diff --git a/include/llvm/Transforms/Utils/ValueMapper.h b/include/llvm/Transforms/Utils/ValueMapper.h
index dd320a3..d612213 100644
--- a/include/llvm/Transforms/Utils/ValueMapper.h
+++ b/include/llvm/Transforms/Utils/ValueMapper.h
@@ -22,10 +22,29 @@
   class Instruction;
   typedef ValueMap<const Value *, TrackingVH<Value> > ValueToValueMapTy;
 
+  /// RemapFlags - These are flags that the value mapping APIs allow.
+  enum RemapFlags {
+    RF_None = 0,
+    
+    /// RF_NoModuleLevelChanges - If this flag is set, the remapper knows that
+    /// only local values within a function (such as an instruction or argument)
+    /// are mapped, not global values like functions and global metadata.
+    RF_NoModuleLevelChanges = 1,
+    
+    /// RF_IgnoreMissingEntries - If this flag is set, the remapper ignores
+    /// entries that are not in the value map.  If it is unset, it aborts if an
+    /// operand is asked to be remapped which doesn't exist in the mapping.
+    RF_IgnoreMissingEntries = 2
+  };
+  
+  static inline RemapFlags operator|(RemapFlags LHS, RemapFlags RHS) {
+    return RemapFlags(unsigned(LHS)|unsigned(RHS));
+  }
+  
   Value *MapValue(const Value *V, ValueToValueMapTy &VM,
-                  bool ModuleLevelChanges);
+                  RemapFlags Flags = RF_None);
   void RemapInstruction(Instruction *I, ValueToValueMapTy &VM,
-                        bool ModuleLevelChanges);
+                        RemapFlags Flags = RF_None);
 } // End llvm namespace
 
 #endif
diff --git a/lib/Linker/LinkModules.cpp b/lib/Linker/LinkModules.cpp
index d99e0a0..3b3d3a4 100644
--- a/lib/Linker/LinkModules.cpp
+++ b/lib/Linker/LinkModules.cpp
@@ -451,8 +451,7 @@
     // Add Src elements into Dest node.
     for (unsigned i = 0, e = SrcNMD->getNumOperands(); i != e; ++i)
       DestNMD->addOperand(cast<MDNode>(MapValue(SrcNMD->getOperand(i),
-                                                ValueMap,
-                                                true)));
+                                                ValueMap)));
   }
 }
 
@@ -814,9 +813,9 @@
     const GlobalVariable *SGV = I;
 
     if (SGV->hasInitializer()) {      // Only process initialized GV's
-      // Figure out what the initializer looks like in the dest module...
+      // Figure out what the initializer looks like in the dest module.
       Constant *SInit =
-        cast<Constant>(MapValue(SGV->getInitializer(), ValueMap, true));
+        cast<Constant>(MapValue(SGV->getInitializer(), ValueMap));
       // Grab destination global variable or alias.
       GlobalValue *DGV = cast<GlobalValue>(ValueMap[SGV]->stripPointerCasts());
 
@@ -996,32 +995,10 @@
   // At this point, all of the instructions and values of the function are now
   // copied over.  The only problem is that they are still referencing values in
   // the Source function as operands.  Loop through all of the operands of the
-  // functions and patch them up to point to the local versions...
-  //
-  // This is the same as RemapInstruction, except that it avoids remapping
-  // instruction and basic block operands.
-  //
+  // functions and patch them up to point to the local versions.
   for (Function::iterator BB = Dest->begin(), BE = Dest->end(); BB != BE; ++BB)
-    for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I) {
-      // Remap operands.
-      for (Instruction::op_iterator OI = I->op_begin(), OE = I->op_end();
-           OI != OE; ++OI)
-        if (!isa<Instruction>(*OI) && !isa<BasicBlock>(*OI))
-          *OI = MapValue(*OI, ValueMap, true);
-
-      // Remap attached metadata.
-      SmallVector<std::pair<unsigned, MDNode *>, 4> MDs;
-      I->getAllMetadata(MDs);
-      for (SmallVectorImpl<std::pair<unsigned, MDNode *> >::iterator
-           MI = MDs.begin(), ME = MDs.end(); MI != ME; ++MI) {
-        Value *Old = MI->second;
-        if (!isa<Instruction>(Old) && !isa<BasicBlock>(Old)) {
-          Value *New = MapValue(Old, ValueMap, true);
-          if (New != Old)
-            I->setMetadata(MI->first, cast<MDNode>(New));
-        }
-      }
-    }
+    for (BasicBlock::iterator I = BB->begin(), E = BB->end(); I != E; ++I)
+      RemapInstruction(I, ValueMap, RF_IgnoreMissingEntries);
 
   // There is no need to map the arguments anymore.
   for (Function::arg_iterator I = Src->arg_begin(), E = Src->arg_end();
diff --git a/lib/Transforms/Scalar/LoopRotation.cpp b/lib/Transforms/Scalar/LoopRotation.cpp
index ba1a279..4ca422e 100644
--- a/lib/Transforms/Scalar/LoopRotation.cpp
+++ b/lib/Transforms/Scalar/LoopRotation.cpp
@@ -22,7 +22,6 @@
 #include "llvm/Transforms/Utils/BasicBlockUtils.h"
 #include "llvm/Transforms/Utils/SSAUpdater.h"
 #include "llvm/Transforms/Utils/ValueMapper.h"
-#include "llvm/Support/CommandLine.h"
 #include "llvm/Support/Debug.h"
 #include "llvm/ADT/Statistic.h"
 using namespace llvm;
@@ -205,6 +204,7 @@
     
     // Otherwise, create a duplicate of the instruction.
     Instruction *C = Inst->clone();
+    
     C->setName(Inst->getName());
     C->insertBefore(LoopEntryBranch);
     ValueMap[Inst] = C;
diff --git a/lib/Transforms/Scalar/LoopUnswitch.cpp b/lib/Transforms/Scalar/LoopUnswitch.cpp
index 20d7019..0fc416d 100644
--- a/lib/Transforms/Scalar/LoopUnswitch.cpp
+++ b/lib/Transforms/Scalar/LoopUnswitch.cpp
@@ -457,19 +457,6 @@
   return true;
 }
 
-// RemapInstruction - Convert the instruction operands from referencing the
-// current values into those specified by VMap.
-//
-static inline void RemapInstruction(Instruction *I,
-                                    ValueToValueMapTy &VMap) {
-  for (unsigned op = 0, E = I->getNumOperands(); op != E; ++op) {
-    Value *Op = I->getOperand(op);
-    ValueToValueMapTy::iterator It = VMap.find(Op);
-    if (It != VMap.end()) Op = It->second;
-    I->setOperand(op, Op);
-  }
-}
-
 /// CloneLoop - Recursively clone the specified loop and all of its children,
 /// mapping the blocks with the specified map.
 static Loop *CloneLoop(Loop *L, Loop *PL, ValueToValueMapTy &VM,
@@ -664,7 +651,7 @@
   for (unsigned i = 0, e = NewBlocks.size(); i != e; ++i)
     for (BasicBlock::iterator I = NewBlocks[i]->begin(),
            E = NewBlocks[i]->end(); I != E; ++I)
-      RemapInstruction(I, VMap);
+      RemapInstruction(I, VMap,RF_NoModuleLevelChanges|RF_IgnoreMissingEntries);
   
   // Rewrite the original preheader to select between versions of the loop.
   BranchInst *OldBR = cast<BranchInst>(loopPreheader->getTerminator());
diff --git a/lib/Transforms/Utils/CloneFunction.cpp b/lib/Transforms/Utils/CloneFunction.cpp
index 80da086..d967ceb 100644
--- a/lib/Transforms/Utils/CloneFunction.cpp
+++ b/lib/Transforms/Utils/CloneFunction.cpp
@@ -112,8 +112,7 @@
     const BasicBlock &BB = *BI;
 
     // Create a new basic block and copy instructions into it!
-    BasicBlock *CBB = CloneBasicBlock(&BB, VMap, NameSuffix, NewFunc,
-                                      CodeInfo);
+    BasicBlock *CBB = CloneBasicBlock(&BB, VMap, NameSuffix, NewFunc, CodeInfo);
     VMap[&BB] = CBB;                       // Add basic block mapping.
 
     if (ReturnInst *RI = dyn_cast<ReturnInst>(CBB->getTerminator()))
@@ -122,12 +121,12 @@
 
   // Loop over all of the instructions in the function, fixing up operand
   // references as we go.  This uses VMap to do all the hard work.
-  //
   for (Function::iterator BB = cast<BasicBlock>(VMap[OldFunc->begin()]),
          BE = NewFunc->end(); BB != BE; ++BB)
     // Loop over all instructions, fixing each one as we find it...
     for (BasicBlock::iterator II = BB->begin(); II != BB->end(); ++II)
-      RemapInstruction(II, VMap, ModuleLevelChanges);
+      RemapInstruction(II, VMap,
+                       ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges);
 }
 
 /// CloneFunction - Return a copy of the specified function, but without
@@ -138,8 +137,7 @@
 /// updated to include mappings from all of the instructions and basicblocks in
 /// the function from their old to new values.
 ///
-Function *llvm::CloneFunction(const Function *F,
-                              ValueToValueMapTy &VMap,
+Function *llvm::CloneFunction(const Function *F, ValueToValueMapTy &VMap,
                               bool ModuleLevelChanges,
                               ClonedCodeInfo *CodeInfo) {
   std::vector<const Type*> ArgTypes;
@@ -322,7 +320,8 @@
   SmallVector<Constant*, 8> Ops;
   for (unsigned i = 0, e = I->getNumOperands(); i != e; ++i)
     if (Constant *Op = dyn_cast_or_null<Constant>(MapValue(I->getOperand(i),
-                                                   VMap, ModuleLevelChanges)))
+                                                           VMap,
+                  ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges)))
       Ops.push_back(Op);
     else
       return 0;  // All operands not constant!
@@ -460,7 +459,8 @@
           I->setDebugLoc(DebugLoc());
         }
       }
-      RemapInstruction(I, VMap, ModuleLevelChanges);
+      RemapInstruction(I, VMap,
+                       ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges);
     }
   }
   
@@ -480,10 +480,10 @@
       PHINode *PN = cast<PHINode>(VMap[OPN]);
       for (unsigned pred = 0, e = NumPreds; pred != e; ++pred) {
         Value *V = VMap[PN->getIncomingBlock(pred)];
-        if (BasicBlock *MappedBlock = 
-            cast_or_null<BasicBlock>(V)) {
+        if (BasicBlock *MappedBlock = cast_or_null<BasicBlock>(V)) {
           Value *InVal = MapValue(PN->getIncomingValue(pred),
-                                  VMap, ModuleLevelChanges);
+                                  VMap, 
+                        ModuleLevelChanges ? RF_None : RF_NoModuleLevelChanges);
           assert(InVal && "Unknown input value?");
           PN->setIncomingValue(pred, InVal);
           PN->setIncomingBlock(pred, MappedBlock);
diff --git a/lib/Transforms/Utils/CloneModule.cpp b/lib/Transforms/Utils/CloneModule.cpp
index b347bf5..1046c38 100644
--- a/lib/Transforms/Utils/CloneModule.cpp
+++ b/lib/Transforms/Utils/CloneModule.cpp
@@ -89,8 +89,7 @@
     GlobalVariable *GV = cast<GlobalVariable>(VMap[I]);
     if (I->hasInitializer())
       GV->setInitializer(cast<Constant>(MapValue(I->getInitializer(),
-                                                 VMap,
-                                                 true)));
+                                                 VMap, RF_None)));
     GV->setLinkage(I->getLinkage());
     GV->setThreadLocal(I->isThreadLocal());
     GV->setConstant(I->isConstant());
@@ -121,7 +120,7 @@
     GlobalAlias *GA = cast<GlobalAlias>(VMap[I]);
     GA->setLinkage(I->getLinkage());
     if (const Constant* C = I->getAliasee())
-      GA->setAliasee(cast<Constant>(MapValue(C, VMap, true)));
+      GA->setAliasee(cast<Constant>(MapValue(C, VMap, RF_None)));
   }
 
   // And named metadata....
@@ -130,7 +129,8 @@
     const NamedMDNode &NMD = *I;
     NamedMDNode *NewNMD = New->getOrInsertNamedMetadata(NMD.getName());
     for (unsigned i = 0, e = NMD.getNumOperands(); i != e; ++i)
-      NewNMD->addOperand(cast<MDNode>(MapValue(NMD.getOperand(i), VMap, true)));
+      NewNMD->addOperand(cast<MDNode>(MapValue(NMD.getOperand(i), VMap,
+                                               RF_None)));
   }
 
   return New;
diff --git a/lib/Transforms/Utils/ValueMapper.cpp b/lib/Transforms/Utils/ValueMapper.cpp
index 9455e53..132c392 100644
--- a/lib/Transforms/Utils/ValueMapper.cpp
+++ b/lib/Transforms/Utils/ValueMapper.cpp
@@ -21,147 +21,106 @@
 using namespace llvm;
 
 Value *llvm::MapValue(const Value *V, ValueToValueMapTy &VM,
-                      bool ModuleLevelChanges) {
-  TrackingVH<Value> &VMSlot = VM[V];
-  if (VMSlot) return VMSlot;      // Does it exist in the map yet?
+                      RemapFlags Flags) {
+  ValueToValueMapTy::iterator I = VM.find(V);
   
-  // NOTE: VMSlot can be invalidated by any reference to VM, which can grow the
-  // DenseMap.  This includes any recursive calls to MapValue.
-
+  // If the value already exists in the map, use it.
+  if (I != VM.end() && I->second) return I->second;
+  
   // Global values do not need to be seeded into the VM if they
   // are using the identity mapping.
-  if (isa<GlobalValue>(V) || isa<InlineAsm>(V) || isa<MDString>(V) ||
-      (isa<MDNode>(V) && !cast<MDNode>(V)->isFunctionLocal() &&
-       !ModuleLevelChanges))
-    return VMSlot = const_cast<Value*>(V);
+  if (isa<GlobalValue>(V) || isa<InlineAsm>(V) || isa<MDString>(V))
+    return VM[V] = const_cast<Value*>(V);
 
   if (const MDNode *MD = dyn_cast<MDNode>(V)) {
-    // Start by assuming that we'll use the identity mapping.
-    VMSlot = const_cast<Value*>(V);
-
+    // If this is a module-level metadata and we know that nothing at the module
+    // level is changing, then use an identity mapping.
+    if (!MD->isFunctionLocal() && (Flags & RF_NoModuleLevelChanges))
+      return VM[V] = const_cast<Value*>(V);
+    
     // Check all operands to see if any need to be remapped.
     for (unsigned i = 0, e = MD->getNumOperands(); i != e; ++i) {
       Value *OP = MD->getOperand(i);
-      if (!OP || MapValue(OP, VM, ModuleLevelChanges) == OP) continue;
+      if (OP == 0 || MapValue(OP, VM, Flags) == OP) continue;
 
-      // Ok, at least one operand needs remapping.
+      // Ok, at least one operand needs remapping.  Create a dummy node in case
+      // we have a metadata cycle.
       MDNode *Dummy = MDNode::getTemporary(V->getContext(), 0, 0);
       VM[V] = Dummy;
       SmallVector<Value*, 4> Elts;
       Elts.reserve(MD->getNumOperands());
-      for (i = 0; i != e; ++i)
-        Elts.push_back(MD->getOperand(i) ? 
-                       MapValue(MD->getOperand(i), VM, ModuleLevelChanges) : 0);
+      for (i = 0; i != e; ++i) {
+        Value *Op = MD->getOperand(i);
+        Elts.push_back(Op ? MapValue(Op, VM, Flags) : 0);
+      }
       MDNode *NewMD = MDNode::get(V->getContext(), Elts.data(), Elts.size());
       Dummy->replaceAllUsesWith(NewMD);
       MDNode::deleteTemporary(Dummy);
       return VM[V] = NewMD;
     }
 
-    // No operands needed remapping; keep the identity map.
-    return const_cast<Value*>(V);
+    // No operands needed remapping.  Use an identity mapping.
+    return VM[V] = const_cast<Value*>(V);
   }
 
+  // Okay, this either must be a constant (which may or may not be mappable) or
+  // is something that is not in the mapping table.
   Constant *C = const_cast<Constant*>(dyn_cast<Constant>(V));
   if (C == 0)
     return 0;
   
-  if (isa<ConstantInt>(C) || isa<ConstantFP>(C) ||
-      isa<ConstantPointerNull>(C) || isa<ConstantAggregateZero>(C) ||
-      isa<UndefValue>(C))
-    return VMSlot = C;           // Primitive constants map directly
-  
-  if (ConstantArray *CA = dyn_cast<ConstantArray>(C)) {
-    for (User::op_iterator b = CA->op_begin(), i = b, e = CA->op_end();
-         i != e; ++i) {
-      Value *MV = MapValue(*i, VM, ModuleLevelChanges);
-      if (MV != *i) {
-        // This array must contain a reference to a global, make a new array
-        // and return it.
-        //
-        std::vector<Constant*> Values;
-        Values.reserve(CA->getNumOperands());
-        for (User::op_iterator j = b; j != i; ++j)
-          Values.push_back(cast<Constant>(*j));
-        Values.push_back(cast<Constant>(MV));
-        for (++i; i != e; ++i)
-          Values.push_back(cast<Constant>(MapValue(*i, VM,
-                                                   ModuleLevelChanges)));
-        return VM[V] = ConstantArray::get(CA->getType(), Values);
-      }
-    }
-    return VM[V] = C;
+  if (BlockAddress *BA = dyn_cast<BlockAddress>(C)) {
+    Function *F = cast<Function>(MapValue(BA->getFunction(), VM, Flags));
+    BasicBlock *BB = cast_or_null<BasicBlock>(MapValue(BA->getBasicBlock(), VM,
+                                                       Flags));
+    return VM[V] = BlockAddress::get(F, BB ? BB : BA->getBasicBlock());
   }
   
-  if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C)) {
-    for (User::op_iterator b = CS->op_begin(), i = b, e = CS->op_end();
-         i != e; ++i) {
-      Value *MV = MapValue(*i, VM, ModuleLevelChanges);
-      if (MV != *i) {
-        // This struct must contain a reference to a global, make a new struct
-        // and return it.
-        //
-        std::vector<Constant*> Values;
-        Values.reserve(CS->getNumOperands());
-        for (User::op_iterator j = b; j != i; ++j)
-          Values.push_back(cast<Constant>(*j));
-        Values.push_back(cast<Constant>(MV));
-        for (++i; i != e; ++i)
-          Values.push_back(cast<Constant>(MapValue(*i, VM,
-                                                   ModuleLevelChanges)));
-        return VM[V] = ConstantStruct::get(CS->getType(), Values);
-      }
-    }
-    return VM[V] = C;
-  }
-  
-  if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C)) {
+  for (unsigned i = 0, e = C->getNumOperands(); i != e; ++i) {
+    Value *Op = C->getOperand(i);
+    Value *Mapped = MapValue(Op, VM, Flags);
+    if (Mapped == C) continue;
+    
+    // Okay, the operands don't all match.  We've already processed some or all
+    // of the operands, set them up now.
     std::vector<Constant*> Ops;
-    for (User::op_iterator i = CE->op_begin(), e = CE->op_end(); i != e; ++i)
-      Ops.push_back(cast<Constant>(MapValue(*i, VM, ModuleLevelChanges)));
-    return VM[V] = CE->getWithOperands(Ops);
+    Ops.reserve(C->getNumOperands());
+    for (unsigned j = 0; j != i; ++j)
+      Ops.push_back(cast<Constant>(C->getOperand(i)));
+    Ops.push_back(cast<Constant>(Mapped));
+    
+    // Map the rest of the operands that aren't processed yet.
+    for (++i; i != e; ++i)
+      Ops.push_back(cast<Constant>(MapValue(C->getOperand(i), VM, Flags)));
+    
+    if (ConstantExpr *CE = dyn_cast<ConstantExpr>(C))
+      return VM[V] = CE->getWithOperands(Ops);
+    if (ConstantArray *CA = dyn_cast<ConstantArray>(C))
+      return VM[V] = ConstantArray::get(CA->getType(), Ops);
+    if (ConstantStruct *CS = dyn_cast<ConstantStruct>(C))
+      return VM[V] = ConstantStruct::get(CS->getType(), Ops);
+    assert(isa<ConstantVector>(C) && "Unknown mapped constant type");
+    return VM[V] = ConstantVector::get(Ops);
   }
-  
-  if (ConstantVector *CV = dyn_cast<ConstantVector>(C)) {
-    for (User::op_iterator b = CV->op_begin(), i = b, e = CV->op_end();
-         i != e; ++i) {
-      Value *MV = MapValue(*i, VM, ModuleLevelChanges);
-      if (MV != *i) {
-        // This vector value must contain a reference to a global, make a new
-        // vector constant and return it.
-        //
-        std::vector<Constant*> Values;
-        Values.reserve(CV->getNumOperands());
-        for (User::op_iterator j = b; j != i; ++j)
-          Values.push_back(cast<Constant>(*j));
-        Values.push_back(cast<Constant>(MV));
-        for (++i; i != e; ++i)
-          Values.push_back(cast<Constant>(MapValue(*i, VM,
-                                                   ModuleLevelChanges)));
-        return VM[V] = ConstantVector::get(Values);
-      }
-    }
-    return VM[V] = C;
-  }
-  
-  BlockAddress *BA = cast<BlockAddress>(C);
-  Function *F = cast<Function>(MapValue(BA->getFunction(), VM,
-                                        ModuleLevelChanges));
-  BasicBlock *BB = cast_or_null<BasicBlock>(MapValue(BA->getBasicBlock(),VM,
-                                             ModuleLevelChanges));
-  return VM[V] = BlockAddress::get(F, BB ? BB : BA->getBasicBlock());
+
+  // If we reach here, all of the operands of the constant match.
+  return VM[V] = C;
 }
 
 /// RemapInstruction - Convert the instruction operands from referencing the
 /// current values into those specified by VMap.
 ///
 void llvm::RemapInstruction(Instruction *I, ValueToValueMapTy &VMap,
-                            bool ModuleLevelChanges) {
+                            RemapFlags Flags) {
   // Remap operands.
   for (User::op_iterator op = I->op_begin(), E = I->op_end(); op != E; ++op) {
-    Value *V = MapValue(*op, VMap, ModuleLevelChanges);
-    assert(V && "Referenced value not in value map!");
-    *op = V;
+    Value *V = MapValue(*op, VMap, Flags);
+    // If we aren't ignoring missing entries, assert that something happened.
+    if (V != 0)
+      *op = V;
+    else
+      assert((Flags & RF_IgnoreMissingEntries) &&
+             "Referenced value not in value map!");
   }
 
   // Remap attached metadata.
@@ -170,7 +129,7 @@
   for (SmallVectorImpl<std::pair<unsigned, MDNode *> >::iterator
        MI = MDs.begin(), ME = MDs.end(); MI != ME; ++MI) {
     Value *Old = MI->second;
-    Value *New = MapValue(Old, VMap, ModuleLevelChanges);
+    Value *New = MapValue(Old, VMap, Flags);
     if (New != Old)
       I->setMetadata(MI->first, cast<MDNode>(New));
   }