users of PHI nodes.  This will lazily create the
+  // PHIs that are needed for individual elements.  Keep track of what PHIs we
+  // see in InsertedScalarizedValues so that we don't get infinite loops (very
+  // antisocial).  If the PHI is already in InsertedScalarizedValues, it has
+  // already been seen first by another load, so its uses have already been
+  // processed.
+  PHINode *PN = cast<PHINode>(LoadUser);
+  if (!InsertedScalarizedValues.insert(std::make_pair(PN,
+                                              std::vector<Value*>())).second)
+    return;
+
+  // If this is the first time we've seen this PHI, recursively process all
+  // users.
+  for (Value::use_iterator UI = PN->use_begin(), E = PN->use_end(); UI != E; ) {
+    Instruction *User = cast<Instruction>(*UI++);
+    RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite);
+  }
+}
+
+/// RewriteUsesOfLoadForHeapSRoA - We are performing Heap SRoA on a global.  Ptr
+/// is a value loaded from the global.  Eliminate all uses of Ptr, making them
+/// use FieldGlobals instead.  All uses of loaded values satisfy
+/// AllGlobalLoadUsesSimpleEnoughForHeapSRA.
+static void RewriteUsesOfLoadForHeapSRoA(LoadInst *Load,
+               DenseMap<Value*, std::vector<Value*> > &InsertedScalarizedValues,
+                   std::vector<std::pair<PHINode*, unsigned> > &PHIsToRewrite) {
+  for (Value::use_iterator UI = Load->use_begin(), E = Load->use_end();
+       UI != E; ) {
+    Instruction *User = cast<Instruction>(*UI++);
+    RewriteHeapSROALoadUser(User, InsertedScalarizedValues, PHIsToRewrite);
+  }
+
+  if (Load->use_empty()) {
+    Load->eraseFromParent();
+    InsertedScalarizedValues.erase(Load);
+  }
+}
+
+/// PerformHeapAllocSRoA - CI is an allocation of an array of structures.  Break
+/// it up into multiple allocations of arrays of the fields.
+static GlobalVariable *PerformHeapAllocSRoA(GlobalVariable *GV, CallInst *CI,
+                                            Value *NElems, DataLayout *TD,
+                                            const TargetLibraryInfo *TLI) {
+  DEBUG(dbgs() << "SROA HEAP ALLOC: " << *GV << "  MALLOC = " << *CI << '\n');
+  Type *MAT = getMallocAllocatedType(CI, TLI);
+  StructType *STy = cast<StructType>(MAT);
+
+  // There is guaranteed to be at least one use of the malloc (storing
+  // it into GV).  If there are other uses, change them to be uses of
+  // the global to simplify later code.  This also deletes the store
+  // into GV.
+  ReplaceUsesOfMallocWithGlobal(CI, GV);
+
+  // Okay, at this point, there are no users of the malloc.  Insert N
+  // new mallocs at the same place as CI, and N globals.
+  std::vector<Value*> FieldGlobals;
+  std::vector<Value*> FieldMallocs;
+
+  for (unsigned FieldNo = 0, e = STy->getNumElements(); FieldNo != e;++FieldNo){
+    Type *FieldTy = STy->getElementType(FieldNo);
+    PointerType *PFieldTy = PointerType::getUnqual(FieldTy);
+
+    GlobalVariable *NGV =
+      new GlobalVariable(*GV->getParent(),
+                         PFieldTy, false, GlobalValue::InternalLinkage,
+                         Constant::getNullValue(PFieldTy),
+                         GV->getName() + ".f" + Twine(FieldNo), GV,
+                         GV->getThreadLocalMode());
+    FieldGlobals.push_back(NGV);
+
+    unsigned TypeSize = TD->getTypeAllocSize(FieldTy);
+    if (StructType *ST = dyn_cast<StructType>(FieldTy))
+      TypeSize = TD->getStructLayout(ST)->getSizeInBytes();
+    Type *IntPtrTy = TD->getIntPtrType(CI->getType());
+    Value *NMI = CallInst::CreateMalloc(CI, IntPtrTy, FieldTy,
+                                        ConstantInt::get(IntPtrTy, TypeSize),
+                                        NElems, 0,
+                                        CI->getName() + ".f" + Twine(FieldNo));
+    FieldMallocs.push_back(NMI);
+    new StoreInst(NMI, NGV, CI);
+  }
+
+  // The tricky aspect of this transformation is handling the case when malloc
+  // fails.  In the original code, malloc failing would set the result pointer
+  // of malloc to null.  In this case, some mallocs could succeed and others
+  // could fail.  As such, we emit code that looks like this:
+  //    F0 = malloc(field0)
+  //    F1 = malloc(field1)
+  //    F2 = malloc(field2)
+  //    if (F0 == 0 || F1 == 0 || F2 == 0) {
+  //      if (F0) { free(F0); F0 = 0; }
+  //      if (F1) { free(F1); F1 = 0; }
+  //      if (F2) { free(F2); F2 = 0; }
+  //    }
+  // The malloc can also fail if its argument is too large.
+  Constant *ConstantZero = ConstantInt::get(CI->getArgOperand(0)->getType(), 0);
+  Value *RunningOr = new ICmpInst(CI, ICmpInst::ICMP_SLT, CI->getArgOperand(0),
+                                  ConstantZero, "isneg");
+  for (unsigned i = 0, e = FieldMallocs.size(); i != e; ++i) {
+    Value *Cond = new ICmpInst(CI, ICmpInst::ICMP_EQ, FieldMallocs[i],
+                             Constant::getNullValue(FieldMallocs[i]->getType()),
+                               "isnull");
+    RunningOr = BinaryOperator::CreateOr(RunningOr, Cond, "tmp", CI);
+  }
+
+  // Split the basic block at the old malloc.
+  BasicBlock *OrigBB = CI->getParent();
+  BasicBlock *ContBB = OrigBB->splitBasicBlock(CI, "malloc_cont");
+
+  // Create the block to check the first condition.  Put all these blocks at the
+  // end of the function as they are unlikely to be executed.
+  BasicBlock *NullPtrBlock = BasicBlock::Create(OrigBB->getContext(),
+                                                "malloc_ret_null",
+                                                OrigBB->getParent());
+
+  // Remove the uncond branch from OrigBB to ContBB, turning it into a cond
+  // branch on RunningOr.
+  OrigBB->getTerminator()->eraseFromParent();
+  BranchInst::Create(NullPtrBlock, ContBB, RunningOr, OrigBB);
+
+  // Within the NullPtrBlock, we need to emit a comparison and branch for each
+  // pointer, because some may be null while others are not.
+  for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
+    Value *GVVal = new LoadInst(FieldGlobals[i], "tmp", NullPtrBlock);
+    Value *Cmp = new ICmpInst(*NullPtrBlock, ICmpInst::ICMP_NE, GVVal,
+                              Constant::getNullValue(GVVal->getType()));
+    BasicBlock *FreeBlock = BasicBlock::Create(Cmp->getContext(), "free_it",
+                                               OrigBB->getParent());
+    BasicBlock *NextBlock = BasicBlock::Create(Cmp->getContext(), "next",
+                                               OrigBB->getParent());
+    Instruction *BI = BranchInst::Create(FreeBlock, NextBlock,
+                                         Cmp, NullPtrBlock);
+
+    // Fill in FreeBlock.
+    CallInst::CreateFree(GVVal, BI);
+    new StoreInst(Constant::getNullValue(GVVal->getType()), FieldGlobals[i],
+                  FreeBlock);
+    BranchInst::Create(NextBlock, FreeBlock);
+
+    NullPtrBlock = NextBlock;
+  }
+
+  BranchInst::Create(ContBB, NullPtrBlock);
+
+  // CI is no longer needed, remove it.
+  CI->eraseFromParent();
+
+  /// InsertedScalarizedLoads - As we process loads, if we can't immediately
+  /// update all uses of the load, keep track of what scalarized loads are
+  /// inserted for a given load.
+  DenseMap<Value*, std::vector<Value*> > InsertedScalarizedValues;
+  InsertedScalarizedValues[GV] = FieldGlobals;
+
+  std::vector<std::pair<PHINode*, unsigned> > PHIsToRewrite;
+
+  // Okay, the malloc site is completely handled.  All of the uses of GV are now
+  // loads, and all uses of those loads are simple.  Rewrite them to use loads
+  // of the per-field globals instead.
+  for (Value::use_iterator UI = GV->use_begin(), E = GV->use_end(); UI != E;) {
+    Instruction *User = cast<Instruction>(*UI++);
+
+    if (LoadInst *LI = dyn_cast<LoadInst>(User)) {
+      RewriteUsesOfLoadForHeapSRoA(LI, InsertedScalarizedValues, PHIsToRewrite);
+      continue;
+    }
+
+    // Must be a store of null.
+    StoreInst *SI = cast<StoreInst>(User);
+    assert(isa<ConstantPointerNull>(SI->getOperand(0)) &&
+           "Unexpected heap-sra user!");
+
+    // Insert a store of null into each global.
+    for (unsigned i = 0, e = FieldGlobals.size(); i != e; ++i) {
+      PointerType *PT = cast<PointerType>(FieldGlobals[i]->getType());
+      Constant *Null = Constant::getNullValue(PT->getElementType());
+      new StoreInst(Null, FieldGlobals[i], SI);
+    }
+    // Erase the original store.
+    SI->eraseFromParent();
+  }
+
+  // While we have PHIs that are interesting to rewrite, do it.
+  while (!PHIsToRewrite.empty()) {
+    PHINode *PN = PHIsToRewrite.back().first;
+    unsigned FieldNo = PHIsToRewrite.back().second;
+    PHIsToRewrite.pop_back();
+    PHINode *FieldPN = cast<PHINode>(InsertedScalarizedValues[PN][FieldNo]);
+    assert(FieldPN->getNumIncomingValues() == 0 &&"Already processed this phi");
+
+    // Add all the incoming values.  This can materialize more phis.
+    for (unsigned i = 0, e = PN->getNumIncomingValues(); i != e; ++i) {
+      Value *InVal = PN->getIncomingValue(i);
+      InVal = GetHeapSROAValue(InVal, FieldNo, InsertedScalarizedValues,
+                               PHIsToRewrite);
+      FieldPN->addIncoming(InVal, PN->getIncomingBlock(i));
+    }
+  }
+
+  // Drop all inter-phi links and any loads that made it this far.
+  for (DenseMap<Value*, std::vector<Value*> >::iterator
+       I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
+       I != E; ++I) {
+    if (PHINode *PN = dyn_cast<PHINode>(I->first))
+      PN->dropAllReferences();
+    else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
+      LI->dropAllReferences();
+  }
+
+  // Delete all the phis and loads now that inter-references are dead.
+  for (DenseMap<Value*, std::vector<Value*> >::iterator
+       I = InsertedScalarizedValues.begin(), E = InsertedScalarizedValues.end();
+       I != E; ++I) {
+    if (PHINode *PN = dyn_cast<PHINode>(I->first))
+      PN->eraseFromParent();
+    else if (LoadInst *LI = dyn_cast<LoadInst>(I->first))
+      LI->eraseFromParent();
+  }
+
+  // The old global is now dead, remove it.
+  GV->eraseFromParent();
+
+  ++NumHeapSRA;
+  return cast<GlobalVariable>(FieldGlobals[0]);
+}
+
+/// TryToOptimizeStoreOfMallocToGlobal - This function is called when we see a
+/// pointer global variable with a single value stored it that is a malloc or
+/// cast of malloc.
+static bool TryToOptimizeStoreOfMallocToGlobal(GlobalVariable *GV,
+                                               CallInst *CI,
+                                               Type *AllocTy,
+                                               AtomicOrdering Ordering,
+                                               Module::global_iterator &GVI,
+                                               DataLayout *TD,
+                                               TargetLibraryInfo *TLI) {
+  if (!TD)
+    return false;
+
+  // If this is a malloc of an abstract type, don't touch it.
+  if (!AllocTy->isSized())
+    return false;
+
+  // We can't optimize this global unless all uses of it are *known* to be
+  // of the malloc value, not of the null initializer value (consider a use
+  // that compares the global's value against zero to see if the malloc has
+  // been reached).  To do this, we check to see if all uses of the global
+  // would trap if the global were null: this proves that they must all
+  // happen after the malloc.
+  if (!AllUsesOfLoadedValueWillTrapIfNull(GV))
+    return false;
+
+  // We can't optimize this if the malloc itself is used in a complex way,
+  // for example, being stored into multiple globals.  This allows the
+  // malloc to be stored into the specified global, loaded icmp'd, and
+  // GEP'd.  These are all things we could transform to using the global
+  // for.
+  SmallPtrSet<const PHINode*, 8> PHIs;
+  if (!ValueIsOnlyUsedLocallyOrStoredToOneGlobal(CI, GV, PHIs))
+    return false;
+
+  // If we have a global that is only initialized with a fixed size malloc,
+  // transform the program to use global memory instead of malloc'd memory.
+  // This eliminates dynamic allocation, avoids an indirection accessing the
+  // data, and exposes the resultant global to further GlobalOpt.
+  // We cannot optimize the malloc if we cannot determine malloc array size.
+  Value *NElems = getMallocArraySize(CI, TD, TLI, true);
+  if (!NElems)
+    return false;
+
+  if (ConstantInt *NElements = dyn_cast<ConstantInt>(NElems))
+    // Restrict this transformation to only working on small allocations
+    // (2048 bytes currently), as we don't want to introduce a 16M global or
+    // something.
+    if (NElements->getZExtValue() * TD->getTypeAllocSize(AllocTy) < 2048) {
+      GVI = OptimizeGlobalAddressOfMalloc(GV, CI, AllocTy, NElements, TD, TLI);
+      return true;
+    }
+
+  // If the allocation is an array of structures, consider transforming this
+  // into multiple malloc'd arrays, one for each field.  This is basically
+  // SRoA for malloc'd memory.
+
+  if (Ordering != NotAtomic)
+    return false;
+
+  // If this is an allocation of a fixed size array of structs, analyze as a
+  // variable size array.  malloc [100 x struct],1 -> malloc struct, 100
+  if (NElems == ConstantInt::get(CI->getArgOperand(0)->getType(), 1))
+    if (ArrayType *AT = dyn_cast<ArrayType>(AllocTy))
+      AllocTy = AT->getElementType();
+
+  StructType *AllocSTy = dyn_cast<StructType>(AllocTy);
+  if (!AllocSTy)
+    return false;
+
+  // This the structure has an unreasonable number of fields, leave it
+  // alone.
+  if (AllocSTy->getNumElements() <= 16 && AllocSTy->getNumElements() != 0 &&
+      AllGlobalLoadUsesSimpleEnoughForHeapSRA(GV, CI)) {
+
+    // If this is a fixed size array, transform the Malloc to be an alloc of
+    // structs.  malloc [100 x struct],1 -> malloc struct, 100
+    if (ArrayType *AT = dyn_cast<ArrayType>(getMallocAllocatedType(CI, TLI))) {
+      Type *IntPtrTy = TD->getIntPtrType(CI->getType());
+      unsigned TypeSize = TD->getStructLayout(AllocSTy)->getSizeInBytes();
+      Value *AllocSize = ConstantInt::get(IntPtrTy, TypeSize);
+      Value *NumElements = ConstantInt::get(IntPtrTy, AT->getNumElements());
+      Instruction *Malloc = CallInst::CreateMalloc(CI, IntPtrTy, AllocSTy,
+                                                   AllocSize, NumElements,
+                                                   0, CI->getName());
+      Instruction *Cast = new BitCastInst(Malloc, CI->getType(), "tmp", CI);
+      CI->replaceAllUsesWith(Cast);
+      CI->eraseFromParent();
+      if (BitCastInst *BCI = dyn_cast<BitCastInst>(Malloc))
+        CI = cast<CallInst>(BCI->getOperand(0));
+      else
+        CI = cast<CallInst>(Malloc);
+    }
+
+    GVI = PerformHeapAllocSRoA(GV, CI, getMallocArraySize(CI, TD, TLI, true),
+                               TD, TLI);
+    return true;
+  }
+
+  return false;
+}
+
+// OptimizeOnceStoredGlobal - Try to optimize globals based on the knowledge
+// that only one value (besides its initializer) is ever stored to the global.
+static bool OptimizeOnceStoredGlobal(GlobalVariable *GV, Value *StoredOnceVal,
+                                     AtomicOrdering Ordering,
+                                     Module::global_iterator &GVI,
+                                     DataLayout *TD, TargetLibraryInfo *TLI) {
+  // Ignore no-op GEPs and bitcasts.
+  StoredOnceVal = StoredOnceVal->stripPointerCasts();
+
+  // If we are dealing with a pointer global that is initialized to null and
+  // only has one (non-null) value stored into it, then we can optimize any
+  // users of the loaded value (often calls and loads) that would trap if the
+  // value was null.
+  if (GV->getInitializer()->getType()->isPointerTy() &&
+      GV->getInitializer()->isNullValue()) {
+    if (Constant *SOVC = dyn_cast<Constant>(StoredOnceVal)) {
+      if (GV->getInitializer()->getType() != SOVC->getType())
+        SOVC = ConstantExpr::getBitCast(SOVC, GV->getInitializer()->getType());
+
+      // Optimize away any trapping uses of the loaded value.
+      if (OptimizeAwayTrappingUsesOfLoads(GV, SOVC, TD, TLI))
+        return true;
+    } else if (CallInst *CI = extractMallocCall(StoredOnceVal, TLI)) {
+      Type *MallocType = getMallocAllocatedType(CI, TLI);
+      if (MallocType &&
+          TryToOptimizeStoreOfMallocToGlobal(GV, CI, MallocType, Ordering, GVI,
+                                             TD, TLI))
+        return true;
+    }
+  }
+
+  return false;
+}
+
+/// TryToShrinkGlobalToBoolean - At this point, we have learned that the only
+/// two values ever stored into GV are its initializer and OtherVal.  See if we
+/// can shrink the global into a boolean and select between the two values
+/// whenever it is used.  This exposes the values to other scalar optimizations.
+static bool TryToShrinkGlobalToBoolean(GlobalVariable *GV, Constant *OtherVal) {
+  Type *GVElType = GV->getType()->getElementType();
+
+  // If GVElType is already i1, it is already shrunk.  If the type of the GV is
+  // an FP value, pointer or vector, don't do this optimization because a select
+  // between them is very expensive and unlikely to lead to later
+  // simplification.  In these cases, we typically end up with "cond ? v1 : v2"
+  // where v1 and v2 both require constant pool loads, a big loss.
+  if (GVElType == Type::getInt1Ty(GV->getContext()) ||
+      GVElType->isFloatingPointTy() ||
+      GVElType->isPointerTy() || GVElType->isVectorTy())
+    return false;
+
+  // Walk the use list of the global seeing if all the uses are load or store.
+  // If there is anything else, bail out.
+  for (Value::use_iterator I = GV->use_begin(), E = GV->use_end(); I != E; ++I){
+    User *U = *I;
+    if (!isa<LoadInst>(U) && !isa<StoreInst>(U))
+      return false;
+  }
+
+  DEBUG(dbgs() << "   *** SHRINKING TO BOOL: " << *GV);
+
+  // Create the new global, initializing it to false.
+  GlobalVariable *NewGV = new GlobalVariable(Type::getInt1Ty(GV->getContext()),
+                                             false,
+                                             GlobalValue::InternalLinkage,
+                                        ConstantInt::getFalse(GV->getContext()),
+                                             GV->getName()+".b",
+                                             GV->getThreadLocalMode(),
+                                             GV->getType()->getAddressSpace());
+  GV->getParent()->getGlobalList().insert(GV, NewGV);
+
+  Constant *InitVal = GV->getInitializer();
+  assert(InitVal->getType() != Type::getInt1Ty(GV->getContext()) &&
+         "No reason to shrink to bool!");
+
+  // If initialized to zero and storing one into the global, we can use a cast
+  // instead of a select to synthesize the desired value.
+  bool IsOneZero = false;
+  if (ConstantInt *CI = dyn_cast<ConstantInt>(OtherVal))
+    IsOneZero = InitVal->isNullValue() && CI->isOne();
+
+  while (!GV->use_empty()) {
+    Instruction *UI = cast<Instruction>(GV->use_back());
+    if (StoreInst *SI = dyn_cast<StoreInst>(UI)) {
+      // Change the store into a boolean store.
+      bool StoringOther = SI->getOperand(0) == OtherVal;
+      // Only do this if we weren't storing a loaded value.
+      Value *StoreVal;
+      if (StoringOther || SI->getOperand(0) == InitVal) {
+        StoreVal = ConstantInt::get(Type::getInt1Ty(GV->getContext()),
+                                    StoringOther);
+      } else {
+        // Otherwise, we are storing a previously loaded copy.  To do this,
+        // change the copy from copying the original value to just copying the
+        // bool.
+        Instruction *StoredVal = cast<Instruction>(SI->getOperand(0));
+
+        // If we've already replaced the input, StoredVal will be a cast or
+        // select instruction.  If not, it will be a load of the original
+        // global.
+        if (LoadInst *LI = dyn_cast<LoadInst>(StoredVal)) {
+          assert(LI->getOperand(0) == GV && "Not a copy!");
+          // Insert a new load, to preserve the saved value.
+          StoreVal = new LoadInst(NewGV, LI->getName()+".b", false, 0,
+                                  LI->getOrdering(), LI->getSynchScope(), LI);
+        } else {
+          assert((isa<CastInst>(StoredVal) || isa<SelectInst>(StoredVal)) &&
+                 "This is not a form that we understand!");
+          StoreVal = StoredVal->getOperand(0);
+          assert(isa<LoadInst>(StoreVal) && "Not a load of NewGV!");
+        }
+      }
+      new StoreInst(StoreVal, NewGV, false, 0,
+                    SI->getOrdering(), SI->getSynchScope(), SI);
+    } else {
+      // Change the load into a load of bool then a select.
+      LoadInst *LI = cast<LoadInst>(UI);
+      LoadInst *NLI = new LoadInst(NewGV, LI->getName()+".b", false, 0,
+                                   LI->getOrdering(), LI->getSynchScope(), LI);
+      Value *NSI;
+      if (IsOneZero)
+        NSI = new ZExtInst(NLI, LI->getType(), "", LI);
+      else
+        NSI = SelectInst::Create(NLI, OtherVal, InitVal, "", LI);
+      NSI->takeName(LI);
+      LI->replaceAllUsesWith(NSI);
+    }
+    UI->eraseFromParent();
+  }
+
+  // Retain the name of the old global variable. People who are debugging their
+  // programs may expect these variables to be named the same.
+  NewGV->takeName(GV);
+  GV->eraseFromParent();
+  return true;
+}
+
+
+/// ProcessGlobal - Analyze the specified global variable and optimize it if
+/// possible.  If we make a change, return true.
+bool GlobalOpt::ProcessGlobal(GlobalVariable *GV,
+                              Module::global_iterator &GVI) {
+  if (!GV->isDiscardableIfUnused())
+    return false;
+
+  // Do more involved optimizations if the global is internal.
+  GV->removeDeadConstantUsers();
+
+  if (GV->use_empty()) {
+    DEBUG(dbgs() << "GLOBAL DEAD: " << *GV);
+    GV->eraseFromParent();
+    ++NumDeleted;
+    return true;
+  }
+
+  if (!GV->hasLocalLinkage())
+    return false;
+
+  GlobalStatus GS;
+
+  if (GlobalStatus::analyzeGlobal(GV, GS))
+    return false;
+
+  if (!GS.IsCompared && !GV->hasUnnamedAddr()) {
+    GV->setUnnamedAddr(true);
+    NumUnnamed++;
+  }
+
+  if (GV->isConstant() || !GV->hasInitializer())
+    return false;
+
+  return ProcessInternalGlobal(GV, GVI, GS);
+}
+
+/// ProcessInternalGlobal - Analyze the specified global variable and optimize
+/// it if possible.  If we make a change, return true.
+bool GlobalOpt::ProcessInternalGlobal(GlobalVariable *GV,
+                                      Module::global_iterator &GVI,
+                                      const GlobalStatus &GS) {
+  // If this is a first class global and has only one accessing function
+  // and this function is main (which we know is not recursive), we replace
+  // the global with a local alloca in this function.
+  //
+  // NOTE: It doesn't make sense to promote non single-value types since we
+  // are just replacing static memory to stack memory.
+  //
+  // If the global is in different address space, don't bring it to stack.
+  if (!GS.HasMultipleAccessingFunctions &&
+      GS.AccessingFunction && !GS.HasNonInstructionUser &&
+      GV->getType()->getElementType()->isSingleValueType() &&
+      GS.AccessingFunction->getName() == "main" &&
+      GS.AccessingFunction->hasExternalLinkage() &&
+      GV->getType()->getAddressSpace() == 0) {
+    DEBUG(dbgs() << "LOCALIZING GLOBAL: " << *GV);
+    Instruction &FirstI = const_cast<Instruction&>(*GS.AccessingFunction
+                                                   ->getEntryBlock().begin());
+    Type *ElemTy = GV->getType()->getElementType();
+    // FIXME: Pass Global's alignment when globals have alignment
+    AllocaInst *Alloca = new AllocaInst(ElemTy, NULL, GV->getName(), &FirstI);
+    if (!isa<UndefValue>(GV->getInitializer()))
+      new StoreInst(GV->getInitializer(), Alloca, &FirstI);
+
+    GV->replaceAllUsesWith(Alloca);
+    GV->eraseFromParent();
+    ++NumLocalized;
+    return true;
+  }
+
+  // If the global is never loaded (but may be stored to), it is dead.
+  // Delete it now.
+  if (!GS.IsLoaded) {
+    DEBUG(dbgs() << "GLOBAL NEVER LOADED: " << *GV);
+
+    bool Changed;
+    if (isLeakCheckerRoot(GV)) {
+      // Delete any constant stores to the global.
+      Changed = CleanupPointerRootUsers(GV, TLI);
+    } else {
+      // Delete any stores we can find to the global.  We may not be able to
+      // make it completely dead though.
+      Changed = CleanupConstantGlobalUsers(GV, GV->getInitializer(), TD, TLI);
+    }
+
+    // If the global is dead now, delete it.
+    if (GV->use_empty()) {
+      GV->eraseFromParent();
+      ++NumDeleted;
+      Changed = true;
+    }
+    return Changed;
+
+  } else if (GS.StoredType <= GlobalStatus::InitializerStored) {
+    DEBUG(dbgs() << "MARKING CONSTANT: " << *GV << "\n");
+    GV->setConstant(true);
+
+    // Clean up any obviously simplifiable users now.
+    CleanupConstantGlobalUsers(GV, GV->getInitializer(), TD, TLI);
+
+    // If the global is dead now, just nuke it.
+    if (GV->use_empty()) {
+      DEBUG(dbgs() << "   *** Marking constant allowed us to simplify "
+            << "all users and delete global!\n");
+      GV->eraseFromParent();
+      ++NumDeleted;
+    }
+
+    ++NumMarked;
+    return true;
+  } else if (!GV->getInitializer()->getType()->isSingleValueType()) {
+    if (DataLayout *TD = getAnalysisIfAvailable<DataLayout>())
+      if (GlobalVariable *FirstNewGV = SRAGlobal(GV, *TD)) {
+        GVI = FirstNewGV;  // Don't skip the newly produced globals!
+        return true;
+      }
+  } else if (GS.StoredType == GlobalStatus::StoredOnce) {
+    // If the initial value for the global was an undef value, and if only
+    // one other value was stored into it, we can just change the
+    // initializer to be the stored value, then delete all stores to the
+    // global.  This allows us to mark it constant.
+    if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue))
+      if (isa<UndefValue>(GV->getInitializer())) {
+        // Change the initial value here.
+        GV->setInitializer(SOVConstant);
+
+        // Clean up any obviously simplifiable users now.
+        CleanupConstantGlobalUsers(GV, GV->getInitializer(), TD, TLI);
+
+        if (GV->use_empty()) {
+          DEBUG(dbgs() << "   *** Substituting initializer allowed us to "
+                       << "simplify all users and delete global!\n");
+          GV->eraseFromParent();
+          ++NumDeleted;
+        } else {
+          GVI = GV;
+        }
+        ++NumSubstitute;
+        return true;
+      }
+
+    // Try to optimize globals based on the knowledge that only one value
+    // (besides its initializer) is ever stored to the global.
+    if (OptimizeOnceStoredGlobal(GV, GS.StoredOnceValue, GS.Ordering, GVI,
+                                 TD, TLI))
+      return true;
+
+    // Otherwise, if the global was not a boolean, we can shrink it to be a
+    // boolean.
+    if (Constant *SOVConstant = dyn_cast<Constant>(GS.StoredOnceValue)) {
+      if (GS.Ordering == NotAtomic) {
+        if (TryToShrinkGlobalToBoolean(GV, SOVConstant)) {
+          ++NumShrunkToBool;
+          return true;
+        }
+      }
+    }
+  }
+
+  return false;
+}
+
+/// ChangeCalleesToFastCall - Walk all of the direct calls of the specified
+/// function, changing them to FastCC.
+static void ChangeCalleesToFastCall(Function *F) {
+  for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
+    if (isa<BlockAddress>(*UI))
+      continue;
+    CallSite User(cast<Instruction>(*UI));
+    User.setCallingConv(CallingConv::Fast);
+  }
+}
+
+static AttributeSet StripNest(LLVMContext &C, const AttributeSet &Attrs) {
+  for (unsigned i = 0, e = Attrs.getNumSlots(); i != e; ++i) {
+    unsigned Index = Attrs.getSlotIndex(i);
+    if (!Attrs.getSlotAttributes(i).hasAttribute(Index, Attribute::Nest))
+      continue;
+
+    // There can be only one.
+    return Attrs.removeAttribute(C, Index, Attribute::Nest);
+  }
+
+  return Attrs;
+}
+
+static void RemoveNestAttribute(Function *F) {
+  F->setAttributes(StripNest(F->getContext(), F->getAttributes()));
+  for (Value::use_iterator UI = F->use_begin(), E = F->use_end(); UI != E;++UI){
+    if (isa<BlockAddress>(*UI))
+      continue;
+    CallSite User(cast<Instruction>(*UI));
+    User.setAttributes(StripNest(F->getContext(), User.getAttributes()));
+  }
+}
+
+bool GlobalOpt::OptimizeFunctions(Module &M) {
+  bool Changed = false;
+  // Optimize functions.
+  for (Module::iterator FI = M.begin(), E = M.end(); FI != E; ) {
+    Function *F = FI++;
+    // Functions without names cannot be referenced outside this module.
+    if (!F->hasName() && !F->isDeclaration())
+      F->setLinkage(GlobalValue::InternalLinkage);
+    F->removeDeadConstantUsers();
+    if (F->isDefTriviallyDead()) {
+      F->eraseFromParent();
+      Changed = true;
+      ++NumFnDeleted;
+    } else if (F->hasLocalLinkage()) {
+      if (F->getCallingConv() == CallingConv::C && !F->isVarArg() &&
+          !F->hasAddressTaken()) {
+        // If this function has C calling conventions, is not a varargs
+        // function, and is only called directly, promote it to use the Fast
+        // calling convention.
+        F->setCallingConv(CallingConv::Fast);
+        ChangeCalleesToFastCall(F);
+        ++NumFastCallFns;
+        Changed = true;
+      }
+
+      if (F->getAttributes().hasAttrSomewhere(Attribute::Nest) &&
+          !F->hasAddressTaken()) {
+        // The function is not used by a trampoline intrinsic, so it is safe
+        // to remove the 'nest' attribute.
+        RemoveNestAttribute(F);
+        ++NumNestRemoved;
+        Changed = true;
+      }
+    }
+  }
+  return Changed;
+}
+
+bool GlobalOpt::OptimizeGlobalVars(Module &M) {
+  bool Changed = false;
+  for (Module::global_iterator GVI = M.global_begin(), E = M.global_end();
+       GVI != E; ) {
+    GlobalVariable *GV = GVI++;
+    // Global variables without names cannot be referenced outside this module.
+    if (!GV->hasName() && !GV->isDeclaration())
+      GV->setLinkage(GlobalValue::InternalLinkage);
+    // Simplify the initializer.
+    if (GV->hasInitializer())
+      if (ConstantExpr *CE = dyn_cast<ConstantExpr>(GV->getInitializer())) {
+        Constant *New = ConstantFoldConstantExpression(CE, TD, TLI);
+        if (New && New != CE)
+          GV->setInitializer(New);
+      }
+
+    Changed |= ProcessGlobal(GV, GVI);
+  }
+  return Changed;
+}
+
+/// FindGlobalCtors - Find the llvm.global_ctors list, verifying that all
+/// initializers have an init priority of 65535.
+GlobalVariable *GlobalOpt::FindGlobalCtors(Module &M) {
+  GlobalVariable *GV = M.getGlobalVariable("llvm.global_ctors");
+  if (GV == 0) return 0;
+
+  // Verify that the initializer is simple enough for us to handle. We are
+  // only allowed to optimize the initializer if it is unique.
+  if (!GV->hasUniqueInitializer()) return 0;
+
+  if (isa<ConstantAggregateZero>(GV->getInitializer()))
+    return GV;
+  ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
+
+  for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) {
+    if (isa<ConstantAggregateZero>(*i))
+      continue;
+    ConstantStruct *CS = cast<ConstantStruct>(*i);
+    if (isa<ConstantPointerNull>(CS->getOperand(1)))
+      continue;
+
+    // Must have a function or null ptr.
+    if (!isa<Function>(CS->getOperand(1)))
+      return 0;
+
+    // Init priority must be standard.
+    ConstantInt *CI = cast<ConstantInt>(CS->getOperand(0));
+    if (CI->getZExtValue() != 65535)
+      return 0;
+  }
+
+  return GV;
+}
+
+/// ParseGlobalCtors - Given a llvm.global_ctors list that we can understand,
+/// return a list of the functions and null terminator as a vector.
+static std::vector<Function*> ParseGlobalCtors(GlobalVariable *GV) {
+  if (GV->getInitializer()->isNullValue())
+    return std::vector<Function*>();
+  ConstantArray *CA = cast<ConstantArray>(GV->getInitializer());
+  std::vector<Function*> Result;
+  Result.reserve(CA->getNumOperands());
+  for (User::op_iterator i = CA->op_begin(), e = CA->op_end(); i != e; ++i) {
+    ConstantStruct *CS = cast<ConstantStruct>(*i);
+    Result.push_back(dyn_cast<Function>(CS->getOperand(1)));
+  }
+  return Result;
+}
+
+/// InstallGlobalCtors - Given a specified llvm.global_ctors list, install the
+/// specified array, returning the new global to use.
+static GlobalVariable *InstallGlobalCtors(GlobalVariable *GCL,
+                                          const std::vector<Function*> &Ctors) {
+  // If we made a change, reassemble the initializer list.
+  Constant *CSVals[2];
+  CSVals[0] = ConstantInt::get(Type::getInt32Ty(GCL->getContext()), 65535);
+  CSVals[1] = 0;
+
+  StructType *StructTy =
+    cast<StructType>(GCL->getType()->getElementType()->getArrayElementType());
+
+  // Create the new init list.
+  std::vector<Constant*> CAList;
+  for (unsigned i = 0, e = Ctors.size(); i != e; ++i) {
+    if (Ctors[i]) {
+      CSVals[1] = Ctors[i];
+    } else {
+      Type *FTy = FunctionType::get(Type::getVoidTy(GCL->getContext()),
+                                          false);
+      PointerType *PFTy = PointerType::getUnqual(FTy);
+      CSVals[1] = Constant::getNullValue(PFTy);
+      CSVals[0] = ConstantInt::get(Type::getInt32Ty(GCL->getContext()),
+                                   0x7fffffff);
+    }
+    CAList.push_back(ConstantStruct::get(StructTy, CSVals));
+  }
+
+  // Create the array initializer.
+  Constant *CA = ConstantArray::get(ArrayType::get(StructTy,
+                                                   CAList.size()), CAList);
+
+  // If we didn't change the number of elements, don't create a new GV.
+  if (CA->getType() == GCL->getInitializer()->getType()) {
+    GCL->setInitializer(CA);
+    return GCL;
+  }
+
+  // Create the new global and insert it next to the existing list.
+  GlobalVariable *NGV = new GlobalVariable(CA->getType(), GCL->isConstant(),
+                                           GCL->getLinkage(), CA, "",
+                                           GCL->getThreadLocalMode());
+  GCL->getParent()->getGlobalList().insert(GCL, NGV);
+  NGV->takeName(GCL);
+
+  // Nuke the old list, replacing any uses with the new one.
+  if (!GCL->use_empty()) {
+    Constant *V = NGV;
+    if (V->getType() != GCL->getType())
+      V = ConstantExpr::getBitCast(V, GCL->getType());
+    GCL->replaceAllUsesWith(V);
+  }
+  GCL->eraseFromParent();
+
+  if (Ctors.size())
+    return NGV;
+  else
+    return 0;
+}
+
+
+static inline bool
+isSimpleEnoughValueToCommit(Constant *C,
+                            SmallPtrSet<Constant*, 8> &SimpleConstants,
+                            const DataLayout *TD);
+
+
+/// isSimpleEnoughValueToCommit - Return true if the specified constant can be
+/// handled by the code generator.  We don't want to generate something like:
+///   void *X = &X/42;
+/// because the code generator doesn't have a relocation that can handle that.
+///
+/// This function should be called if C was not found (but just got inserted)
+/// in SimpleConstants to avoid having to rescan the same constants all the
+/// time.
+static bool isSimpleEnoughValueToCommitHelper(Constant *C,
+                                   SmallPtrSet<Constant*, 8> &SimpleConstants,
+                                   const DataLayout *TD) {
+  // Simple integer, undef, constant aggregate zero, global addresses, etc are
+  // all supported.
+  if (C->getNumOperands() == 0 || isa<BlockAddress>(C) ||
+      isa<GlobalValue>(C))
+    return true;
+
+  // Aggregate values are safe if all their elements are.
+  if (isa<ConstantArray>(C) || isa<ConstantStruct>(C) ||
+      isa<ConstantVector>(C)) {
+    for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i) {
+      Constant *Op = cast<Constant>(C->getOperand(i));
+      if (!isSimpleEnoughValueToCommit(Op, SimpleConstants, TD))
+        return false;
+    }
+    return true;
+  }
+
+  // We don't know exactly what relocations are allowed in constant expressions,
+  // so we allow &global+constantoffset, which is safe and uniformly supported
+  // across targets.
+  ConstantExpr *CE = cast<ConstantExpr>(C);
+  switch (CE->getOpcode()) {
+  case Instruction::BitCast:
+    // Bitcast is fine if the casted value is fine.
+    return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD);
+
+  case Instruction::IntToPtr:
+  case Instruction::PtrToInt:
+    // int <=> ptr is fine if the int type is the same size as the
+    // pointer type.
+    if (!TD || TD->getTypeSizeInBits(CE->getType()) !=
+               TD->getTypeSizeInBits(CE->getOperand(0)->getType()))
+      return false;
+    return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD);
+
+  // GEP is fine if it is simple + constant offset.
+  case Instruction::GetElementPtr:
+    for (unsigned i = 1, e = CE->getNumOperands(); i != e; ++i)
+      if (!isa<ConstantInt>(CE->getOperand(i)))
+        return false;
+    return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD);
+
+  case Instruction::Add:
+    // We allow simple+cst.
+    if (!isa<ConstantInt>(CE->getOperand(1)))
+      return false;
+    return isSimpleEnoughValueToCommit(CE->getOperand(0), SimpleConstants, TD);
+  }
+  return false;
+}
+
+static inline bool
+isSimpleEnoughValueToCommit(Constant *C,
+                            SmallPtrSet<Constant*, 8> &SimpleConstants,
+                            const DataLayout *TD) {
+  // If we already checked this constant, we win.
+  if (!SimpleConstants.insert(C)) return true;
+  // Check the constant.
+  return isSimpleEnoughValueToCommitHelper(C, SimpleConstants, TD);
+}
+
+
+/// isSimpleEnoughPointerToCommit - Return true if this constant is simple
+/// enough for us to understand.  In particular, if it is a cast to anything
+/// other than from one pointer type to another pointer type, we punt.
+/// We basically just support direct accesses to globals and GEP's of
+/// globals.  This should be kept up to date with CommitValueTo.
+static bool isSimpleEnoughPointerToCommit(Constant *C) {
+  // Conservatively, avoid aggregate types. This is because we don't
+  // want to worry about them partially overlapping other stores.
+  if (!cast<PointerType>(C->getType())->getElementType()->isSingleValueType())
+    return false;
+
+  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(C))
+    // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or
+    // external globals.
+    return GV->hasUniqueInitializer();
+
+  if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
+    // Handle a constantexpr gep.
+    if (CE->getOpcode() == Instruction::GetElementPtr &&
+        isa<GlobalVariable>(CE->getOperand(0)) &&
+        cast<GEPOperator>(CE)->isInBounds()) {
+      GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
+      // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or
+      // external globals.
+      if (!GV->hasUniqueInitializer())
+        return false;
+
+      // The first index must be zero.
+      ConstantInt *CI = dyn_cast<ConstantInt>(*llvm::next(CE->op_begin()));
+      if (!CI || !CI->isZero()) return false;
+
+      // The remaining indices must be compile-time known integers within the
+      // notional bounds of the corresponding static array types.
+      if (!CE->isGEPWithNoNotionalOverIndexing())
+        return false;
+
+      return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
+
+    // A constantexpr bitcast from a pointer to another pointer is a no-op,
+    // and we know how to evaluate it by moving the bitcast from the pointer
+    // operand to the value operand.
+    } else if (CE->getOpcode() == Instruction::BitCast &&
+               isa<GlobalVariable>(CE->getOperand(0))) {
+      // Do not allow weak/*_odr/linkonce/dllimport/dllexport linkage or
+      // external globals.
+      return cast<GlobalVariable>(CE->getOperand(0))->hasUniqueInitializer();
+    }
+  }
+
+  return false;
+}
+
+/// EvaluateStoreInto - Evaluate a piece of a constantexpr store into a global
+/// initializer.  This returns 'Init' modified to reflect 'Val' stored into it.
+/// At this point, the GEP operands of Addr [0, OpNo) have been stepped into.
+static Constant *EvaluateStoreInto(Constant *Init, Constant *Val,
+                                   ConstantExpr *Addr, unsigned OpNo) {
+  // Base case of the recursion.
+  if (OpNo == Addr->getNumOperands()) {
+    assert(Val->getType() == Init->getType() && "Type mismatch!");
+    return Val;
+  }
+
+  SmallVector<Constant*, 32> Elts;
+  if (StructType *STy = dyn_cast<StructType>(Init->getType())) {
+    // Break up the constant into its elements.
+    for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
+      Elts.push_back(Init->getAggregateElement(i));
+
+    // Replace the element that we are supposed to.
+    ConstantInt *CU = cast<ConstantInt>(Addr->getOperand(OpNo));
+    unsigned Idx = CU->getZExtValue();
+    assert(Idx < STy->getNumElements() && "Struct index out of range!");
+    Elts[Idx] = EvaluateStoreInto(Elts[Idx], Val, Addr, OpNo+1);
+
+    // Return the modified struct.
+    return ConstantStruct::get(STy, Elts);
+  }
+
+  ConstantInt *CI = cast<ConstantInt>(Addr->getOperand(OpNo));
+  SequentialType *InitTy = cast<SequentialType>(Init->getType());
+
+  uint64_t NumElts;
+  if (ArrayType *ATy = dyn_cast<ArrayType>(InitTy))
+    NumElts = ATy->getNumElements();
+  else
+    NumElts = InitTy->getVectorNumElements();
+
+  // Break up the array into elements.
+  for (uint64_t i = 0, e = NumElts; i != e; ++i)
+    Elts.push_back(Init->getAggregateElement(i));
+
+  assert(CI->getZExtValue() < NumElts);
+  Elts[CI->getZExtValue()] =
+    EvaluateStoreInto(Elts[CI->getZExtValue()], Val, Addr, OpNo+1);
+
+  if (Init->getType()->isArrayTy())
+    return ConstantArray::get(cast<ArrayType>(InitTy), Elts);
+  return ConstantVector::get(Elts);
+}
+
+/// CommitValueTo - We have decided that Addr (which satisfies the predicate
+/// isSimpleEnoughPointerToCommit) should get Val as its value.  Make it happen.
+static void CommitValueTo(Constant *Val, Constant *Addr) {
+  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Addr)) {
+    assert(GV->hasInitializer());
+    GV->setInitializer(Val);
+    return;
+  }
+
+  ConstantExpr *CE = cast<ConstantExpr>(Addr);
+  GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
+  GV->setInitializer(EvaluateStoreInto(GV->getInitializer(), Val, CE, 2));
+}
+
+namespace {
+
+/// Evaluator - This class evaluates LLVM IR, producing the Constant
+/// representing each SSA instruction.  Changes to global variables are stored
+/// in a mapping that can be iterated over after the evaluation is complete.
+/// Once an evaluation call fails, the evaluation object should not be reused.
+class Evaluator {
+public:
+  Evaluator(const DataLayout *TD, const TargetLibraryInfo *TLI)
+    : TD(TD), TLI(TLI) {
+    ValueStack.push_back(new DenseMap<Value*, Constant*>);
+  }
+
+  ~Evaluator() {
+    DeleteContainerPointers(ValueStack);
+    while (!AllocaTmps.empty()) {
+      GlobalVariable *Tmp = AllocaTmps.back();
+      AllocaTmps.pop_back();
+
+      // If there are still users of the alloca, the program is doing something
+      // silly, e.g. storing the address of the alloca somewhere and using it
+      // later.  Since this is undefined, we'll just make it be null.
+      if (!Tmp->use_empty())
+        Tmp->replaceAllUsesWith(Constant::getNullValue(Tmp->getType()));
+      delete Tmp;
+    }
+  }
+
+  /// EvaluateFunction - Evaluate a call to function F, returning true if
+  /// successful, false if we can't evaluate it.  ActualArgs contains the formal
+  /// arguments for the function.
+  bool EvaluateFunction(Function *F, Constant *&RetVal,
+                        const SmallVectorImpl<Constant*> &ActualArgs);
+
+  /// EvaluateBlock - Evaluate all instructions in block BB, returning true if
+  /// successful, false if we can't evaluate it.  NewBB returns the next BB that
+  /// control flows into, or null upon return.
+  bool EvaluateBlock(BasicBlock::iterator CurInst, BasicBlock *&NextBB);
+
+  Constant *getVal(Value *V) {
+    if (Constant *CV = dyn_cast<Constant>(V)) return CV;
+    Constant *R = ValueStack.back()->lookup(V);
+    assert(R && "Reference to an uncomputed value!");
+    return R;
+  }
+
+  void setVal(Value *V, Constant *C) {
+    ValueStack.back()->operator[](V) = C;
+  }
+
+  const DenseMap<Constant*, Constant*> &getMutatedMemory() const {
+    return MutatedMemory;
+  }
+
+  const SmallPtrSet<GlobalVariable*, 8> &getInvariants() const {
+    return Invariants;
+  }
+
+private:
+  Constant *ComputeLoadResult(Constant *P);
+
+  /// ValueStack - As we compute SSA register values, we store their contents
+  /// here. The back of the vector contains the current function and the stack
+  /// contains the values in the calling frames.
+  SmallVector<DenseMap<Value*, Constant*>*, 4> ValueStack;
+
+  /// CallStack - This is used to detect recursion.  In pathological situations
+  /// we could hit exponential behavior, but at least there is nothing
+  /// unbounded.
+  SmallVector<Function*, 4> CallStack;
+
+  /// MutatedMemory - For each store we execute, we update this map.  Loads
+  /// check this to get the most up-to-date value.  If evaluation is successful,
+  /// this state is committed to the process.
+  DenseMap<Constant*, Constant*> MutatedMemory;
+
+  /// AllocaTmps - To 'execute' an alloca, we create a temporary global variable
+  /// to represent its body.  This vector is needed so we can delete the
+  /// temporary globals when we are done.
+  SmallVector<GlobalVariable*, 32> AllocaTmps;
+
+  /// Invariants - These global variables have been marked invariant by the
+  /// static constructor.
+  SmallPtrSet<GlobalVariable*, 8> Invariants;
+
+  /// SimpleConstants - These are constants we have checked and know to be
+  /// simple enough to live in a static initializer of a global.
+  SmallPtrSet<Constant*, 8> SimpleConstants;
+
+  const DataLayout *TD;
+  const TargetLibraryInfo *TLI;
+};
+
+}  // anonymous namespace
+
+/// ComputeLoadResult - Return the value that would be computed by a load from
+/// P after the stores reflected by 'memory' have been performed.  If we can't
+/// decide, return null.
+Constant *Evaluator::ComputeLoadResult(Constant *P) {
+  // If this memory location has been recently stored, use the stored value: it
+  // is the most up-to-date.
+  DenseMap<Constant*, Constant*>::const_iterator I = MutatedMemory.find(P);
+  if (I != MutatedMemory.end()) return I->second;
+
+  // Access it.
+  if (GlobalVariable *GV = dyn_cast<GlobalVariable>(P)) {
+    if (GV->hasDefinitiveInitializer())
+      return GV->getInitializer();
+    return 0;
+  }
+
+  // Handle a constantexpr getelementptr.
+  if (ConstantExpr *CE = dyn_cast<ConstantExpr>(P))
+    if (CE->getOpcode() == Instruction::GetElementPtr &&
+        isa<GlobalVariable>(CE->getOperand(0))) {
+      GlobalVariable *GV = cast<GlobalVariable>(CE->getOperand(0));
+      if (GV->hasDefinitiveInitializer())
+        return ConstantFoldLoadThroughGEPConstantExpr(GV->getInitializer(), CE);
+    }
+
+  return 0;  // don't know how to evaluate.
+}
+
+/// EvaluateBlock - Evaluate all instructions in block BB, returning true if
+/// successful, false if we can't evaluate it.  NewBB returns the next BB that
+/// control flows into, or null upon return.
+bool Evaluator::EvaluateBlock(BasicBlock::iterator CurInst,
+                              BasicBlock *&NextBB) {
+  // This is the main evaluation loop.
+  while (1) {
+    Constant *InstResult = 0;
+
+    DEBUG(dbgs() << "Evaluating Instruction: " << *CurInst << "\n");
+
+    if (StoreInst *SI = dyn_cast<StoreInst>(CurInst)) {
+      if (!SI->isSimple()) {
+        DEBUG(dbgs() << "Store is not simple! Can not evaluate.\n");
+        return false;  // no volatile/atomic accesses.
+      }
+      Constant *Ptr = getVal(SI->getOperand(1));
+      if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) {
+        DEBUG(dbgs() << "Folding constant ptr expression: " << *Ptr);
+        Ptr = ConstantFoldConstantExpression(CE, TD, TLI);
+        DEBUG(dbgs() << "; To: " << *Ptr << "\n");
+      }
+      if (!isSimpleEnoughPointerToCommit(Ptr)) {
+        // If this is too complex for us to commit, reject it.
+        DEBUG(dbgs() << "Pointer is too complex for us to evaluate store.");
+        return false;
+      }
+
+      Constant *Val = getVal(SI->getOperand(0));
+
+      // If this might be too difficult for the backend to handle (e.g. the addr
+      // of one global variable divided by another) then we can't commit it.
+      if (!isSimpleEnoughValueToCommit(Val, SimpleConstants, TD)) {
+        DEBUG(dbgs() << "Store value is too complex to evaluate store. " << *Val
+              << "\n");
+        return false;
+      }
+
+      if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) {
+        if (CE->getOpcode() == Instruction::BitCast) {
+          DEBUG(dbgs() << "Attempting to resolve bitcast on constant ptr.\n");
+          // If we're evaluating a store through a bitcast, then we need
+          // to pull the bitcast off the pointer type and push it onto the
+          // stored value.
+          Ptr = CE->getOperand(0);
+
+          Type *NewTy = cast<PointerType>(Ptr->getType())->getElementType();
+
+          // In order to push the bitcast onto the stored value, a bitcast
+          // from NewTy to Val's type must be legal.  If it's not, we can try
+          // introspecting NewTy to find a legal conversion.
+          while (!Val->getType()->canLosslesslyBitCastTo(NewTy)) {
+            // If NewTy is a struct, we can convert the pointer to the struct
+            // into a pointer to its first member.
+            // FIXME: This could be extended to support arrays as well.
+            if (StructType *STy = dyn_cast<StructType>(NewTy)) {
+              NewTy = STy->getTypeAtIndex(0U);
+
+              IntegerType *IdxTy = IntegerType::get(NewTy->getContext(), 32);
+              Constant *IdxZero = ConstantInt::get(IdxTy, 0, false);
+              Constant * const IdxList[] = {IdxZero, IdxZero};
+
+              Ptr = ConstantExpr::getGetElementPtr(Ptr, IdxList);
+              if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr))
+                Ptr = ConstantFoldConstantExpression(CE, TD, TLI);
+
+            // If we can't improve the situation by introspecting NewTy,
+            // we have to give up.
+            } else {
+              DEBUG(dbgs() << "Failed to bitcast constant ptr, can not "
+                    "evaluate.\n");
+              return false;
+            }
+          }
+
+          // If we found compatible types, go ahead and push the bitcast
+          // onto the stored value.
+          Val = ConstantExpr::getBitCast(Val, NewTy);
+
+          DEBUG(dbgs() << "Evaluated bitcast: " << *Val << "\n");
+        }
+      }
+
+      MutatedMemory[Ptr] = Val;
+    } else if (BinaryOperator *BO = dyn_cast<BinaryOperator>(CurInst)) {
+      InstResult = ConstantExpr::get(BO->getOpcode(),
+                                     getVal(BO->getOperand(0)),
+                                     getVal(BO->getOperand(1)));
+      DEBUG(dbgs() << "Found a BinaryOperator! Simplifying: " << *InstResult
+            << "\n");
+    } else if (CmpInst *CI = dyn_cast<CmpInst>(CurInst)) {
+      InstResult = ConstantExpr::getCompare(CI->getPredicate(),
+                                            getVal(CI->getOperand(0)),
+                                            getVal(CI->getOperand(1)));
+      DEBUG(dbgs() << "Found a CmpInst! Simplifying: " << *InstResult
+            << "\n");
+    } else if (CastInst *CI = dyn_cast<CastInst>(CurInst)) {
+      InstResult = ConstantExpr::getCast(CI->getOpcode(),
+                                         getVal(CI->getOperand(0)),
+                                         CI->getType());
+      DEBUG(dbgs() << "Found a Cast! Simplifying: " << *InstResult
+            << "\n");
+    } else if (SelectInst *SI = dyn_cast<SelectInst>(CurInst)) {
+      InstResult = ConstantExpr::getSelect(getVal(SI->getOperand(0)),
+                                           getVal(SI->getOperand(1)),
+                                           getVal(SI->getOperand(2)));
+      DEBUG(dbgs() << "Found a Select! Simplifying: " << *InstResult
+            << "\n");
+    } else if (GetElementPtrInst *GEP = dyn_cast<GetElementPtrInst>(CurInst)) {
+      Constant *P = getVal(GEP->getOperand(0));
+      SmallVector<Constant*, 8> GEPOps;
+      for (User::op_iterator i = GEP->op_begin() + 1, e = GEP->op_end();
+           i != e; ++i)
+        GEPOps.push_back(getVal(*i));
+      InstResult =
+        ConstantExpr::getGetElementPtr(P, GEPOps,
+                                       cast<GEPOperator>(GEP)->isInBounds());
+      DEBUG(dbgs() << "Found a GEP! Simplifying: " << *InstResult
+            << "\n");
+    } else if (LoadInst *LI = dyn_cast<LoadInst>(CurInst)) {
+
+      if (!LI->isSimple()) {
+        DEBUG(dbgs() << "Found a Load! Not a simple load, can not evaluate.\n");
+        return false;  // no volatile/atomic accesses.
+      }
+
+      Constant *Ptr = getVal(LI->getOperand(0));
+      if (ConstantExpr *CE = dyn_cast<ConstantExpr>(Ptr)) {
+        Ptr = ConstantFoldConstantExpression(CE, TD, TLI);
+        DEBUG(dbgs() << "Found a constant pointer expression, constant "
+              "folding: " << *Ptr << "\n");
+      }
+      InstResult = ComputeLoadResult(Ptr);
+      if (InstResult == 0) {
+        DEBUG(dbgs() << "Failed to compute load result. Can not evaluate load."
+              "\n");
+        return false; // Could not evaluate load.
+      }
+
+      DEBUG(dbgs() << "Evaluated load: " << *InstResult << "\n");
+    } else if (AllocaInst *AI = dyn_cast<AllocaInst>(CurInst)) {
+      if (AI->isArrayAllocation()) {
+        DEBUG(dbgs() << "Found an array alloca. Can not evaluate.\n");
+        return false;  // Cannot handle array allocs.
+      }
+      Type *Ty = AI->getType()->getElementType();
+      AllocaTmps.push_back(new GlobalVariable(Ty, false,
+                                              GlobalValue::InternalLinkage,
+                                              UndefValue::get(Ty),
+                                              AI->getName()));
+      InstResult = AllocaTmps.back();
+      DEBUG(dbgs() << "Found an alloca. Result: " << *InstResult << "\n");
+    } else if (isa<CallInst>(CurInst) || isa<InvokeInst>(CurInst)) {
+      CallSite CS(CurInst);
+
+      // Debug info can safely be ignored here.
+      if (isa<DbgInfoIntrinsic>(CS.getInstruction())) {
+        DEBUG(dbgs() << "Ignoring debug info.\n");
+        ++CurInst;
+        continue;
+      }
+
+      // Cannot handle inline asm.
+      if (isa<InlineAsm>(CS.getCalledValue())) {
+        DEBUG(dbgs() << "Found inline asm, can not evaluate.\n");
+        return false;
+      }
+
+      if (IntrinsicInst *II = dyn_cast<IntrinsicInst>(CS.getInstruction())) {
+        if (MemSetInst *MSI = dyn_cast<MemSetInst>(II)) {
+          if (MSI->isVolatile()) {
+            DEBUG(dbgs() << "Can not optimize a volatile memset " <<
+                  "intrinsic.\n");
+            return false;
+          }
+          Constant *Ptr = getVal(MSI->getDest());
+          Constant *Val = getVal(MSI->getValue());
+          Constant *DestVal = ComputeLoadResult(getVal(Ptr));
+          if (Val->isNullValue() && DestVal && DestVal->isNullValue()) {
+            // This memset is a no-op.
+            DEBUG(dbgs() << "Ignoring no-op memset.\n");
+            ++CurInst;
+            continue;
+          }
+        }
+
+        if (II->getIntrinsicID() == Intrinsic::lifetime_start ||
+            II->getIntrinsicID() == Intrinsic::lifetime_end) {
+          DEBUG(dbgs() << "Ignoring lifetime intrinsic.\n");
+          ++CurInst;
+          continue;
+        }
+
+        if (II->getIntrinsicID() == Intrinsic::invariant_start) {
+          // We don't insert an entry into Values, as it doesn't have a
+          // meaningful return value.
+          if (!II->use_empty()) {
+            DEBUG(dbgs() << "Found unused invariant_start. Cant evaluate.\n");
+            return false;
+          }
+          ConstantInt *Size = cast<ConstantInt>(II->getArgOperand(0));
+          Value *PtrArg = getVal(II->getArgOperand(1));
+          Value *Ptr = PtrArg->stripPointerCasts();
+          if (GlobalVariable *GV = dyn_cast<GlobalVariable>(Ptr)) {
+            Type *ElemTy = cast<PointerType>(GV->getType())->getElementType();
+            if (TD && !Size->isAllOnesValue() &&
+                Size->getValue().getLimitedValue() >=
+                TD->getTypeStoreSize(ElemTy)) {
+              Invariants.insert(GV);
+              DEBUG(dbgs() << "Found a global var that is an invariant: " << *GV
+                    << "\n");
+            } else {
+              DEBUG(dbgs() << "Found a global var, but can not treat it as an "
+                    "invariant.\n");
+            }
+          }
+          // Continue even if we do nothing.
+          ++CurInst;
+          continue;
+        }
+
+        DEBUG(dbgs() << "Unknown intrinsic. Can not evaluate.\n");
+        return false;
+      }
+
+      // Resolve function pointers.
+      Function *Callee = dyn_cast<Function>(getVal(CS.getCalledValue()));
+      if (!Callee || Callee->mayBeOverridden()) {
+        DEBUG(dbgs() << "Can not resolve function pointer.\n");
+        return false;  // Cannot resolve.
+      }
+
+      SmallVector<Constant*, 8> Formals;
+      for (User::op_iterator i = CS.arg_begin(), e = CS.arg_end(); i != e; ++i)
+        Formals.push_back(getVal(*i));
+
+      if (Callee->isDeclaration()) {
+        // If this is a function we can constant fold, do it.
+        if (Constant *C = ConstantFoldCall(Callee, Formals, TLI)) {
+          InstResult = C;
+          DEBUG(dbgs() << "Constant folded function call. Result: " <<
+                *InstResult << "\n");
+        } else {
+          DEBUG(dbgs() << "Can not constant fold function call.\n");
+          return false;
+        }
+      } else {
+        if (Callee->getFunctionType()->isVarArg()) {
+          DEBUG(dbgs() << "Can not constant fold vararg function call.\n");
+          return false;
+        }
+
+        Constant *RetVal = 0;
+        // Execute the call, if successful, use the return value.
+        ValueStack.push_back(new DenseMap<Value*, Constant*>);
+        if (!EvaluateFunction(Callee, RetVal, Formals)) {
+          DEBUG(dbgs() << "Failed to evaluate function.\n");
+          return false;
+        }
+        delete ValueStack.pop_back_val();
+        InstResult = RetVal;
+
+        if (InstResult != NULL) {
+          DEBUG(dbgs() << "Successfully evaluated function. Result: " <<
+                InstResult << "\n\n");
+        } else {
+          DEBUG(dbgs() << "Successfully evaluated function. Result: 0\n\n");
+        }
+      }
+    } else if (isa<TerminatorInst>(CurInst)) {
+      DEBUG(dbgs() << "Found a terminator instruction.\n");
+
+      if (BranchInst *BI = dyn_cast<BranchInst>(CurInst)) {
+        if (BI->isUnconditional()) {
+          NextBB = BI->getSuccessor(0);
+        } else {
+          ConstantInt *Cond =
+            dyn_cast<ConstantInt>(getVal(BI->getCondition()));
+          if (!Cond) return false;  // Cannot determine.
+
+          NextBB = BI->getSuccessor(!Cond->getZExtValue());
+        }
+      } else if (SwitchInst *SI = dyn_cast<SwitchInst>(CurInst)) {
+        ConstantInt *Val =
+          dyn_cast<ConstantInt>(getVal(SI->getCondition()));
+        if (!Val) return false;  // Cannot determine.
+        NextBB = SI->findCaseValue(Val).getCaseSuccessor();
+      } else if (IndirectBrInst *IBI = dyn_cast<IndirectBrInst>(CurInst)) {
+        Value *Val = getVal(IBI->getAddress())->stripPointerCasts();
+        if (BlockAddress *BA = dyn_cast<BlockAddress>(Val))
+          NextBB = BA->getBasicBlock();
+        else
+          return false;  // Cannot determine.
+      } else if (isa<ReturnInst>(CurInst)) {
+        NextBB = 0;
+      } else {
+        // invoke, unwind, resume, unreachable.
+        DEBUG(dbgs() << "Can not handle terminator.");
+        return false;  // Cannot handle this terminator.
+      }
+
+      // We succeeded at evaluating this block!
+      DEBUG(dbgs() << "Successfully evaluated block.\n");
+      return true;
+    } else {
+      // Did not know how to evaluate this!
+      DEBUG(dbgs() << "Failed to evaluate block due to unhandled instruction."
+            "\n");
+      return false;
+    }
+
+    if (!CurInst->use_empty()) {
+      if (ConstantExpr *CE = dyn_cast<ConstantExpr>(InstResult))
+        InstResult = ConstantFoldConstantExpression(CE, TD, TLI);
+
+      setVal(CurInst, InstResult);
+    }
+
+    // If we just processed an invoke, we finished evaluating the block.
+    if (InvokeInst *II = dyn_cast<InvokeInst>(CurInst)) {
+      NextBB = II->getNormalDest();
+      DEBUG(dbgs() << "Found an invoke instruction. Finished Block.\n\n");
+      return true;
+    }
+
+    // Advance program counter.
+    ++CurInst;
+  }
+}
+
+/// EvaluateFunction - Evaluate a call to function F, returning true if
+/// successful, false if we can't evaluate it.  ActualArgs contains the formal
+/// arguments for the function.
+bool Evaluator::EvaluateFunction(Function *F, Constant *&RetVal,
+                                 const SmallVectorImpl<Constant*> &ActualArgs) {
+  // Check to see if this function is already executing (recursion).  If so,
+  // bail out.  TODO: we might want to accept limited recursion.
+  if (std::find(CallStack.begin(), CallStack.end(), F) != CallStack.end())
+    return false;
+
+  CallStack.push_back(F);
+
+  // Initialize arguments to the incoming values specified.
+  unsigned ArgNo = 0;
+  for (Function::arg_iterator AI = F->arg_begin(), E = F->arg_end(); AI != E;
+       ++AI, ++ArgNo)
+    setVal(AI, ActualArgs[ArgNo]);
+
+  // ExecutedBlocks - We only handle non-looping, non-recursive code.  As such,
+  // we can only evaluate any one basic block at most once.  This set keeps
+  // track of what we have executed so we can detect recursive cases etc.
+  SmallPtrSet<BasicBlock*, 32> ExecutedBlocks;
+
+  // CurBB - The current basic block we're evaluating.
+  BasicBlock *CurBB = F->begin();
+
+  BasicBlock::iterator CurInst = CurBB->begin();
+
+  while (1) {
+    BasicBlock *NextBB = 0; // Initialized to avoid compiler warnings.
+    DEBUG(dbgs() << "Trying to evaluate BB: " << *CurBB << "\n");
+
+    if (!EvaluateBlock(CurInst, NextBB))
+      return false;
+
+    if (NextBB == 0) {
+      // Successfully running until there's no next block means that we found
+      // the return.  Fill it the return value and pop the call stack.
+      ReturnInst *RI = cast<ReturnInst>(CurBB->getTerminator());
+      if (RI->getNumOperands())
+        RetVal = getVal(RI->getOperand(0));
+      CallStack.pop_back();
+      return true;
+    }
+
+    // Okay, we succeeded in evaluating this control flow.  See if we have
+    // executed the new block before.  If so, we have a looping function,
+    // which we cannot evaluate in reasonable time.
+    if (!ExecutedBlocks.insert(NextBB))
+      return false;  // looped!
+
+    // Okay, we have never been in this block before.  Check to see if there
+    // are any PHI nodes.  If so, evaluate them with information about where
+    // we came from.
+    PHINode *PN = 0;
+    for (CurInst = NextBB->begin();
+         (PN = dyn_cast<PHINode>(CurInst)); ++CurInst)
+      setVal(PN, getVal(PN->getIncomingValueForBlock(CurBB)));
+
+    // Advance to the next block.
+    CurBB = NextBB;
+  }
+}
+
+/// EvaluateStaticConstructor - Evaluate static constructors in the function, if
+/// we can.  Return true if we can, false otherwise.
+static bool EvaluateStaticConstructor(Function *F, const DataLayout *TD,
+                                      const TargetLibraryInfo *TLI) {
+  // Call the function.
+  Evaluator Eval(TD, TLI);
+  Constant *RetValDummy;
+  bool EvalSuccess = Eval.EvaluateFunction(F, RetValDummy,
+                                           SmallVector<Constant*, 0>());
+
+  if (EvalSuccess) {
+    // We succeeded at evaluation: commit the result.
+    DEBUG(dbgs() << "FULLY EVALUATED GLOBAL CTOR FUNCTION '"
+          << F->getName() << "' to " << Eval.getMutatedMemory().size()
+          << " stores.\n");
+    for (DenseMap<Constant*, Constant*>::const_iterator I =
+           Eval.getMutatedMemory().begin(), E = Eval.getMutatedMemory().end();
+         I != E; ++I)
+      CommitValueTo(I->second, I->first);
+    for (SmallPtrSet<GlobalVariable*, 8>::const_iterator I =
+           Eval.getInvariants().begin(), E = Eval.getInvariants().end();
+         I != E; ++I)
+      (*I)->setConstant(true);
+  }
+
+  return EvalSuccess;
+}
+
+/// OptimizeGlobalCtorsList - Simplify and evaluation global ctors if possible.
+/// Return true if anything changed.
+bool GlobalOpt::OptimizeGlobalCtorsList(GlobalVariable *&GCL) {
+  std::vector<Function*> Ctors = ParseGlobalCtors(GCL);
+  bool MadeChange = false;
+  if (Ctors.empty()) return false;
+
+  // Loop over global ctors, optimizing them when we can.
+  for (unsigned i = 0; i != Ctors.size(); ++i) {
+    Function *F = Ctors[i];
+    // Found a null terminator in the middle of the list, prune off the rest of
+    // the list.
+    if (F == 0) {
+      if (i != Ctors.size()-1) {
+        Ctors.resize(i+1);
+        MadeChange = true;
+      }
+      break;
+    }
+    DEBUG(dbgs() << "Optimizing Global Constructor: " << *F << "\n");
+
+    // We cannot simplify external ctor functions.
+    if (F->empty()) continue;
+
+    // If we can evaluate the ctor at compile time, do.
+    if (EvaluateStaticConstructor(F, TD, TLI)) {
+      Ctors.erase(Ctors.begin()+i);
+      MadeChange = true;
+      --i;
+      ++NumCtorsEvaluated;
+      continue;
+    }
+  }
+
+  if (!MadeChange) return false;
+
+  GCL = InstallGlobalCtors(GCL, Ctors);
+  return true;
+}
+
+static int compareNames(Constant *const *A, Constant *const *B) {
+  return (*A)->getName().compare((*B)->getName());
+}
+
+static void setUsedInitializer(GlobalVariable &V,
+                               SmallPtrSet<GlobalValue *, 8> Init) {
+  if (Init.empty()) {
+    V.eraseFromParent();
+    return;
+  }
+
+  SmallVector<llvm::Constant *, 8> UsedArray;
+  PointerType *Int8PtrTy = Type::getInt8PtrTy(V.getContext());
+
+  for (SmallPtrSet<GlobalValue *, 8>::iterator I = Init.begin(), E = Init.end();
+       I != E; ++I) {
+    Constant *Cast = llvm::ConstantExpr::getBitCast(*I, Int8PtrTy);
+    UsedArray.push_back(Cast);
+  }
+  // Sort to get deterministic order.
+  array_pod_sort(UsedArray.begin(), UsedArray.end(), compareNames);
+  ArrayType *ATy = ArrayType::get(Int8PtrTy, UsedArray.size());
+
+  Module *M = V.getParent();
+  V.removeFromParent();
+  GlobalVariable *NV =
+      new GlobalVariable(*M, ATy, false, llvm::GlobalValue::AppendingLinkage,
+                         llvm::ConstantArray::get(ATy, UsedArray), "");
+  NV->takeName(&V);
+  NV->setSection("llvm.metadata");
+  delete &V;
+}
+
+namespace {
+/// \brief An easy to access representation of llvm.used and llvm.compiler.used.
+class LLVMUsed {
+  SmallPtrSet<GlobalValue *, 8> Used;
+  SmallPtrSet<GlobalValue *, 8> CompilerUsed;
+  GlobalVariable *UsedV;
+  GlobalVariable *CompilerUsedV;
+
+public:
+  LLVMUsed(Module &M) {
+    UsedV = collectUsedGlobalVariables(M, Used, false);
+    CompilerUsedV = collectUsedGlobalVariables(M, CompilerUsed, true);
+  }
+  typedef SmallPtrSet<GlobalValue *, 8>::iterator iterator;
+  iterator usedBegin() { return Used.begin(); }
+  iterator usedEnd() { return Used.end(); }
+  iterator compilerUsedBegin() { return CompilerUsed.begin(); }
+  iterator compilerUsedEnd() { return CompilerUsed.end(); }
+  bool usedCount(GlobalValue *GV) const { return Used.count(GV); }
+  bool compilerUsedCount(GlobalValue *GV) const {
+    return CompilerUsed.count(GV);
+  }
+  bool usedErase(GlobalValue *GV) { return Used.erase(GV); }
+  bool compilerUsedErase(GlobalValue *GV) { return CompilerUsed.erase(GV); }
+  bool usedInsert(GlobalValue *GV) { return Used.insert(GV); }
+  bool compilerUsedInsert(GlobalValue *GV) { return CompilerUsed.insert(GV); }
+
+  void syncVariablesAndSets() {
+    if (UsedV)
+      setUsedInitializer(*UsedV, Used);
+    if (CompilerUsedV)
+      setUsedInitializer(*CompilerUsedV, CompilerUsed);
+  }
+};
+}
+
+static bool hasUseOtherThanLLVMUsed(GlobalAlias &GA, const LLVMUsed &U) {
+  if (GA.use_empty()) // No use at all.
+    return false;
+
+  assert((!U.usedCount(&GA) || !U.compilerUsedCount(&GA)) &&
+         "We should have removed the duplicated "
+         "element from llvm.compiler.used");
+  if (!GA.hasOneUse())
+    // Strictly more than one use. So at least one is not in llvm.used and
+    // llvm.compiler.used.
+    return true;
+
+  // Exactly one use. Check if it is in llvm.used or llvm.compiler.used.
+  return !U.usedCount(&GA) && !U.compilerUsedCount(&GA);
+}
+
+static bool hasMoreThanOneUseOtherThanLLVMUsed(GlobalValue &V,
+                                               const LLVMUsed &U) {
+  unsigned N = 2;
+  assert((!U.usedCount(&V) || !U.compilerUsedCount(&V)) &&
+         "We should have removed the duplicated "
+         "element from llvm.compiler.used");
+  if (U.usedCount(&V) || U.compilerUsedCount(&V))
+    ++N;
+  return V.hasNUsesOrMore(N);
+}
+
+static bool mayHaveOtherReferences(GlobalAlias &GA, const LLVMUsed &U) {
+  if (!GA.hasLocalLinkage())
+    return true;
+
+  return U.usedCount(&GA) || U.compilerUsedCount(&GA);
+}
+
+static bool hasUsesToReplace(GlobalAlias &GA, LLVMUsed &U, bool &RenameTarget) {
+  RenameTarget = false;
+  bool Ret = false;
+  if (hasUseOtherThanLLVMUsed(GA, U))
+    Ret = true;
+
+  // If the alias is externally visible, we may still be able to simplify it.
+  if (!mayHaveOtherReferences(GA, U))
+    return Ret;
+
+  // If the aliasee has internal linkage, give it the name and linkage
+  // of the alias, and delete the alias.  This turns:
+  //   define internal ... @f(...)
+  //   @a = alias ... @f
+  // into:
+  //   define ... @a(...)
+  Constant *Aliasee = GA.getAliasee();
+  GlobalValue *Target = cast<GlobalValue>(Aliasee->stripPointerCasts());
+  if (!Target->hasLocalLinkage())
+    return Ret;
+
+  // Do not perform the transform if multiple aliases potentially target the
+  // aliasee. This check also ensures that it is safe to replace the section
+  // and other attributes of the aliasee with those of the alias.
+  if (hasMoreThanOneUseOtherThanLLVMUsed(*Target, U))
+    return Ret;
+
+  RenameTarget = true;
+  return true;
+}
+
+bool GlobalOpt::OptimizeGlobalAliases(Module &M) {
+  bool Changed = false;
+  LLVMUsed Used(M);
+
+  for (SmallPtrSet<GlobalValue *, 8>::iterator I = Used.usedBegin(),
+                                               E = Used.usedEnd();
+       I != E; ++I)
+    Used.compilerUsedErase(*I);
+
+  for (Module::alias_iterator I = M.alias_begin(), E = M.alias_end();
+       I != E;) {
+    Module::alias_iterator J = I++;
+    // Aliases without names cannot be referenced outside this module.
+    if (!J->hasName() && !J->isDeclaration())
+      J->setLinkage(GlobalValue::InternalLinkage);
+    // If the aliasee may change at link time, nothing can be done - bail out.
+    if (J->mayBeOverridden())
+      continue;
+
+    Constant *Aliasee = J->getAliasee();
+    GlobalValue *Target = cast<GlobalValue>(Aliasee->stripPointerCasts());
+    Target->removeDeadConstantUsers();
+
+    // Make all users of the alias use the aliasee instead.
+    bool RenameTarget;
+    if (!hasUsesToReplace(*J, Used, RenameTarget))
+      continue;
+
+    J->replaceAllUsesWith(Aliasee);
+    ++NumAliasesResolved;
+    Changed = true;
+
+    if (RenameTarget) {
+      // Give the aliasee the name, linkage and other attributes of the alias.
+      Target->takeName(J);
+      Target->setLinkage(J->getLinkage());
+      Target->GlobalValue::copyAttributesFrom(J);
+
+      if (Used.usedErase(J))
+        Used.usedInsert(Target);
+
+      if (Used.compilerUsedErase(J))
+        Used.compilerUsedInsert(Target);
+    } else if (mayHaveOtherReferences(*J, Used))
+      continue;
+
+    // Delete the alias.
+    M.getAliasList().erase(J);
+    ++NumAliasesRemoved;
+    Changed = true;
+  }
+
+  Used.syncVariablesAndSets();
+
+  return Changed;
+}
+
+static Function *FindCXAAtExit(Module &M, TargetLibraryInfo *TLI) {
+  if (!TLI->has(LibFunc::cxa_atexit))
+    return 0;
+
+  Function *Fn = M.getFunction(TLI->getName(LibFunc::cxa_atexit));
+
+  if (!Fn)
+    return 0;
+
+  FunctionType *FTy = Fn->getFunctionType();
+
+  // Checking that the function has the right return type, the right number of
+  // parameters and that they all have pointer types should be enough.
+  if (!FTy->getReturnType()->isIntegerTy() ||
+      FTy->getNumParams() != 3 ||
+      !FTy->getParamType(0)->isPointerTy() ||
+      !FTy->getParamType(1)->isPointerTy() ||
+      !FTy->getParamType(2)->isPointerTy())
+    return 0;
+
+  return Fn;
+}
+
+/// cxxDtorIsEmpty - Returns whether the given function is an empty C++
+/// destructor and can therefore be eliminated.
+/// Note that we assume that other optimization passes have already simplified
+/// the code so we only look for a function with a single basic block, where
+/// the only allowed instructions are 'ret', 'call' to an empty C++ dtor and
+/// other side-effect free instructions.
+static bool cxxDtorIsEmpty(const Function &Fn,
+                           SmallPtrSet<const Function *, 8> &CalledFunctions) {
+  // FIXME: We could eliminate C++ destructors if they're readonly/readnone and
+  // nounwind, but that doesn't seem worth doing.
+  if (Fn.isDeclaration())
+    return false;
+
+  if (++Fn.begin() != Fn.end())
+    return false;
+
+  const BasicBlock &EntryBlock = Fn.getEntryBlock();
+  for (BasicBlock::const_iterator I = EntryBlock.begin(), E = EntryBlock.end();
+       I != E; ++I) {
+    if (const CallInst *CI = dyn_cast<CallInst>(I)) {
+      // Ignore debug intrinsics.
+      if (isa<DbgInfoIntrinsic>(CI))
+        continue;
+
+      const Function *CalledFn = CI->getCalledFunction();
+
+      if (!CalledFn)
+        return false;
+
+      SmallPtrSet<const Function *, 8> NewCalledFunctions(CalledFunctions);
+
+      // Don't treat recursive functions as empty.
+      if (!NewCalledFunctions.insert(CalledFn))
+        return false;
+
+      if (!cxxDtorIsEmpty(*CalledFn, NewCalledFunctions))
+        return false;
+    } else if (isa<ReturnInst>(*I))
+      return true; // We're done.
+    else if (I->mayHaveSideEffects())
+      return false; // Destructor with side effects, bail.
+  }
+
+  return false;
+}
+
+bool GlobalOpt::OptimizeEmptyGlobalCXXDtors(Function *CXAAtExitFn) {
+  /// Itanium C++ ABI p3.3.5:
+  ///
+  ///   After constructing a global (or local static) object, that will require
+  ///   destruction on exit, a termination function is registered as follows:
+  ///
+  ///   extern "C" int __cxa_atexit ( void (*f)(void *), void *p, void *d );
+  ///
+  ///   This registration, e.g. __cxa_atexit(f,p,d), is intended to cause the
+  ///   call f(p) when DSO d is unloaded, before all such termination calls
+  ///   registered before this one. It returns zero if registration is
+  ///   successful, nonzero on failure.
+
+  // This pass will look for calls to __cxa_atexit where the function is trivial
+  // and remove them.
+  bool Changed = false;
+
+  for (Function::use_iterator I = CXAAtExitFn->use_begin(),
+       E = CXAAtExitFn->use_end(); I != E;) {
+    // We're only interested in calls. Theoretically, we could handle invoke
+    // instructions as well, but neither llvm-gcc nor clang generate invokes
+    // to __cxa_atexit.
+    CallInst *CI = dyn_cast<CallInst>(*I++);
+    if (!CI)
+      continue;
+
+    Function *DtorFn =
+      dyn_cast<Function>(CI->getArgOperand(0)->stripPointerCasts());
+    if (!DtorFn)
+      continue;
+
+    SmallPtrSet<const Function *, 8> CalledFunctions;
+    if (!cxxDtorIsEmpty(*DtorFn, CalledFunctions))
+      continue;
+
+    // Just remove the call.
+    CI->replaceAllUsesWith(Constant::getNullValue(CI->getType()));
+    CI->eraseFromParent();
+
+    ++NumCXXDtorsRemoved;
+
+    Changed |= true;
+  }
+
+  return Changed;
+}
+
+bool GlobalOpt::runOnModule(Module &M) {
+  bool Changed = false;
+
+  TD = getAnalysisIfAvailable<DataLayout>();
+  TLI = &getAnalysis<TargetLibraryInfo>();
+
+  // Try to find the llvm.globalctors list.
+  GlobalVariable *GlobalCtors = FindGlobalCtors(M);
+
+  bool LocalChange = true;
+  while (LocalChange) {
+    LocalChange = false;
+
+    // Delete functions that are trivially dead, ccc -> fastcc
+    LocalChange |= OptimizeFunctions(M);
+
+    // Optimize global_ctors list.
+    if (GlobalCtors)
+      LocalChange |= OptimizeGlobalCtorsList(GlobalCtors);
+
+    // Optimize non-address-taken globals.
+    LocalChange |= OptimizeGlobalVars(M);
+
+    // Resolve aliases, when possible.
+    LocalChange |= OptimizeGlobalAliases(M);
+
+    // Try to remove trivial global destructors if they are not removed
+    // already.
+    Function *CXAAtExitFn = FindCXAAtExit(M, TLI);
+    if (CXAAtExitFn)
+      LocalChange |= OptimizeEmptyGlobalCXXDtors(CXAAtExitFn);
+
+    Changed |= LocalChange;
+  }
+
+  // TODO: Move all global ctors functions to the end of the module for code
+  // layout.
+
+  return Changed;
+}