//===-- PointerCompress.cpp - Pointer Compression Pass --------------------===//
// 
//                     The LLVM Compiler Infrastructure
//
// This file was developed by the LLVM research group and is distributed under
// the University of Illinois Open Source License. See LICENSE.TXT for details.
// 
//===----------------------------------------------------------------------===//
//
// This file implements the -pointercompress pass.
//
//===----------------------------------------------------------------------===//

#define DEBUG_TYPE "pointercompress"

#include "dsa/DataStructure.h"
#include "dsa/DSGraph.h"
#include "poolalloc/PoolAllocate.h"
#include "Heuristic.h"
#include "llvm/Constants.h"
#include "llvm/Instructions.h"
#include "llvm/Module.h"
#include "llvm/ADT/Statistic.h"
#include "llvm/ADT/STLExtras.h"
#include "llvm/Support/CommandLine.h"
#include "llvm/Support/Debug.h"
#include "llvm/Support/GetElementPtrTypeIterator.h"
#include "llvm/Support/InstVisitor.h"
#include "llvm/Support/FormattedStream.h"

#include "llvm/Transforms/Utils/Cloning.h"

using namespace llvm;

/// MEMUINTTYPE - This is the actual type we are compressing to.  This is really
/// only capable of being Int32Ty, except when we are doing tests for 16-bit
/// integers, when it's Int16Ty.
static const Type *MEMUINTTYPE;

/// SCALARUINTTYPE - We keep scalars the same size as the machine word on the
/// system (e.g. 64-bits), only keeping memory objects in MEMUINTTYPE.
static const Type *SCALARUINTTYPE;

static const Type * VoidType  = 0;
static const Type * Int8Type  = 0;
static const Type * Int16Type = 0;
static const Type * Int32Type = 0;
static const Type * Int64Type = 0;

namespace {
  cl::opt<bool>
  SmallIntCompress("compress-to-16-bits",
                   cl::desc("Pointer compress data structures to 16 bit "
                            "integers instead of 32-bit integers"));
  cl::opt<bool>
  DisablePoolBaseASR("disable-ptrcomp-poolbase-aggregation",
                     cl::desc("Don't optimize pool base loads"));
  cl::opt<bool>
  ADLFix("adl-pc",
         cl::desc("Enable Andrew's fixes/hacks"));
  

  STATISTIC (NumCompressed, "Number of pools pointer compressed");
  STATISTIC (NumNotCompressed, "Number of pools not compressible");
  STATISTIC (NumCloned    , "Number of functions cloned");

  class CompressedPoolInfo;

  /// FunctionCloneRecord - One of these is kept for each function that is
  /// cloned.
  struct FunctionCloneRecord {
    /// PAFn - The pool allocated input function that we compressed.
    ///
    Function *PAFn;
    FunctionCloneRecord(Function *pafn) : PAFn(pafn) {}

    /// PoolDescriptors - The Value* which defines the pool descriptor for this
    /// DSNode.  Note: Does not necessarily include pool arguments that are
    /// passed in because of indirect function calls that are not used in the
    /// function.
    std::map<const DSNode*, Value*> PoolDescriptors;

    /// NewToOldValueMap - This is a mapping from the values in the cloned body
    /// to the values in PAFn.
    std::map<Value*, const Value*> NewToOldValueMap;

    const Value *getValueInOriginalFunction(Value *V) const {
      std::map<Value*, const Value*>::const_iterator I =
        NewToOldValueMap.find(V);
      if (I == NewToOldValueMap.end()) {
        for (I = NewToOldValueMap.begin(); I != NewToOldValueMap.end(); ++I)
          errs() << "MAP: " << *I->first << " TO: " << *I->second << "\n";
      }
      assert (I != NewToOldValueMap.end() && "Value did not come from clone!");
      return I->second;
    }
  };

  /// PointerCompress - This transformation hacks on type-safe pool allocated
  /// data structures to reduce the size of pointers in the program.
  class PointerCompress : public ModulePass {
    PoolAllocate *PoolAlloc;
    CompleteBUDataStructures *ECG;

    /// ClonedFunctionMap - Every time we clone a function to compress its
    /// arguments, keep track of the clone and which arguments are compressed.
    typedef std::pair<Function*, std::set<const DSNode*> > CloneID;
    std::map<CloneID, Function *> ClonedFunctionMap;

    std::map<std::pair<Function*, std::vector<unsigned> >,
             Function*> ExtCloneFunctionMap;

    /// ClonedFunctionInfoMap - This identifies the pool allocated function that
    /// a clone came from.
    std::map<Function*, FunctionCloneRecord> ClonedFunctionInfoMap;
    
    /// CompressedGlobalPools - Keep track of which DSNodes in the globals graph
    /// are both pool allocated and should be compressed, and which GlobalValue
    /// their pool descriptor is.
    std::map<const DSNode*, GlobalValue*> CompressedGlobalPools;

  public:
    Constant *PoolInitPC, *PoolDestroyPC, *PoolAllocPC;
    typedef std::map<const DSNode*, CompressedPoolInfo> PoolInfoMap;
    static char ID;

    PointerCompress() : ModulePass((intptr_t)&ID) {}
    /// NoArgFunctionsCalled - When we are walking the call graph, keep track of
    /// which functions are called that don't need their prototype to be
    /// changed.
    std::vector<Function*> NoArgFunctionsCalled;

    bool runOnModule(Module &M);

    void HandleGlobalPools(Module &M);


    void getAnalysisUsage(AnalysisUsage &AU) const;

    PoolAllocate *getPoolAlloc() const { return PoolAlloc; }

    const DSGraph* getGraphForFunc(PA::FuncInfo *FI) const {
      return ECG->getDSGraph(FI->F);
    }

    /// getCloneInfo - If the specified function is a clone, return the
    /// information about the cloning process for it.  Otherwise, return a null
    /// pointer.
    FunctionCloneRecord *getCloneInfo(Function &F) {
      std::map<Function*, FunctionCloneRecord>::iterator I = 
        ClonedFunctionInfoMap.find(&F);
      return I == ClonedFunctionInfoMap.end() ? 0 : &I->second;
    }

    Function *GetFunctionClone(Function *F, 
                               std::set<const DSNode*> &PoolsToCompress,
                               PA::FuncInfo &FI, const DSGraph &CG);
    Function *GetExtFunctionClone(Function *F,
                                  const std::vector<unsigned> &Args);

  private:
    void InitializePoolLibraryFunctions(Module &M);
    bool CompressPoolsInFunction(Function &F,
                std::vector<std::pair<Value*, Value*> > *PremappedVals = 0,
                std::set<const DSNode*> *ExternalPoolsToCompress = 0);

    void FindPoolsToCompress(std::set<const DSNode*> &Pools,
                             std::map<const DSNode*, Value*> &PreassignedPools,
                             Function &F, DSGraph* DSG, PA::FuncInfo *FI);
  };

  char PointerCompress::ID = 0;
  RegisterPass<PointerCompress>
  X("pointercompress", "Compress type-safe data structures");
}

//===----------------------------------------------------------------------===//
//               CompressedPoolInfo Class and Implementation
//===----------------------------------------------------------------------===//

namespace {
  /// CompressedPoolInfo - An instance of this structure is created for each
  /// pool that is compressed.
  class CompressedPoolInfo {
    const DSNode *Pool;
    Value *PoolDesc;
    const Type *NewTy;
    unsigned NewSize;
    mutable Value *PoolBase;
  public:
    CompressedPoolInfo(const DSNode *N, Value *PD)
      : Pool(N), PoolDesc(PD), NewTy(0), PoolBase(0) {}
    
    /// Initialize - When we know all of the pools in a function that are going
    /// to be compressed, initialize our state based on that data.
    void Initialize(std::map<const DSNode*, CompressedPoolInfo> &Nodes,
                    const TargetData &TD);

    const DSNode *getNode() const { return Pool; }
    const Type *getNewType() const { return NewTy; }

    /// getNewSize - Return the size of each node after compression.
    ///
    unsigned getNewSize() const { return NewSize; }
    
    /// getPoolDesc - Return the Value* for the pool descriptor for this pool.
    ///
    Value *getPoolDesc() const { return PoolDesc; }

    /// EmitPoolBaseLoad - Emit code to load the pool base value for this pool
    /// before the specified instruction.
    Value *EmitPoolBaseLoad(Instruction &I) const;
    void setPoolBase(Value *PB) const { PoolBase = PB; }

    // dump - Emit a debugging dump of this pool info.
    void dump() const;

  private:
    const Type *ComputeCompressedType(const Type *OrigTy, unsigned NodeOffset,
                           std::map<const DSNode*, CompressedPoolInfo> &Nodes);
  };
}

/// Initialize - When we know all of the pools in a function that are going
/// to be compressed, initialize our state based on that data.
void CompressedPoolInfo::Initialize(std::map<const DSNode*, 
                                             CompressedPoolInfo> &Nodes,
                                    const TargetData &TD) {
  // First step, compute the type of the compressed node.  This basically
  // replaces all pointers to compressed pools with uints.
//FIXME: TYPE
  //  NewTy = ComputeCompressedType(Pool->getType(), 0, Nodes);
  NewTy = 0;

  // Get the compressed type size.
  //NewSize = NewTy->isSized() ? TD.getTypeAllocSize(NewTy) : 0;
  NewSize = 0;
}


/// ComputeCompressedType - Recursively compute the new type for this node after
/// pointer compression.  This involves compressing any pointers that point into
/// compressed pools.
const Type *CompressedPoolInfo::
ComputeCompressedType(const Type *OrigTy, unsigned NodeOffset,
                      std::map<const DSNode*, CompressedPoolInfo> &Nodes) {
  if (dyn_cast<PointerType>(OrigTy)) {
    if (ADLFix) {
      DSNode *PointeeNode = getNode()->getLink(NodeOffset).getNode();
      if (PointeeNode == getNode())
        return MEMUINTTYPE;
      return OrigTy;
    }

    // Okay, we have a pointer.  Check to see if the node pointed to is actually
    // compressed!
    //DSNode *PointeeNode = getNode()->getLink(NodeOffset).getNode();
    //if (PointeeNode && Nodes.count(PointeeNode))
      return MEMUINTTYPE;
    // Otherwise, it points to a non-compressed node.
    return OrigTy;
  } else if (OrigTy->isFirstClassType() || OrigTy == VoidType)
    return OrigTy;


  const TargetData &TD = getNode()->getParentGraph()->getTargetData();

  // Okay, we have an aggregate type.
  if (const StructType *STy = dyn_cast<StructType>(OrigTy)) {
    std::vector<const Type*> Elements;
    Elements.reserve(STy->getNumElements());

    const StructLayout *SL = TD.getStructLayout(STy);

    for (unsigned i = 0, e = STy->getNumElements(); i != e; ++i)
      Elements.push_back(ComputeCompressedType(STy->getElementType(i),
                                               NodeOffset+SL->getElementOffset(i),
                                               Nodes));
    return StructType::get(STy->getContext(),Elements);
  } else if (const ArrayType *ATy = dyn_cast<ArrayType>(OrigTy)) {
    return ArrayType::get(ComputeCompressedType(ATy->getElementType(),
                                                NodeOffset, Nodes),
                          ATy->getNumElements());
  } else {
    errs() << "TYPE: " << *OrigTy << "\n";
    assert(0 && "FIXME: Unhandled aggregate type!");
    abort();
  }
}

/// EmitPoolBaseLoad - Emit code to load the pool base value for this pool
/// before the specified instruction.
Value *CompressedPoolInfo::EmitPoolBaseLoad(Instruction &I) const {
  if (DisablePoolBaseASR) {
    assert(PoolBase == 0 && "Mixing and matching optimized vs not!");
    
    // Get the pool base pointer.
    Constant *Zero = ConstantInt::get(Int32Type, 0);
    Value *Opts[2] = {Zero, Zero};
    Value *BasePtrPtr = GetElementPtrInst::Create(getPoolDesc(), Opts, Opts + 2,
                                              "poolbaseptrptr", &I);
    return new LoadInst(BasePtrPtr, "poolbaseptr", &I);
  } else {
    // If this is a pool descriptor passed into the function, and this is the
    // first use, emit a load of the pool base into the entry of the function.
    if (PoolBase == 0 && (isa<Argument>(PoolDesc) || 
                          isa<GlobalVariable>(PoolDesc))) {
      BasicBlock::iterator IP = I.getParent()->getParent()->begin()->begin();
      while (isa<AllocaInst>(IP)) ++IP;
      Constant *Zero = ConstantInt::get(Int32Type, 0);
      Value *Opts[2] = {Zero, Zero};
      Value *BasePtrPtr = GetElementPtrInst::Create(getPoolDesc(), Opts, Opts + 2,
                                                "poolbaseptrptr", IP);
      PoolBase = new LoadInst(BasePtrPtr, "poolbaseptr", IP);
    }
    
    assert(PoolBase && "Mixing and matching optimized vs not!");
    return PoolBase;
  }
}


/// dump - Emit a debugging dump for this pool info.
///
void CompressedPoolInfo::dump() const {
//  const TargetData &TD = getNode()->getParentGraph()->getTargetData();
//FIXME: type
  //errs() << "  From size: "
//            << (getNode()->getType()->isSized() ?
//                        TD.getTypeAllocSize(getNode()->getType()) : 0)
//            << "  To size: "
//            << (NewTy->isSized() ? TD.getTypeAllocSize(NewTy) : 0) << "\n";
//  errs() << "Node: "; getNode()->dump();
//  errs() << "New Type: " << *NewTy << "\n";
}


//===----------------------------------------------------------------------===//
//                    InstructionRewriter Implementation
//===----------------------------------------------------------------------===//

namespace {
  /// InstructionRewriter - This class implements the rewriting neccesary to
  /// transform a function body from normal pool allocation to pointer
  /// compression.  It is constructed, then the 'visit' method is called on a
  /// function.  If is responsible for rewriting all instructions that refer to
  /// pointers into compressed pools.
  class InstructionRewriter : public llvm::InstVisitor<InstructionRewriter> {
    /// OldToNewValueMap - This keeps track of what new instructions we create
    /// for instructions that used to produce pointers into our pool.
    std::map<Value*, Value*> OldToNewValueMap;
  
    const PointerCompress::PoolInfoMap &PoolInfo;

    /// TD - The TargetData object for the current target.
    ///
    const TargetData &TD;


    DSGraph* DSG;

    /// PAFuncInfo - Information about the transformation the pool allocator did
    /// to the original function.
    PA::FuncInfo &PAFuncInfo;

    /// FCR - If we are compressing a clone of a pool allocated function (as
    /// opposed to the pool allocated function itself), this contains
    /// information about the clone.
    FunctionCloneRecord *FCR;

    PointerCompress &PtrComp;
  public:
    InstructionRewriter(const PointerCompress::PoolInfoMap &poolInfo,
                        DSGraph* dsg, PA::FuncInfo &pafi,
                        FunctionCloneRecord *fcr, PointerCompress &ptrcomp)
      : PoolInfo(poolInfo), TD(dsg->getTargetData()), DSG(dsg),
        PAFuncInfo(pafi), FCR(fcr), PtrComp(ptrcomp) {
    }

    ~InstructionRewriter();

    /// PremapValues - Seed the transformed value map with the specified values.
    /// This indicates that the first value (a pointer) will map to the second
    /// value (an integer).  When the InstructionRewriter is complete, all of
    /// the pointers in this vector are deleted.
    void PremapValues(std::vector<std::pair<Value*, Value*> > &Vals) {
      for (unsigned i = 0, e = Vals.size(); i != e; ++i)
        OldToNewValueMap.insert(Vals[i]);
    }

    /// getTransformedValue - Return the transformed version of the specified
    /// value, creating a new forward ref value as needed.
    Value *getTransformedValue(Value *V) {
      if (isa<ConstantPointerNull>(V))                // null -> uint 0
        return ConstantInt::get(SCALARUINTTYPE, 0);
      if (isa<UndefValue>(V))                // undef -> uint undef
        return UndefValue::get(SCALARUINTTYPE);

      if (!getNodeIfCompressed(V))
        assert(getNodeIfCompressed(V) && "Value is not compressed!");
      Value *&RV = OldToNewValueMap[V];
      if (RV) return RV;

      RV = new Argument(SCALARUINTTYPE);
      return RV;
    }

    /// setTransformedValue - When we create a new value, this method sets it as
    /// the current value.
    void setTransformedValue(Instruction &Old, Value *New) {
      Value *&EV = OldToNewValueMap[&Old];
      if (EV) {
        assert(isa<Argument>(EV) && "Not a forward reference!");
        EV->replaceAllUsesWith(New);
        delete EV;
      }
      EV = New;
    }

    /// getMappedNodeHandle - Given a pointer value that may be cloned multiple
    /// times (once for PA, once for PC) return the node handle in DSG, or a
    /// null descriptor if the value didn't exist.
    DSNodeHandle getMappedNodeHandle(Value *V) {
      assert(isa<PointerType>(V->getType()) && "Not a pointer value!");

      // If this is a function clone, map the value to the original function.
      if (FCR)
        V = const_cast<Value*>(FCR->getValueInOriginalFunction(V));

      // If this is a pool allocator clone, map the value to the REAL original
      // function.
      if (!PAFuncInfo.NewToOldValueMap.empty())
        if ((V = PAFuncInfo.MapValueToOriginal(V)) == 0)
          // Value didn't exist in the orig program (pool desc?).
          return DSNodeHandle();

      return DSG->getNodeForValue(V);
    }

    /// getNodeIfCompressed - If the specified value is a pointer that will be
    /// compressed, return the DSNode corresponding to the pool it belongs to.
    const DSNode *getNodeIfCompressed(Value *V) {
      if (!isa<PointerType>(V->getType()) || isa<ConstantPointerNull>(V) ||
          isa<Function>(V))
        return 0;

      DSNode *N = getMappedNodeHandle(V).getNode();
      return PoolInfo.count(N) ? N : 0;
    }

    /// getPoolInfo - Return the pool info for the specified compressed pool.
    ///
    const CompressedPoolInfo &getPoolInfo(const DSNode *N) {
      assert(N && "Pool not compressed!");
      PointerCompress::PoolInfoMap::const_iterator I = PoolInfo.find(N);
      assert(I != PoolInfo.end() && "Pool is not compressed!");
      return I->second;
    }

    /// getPoolInfo - Return the pool info object for the specified value if the
    /// pointer points into a compressed pool, otherwise return null.
    const CompressedPoolInfo *getPoolInfo(Value *V) {
      if (const DSNode *N = getNodeIfCompressed(V))
        return &getPoolInfo(N);
      return 0;
    }

    /// getPoolInfoForPoolDesc - Given a pool descriptor as a Value*, return the
    /// pool info for the pool if it is compressed.
    const CompressedPoolInfo *getPoolInfoForPoolDesc(Value *PD) const {
      for (PointerCompress::PoolInfoMap::const_iterator I = PoolInfo.begin(),
             E = PoolInfo.end(); I != E; ++I)
        if (I->second.getPoolDesc() == PD)
          return &I->second;
      return 0;
    }

    /// ValueRemoved - Whenever we remove a value from the current function,
    /// update any maps that contain that pointer so we don't have stale
    /// pointers hanging around.
    void ValueRemoved(Value *V) {
      if (FCR) {
        // If this is in a pointer-compressed clone, update our map.
        FCR->NewToOldValueMap.erase(V);
      } else if (!PAFuncInfo.NewToOldValueMap.empty()) {
        // Otherwise if this exists in a pool allocator clone, update it now.
        PAFuncInfo.NewToOldValueMap.erase(V);
      } else {
        // Otherwise if this was in the original function, remove it from the
        // DSG scalar map if it is there.
        DSG->getScalarMap().eraseIfExists(V);
      }
    }

    /// ValueReplaced - Whenever we replace a value from the current function,
    /// update any maps that contain that value so we don't have stale pointers
    /// hanging around.
    void ValueReplaced(Value &Old, Value *New) {
      // If this value exists in a pointer compress clone, update it now.
      if (FCR) {
        std::map<Value*, const Value*>::iterator I =
          FCR->NewToOldValueMap.find(&Old);
        assert(I != FCR->NewToOldValueMap.end() && "Didn't find element!?");
        FCR->NewToOldValueMap.insert(std::make_pair(New, I->second));
        FCR->NewToOldValueMap.erase(I);
      } else if (!PAFuncInfo.NewToOldValueMap.empty()) {
        // Otherwise if this exists in a pool allocator clone, update it now.
        PA::FuncInfo::NewToOldValueMapTy::iterator I =
          PAFuncInfo.NewToOldValueMap.find(&Old);
        if (I != PAFuncInfo.NewToOldValueMap.end()) {
          PAFuncInfo.NewToOldValueMap[New] = I->second;
          PAFuncInfo.NewToOldValueMap.erase(I);
        }
      
      } else {
        // Finally, if this occurred in a function that neither the pool
        // allocator nor the ptr compression implementation had to change,
        // update the DSGraph.
        if (DSG->getScalarMap().count(&Old))
          DSG->getScalarMap().replaceScalar(&Old, New);
      }
    }

    //===------------------------------------------------------------------===//
    // Visitation methods.  These do all of the heavy lifting for the various
    // cases we have to handle.

    void visitReturnInst(ReturnInst &RI);
    void visitCastInst(CastInst &CI);
    void visitPHINode(PHINode &PN);
    void visitSelectInst(SelectInst &SI);
    void visitICmpInst(ICmpInst &I);
    void visitFCmpInst(FCmpInst &I);
    void visitGetElementPtrInst(GetElementPtrInst &GEPI);
    void visitLoadInst(LoadInst &LI);
    void visitStoreInst(StoreInst &SI);

    void visitCallInst(CallInst &CI);
    void visitPoolInit(CallInst &CI);
    void visitPoolAlloc(CallInst &CI);
    void visitPoolDestroy(CallInst &CI);

    void visitInstruction(Instruction &I) {
#ifndef NDEBUG
      bool Unhandled = !!getNodeIfCompressed(&I);
      for (unsigned i = 0, e = I.getNumOperands(); i != e; ++i)
        Unhandled |= !!getNodeIfCompressed(I.getOperand(i));

      if (Unhandled) {
        errs() << "ERROR: UNHANDLED INSTRUCTION: " << I;
        //assert(0);
        //abort();
      }
#endif
    }
  };
} // end anonymous namespace.


InstructionRewriter::~InstructionRewriter() {
  // Nuke all of the old values from the program.
  for (std::map<Value*, Value*>::iterator I = OldToNewValueMap.begin(),
         E = OldToNewValueMap.end(); I != E; ++I) {
    assert((!isa<Argument>(I->second) || cast<Argument>(I->second)->getParent())
           && "ERROR: Unresolved value still left in the program!");
    // If there is anything still using this, provide a temporary value.
    if (!I->first->use_empty())
      I->first->replaceAllUsesWith(UndefValue::get(I->first->getType()));

    // Finally, remove it from the program.
    if (Instruction *Inst = dyn_cast<Instruction>(I->first)) {
      ValueRemoved(Inst);
      Inst->eraseFromParent();
    } else if (Argument *Arg = dyn_cast<Argument>(I->first)) {
      assert(Arg->getParent() == 0 && "Unexpected argument type here!");
      delete Arg;  // Marker node used when cloning.
    } else {
      assert(0 && "Unknown entry in this map!");
    }
  }
}

void InstructionRewriter::visitReturnInst(ReturnInst &RI) {
  if (RI.getNumOperands() && isa<PointerType>(RI.getOperand(0)->getType()))
    if (!isa<PointerType>(RI.getParent()->getParent()->getReturnType())) {
      // Compressing the return value.  
      ReturnInst::Create(RI.getContext(),
                         getTransformedValue(RI.getOperand(0)), &RI);
      RI.eraseFromParent();
    }
}


void InstructionRewriter::visitCastInst(CastInst &CI) {
  if (!isa<PointerType>(CI.getType())) {
    // If this is a pointer -> integer cast, turn this into an idx -> integer
    // cast.
    if (isa<PointerType>(CI.getOperand(0)->getType()) &&
        getPoolInfo(CI.getOperand(0)))
      CI.setOperand(0, getTransformedValue(CI.getOperand(0)));
    return;
  }

  const CompressedPoolInfo *PI = getPoolInfo(&CI);
  if (!PI) return;
  assert(getPoolInfo(CI.getOperand(0)) == PI && "Not cast from ptr -> ptr?");

  // A cast from one pointer to another turns into a cast from uint -> uint,
  // which is a noop.
  setTransformedValue(CI, getTransformedValue(CI.getOperand(0)));
}

void InstructionRewriter::visitPHINode(PHINode &PN) {
  const CompressedPoolInfo *DestPI = getPoolInfo(&PN);
  if (DestPI == 0) return;

  PHINode *New = PHINode::Create (SCALARUINTTYPE, PN.getName(), &PN);
  New->reserveOperandSpace(PN.getNumIncomingValues());

  for (unsigned i = 0, e = PN.getNumIncomingValues(); i != e; ++i)
    New->addIncoming(getTransformedValue(PN.getIncomingValue(i)),
                     PN.getIncomingBlock(i));
  setTransformedValue(PN, New);
}

void InstructionRewriter::visitSelectInst(SelectInst &SI) {
  const CompressedPoolInfo *DestPI = getPoolInfo(&SI);
  if (DestPI == 0) return;

  setTransformedValue(SI, SelectInst::Create(SI.getOperand(0),
                                         getTransformedValue(SI.getOperand(1)),
                                         getTransformedValue(SI.getOperand(2)),
                                         SI.getName(), &SI));
}

void InstructionRewriter::visitICmpInst(ICmpInst &SCI) {
  if (!isa<PointerType>(SCI.getOperand(0)->getType())) return;
  Value *NonNullPtr = SCI.getOperand(0);
  if (isa<ConstantPointerNull>(NonNullPtr)) {
    NonNullPtr = SCI.getOperand(1);
    if (isa<ConstantPointerNull>(NonNullPtr))
      return;  // setcc null, null
  }

  const CompressedPoolInfo *SrcPI = getPoolInfo(NonNullPtr);
  if (SrcPI == 0) return;   // comparing non-compressed pointers.
 
  std::string Name = SCI.getName(); SCI.setName("");
  Value *New = new ICmpInst(&SCI, SCI.getPredicate(),
                            getTransformedValue(SCI.getOperand(0)),
                            getTransformedValue(SCI.getOperand(1)),
                            Name);
  SCI.replaceAllUsesWith(New);
  ValueReplaced(SCI, New);
  SCI.eraseFromParent();
}

void InstructionRewriter::visitFCmpInst(FCmpInst &SCI) {
  if (!isa<PointerType>(SCI.getOperand(0)->getType())) return;
  Value *NonNullPtr = SCI.getOperand(0);
  if (isa<ConstantPointerNull>(NonNullPtr)) {
    NonNullPtr = SCI.getOperand(1);
    if (isa<ConstantPointerNull>(NonNullPtr))
      return;  // setcc null, null
  }

  const CompressedPoolInfo *SrcPI = getPoolInfo(NonNullPtr);
  if (SrcPI == 0) return;   // comparing non-compressed pointers.
 
  std::string Name = SCI.getName(); SCI.setName("");
  Value *New = new FCmpInst(&SCI, SCI.getPredicate(),
                            getTransformedValue(SCI.getOperand(0)),
                            getTransformedValue(SCI.getOperand(1)),
                            Name);
  SCI.replaceAllUsesWith(New);
  ValueReplaced(SCI, New);
  SCI.eraseFromParent();
}

void InstructionRewriter::visitGetElementPtrInst(GetElementPtrInst &GEPI) {
  const CompressedPoolInfo *PI = getPoolInfo(&GEPI);
  if (PI == 0) return;

  // Get the base index.
  Value *Val = getTransformedValue(GEPI.getOperand(0));

  bool AllZeros = true;
  for (unsigned i = 1, e = GEPI.getNumOperands(); i != e; ++i)
    if (!isa<Constant>(GEPI.getOperand(i)) ||
        !cast<Constant>(GEPI.getOperand(i))->isNullValue()) {
      AllZeros = false;
      break;
    }
  if (AllZeros) {
    // We occasionally get non-type-matching GEP instructions with zeros.  These
    // are effectively pointer casts, so treat them as such.
    setTransformedValue(GEPI, Val);
    return;
  }

  // The compressed type for the pool.  FIXME: NOTE: This only works if 'Val'
  // pointed to the start of a node!
  const Type *NTy = PointerType::getUnqual(PI->getNewType());

  //Check if we have a pointer to an array of Original Types this happens if
  //you do a malloc of [n x OrigTy] for a pool of Type OrigTy
  if(isa<PointerType>(GEPI.getOperand(0)->getType())) {
    const Type* PT =
      cast<PointerType>(GEPI.getOperand(0)->getType())->getElementType();
    if(isa<ArrayType>(PT)) {
      //FIXME: TYPE
//      if (cast<ArrayType>(PT)->getElementType() == PI->getNode()->getType())
//        NTy = PointerType::getUnqual(ArrayType::get(PI->getNewType(),
//                                              cast<ArrayType>(PT)->getNumElements()));
    }
  }


  gep_type_iterator GTI = gep_type_begin(GEPI), E = gep_type_end(GEPI);
  for (unsigned i = 1, e = GEPI.getNumOperands(); i != e; ++i, ++GTI) {
    Value *Idx = GEPI.getOperand(i);
    if (const StructType *STy = dyn_cast<StructType>(*GTI)) {
      uint64_t Field = (unsigned)cast<ConstantInt>(Idx)->getZExtValue();
      if (Field) {
        uint64_t FieldOffs = TD.getStructLayout(cast<StructType>(NTy))
          ->getElementOffset(Field);
        Constant *FieldOffsCst = ConstantInt::get(SCALARUINTTYPE, FieldOffs);
        Val = BinaryOperator::CreateAdd(Val, FieldOffsCst,
                                        GEPI.getName(), &GEPI);
      }

      // If this is a one element struct, NTy may not have the structure type.
      if (STy->getNumElements() > 1 ||
          (isa<StructType>(NTy) &&
           cast<StructType>(NTy)->getNumElements() == 1))
        NTy = cast<StructType>(NTy)->getElementType(Field);
    } else {
      assert(isa<SequentialType>(*GTI) && "Not struct or sequential?");
      const SequentialType *STy = cast<SequentialType>(*GTI);
      if (!isa<Constant>(Idx) || !cast<Constant>(Idx)->isNullValue()) {
        // Add Idx*sizeof(NewElementType) to the index.
        const Type *ElTy = cast<SequentialType>(NTy)->getElementType();
        if (Idx->getType() != SCALARUINTTYPE)
          Idx = CastInst::CreateSExtOrBitCast(Idx, SCALARUINTTYPE, Idx->getName(), &GEPI);

        Constant *Scale = ConstantInt::get(SCALARUINTTYPE,
					   TD.getTypeAllocSize(ElTy));
        Idx = BinaryOperator::CreateMul(Idx, Scale, "fieldidx", &GEPI);
        Val = BinaryOperator::CreateAdd(Val, Idx, GEPI.getName(), &GEPI);
      }

      // If this is a one element array type, NTy may not reflect the array.
      if (!isa<ArrayType>(STy) || cast<ArrayType>(STy)->getNumElements() != 1 ||
          (isa<ArrayType>(NTy) && cast<ArrayType>(NTy)->getNumElements() == 1))
        NTy = cast<SequentialType>(NTy)->getElementType();
    }
  }

  setTransformedValue(GEPI, Val);
}

void InstructionRewriter::visitLoadInst(LoadInst &LI) {
  const CompressedPoolInfo *SrcPI = getPoolInfo(LI.getOperand(0));
  if (SrcPI == 0) {
    // If we are loading a compressed pointer from a non-compressessed memory
    // object, retain the load, but cast from the pointer type to our scalar
    // type.
    if (getPoolInfo(&LI)) {
      Value *NLI = new LoadInst(LI.getOperand(0), LI.getName()+".cp", &LI);
      Value *NC = CastInst::CreateZExtOrBitCast(NLI, SCALARUINTTYPE, NLI->getName(), &LI);
      setTransformedValue(LI, NC);
    }
    return;
  }

  // We care about two cases, here:
  //  1. Loading a normal value from a ptr compressed data structure.
  //  2. Loading a compressed ptr from a ptr compressed data structure.
  bool LoadingCompressedPtr = getNodeIfCompressed(&LI) != 0;

  Value *BasePtr = SrcPI->EmitPoolBaseLoad(LI);

  // Get the pointer to load from.
  Value* Ops = getTransformedValue(LI.getOperand(0));
  if (Ops->getType() == Int16Type)
    Ops = CastInst::CreateZExtOrBitCast(Ops, Int32Type, "extend_idx", &LI);
  Value *SrcPtr = GetElementPtrInst::Create(BasePtr, Ops,
                                        LI.getOperand(0)->getName()+".pp", &LI);
  const Type *DestTy = LoadingCompressedPtr ? MEMUINTTYPE : LI.getType();
  SrcPtr = CastInst::CreatePointerCast(SrcPtr, PointerType::getUnqual(DestTy),
                                      SrcPtr->getName(), &LI);
  std::string OldName = LI.getName(); LI.setName("");
  Value *NewLoad = new LoadInst(SrcPtr, OldName, &LI);

  if (LoadingCompressedPtr) {
    // Convert from MEMUINTTYPE to SCALARUINTTYPE if different.
    if (MEMUINTTYPE != SCALARUINTTYPE)
      NewLoad = CastInst::CreateZExtOrBitCast(NewLoad, SCALARUINTTYPE, NewLoad->getName(), &LI);

    setTransformedValue(LI, NewLoad);
  } else {
    LI.replaceAllUsesWith(NewLoad);
    ValueReplaced(LI, NewLoad);
    LI.eraseFromParent();
  }
}


void InstructionRewriter::visitStoreInst(StoreInst &SI) {
  const CompressedPoolInfo *DestPI = getPoolInfo(SI.getOperand(1));
  if (DestPI == 0) {
    // If we are storing a compressed pointer into uncompressed memory, just
    // cast the index to a pointer type and store that.
    if (getPoolInfo(SI.getOperand(0))) {
      Value *SrcVal = getTransformedValue(SI.getOperand(0));
      SrcVal = CastInst::CreatePointerCast(SrcVal, SI.getOperand(0)->getType(),
                                           SrcVal->getName(), &SI);
      SI.setOperand(0, SrcVal);
    }
    return;
  }

  // We care about two cases, here:
  //  1. Storing a normal value into a ptr compressed data structure.
  //  2. Storing a compressed ptr into a ptr compressed data structure.  Note
  //     that we cannot use the src value to decide if this is a compressed
  //     pointer if it's a null pointer.  We have to try harder.
  //
  Value *SrcVal = SI.getOperand(0);
  if (!isa<ConstantPointerNull>(SrcVal)) {
    if (getPoolInfo(SrcVal)) {
      // If the stored value is compressed, get the xformed version
      SrcVal = getTransformedValue(SrcVal);

      // If SCALAR type is not the MEM type, reduce it now.
      if (SrcVal->getType() != MEMUINTTYPE)
        SrcVal = CastInst::CreateZExtOrBitCast(SrcVal, MEMUINTTYPE, SrcVal->getName(), &SI);
    }
  } else {
    // FIXME: This assumes that all null pointers are compressed!
    SrcVal = ConstantInt::get(MEMUINTTYPE, 0);
  }
  
  // Get the pool base pointer.
  Value *BasePtr = DestPI->EmitPoolBaseLoad(SI);

  // Get the pointer to store to.
  Value* Ops = getTransformedValue(SI.getOperand(1));
  if (Ops->getType() == Int16Type)
    Ops = CastInst::CreateZExtOrBitCast(Ops, Int32Type, "extend_idx", &SI);

  Value *DestPtr = GetElementPtrInst::Create(BasePtr, Ops,
                                         SI.getOperand(1)->getName()+".pp",
                                         &SI);
  DestPtr = CastInst::CreatePointerCast(DestPtr,
                                        PointerType::getUnqual(SrcVal->getType()),
                                        DestPtr->getName(), &SI);
  new StoreInst(SrcVal, DestPtr, &SI);

  // Finally, explicitly remove the store from the program, as it does not
  // produce a pointer result.
  SI.eraseFromParent();
}


void InstructionRewriter::visitPoolInit(CallInst &CI) {
  // Transform to poolinit_pc if this is initializing a pool that we are
  // compressing.
  const CompressedPoolInfo *PI = getPoolInfoForPoolDesc(CI.getOperand(1));
  if (PI == 0) return;  // Pool isn't compressed.

  std::vector<Value*> Ops;
  Ops.push_back(CI.getOperand(1));
  // Transform to pass in the compressed size.
  Ops.push_back(ConstantInt::get(Int32Type, PI->getNewSize()));

  // Pointer compression can reduce the alignment restriction to 4 bytes from 8.
  // Reevaluate the desired alignment.
  Ops.push_back(ConstantInt::get(Int32Type,
             PA::Heuristic::getRecommendedAlignment(PI->getNewType(), TD)));
  // TODO: Compression could reduce the alignment restriction for the pool!
  Value *PB = CallInst::Create(PtrComp.PoolInitPC, Ops.begin(), Ops.end(), "", &CI);

  if (!DisablePoolBaseASR) { // Load the pool base immediately.
    PB->setName(CI.getOperand(1)->getName()+".poolbase");
    // Remember the pool base for this pool.
    PI->setPoolBase(PB);
  }

  CI.eraseFromParent();
}

void InstructionRewriter::visitPoolDestroy(CallInst &CI) {
  // Transform to pooldestroy_pc if this is destroying a pool that we are
  // compressing.
  const CompressedPoolInfo *PI = getPoolInfoForPoolDesc(CI.getOperand(1));
  if (PI == 0) return;  // Pool isn't compressed.

  CallInst::Create(PtrComp.PoolDestroyPC, CI.getOperand(1), "", &CI);
  CI.eraseFromParent();
}

void InstructionRewriter::visitPoolAlloc(CallInst &CI) {
  const CompressedPoolInfo *PI = getPoolInfo(&CI);
  if (PI == 0) return;  // Pool isn't compressed.

  Value *Size = CI.getOperand(2);

  // If there was a recommended size, shrink it down now.
  if (unsigned OldSizeV = PA::Heuristic::getRecommendedSize(PI->getNode()))
    if (OldSizeV != PI->getNewSize()) {
      // Emit code to scale the allocated size down by the old size then up by
      // the new size.  We actually compute (N+OS-1)/OS * NS.
      Value *OldSize = ConstantInt::get(Int32Type, OldSizeV);
      Value *NewSize = ConstantInt::get(Int32Type, PI->getNewSize());

      Size = BinaryOperator::CreateAdd(Size,
				       ConstantInt::get(Int32Type, 
							OldSizeV-1),
                                       "roundup", &CI);
      Size = BinaryOperator::CreateUDiv(Size, OldSize, "numnodes", &CI);
      Size = BinaryOperator::CreateMul(Size, NewSize, "newbytes", &CI);
    }

  Value *Opts[2] = {CI.getOperand(1), Size};
  Value *NC = CallInst::Create(PtrComp.PoolAllocPC, Opts, Opts + 2, CI.getName(), &CI);
  setTransformedValue(CI, NC);
}


void InstructionRewriter::visitCallInst(CallInst &CI) {
  if (Function *F = CI.getCalledFunction()) {
    // These functions are handled specially.
    if (F->getName() == "poolinit") {
      visitPoolInit(CI);
      return;
    } else if (F->getName() == "pooldestroy") {
      visitPoolDestroy(CI);
      return;
    } else if (F->getName() == "poolalloc") {
      visitPoolAlloc(CI);
      return;
    }
  }

  // Normal function call: check to see if this call produces or uses a pointer
  // into a compressed pool.  If so, we will need to transform the callee or use
  // a previously transformed version.

  // PoolsToCompress - Keep track of which pools we are supposed to compress,
  // with the nodes from the callee's graph.
  std::set<const DSNode*> PoolsToCompress;

  // If this is a direct call, get the information about the callee.
  PA::FuncInfo *FI = 0;
  const DSGraph *CG = 0;
  Function *Callee = CI.getCalledFunction();
  if (Callee)
    if ((FI = PtrComp.getPoolAlloc()->getFuncInfoOrClone(*Callee)))
      CG = PtrComp.getGraphForFunc(FI);

  if (!Callee) {
    // Indirect call: you CAN'T passed compress pointers in.  Don't even think
    // about it.
    return;
  } else if (Callee->isDeclaration()) {
    // We don't have a DSG for the callee in this case.  Assume that things will
    // work out if we pass compressed pointers.
    std::vector<Value*> Operands;
    Operands.reserve(CI.getNumOperands()-1);

    // If this is one of the functions we know about, just materialize the
    // compressed pointer as a real pointer, and pass it.
    if (Callee->getName() == "printf" || Callee->getName() == "sprintf") {
      for (unsigned i = 1, e = CI.getNumOperands(); i != e; ++i)
        if (isa<PointerType>(CI.getOperand(i)->getType()) &&
            getPoolInfo(CI.getOperand(i)))
          CI.setOperand(i, getTransformedValue(CI.getOperand(i)));
      return;
    } else if (Callee->getName() == "read") {
      if (const CompressedPoolInfo *DestPI = getPoolInfo(CI.getOperand(2))) {
        Value *BasePtr = DestPI->EmitPoolBaseLoad(CI);
        Value *SrcPtr = GetElementPtrInst::Create(BasePtr, getTransformedValue(CI.getOperand(2)),
                                       CI.getOperand(2)->getName()+".pp", &CI);
        SrcPtr = CastInst::CreatePointerCast(SrcPtr, CI.getOperand(2)->getType(), "", &CI);
        CI.setOperand(2, SrcPtr);
        return;
      }
    } else if (Callee->getName() == "fwrite") {
      if (const CompressedPoolInfo *DestPI = getPoolInfo(CI.getOperand(1))) {
        Value *BasePtr = DestPI->EmitPoolBaseLoad(CI);
        Value *SrcPtr = GetElementPtrInst::Create(BasePtr, getTransformedValue(CI.getOperand(1)),
                                       CI.getOperand(1)->getName()+".pp", &CI);
        SrcPtr = CastInst::CreatePointerCast(SrcPtr, CI.getOperand(1)->getType(), "", &CI);
        CI.setOperand(1, SrcPtr);
        return;
      }
    } else if (Callee->getName() == "llvm.memset" ||
               Callee->getName() == "llvm.memset.i32" ||
               Callee->getName() == "llvm.memset.i64") {
      if (const CompressedPoolInfo *DestPI = getPoolInfo(CI.getOperand(1))) {
        Value *BasePtr = DestPI->EmitPoolBaseLoad(CI);
        Value *SrcPtr = GetElementPtrInst::Create(BasePtr, getTransformedValue(CI.getOperand(1)),
                                       CI.getOperand(1)->getName()+".pp", &CI);
        SrcPtr = CastInst::CreatePointerCast(SrcPtr, CI.getOperand(1)->getType(), "", &CI);
        CI.setOperand(1, SrcPtr);
        return;
      }
    } else if (Callee->getName() == "llvm.memcpy" ||
               Callee->getName() == "llvm.memcpy.i32" ||
               Callee->getName() == "llvm.memcpy.i64") {
      bool doret = false;
      if (const CompressedPoolInfo *DestPI = getPoolInfo(CI.getOperand(1))) {
        Value *BasePtr = DestPI->EmitPoolBaseLoad(CI);
        Value *SrcPtr = GetElementPtrInst::Create(BasePtr, getTransformedValue(CI.getOperand(1)),
                                       CI.getOperand(1)->getName()+".pp", &CI);
        SrcPtr = CastInst::CreatePointerCast(SrcPtr, CI.getOperand(1)->getType(), "", &CI);
        CI.setOperand(1, SrcPtr);
        doret = true;
      }
      if (const CompressedPoolInfo *DestPI = getPoolInfo(CI.getOperand(2))) {
        Value *BasePtr = DestPI->EmitPoolBaseLoad(CI);
        Value *SrcPtr = GetElementPtrInst::Create(BasePtr, getTransformedValue(CI.getOperand(2)),
                                       CI.getOperand(2)->getName()+".pp", &CI);
        SrcPtr = CastInst::CreatePointerCast(SrcPtr, CI.getOperand(2)->getType(), "", &CI);
        CI.setOperand(2, SrcPtr);
        doret = true;
      }
      if (doret) return;
    }


    std::vector<unsigned> CompressedArgs;
    if (isa<PointerType>(CI.getType()) && getPoolInfo(&CI))
      CompressedArgs.push_back(0);  // Compress retval.
  
    for (unsigned i = 1, e = CI.getNumOperands(); i != e; ++i)
      if (isa<PointerType>(CI.getOperand(i)->getType()) &&
          getPoolInfo(CI.getOperand(i))) {
        CompressedArgs.push_back(i);
        Operands.push_back(getTransformedValue(CI.getOperand(i)));
      } else {
        Operands.push_back(CI.getOperand(i));
      }

    if (CompressedArgs.empty()) {
      PtrComp.NoArgFunctionsCalled.push_back(Callee);
      return;  // Nothing to compress!
    }

    Function *Clone = PtrComp.GetExtFunctionClone(Callee, CompressedArgs);
    Value *NC = CallInst::Create(Clone, Operands.begin(), Operands.end(), CI.getName(), &CI);
    if (NC->getType() != CI.getType())      // Compressing return value?
      setTransformedValue(CI, NC);
    else {
      if (CI.getType() != VoidType)
        CI.replaceAllUsesWith(NC);
      ValueReplaced(CI, NC);
      CI.eraseFromParent();
    }
    return;
  }

  // CalleeCallerMap: Mapping from nodes in the callee to nodes in the caller.
  DSGraph::NodeMapTy CalleeCallerMap;
  
  // Do we need to compress the return value?
  if (isa<PointerType>(CI.getType()))
    DSGraph::computeNodeMapping(CG->getReturnNodeFor(FI->F),
                                getMappedNodeHandle(&CI), CalleeCallerMap);
    
  // Find the arguments we need to compress.
  unsigned NumPoolArgs = FI ? FI->ArgNodes.size() : 0;
  //only search non-vararg arguments
  //FIXME: suspect hack to prevent crashing on user-defined vaarg functions
  unsigned NumSearch = FI ? FI->F.arg_size() + 1: CI.getNumOperands();
  for (unsigned i = 1, e = NumSearch; i != e; ++i)
    if (isa<PointerType>(CI.getOperand(i)->getType()) && i > NumPoolArgs) {
      Argument *FormalArg = next(FI->F.arg_begin(), i-1-NumPoolArgs);
        
      DSGraph::computeNodeMapping(CG->getNodeForValue(FormalArg),
                                  getMappedNodeHandle(CI.getOperand(i)),
                                  CalleeCallerMap);
    }

  // Now that we know the basic pools passed/returned through the
  // argument/retval of the call, add the compressed pools that are reachable
  // from them.  The CalleeCallerMap contains a mapping from callee nodes to the
  // caller nodes they correspond to (a many-to-one mapping).
  for (DSGraph::NodeMapTy::iterator I = CalleeCallerMap.begin(),
         E = CalleeCallerMap.end(); I != E; ++I) {
    // If the destination is compressed, so should the source be.
    if (PoolInfo.count(I->second.getNode()))
      PoolsToCompress.insert(I->first);
  }

  // If this function doesn't require compression, there is nothing to do!
  // However, this function still needs to be transformed; it may just be
  // using a global pool descriptor.
  if (PoolsToCompress.empty()) {
    PtrComp.NoArgFunctionsCalled.push_back(Callee);
    return;
  }
    
    
  // Get the clone of this function that uses compressed pointers instead of
  // normal pointers.
  Function *Clone = PtrComp.GetFunctionClone(Callee, PoolsToCompress,
                                             *FI, *CG);


  // Okay, we now have our clone: rewrite the call instruction.
  std::vector<Value*> Operands;
  Operands.reserve(CI.getNumOperands()-1);

  Function::arg_iterator AI = FI->F.arg_begin();
  
  // Pass pool descriptors.
  for (unsigned i = 1; i != NumPoolArgs+1; ++i)
    Operands.push_back(CI.getOperand(i));

  for (unsigned i = NumPoolArgs+1, e = CI.getNumOperands(); i != e; ++i, ++AI)
    if (isa<PointerType>(CI.getOperand(i)->getType()) &&
        PoolsToCompress.count(CG->getNodeForValue(AI).getNode()))
      Operands.push_back(getTransformedValue(CI.getOperand(i)));
    else
      Operands.push_back(CI.getOperand(i));

  Value *NC = CallInst::Create(Clone, Operands.begin(), Operands.end(), CI.getName(), &CI);
  if (NC->getType() != CI.getType())      // Compressing return value?
    setTransformedValue(CI, NC);
  else {
    if (CI.getType() != VoidType)
      CI.replaceAllUsesWith(NC);
    ValueReplaced(CI, NC);
    CI.eraseFromParent();
  }
}


//===----------------------------------------------------------------------===//
//                    PointerCompress Implementation
//===----------------------------------------------------------------------===//

void PointerCompress::getAnalysisUsage(AnalysisUsage &AU) const {
  // Need information about how pool allocation happened.
  AU.addRequired<PoolAllocatePassAllPools>();

  // Need information from DSA.
  AU.addRequired<CompleteBUDataStructures>();
}

/// PoolIsCompressible - Return true if we can pointer compress this node.
/// If not, we should DEBUG print out why.
static bool PoolIsCompressible(const DSNode *N) {
  assert(!N->isForwarding() && "Should not be dealing with merged nodes!");
  if (N->isNodeCompletelyFolded()) {
    DEBUG(errs() << "Node is not type-safe:\n");
    return false;
  }

  // FIXME: If any non-type-safe nodes point to this one, we cannot compress it.
#if 0
  bool HasFields = false;
  for (DSNode::const_edge_iterator I = N->edge_begin(), E = N->edge_end();
       I != E; ++I)
    if (!I->isNull()) {
      HasFields = true;
      if (I->getNode() != N) {
        // We currently only handle trivially self cyclic DS's right now.
        DEBUG(errs() << "Node points to nodes other than itself:\n");
        return false;
      }        
    }

  if (!HasFields) {
    DEBUG(errs() << "Node does not contain any pointers to compress:\n");
    return false;
  }
#endif

  if ((N->getNodeFlags() & DSNode::Composition) != DSNode::HeapNode) {
    DEBUG(errs() << "Node contains non-heap values:\n");
    return false;
  }

  return true;
}

/// FindPoolsToCompress - Inspect the specified function and find pools that are
/// compressible that are homed in that function.  Return those pools in the
/// Pools set.
void PointerCompress::FindPoolsToCompress(std::set<const DSNode*> &Pools,
                                          std::map<const DSNode*,
                                          Value*> &PreassignedPools,
                                          Function &F, DSGraph* DSG,
                                          PA::FuncInfo *FI) {
  DEBUG(errs() << "In function '" << F.getNameStr() << "':\n");
  for (unsigned i = 0, e = FI->NodesToPA.size(); i != e; ++i) {
    const DSNode *N = FI->NodesToPA[i];

    // Ignore potential pools that the pool allocation heuristic decided not to
    // pool allocated.
    if (!isa<ConstantPointerNull>(FI->PoolDescriptors[N])) {
      if (PoolIsCompressible(N)) {
        Pools.insert(N);
        ++NumCompressed;
      } else {
        DEBUG(errs() << "PCF: "; N->dump());
        ++NumNotCompressed;
      }
    }
  }

  // If there are no compressed global pools, don't bother to look for them.
  if (CompressedGlobalPools.empty()) return;

  // Calculate which DSNodes are reachable from globals.  If a node is reachable
  // from a global, we check to see if the global pool is compressed.
  ECG->getGlobalsGraph();

  // Map all node reachable from this global to the corresponding nodes in the
  // globals graph.
  DSGraph::NodeMapTy GlobalsGraphNodeMapping;
  DSG->computeGToGGMapping(GlobalsGraphNodeMapping);

  // See if there are nodes in this graph that correspond to nodes in the
  // globals graph, and if so, if it is compressed.
  for (DSGraph::node_iterator I = DSG->node_begin(), E = DSG->node_end();
       I != E;++I)
    if (GlobalsGraphNodeMapping.count(I)) {
      // If it is a global pool, set up the pool descriptor appropriately.
      DSNode *GGN = GlobalsGraphNodeMapping[I].getNode();
      if (CompressedGlobalPools.count(GGN)) {
        Pools.insert(I);
        PreassignedPools[I] = CompressedGlobalPools[GGN];
      }
    }
}


/// CompressPoolsInFunction - Find all pools that are compressible in this
/// function and compress them.
bool PointerCompress::
CompressPoolsInFunction(Function &F,
                        std::vector<std::pair<Value*, Value*> > *PremappedVals,
                        std::set<const DSNode*> *ExternalPoolsToCompress){
  if (F.isDeclaration()) return false;

  // If this is a pointer compressed clone of a pool allocated function, get the
  // the pool allocated function.  Rewriting a clone means that there are
  // incoming arguments that point into compressed pools.
  FunctionCloneRecord *FCR = getCloneInfo(F);
  Function *CloneSource = FCR ? FCR->PAFn : 0;

  PA::FuncInfo *FI;
  if (CloneSource)
    FI = PoolAlloc->getFuncInfoOrClone(*CloneSource);
  else
    FI = PoolAlloc->getFuncInfoOrClone(F);

  if (FI == 0) {
    errs() << "DIDN'T FIND POOL INFO FOR: "
              << *F.getType() << F.getNameStr() << "!\n";
    return false;
  }

  // If this function was cloned, and this is the original function, ignore it
  // (it's dead).  We'll deal with the cloned version later when we run into it
  // again.
  if (FI->Clone && &FI->F == &F)
    return false;

  // Get the DSGraph for this function.
  DSGraph* DSG = ECG->getDSGraph(FI->F);

  std::set<const DSNode*> PoolsToCompressSet;

  // Compute the set of compressible pools in this function that are hosted
  // here.
  std::map<const DSNode*, Value*> PreassignedPools;
  FindPoolsToCompress(PoolsToCompressSet, PreassignedPools, F, DSG, FI);

  // Handle pools that are passed into the function through arguments or
  // returned by the function.  If this occurs, we must be dealing with a ptr
  // compressed clone of the pool allocated clone of the original function.
  if (ExternalPoolsToCompress)
    PoolsToCompressSet.insert(ExternalPoolsToCompress->begin(),
                              ExternalPoolsToCompress->end());

  // If there is nothing that we can compress, exit now.
  if (PoolsToCompressSet.empty()) return false;

  // Compute the initial collection of compressed pointer infos.
  std::map<const DSNode*, CompressedPoolInfo> PoolsToCompress;

  for (std::set<const DSNode*>::iterator I = PoolsToCompressSet.begin(),
         E = PoolsToCompressSet.end(); I != E; ++I) {
    Value *PD;
    if (Value *PAPD = PreassignedPools[*I])
      PD = PAPD;                             // Must be a global pool.
    else if (FCR)
      PD = FCR->PoolDescriptors.find(*I)->second;
    else
      PD = FI->PoolDescriptors[*I];
    assert(PD && "No pool descriptor available for this pool???");
    
    PoolsToCompress.insert(std::make_pair(*I, CompressedPoolInfo(*I, PD)));
  }

  // Use these to compute the closure of compression information.  In
  // particular, if one pool points to another, we need to know if the outgoing
  // pointer is compressed.
  const TargetData &TD = DSG->getTargetData();
  errs() << "In function '" << F.getNameStr() << "':\n";
  for (std::map<const DSNode*, CompressedPoolInfo>::iterator
         I = PoolsToCompress.begin(), E = PoolsToCompress.end(); I != E; ++I) {

    I->second.Initialize(PoolsToCompress, TD);

    // Only dump info about a compressed pool if this is the home for it.
    if (isa<AllocaInst>(I->second.getPoolDesc()) ||
        (isa<GlobalValue>(I->second.getPoolDesc()) &&
         F.hasExternalLinkage() && F.getNameStr() == "main")) {
      errs() << "  COMPRESSING POOL:\nPCS:";
      I->second.dump();
    }
  }
  
  // Finally, rewrite the function body to use compressed pointers!
  InstructionRewriter IR(PoolsToCompress, DSG, *FI, FCR, *this);
  if (PremappedVals)
    IR.PremapValues(*PremappedVals);
  IR.visit(F);
  return true;
}


/// GetExtFunctionClone - Return a clone of the specified external function with
/// the specified arguments compressed.
Function *PointerCompress::
GetExtFunctionClone(Function *F, const std::vector<unsigned> &ArgsToComp) {
  assert(!ArgsToComp.empty() && "No reason to make a clone!");
  Function *&Clone = ExtCloneFunctionMap[std::make_pair(F, ArgsToComp)];
  if (Clone) return Clone;

  const FunctionType *FTy = F->getFunctionType();
  const Type *RetTy = FTy->getReturnType();
  unsigned ArgIdx = 0;
  if (isa<PointerType>(RetTy) && ArgsToComp[0] == 0) {
    RetTy = SCALARUINTTYPE;
    ++ArgIdx;
  }

  std::vector<const Type*> ParamTypes;

  for (unsigned i = 0, e = FTy->getNumParams(); i != e; ++i)
    if (ArgIdx < ArgsToComp.size() && ArgsToComp[ArgIdx]-1 == i) {
      // Compressed pool, pass an index.
      ParamTypes.push_back(SCALARUINTTYPE);
      ++ArgIdx;
    } else {
      ParamTypes.push_back(FTy->getParamType(i));
    }
  FunctionType *CFTy = FunctionType::get(RetTy, ParamTypes, FTy->isVarArg());

  // Next, create the clone prototype and insert it into the module.
  Clone = Function::Create (CFTy, GlobalValue::ExternalLinkage,
                       F->getNameStr()+"_pc");
  F->getParent()->getFunctionList().insert(F, Clone);
  return Clone;
}

/// GetFunctionClone - Lazily create clones of pool allocated functions that we
/// need in compressed form.  This memoizes the functions that have been cloned
/// to allow only one clone of each function in a desired permutation.
Function *PointerCompress::
GetFunctionClone(Function *F, std::set<const DSNode*> &PoolsToCompress,
                 PA::FuncInfo &FI, const DSGraph &CG) {
  assert(!PoolsToCompress.empty() && "No clone needed!");

  // Check to see if we have already compressed this function, if so, there is
  // no need to make another clone.  This is also important to avoid infinite
  // recursion.
  Function *&Clone = ClonedFunctionMap[std::make_pair(F, PoolsToCompress)];
  if (Clone) return Clone;

  // First step, construct the new function prototype.
  const FunctionType *FTy = F->getFunctionType();
  const Type *RetTy = FTy->getReturnType();
  if (isa<PointerType>(RetTy) &&
      PoolsToCompress.count(CG.getReturnNodeFor(FI.F).getNode())) {
    RetTy = SCALARUINTTYPE;
  }
  std::vector<const Type*> ParamTypes;
  unsigned NumPoolArgs = FI.ArgNodes.size();

  // Pass all pool args unmodified.
  for (unsigned i = 0; i != NumPoolArgs; ++i)
    ParamTypes.push_back(FTy->getParamType(i));

  Function::arg_iterator AI = FI.F.arg_begin();
  for (unsigned i = NumPoolArgs, e = FTy->getNumParams(); i != e; ++i, ++AI)
    if (isa<PointerType>(FTy->getParamType(i)) &&
        PoolsToCompress.count(CG.getNodeForValue(AI).getNode())) {
      // Compressed pool, pass an index.
      ParamTypes.push_back(SCALARUINTTYPE);
    } else {
      ParamTypes.push_back(FTy->getParamType(i));
    }
  FunctionType *CFTy = FunctionType::get(RetTy, ParamTypes, FTy->isVarArg());

  // Next, create the clone prototype and insert it into the module.
  Clone = Function::Create (CFTy, GlobalValue::InternalLinkage,
                            F->getNameStr()+".pc");
  F->getParent()->getFunctionList().insert(F, Clone);

  // Remember where this clone came from.
  FunctionCloneRecord &CFI = 
    ClonedFunctionInfoMap.insert(std::make_pair(Clone, F)).first->second;

  ++NumCloned;
  errs() << " CLONING FUNCTION: " << F->getNameStr() << " -> "
            << Clone->getNameStr() << "\n";

  if (F->isDeclaration()) {
    Clone->setLinkage(GlobalValue::ExternalLinkage);
    return Clone;
  }

  DenseMap<const Value*, Value*> ValueMap;

  // Create dummy Value*'s of pointer type for any arguments that are
  // compressed.  These are needed to satisfy typing constraints before the
  // function body has been rewritten.
  std::vector<std::pair<Value*,Value*> > RemappedArgs;

  // Process arguments, setting up the ValueMap for them.
  Function::arg_iterator CI = Clone->arg_begin();// Iterate over cloned fn args.
  for (Function::arg_iterator I = F->arg_begin(), E = F->arg_end();
       I != E; ++I, ++CI) {
    // Transfer the argument names over.
    CI->setName(I->getNameStr());

    // If we are compressing this argument, set up RemappedArgs.
    if (CI->getType() != I->getType()) {
      // Create a useless value* that is only needed to hold the uselist for the
      // argument.
      Value *V = new Argument(I->getType());   // dummy argument
      RemappedArgs.push_back(std::make_pair(V, CI));
      ValueMap[I] = V;
    } else {
      // Otherwise, just remember the mapping.
      ValueMap[I] = CI;
    }
  }

  // Clone the actual function body over.
  SmallVector<ReturnInst*,100> Returns;
  CloneFunctionInto(Clone, F, ValueMap, Returns);
  Returns.clear();  // Don't need this.
  
  // Invert the ValueMap into the NewToOldValueMap
  std::map<Value*, const Value*> &NewToOldValueMap = CFI.NewToOldValueMap;
  for (DenseMap<const Value*, Value*>::iterator I = ValueMap.begin(),
         E = ValueMap.end(); I != E; ++I)
    NewToOldValueMap.insert(std::make_pair(I->second, I->first));

  // Compute the PoolDescriptors map for the cloned function.
  for (std::map<const DSNode*, Value*>::iterator I =
         FI.PoolDescriptors.begin(), E = FI.PoolDescriptors.end();
       I != E; ++I)
    CFI.PoolDescriptors[I->first] = ValueMap[I->second];
  
  ValueMap.clear();
  
  // Recursively transform the function.
  CompressPoolsInFunction(*Clone, &RemappedArgs, &PoolsToCompress);
  return Clone;
}


// Handle all pools pointed to by global variables.
void PointerCompress::HandleGlobalPools(Module &M) {
  if (PoolAlloc->GlobalNodes.empty()) return;

  DEBUG(errs() << "Inspecting global nodes:\n");

  // Loop over all of the global nodes identified by the pool allocator.
  for (std::map<const DSNode*, Value*>::iterator I =
         PoolAlloc->GlobalNodes.begin(), E = PoolAlloc->GlobalNodes.end();
       I != E; ++I) {
    const DSNode *N = I->first;

    // Ignore potential pools that the pool allocation heuristic decided not to
    // pool allocated.
    if (!isa<ConstantPointerNull>(I->second)) {
      if (PoolIsCompressible(N)) {
        CompressedGlobalPools.insert(std::make_pair(N, 
                                             cast<GlobalValue>(I->second)));
        ++NumCompressed;
      } else {
        DEBUG(errs() << "PCF: "; N->dump());
        ++NumNotCompressed;
      }
    }
  }
}


/// InitializePoolLibraryFunctions - Create the function prototypes for pointer
/// compress runtime library functions.
void PointerCompress::InitializePoolLibraryFunctions(Module &M) {
  const Type *VoidPtrTy = PointerType::getUnqual(Int8Type);
  const Type *PoolDescPtrTy = PointerType::getUnqual(ArrayType::get(VoidPtrTy, 16));

  PoolInitPC = M.getOrInsertFunction("poolinit_pc", VoidPtrTy, PoolDescPtrTy, 
                                     Int32Type, Int32Type, NULL);
  PoolDestroyPC = M.getOrInsertFunction("pooldestroy_pc", VoidType,
                                        PoolDescPtrTy, NULL);
  PoolAllocPC = M.getOrInsertFunction("poolalloc_pc", SCALARUINTTYPE,
                                      PoolDescPtrTy, Int32Type, NULL);
  // FIXME: Need bumppointer versions as well as realloc??/memalign??
}

bool PointerCompress::runOnModule(Module &M) {
  //
  // Get pointers to 8 and 32 bit LLVM integer types.
  //
  VoidType  = Type::getVoidTy(M.getContext());
  Int8Type  = IntegerType::getInt8Ty(M.getContext());
  Int16Type = IntegerType::getInt16Ty(M.getContext());
  Int32Type = IntegerType::getInt32Ty(M.getContext());
  Int64Type = IntegerType::getInt64Ty(M.getContext());

  PoolAlloc = &getAnalysis<PoolAllocatePassAllPools>();
  ECG = &getAnalysis<CompleteBUDataStructures>();
  
  if (SmallIntCompress)
    MEMUINTTYPE = Int16Type;
  else 
    MEMUINTTYPE = Int32Type;

  // FIXME: make this IntPtrTy.
  SCALARUINTTYPE = Int64Type;

  // Create the function prototypes for pointer compress runtime library
  // functions.
  InitializePoolLibraryFunctions(M);

  // Handle all pools pointed to by global variables.
  HandleGlobalPools(M);

  std::set<Function*> TransformedFns;

  // Iterate over all functions in the module, looking for compressible data
  // structures.
  bool Changed = false;
  for (Module::iterator I = M.begin(), E = M.end(); I != E; ++I)
    // If this function is not a pointer-compressed or pool allocated clone,
    // compress any pools in it now.
    if (I->hasExternalLinkage()) {
      Changed |= CompressPoolsInFunction(*I);
      TransformedFns.insert(I);
    }

  // If compressing external functions (e.g. main), required other function
  // bodies to be compressed that do not take pool arguments, handle them now.
  for (unsigned i = 0; i != NoArgFunctionsCalled.size(); ++i)
    if (TransformedFns.insert(NoArgFunctionsCalled[i]).second)
      Changed |= CompressPoolsInFunction(*NoArgFunctionsCalled[i]);

  NoArgFunctionsCalled.clear();
  ClonedFunctionMap.clear();
  return Changed;
}