PNaCl: Add ReplacePtrsWithInts pass for stripping out pointer types

lib/Transforms/NaCl/ReplacePtrsWithInts.cpp

+//===- ReplacePtrsWithInts.cpp - Convert pointer values to integer values--===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This pass strips out aggregate pointer types and replaces them with
+// the integer type iPTR, which is i32 for PNaCl (though this pass
+// will allow iPTR to be i64 if the DataLayout specifies 64-bit
+// pointers).
+//
+// The pass converts IR to the following normal form:
+//
+// All inttoptr and ptrtoint instructions use the same integer size
+// (iPTR), so they do not implicitly truncate or zero-extend.
+//
+// alloca always allocates an i8 array type.
+//
+// Pointer types only appear in the following instructions:
+//  * loads and stores:  the pointer operand is a NormalizedPtr.
+//  * function calls:  the function operand is a NormalizedPtr.
+//  * intrinsic calls:  any pointer arguments are NormalizedPtrs.
+//  * alloca
+//  * bitcast and inttoptr:  only used as part of a NormalizedPtr.
+//  * ptrtoint:  the operand is an InherentPtr.
+//
+// Where an InherentPtr is defined as a pointer value that is:
+//  * an alloca;
+//  * a GlobalValue (a function or global variable); or
+//  * an intrinsic call.
+//
+// And a NormalizedPtr is defined as a pointer value that is:
+//  * an inttoptr instruction;
+//  * an InherentPtr; or
+//  * a bitcast of an InherentPtr.
+//
+// This pass currently strips out lifetime markers (that is, calls to
+// the llvm.lifetime.start/end intrinsics).
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/IR/DataLayout.h"
+#include "llvm/IR/DerivedTypes.h"
+#include "llvm/IR/Function.h"
+#include "llvm/IR/IRBuilder.h"
+#include "llvm/IR/Instructions.h"
+#include "llvm/IR/IntrinsicInst.h"
+#include "llvm/IR/Module.h"
+#include "llvm/IR/Type.h"
+#include "llvm/Pass.h"
+#include "llvm/Support/raw_ostream.h"
+#include "llvm/Transforms/NaCl.h"
+
+using namespace llvm;
+
+namespace {
+  // This is a ModulePass because the pass must recreate functions in
+  // order to change their argument and return types.
+  struct ReplacePtrsWithInts : public ModulePass {
+    static char ID; // Pass identification, replacement for typeid
+    ReplacePtrsWithInts() : ModulePass(ID) {
+      initializeReplacePtrsWithIntsPass(*PassRegistry::getPassRegistry());
+    }
+
+    virtual bool runOnModule(Module &M);
+  };
+
+  // FunctionConverter stores the state for mapping old instructions
+  // (of pointer type) to converted instructions (of integer type)
+  // within a function, and provides methods for doing the conversion.
+  class FunctionConverter {
+    // Int type that pointer types are to be replaced with, typically i32.
+    Type *IntPtrType;
+
+    struct RewrittenVal {
+      RewrittenVal(): IsPlaceholder(true), NewIntVal(NULL) {}
+      bool IsPlaceholder;
+      Value *NewIntVal;
+    };
+    // Maps from old values (of pointer type) to converted values (of
+    // IntPtrType type).
+    DenseMap<Value *, RewrittenVal> RewriteMap;
+    // Number of placeholders; used for detecting unhandled cases.
+    int PlaceholderCount;
+    // List of instructions whose deletion has been deferred.
+    SmallVector<Instruction *, 20> ToErase;
+
+  public:
+    FunctionConverter(Type *IntPtrType)
+      : IntPtrType(IntPtrType), PlaceholderCount(0) {}
+
+    // Returns the normalized version of the given type, converting
+    // pointer types to IntPtrType.
+    Type *convertType(Type *Ty);
+    // Returns the normalized version of the given function type by
+    // normalizing the function's argument types.
+    FunctionType *convertFuncType(FunctionType *FTy);
+
+    // Records that 'To' is the normalized version of 'From'.  If 'To'
+    // is not of pointer type, no type conversion is required, so this
+    // can take the short cut of replacing 'To' with 'From'.
+    void recordConverted(Value *From, Value *To);
+    void recordConvertedAndErase(Instruction *From, Value *To);
+
+    // Returns the normalized version of the given value.
+    Value *convert(Value *Val);
+    // Returns the NormalizedPtr form of the given pointer value.
+    // Inserts conversion instructions at InsertPt.
+    Value *convertBackToPtr(Value *Val, Instruction *InsertPt);
+    // Returns the NormalizedPtr form of the given function pointer.
+    // Inserts conversion instructions at InsertPt.
+    Value *convertFunctionPtr(Value *Callee, Instruction *InsertPt);
+    // Converts an instruction without recreating it, by wrapping its
+    // operands and result.
+    void convertInPlace(Instruction *Inst);
+
+    void eraseReplacedInstructions();
+  };
+}
+
+Type *FunctionConverter::convertType(Type *Ty) {
+  if (Ty->isPointerTy())
+    return IntPtrType;
+  return Ty;
+}
+
+FunctionType *FunctionConverter::convertFuncType(FunctionType *FTy) {
+  SmallVector<Type *, 8> ArgTypes;
+  for (FunctionType::param_iterator ArgTy = FTy->param_begin(),
+           E = FTy->param_end(); ArgTy != E; ++ArgTy) {
+    ArgTypes.push_back(convertType(*ArgTy));
+  }
+  return FunctionType::get(convertType(FTy->getReturnType()), ArgTypes,
+                           FTy->isVarArg());
+}
+
+void FunctionConverter::recordConverted(Value *From, Value *To) {
+  if (!From->getType()->isPointerTy()) {
+    From->replaceAllUsesWith(To);
+    return;
+  }
+  RewrittenVal *RV = &RewriteMap[From];
+  if (RV->NewIntVal) {
+    assert(RV->IsPlaceholder);
+    // Resolve placeholder.
+    RV->NewIntVal->replaceAllUsesWith(To);
+    delete RV->NewIntVal;
+    RV->IsPlaceholder = false;
+    --PlaceholderCount;
+  }
+  RV->NewIntVal = To;
+}
+
+void FunctionConverter::recordConvertedAndErase(Instruction *From, Value *To) {
+  recordConverted(From, To);
+  // There may still be references to this value, so defer deleting it.
+  ToErase.push_back(From);
+}
+
+Value *FunctionConverter::convert(Value *Val) {
+  if (!Val->getType()->isPointerTy())
+    return Val;
+  if (Constant *C = dyn_cast<Constant>(Val))
+    return ConstantExpr::getPtrToInt(C, IntPtrType);
+  RewrittenVal *RV = &RewriteMap[Val];
+  if (!RV->NewIntVal) {
+    // No converted value available yet, so create a placeholder.
+    Argument *Placeholder = new Argument(convertType(Val->getType()));
+    RV->NewIntVal = Placeholder;
+    ++PlaceholderCount;
+  }
+  return RV->NewIntVal;
+}
+
+Value *FunctionConverter::convertBackToPtr(Value *Val, Instruction *InsertPt) {
+  Type *NewTy =
+    convertType(Val->getType()->getPointerElementType())->getPointerTo();
+  Value *Conv = convert(Val);
+  return new IntToPtrInst(Conv, NewTy, Conv->getName() + ".asptr", InsertPt);
+}
+
+Value *FunctionConverter::convertFunctionPtr(Value *Callee,
+                                             Instruction *InsertPt) {
+  FunctionType *FuncType = cast<FunctionType>(
+      Callee->getType()->getPointerElementType());
+  Value *Conv = convert(Callee);
+  return new IntToPtrInst(Conv, convertFuncType(FuncType)->getPointerTo(),
+                          Conv->getName() + ".asfuncptr", InsertPt);
+}
+
+static bool ShouldLeaveAlone(Value *V) {
+  if (Function *F = dyn_cast<Function>(V))
+    return F->isIntrinsic();
+  if (isa<InlineAsm>(V))
+    return true;
+  return false;
+}
+
+void FunctionConverter::convertInPlace(Instruction *Inst) {
+  // Convert operands.
+  for (unsigned I = 0; I < Inst->getNumOperands(); ++I) {
+    Value *Arg = Inst->getOperand(I);
+    if (Arg->getType()->isPointerTy() && !ShouldLeaveAlone(Arg)) {
+      Value *Conv = convert(Arg);
+      Inst->setOperand(I, new IntToPtrInst(convert(Arg), Arg->getType(),
+                                           Conv->getName() + ".asptr", Inst));
+    }
+  }
+  // Convert result.
+  if (Inst->getType()->isPointerTy()) {
+    Instruction *Cast = new PtrToIntInst(
+        Inst, convertType(Inst->getType()), Inst->getName() + ".asint");
+    Cast->insertAfter(Inst);
+    recordConverted(Inst, Cast);
+  }
+}
+
+void FunctionConverter::eraseReplacedInstructions() {
+  if (PlaceholderCount) {
+    for (DenseMap<Value *, RewrittenVal>::iterator I = RewriteMap.begin(),
+             E = RewriteMap.end(); I != E; ++I) {
+      if (I->second.IsPlaceholder)
+        errs() << "Not converted: " << *I->first << "\n";
+    }
+    report_fatal_error("Case not handled in ReplacePtrsWithInts");
+  }
+  // We must do dropAllReferences() before doing eraseFromParent(),
+  // otherwise we will try to erase instructions that are still
+  // referenced.
+  for (SmallVectorImpl<Instruction *>::iterator I = ToErase.begin(),
+           E = ToErase.end();
+       I != E; ++I) {
+    (*I)->dropAllReferences();
+  }
+  for (SmallVectorImpl<Instruction *>::iterator I = ToErase.begin(),
+           E = ToErase.end();
+       I != E; ++I) {
+    (*I)->eraseFromParent();
+  }
+}
+
+static void ConvertMetadataOperand(FunctionConverter *FC,
+                                   IntrinsicInst *Call, int Index) {
+  MDNode *MD = cast<MDNode>(Call->getArgOperand(Index));
+  if (MD->getNumOperands() != 1)
+    return;
+  Value *MDArg = MD->getOperand(0);
+  if (MDArg && (isa<Argument>(MDArg) || isa<Instruction>(MDArg))) {
+    MDArg = FC->convert(MDArg);
+    if (PtrToIntInst *Cast = dyn_cast<PtrToIntInst>(MDArg)) {
+      // Unwrapping this is necessary for llvm.dbg.declare to work.
+      MDArg = Cast->getPointerOperand();
+    }
+    SmallVector<Value *, 1> Args;
+    Args.push_back(MDArg);
+    Call->setArgOperand(Index, MDNode::get(Call->getContext(), Args));
+  }
+}
+
+// Remove attributes that only apply to pointer arguments.  Returns
+// the updated AttributeSet.
+static AttributeSet RemovePointerAttrs(LLVMContext &Context,
+                                       AttributeSet Attrs) {
+  SmallVector<AttributeSet, 8> AttrList;
+  for (unsigned Slot = 0; Slot < Attrs.getNumSlots(); ++Slot) {
+    unsigned Index = Attrs.getSlotIndex(Slot);
+    AttrBuilder AB;
+    for (AttributeSet::iterator Attr = Attrs.begin(Slot), E = Attrs.end(Slot);
+         Attr != E; ++Attr) {
+      switch (Attr->getKindAsEnum()) {
+        // ByVal and StructRet should already have been removed by the
+        // ExpandByVal pass.
+        case Attribute::ByVal:
+        case Attribute::StructRet:
+        case Attribute::Nest:
+          Attrs.dump();
+          report_fatal_error("ReplacePtrsWithInts cannot handle "
+                             "byval, sret or nest attrs");
+          break;
+        // Strip NoCapture and NoAlias because they are only allowed
+        // on arguments of pointer type, and we are removing the
+        // pointer types.
+        case Attribute::NoCapture:
+        case Attribute::NoAlias:
+          break;
+        default:
+          AB.addAttribute(*Attr);
+      }
+    }
+    AttrList.push_back(AttributeSet::get(Context, Index, AB));
+  }
+  return AttributeSet::get(Context, AttrList);
+}
+
+template <class InstType>
+static void CopyLoadOrStoreAttrs(InstType *Dest, InstType *Src) {
+  Dest->setVolatile(Src->isVolatile());
+  Dest->setAlignment(Src->getAlignment());
+  Dest->setOrdering(Src->getOrdering());
+  Dest->setSynchScope(Src->getSynchScope());
+}
+
+static void ConvertInstruction(DataLayout *DL, Type *IntPtrType,
+                               FunctionConverter *FC, Instruction *Inst) {
+  if (ReturnInst *Ret = dyn_cast<ReturnInst>(Inst)) {
+    Value *Result = Ret->getReturnValue();
+    if (Result)
+      Result = FC->convert(Result);
+    CopyDebug(ReturnInst::Create(Ret->getContext(), Result, Ret), Inst);
+    Ret->eraseFromParent();
+  } else if (PHINode *Phi = dyn_cast<PHINode>(Inst)) {
+    PHINode *Phi2 = PHINode::Create(FC->convertType(Phi->getType()),
+                                    Phi->getNumIncomingValues(),
+                                    "", Phi);
+    CopyDebug(Phi2, Phi);
+    for (unsigned I = 0; I < Phi->getNumIncomingValues(); ++I) {
+      Phi2->addIncoming(FC->convert(Phi->getIncomingValue(I)),
+                        Phi->getIncomingBlock(I));
+    }
+    Phi2->takeName(Phi);
+    FC->recordConvertedAndErase(Phi, Phi2);
+  } else if (SelectInst *Op = dyn_cast<SelectInst>(Inst)) {
+    Instruction *Op2 = SelectInst::Create(Op->getCondition(),
+                                         FC->convert(Op->getTrueValue()),
+                                         FC->convert(Op->getFalseValue()),
+                                         "", Op);
+    CopyDebug(Op2, Op);
+    Op2->takeName(Op);
+    FC->recordConvertedAndErase(Op, Op2);
+  } else if (isa<PtrToIntInst>(Inst) || isa<IntToPtrInst>(Inst)) {
+    Value *Arg = FC->convert(Inst->getOperand(0));
+    Type *ResultTy = FC->convertType(Inst->getType());
+    IRBuilder<> Builder(Inst);
+    Builder.SetCurrentDebugLocation(Inst->getDebugLoc());
+    Value *Result = Builder.CreateZExtOrTrunc(Arg, ResultTy, "");
+    if (Result != Arg)
+      Result->takeName(Inst);
+    FC->recordConvertedAndErase(Inst, Result);
+  } else if (isa<BitCastInst>(Inst)) {
+    if (Inst->getType()->isPointerTy()) {
+      FC->recordConvertedAndErase(Inst, FC->convert(Inst->getOperand(0)));
+    }
+  } else if (ICmpInst *Cmp = dyn_cast<ICmpInst>(Inst)) {
+    Value *Cmp2 = CopyDebug(new ICmpInst(Inst, Cmp->getPredicate(),
+                                         FC->convert(Cmp->getOperand(0)),
+                                         FC->convert(Cmp->getOperand(1)), ""),
+                            Inst);
+    Cmp2->takeName(Cmp);
+    Cmp->replaceAllUsesWith(Cmp2);
+    Cmp->eraseFromParent();
+  } else if (LoadInst *Load = dyn_cast<LoadInst>(Inst)) {
+    Value *Ptr = FC->convertBackToPtr(Load->getPointerOperand(), Inst);
+    LoadInst *Result = new LoadInst(Ptr, "", Inst);
+    Result->takeName(Inst);
+    CopyDebug(Result, Inst);
+    CopyLoadOrStoreAttrs(Result, Load);
+    FC->recordConvertedAndErase(Inst, Result);
+  } else if (StoreInst *Store = dyn_cast<StoreInst>(Inst)) {
+    Value *Ptr = FC->convertBackToPtr(Store->getPointerOperand(), Inst);
+    StoreInst *Result = new StoreInst(FC->convert(Store->getValueOperand()),
+                                      Ptr, Inst);
+    CopyDebug(Result, Inst);
+    CopyLoadOrStoreAttrs(Result, Store);
+    Inst->eraseFromParent();
+  } else if (CallInst *Call = dyn_cast<CallInst>(Inst)) {
+    if (IntrinsicInst *ICall = dyn_cast<IntrinsicInst>(Inst)) {
+      if (ICall->getIntrinsicID() == Intrinsic::lifetime_start ||
+          ICall->getIntrinsicID() == Intrinsic::lifetime_end) {
+        // Remove alloca lifetime markers for now.  This is because
+        // the GVN pass can introduce lifetime markers taking PHI
+        // nodes as arguments.  If ReplacePtrsWithInts converts the
+        // PHI node to int type, we will render those lifetime markers
+        // ineffective.  But dropping a subset of lifetime markers is
+        // not safe in general.  So, until LLVM better defines the
+        // semantics of lifetime markers, we drop them all.  See:
+        // https://code.google.com/p/nativeclient/issues/detail?id=3443
+        Inst->eraseFromParent();
+      } else {
+        if (ICall->getIntrinsicID() == Intrinsic::dbg_declare) {
+          ConvertMetadataOperand(FC, ICall, 0);
+        }
+        FC->convertInPlace(Inst);
+      }
+    } else if (isa<InlineAsm>(Call->getCalledValue())) {
+      FC->convertInPlace(Inst);
+    } else {
+      SmallVector<Value *, 10> Args;
+      for (unsigned I = 0; I < Call->getNumArgOperands(); ++I)
+        Args.push_back(FC->convert(Call->getArgOperand(I)));
+      CallInst *NewCall = CallInst::Create(
+          FC->convertFunctionPtr(Call->getCalledValue(), Call),
+          Args, "", Inst);
+      CopyDebug(NewCall, Call);
+      NewCall->setAttributes(RemovePointerAttrs(Call->getContext(),
+                                                Call->getAttributes()));
+      NewCall->setCallingConv(Call->getCallingConv());
+      NewCall->takeName(Call);
+      FC->recordConvertedAndErase(Call, NewCall);
+    }
+  } else if (InvokeInst *Call = dyn_cast<InvokeInst>(Inst)) {
+    SmallVector<Value *, 10> Args;
+    for (unsigned I = 0; I < Call->getNumArgOperands(); ++I)
+      Args.push_back(FC->convert(Call->getArgOperand(I)));
+    InvokeInst *NewCall = InvokeInst::Create(
+        FC->convertFunctionPtr(Call->getCalledValue(), Call),
+        Call->getNormalDest(),
+        Call->getUnwindDest(),
+        Args, "", Inst);
+    CopyDebug(NewCall, Call);
+    NewCall->setAttributes(RemovePointerAttrs(Call->getContext(),
+                                              Call->getAttributes()));
+    NewCall->setCallingConv(Call->getCallingConv());
+    NewCall->takeName(Call);
+    FC->recordConvertedAndErase(Call, NewCall);
+  } else if (AllocaInst *Alloca = dyn_cast<AllocaInst>(Inst)) {
+    Type *ElementTy = Inst->getType()->getPointerElementType();
+    Type *ElementTy2 = ArrayType::get(Type::getInt8Ty(Inst->getContext()),
+                                      DL->getTypeAllocSize(ElementTy));
+    unsigned Alignment = Alloca->getAlignment();
+    if (Alignment == 0)
+      Alignment = DL->getPrefTypeAlignment(ElementTy);
+    Value *Tmp = CopyDebug(new AllocaInst(ElementTy2, Alloca->getArraySize(),
+                                          Alignment, "", Inst),
+                           Inst);
+    Tmp->takeName(Alloca);
+    Value *Alloca2 = new PtrToIntInst(Tmp, IntPtrType,
+                                      Tmp->getName() + ".asint", Inst);
+    FC->recordConvertedAndErase(Alloca, Alloca2);
+  } else if (// These atomics only operate on integer pointers, not
+             // other pointers, so we don't need to recreate the
+             // instruction.
+             isa<AtomicCmpXchgInst>(Inst) ||
+             isa<AtomicRMWInst>(Inst) ||
+             // Handle these instructions as a convenience to allow
+             // the pass to be used in more situations, even though we
+             // don't expect them in PNaCl's stable ABI.
+             isa<GetElementPtrInst>(Inst) ||
+             isa<VAArgInst>(Inst) ||
+             isa<IndirectBrInst>(Inst) ||
+             isa<ExtractValueInst>(Inst) ||
+             isa<InsertValueInst>(Inst)) {
+    FC->convertInPlace(Inst);
+  }
+}
+
+// Convert ptrtoint+inttoptr to a bitcast because it's shorter and
+// because some intrinsics work on bitcasts but not on
+// ptrtoint+inttoptr, in particular:
+//  * llvm.lifetime.start/end (although we strip these out)
+//  * llvm.eh.typeid.for
+static void SimplifyCasts(Instruction *Inst, Type *IntPtrType) {
+  if (IntToPtrInst *Cast1 = dyn_cast<IntToPtrInst>(Inst)) {
+    if (PtrToIntInst *Cast2 = dyn_cast<PtrToIntInst>(Cast1->getOperand(0))) {
+      assert(Cast2->getType() == IntPtrType);
+      Value *V = Cast2->getPointerOperand();
+      if (V->getType() != Cast1->getType())
+        V = new BitCastInst(V, Cast1->getType(), V->getName() + ".bc", Cast1);
+      Cast1->replaceAllUsesWith(V);
+      if (Cast1->use_empty())
+        Cast1->eraseFromParent();
+      if (Cast2->use_empty())
+        Cast2->eraseFromParent();
+    }
+  }
+}
+
+static void CleanUpFunction(Function *Func, Type *IntPtrType) {
+  // Remove the ptrtoint/bitcast ConstantExprs we introduced for
+  // referencing globals.
+  FunctionPass *Pass = createExpandConstantExprPass();
+  Pass->runOnFunction(*Func);
+  delete Pass;
+
+  for (Function::iterator BB = Func->begin(), E = Func->end();
+       BB != E; ++BB) {
+    for (BasicBlock::iterator Iter = BB->begin(), E = BB->end();
+         Iter != E; ) {
+      SimplifyCasts(Iter++, IntPtrType);
+    }
+  }
+  // Cleanup: Remove ptrtoints that were introduced for allocas but not used.
+  for (Function::iterator BB = Func->begin(), E = Func->end();
+       BB != E; ++BB) {
+    for (BasicBlock::iterator Iter = BB->begin(), E = BB->end();
+         Iter != E; ) {
+      Instruction *Inst = Iter++;
+      if (isa<PtrToIntInst>(Inst) && Inst->use_empty())
+        Inst->eraseFromParent();
+    }
+  }
+}
+
+char ReplacePtrsWithInts::ID = 0;
+INITIALIZE_PASS(ReplacePtrsWithInts, "replace-ptrs-with-ints",
+                "Convert pointer values to integer values",
+                false, false)
+
+bool ReplacePtrsWithInts::runOnModule(Module &M) {
+  DataLayout DL(&M);
+  Type *IntPtrType = DL.getIntPtrType(M.getContext());
+
+  for (Module::iterator Iter = M.begin(), E = M.end(); Iter != E; ) {
+    Function *OldFunc = Iter++;
+    // Intrinsics' types must be left alone.
+    if (OldFunc->isIntrinsic())
+      continue;
+
+    FunctionConverter FC(IntPtrType);
+    FunctionType *NFTy = FC.convertFuncType(OldFunc->getFunctionType());
+
+    // In order to change the function's argument types, we have to
+    // recreate the function.
+    Function *NewFunc = Function::Create(NFTy, OldFunc->getLinkage());
+    NewFunc->copyAttributesFrom(OldFunc);
+    NewFunc->setAttributes(RemovePointerAttrs(M.getContext(),
+                                              NewFunc->getAttributes()));
+    M.getFunctionList().insert(OldFunc, NewFunc);
+    NewFunc->takeName(OldFunc);
+    NewFunc->getBasicBlockList().splice(NewFunc->begin(),
+                                        OldFunc->getBasicBlockList());
+
+    // Move the arguments across to the new function.
+    for (Function::arg_iterator Arg = OldFunc->arg_begin(),
+             E = OldFunc->arg_end(), NewArg = NewFunc->arg_begin();
+         Arg != E; ++Arg, ++NewArg) {
+      FC.recordConverted(Arg, NewArg);
+      NewArg->takeName(Arg);
+    }
+
+    // Convert the function body.
+    for (Function::iterator BB = NewFunc->begin(), E = NewFunc->end();
+         BB != E; ++BB) {
+      for (BasicBlock::iterator Iter = BB->begin(), E = BB->end();
+           Iter != E; ) {
+        ConvertInstruction(&DL, IntPtrType, &FC, Iter++);
+      }
+    }
+    FC.eraseReplacedInstructions();
+    OldFunc->replaceAllUsesWith(ConstantExpr::getBitCast(NewFunc,
+                                                         OldFunc->getType()));
+    OldFunc->eraseFromParent();
+  }
+  // Now that all functions have their normalized types, we can remove
+  // various casts.
+  for (Module::iterator Func = M.begin(), E = M.end(); Func != E; ++Func) {
+    CleanUpFunction(Func, IntPtrType);
+  }
+  return true;
+}
+
+ModulePass *llvm::createReplacePtrsWithIntsPass() {
+  return new ReplacePtrsWithInts();
+}