poolalloc/include/dsa/DSGraph.h

//===- DSGraph.h - Represent a collection of data structures ----*- C++ -*-===//
//
//                     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 header defines the data structure graph (DSGraph) and the
// ReachabilityCloner class.
//
//===----------------------------------------------------------------------===//

#ifndef LLVM_ANALYSIS_DSGRAPH_H
#define LLVM_ANALYSIS_DSGRAPH_H

#include "dsa/DSNode.h"
#include "dsa/DSCallGraph.h"
#include "llvm/ADT/EquivalenceClasses.h"
#include "llvm/IR/Function.h"

#include <list>
#include <map>
#include <set>

namespace llvm {

class DataLayout;
class GlobalValue;

//===----------------------------------------------------------------------===//
/// DSScalarMap - An instance of this class is used to keep track of all of
/// which DSNode each scalar in a function points to.  This is specialized to
/// keep track of globals with nodes in the function, and to keep track of the
/// unique DSNodeHandle being used by the scalar map.
///
/// This class is crucial to the efficiency of DSA with some large SCC's.  In
/// these cases, the cost of iterating over the scalar map dominates the cost
/// of DSA.  In all of these cases, the DSA phase is really trying to identify
/// globals or unique node handles active in the function.
///
class DSScalarMap {
  typedef std::map<const Value*, DSNodeHandle> ValueMapTy;
  ValueMapTy ValueMap;

  typedef std::set<const GlobalValue*> GlobalSetTy;
  GlobalSetTy GlobalSet;

  EquivalenceClasses<const GlobalValue*> &GlobalECs;
public:
  DSScalarMap(EquivalenceClasses<const GlobalValue*> &ECs) : GlobalECs(ECs) {}

  EquivalenceClasses<const GlobalValue*> &getGlobalECs() const { return GlobalECs; }

  // Compatibility methods: provide an interface compatible with a map of
  // Value* to DSNodeHandle's.
  typedef ValueMapTy::const_iterator const_iterator;
  typedef ValueMapTy::iterator iterator;
  iterator begin() { return ValueMap.begin(); }
  iterator end()   { return ValueMap.end(); }
  const_iterator begin() const { return ValueMap.begin(); }
  const_iterator end() const { return ValueMap.end(); }

  const GlobalValue *getLeaderForGlobal(const GlobalValue *GV) const {
    EquivalenceClasses<const GlobalValue*>::iterator ECI = GlobalECs.findValue(GV);
    if (ECI == GlobalECs.end()) return GV;
    return *GlobalECs.findLeader(ECI);
  }


  iterator find(const Value *V) {
    assert(V);
    iterator I = ValueMap.find(V);
    if (I != ValueMap.end()) return I;

    if (const GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
      // If this is a global, check to see if it is equivalenced to something
      // in the map.
      const GlobalValue *Leader = getLeaderForGlobal(GV);
      if (Leader != GV)
        I = ValueMap.find((const Value*)Leader);
    }
    return I;
  }
  const_iterator find(const Value *V) const {
    assert(V);
    const_iterator I = ValueMap.find(V);
    if (I != ValueMap.end()) return I;

    if (const GlobalValue *GV = dyn_cast<GlobalValue>(V)) {
      // If this is a global, check to see if it is equivalenced to something
      // in the map.
      const GlobalValue *Leader = getLeaderForGlobal(GV);
      if (Leader != GV)
        I = ValueMap.find((const Value*)Leader);
    }
    return I;
  }

  /// getRawEntryRef - This method can be used by clients that are aware of the
  /// global value equivalence class in effect.
  DSNodeHandle &getRawEntryRef(const Value *V) {
    std::pair<iterator,bool> IP =
      ValueMap.insert(std::make_pair(V, DSNodeHandle()));
     if (IP.second)   // Inserted the new entry into the map.
       if (const GlobalValue *GV = dyn_cast<GlobalValue>(V))
         GlobalSet.insert(GV);
     return IP.first->second;
  }

  unsigned count(const Value *V) const { return ValueMap.find(V) != ValueMap.end(); }

  void erase(const Value *V) { erase(ValueMap.find(V)); }

  void eraseIfExists(const Value *V) {
    iterator I = find(V);
    if (I != end()) erase(I);
  }

  /// replaceScalar - When an instruction needs to be modified, this method can
  /// be used to update the scalar map to remove the old and insert the new.
  ///
  void replaceScalar(const Value *Old, const Value *New) {
    iterator I = find(Old);
    assert(I != end() && "Old value is not in the map!");
    ValueMap.insert(std::make_pair(New, I->second));
    erase(I);
  }

  /// copyScalarIfExists - If Old exists in the scalar map, make New point to
  /// whatever Old did.
  void copyScalarIfExists(const Value *Old, const Value *New) {
    iterator I = find(Old);
    if (I != end())
      ValueMap.insert(std::make_pair(New, I->second));
  }

  /// operator[] - Return the DSNodeHandle for the specified value, creating a
  /// new null handle if there is no entry yet.
  DSNodeHandle &operator[](const Value *V) {
    assert(V);
    iterator I = ValueMap.find(V);
    if (I != ValueMap.end())
      return I->second;   // Return value if already exists.

    if (const GlobalValue *GV = dyn_cast<GlobalValue>(V))
      return AddGlobal(GV);

    return ValueMap.insert(std::make_pair(V, DSNodeHandle())).first->second;
  }

  void erase(iterator I) {
    assert(I != ValueMap.end() && "Cannot erase end!");
    if (const GlobalValue *GV = dyn_cast<GlobalValue>(I->first))
      GlobalSet.erase(GV);
    ValueMap.erase(I);
  }

  void clear_scalars() {
    for(iterator ii = begin(); ii != end(); )
      if (isa<GlobalValue>(ii->first))
        ++ii;
      else {
        iterator next = ii;
        ++ii;
        erase(next);
      }
  }

  void clear() {
    ValueMap.clear();
    GlobalSet.clear();
  }

  /// spliceFrom - Copy all entries from RHS, then clear RHS.
  ///
  void spliceFrom(DSScalarMap &RHS);

  // Access to the global set: the set of all globals currently in the
  // scalar map.
  typedef GlobalSetTy::const_iterator global_iterator;
  global_iterator global_begin() const { return GlobalSet.begin(); }
  global_iterator global_end() const { return GlobalSet.end(); }
  unsigned global_size() const { return GlobalSet.size(); }
  unsigned global_count(const GlobalValue *GV) const { return GlobalSet.count(GV); }
private:
  DSNodeHandle &AddGlobal(const GlobalValue *GV);
};

//===----------------------------------------------------------------------===//
/// DSGraph - The graph that represents a function.
///
class DSGraph {
public:
  // Public data-type declarations...
  typedef DSScalarMap ScalarMapTy;
  typedef std::map<const Function*, DSNodeHandle> ReturnNodesTy;
  typedef std::map<const Function*, DSNodeHandle> VANodesTy;
  typedef ilist<DSNode> NodeListTy;

  /// NodeMapTy - This data type is used when cloning one graph into another to
  /// keep track of the correspondence between the nodes in the old and new
  /// graphs.
  typedef std::map<const DSNode*, DSNodeHandle> NodeMapTy;

  // InvNodeMapTy - This data type is used to represent the inverse of a node
  // map.
  typedef std::multimap<DSNodeHandle, const DSNode*> InvNodeMapTy;
  typedef std::list<DSCallSite> FunctionListTy;
private:
  DSGraph *GlobalsGraph;   // Pointer to the common graph of global objects

  // This is use to differentiate between Local and the rest of the passes.
  // Local should use the FunctionCalls vector that has all the DSCallSites.
  // All other passes, shoud use the Aux calls vector, as they process and 
  // subsequently might remove some DSCall Sites. Once those call sites
  // have been resolved, we must not revisit them again.
  // UseAuxCalls is false for Local. And true for the other passes.

  bool UseAuxCalls;      // Should this pass use the Aux calls vector?

  NodeListTy Nodes;
  ScalarMapTy ScalarMap;

  // ReturnNodes - A return value for every function merged into this graph.
  // Each DSGraph may have multiple functions merged into it at any time, which
  // is used for representing SCCs.
  //
  ReturnNodesTy ReturnNodes;

  // VANodes - Special "Variable Argument" Node for each function
  //
  VANodesTy VANodes;

  // FunctionCalls - This list maintains a single entry for each call
  // instruction in the current graph.  The first entry in the vector is the
  // scalar that holds the return value for the call, the second is the function
  // scalar being invoked, and the rest are pointer arguments to the function.
  // This vector is built by the Local graph and is never modified after that.
  //
  FunctionListTy FunctionCalls;

  // AuxFunctionCalls - This vector contains call sites that have been processed
  // by some mechanism.  In pratice, the BU Analysis uses this vector to hold
  // the _unresolved_ call sites, because it cannot modify FunctionCalls.
  //
  FunctionListTy AuxFunctionCalls;

  /// TD - This is the target data object for the machine this graph is
  /// constructed for.
  const DataLayout &TD;

  SuperSet<Type*>& TypeSS;

  void operator=(const DSGraph &); // DO NOT IMPLEMENT
  DSGraph(const DSGraph&);         // DO NOT IMPLEMENT
public:
  // Create a new, empty, DSGraph.
  DSGraph(EquivalenceClasses<const GlobalValue*> &ECs, const DataLayout &td,
          SuperSet<Type*>& tss,
          DSGraph *GG = 0) 
    :GlobalsGraph(GG), UseAuxCalls(false), 
     ScalarMap(ECs), TD(td), TypeSS(tss)
  { }

  // Copy ctor - If you want to capture the node mapping between the source and
  // destination graph, you may optionally do this by specifying a map to record
  // this into.
  //
  // Note that a copied graph does not retain the GlobalsGraph pointer of the
  // source.  You need to set a new GlobalsGraph with the setGlobalsGraph
  // method.
  //
  DSGraph( DSGraph* DSG, EquivalenceClasses<const GlobalValue*> &ECs,
          SuperSet<Type*>& tss,
          unsigned CloneFlags = 0);
  ~DSGraph();

  DSGraph *getGlobalsGraph() const { return GlobalsGraph; }
  void setGlobalsGraph(DSGraph *G) { GlobalsGraph = G; }

  /// getGlobalECs - Return the set of equivalence classes that the global
  /// variables in the program form.
  EquivalenceClasses<const GlobalValue*> &getGlobalECs() const {
    return ScalarMap.getGlobalECs();
  }

  SuperSet<Type*>& getTypeSS() const {
    return TypeSS;
  }

  /// getDataLayout - Return the DataLayout object for the current target.
  ///
  const DataLayout &getDataLayout() const { return TD; }

  /// setUseAuxCalls - If you call this method, the auxillary call vector will
  /// be used instead of the standard call vector to the dot file.
  ///
  void setUseAuxCalls() { UseAuxCalls = true; }
  bool shouldUseAuxCalls() const { return UseAuxCalls; }

  /// node_iterator/begin/end - Iterate over all of the nodes in the graph.  Be
  /// extremely careful with these methods because any merging of nodes could
  /// cause the node to be removed from this list.  This means that if you are
  /// iterating over nodes and doing something that could cause _any_ node to
  /// merge, your node_iterators into this graph can be invalidated.
  typedef NodeListTy::iterator node_iterator;
  node_iterator node_begin() { return Nodes.begin(); }
  node_iterator node_end()   { return Nodes.end(); }

  typedef NodeListTy::const_iterator node_const_iterator;
  node_const_iterator node_begin() const { return Nodes.begin(); }
  node_const_iterator node_end()   const { return Nodes.end(); }

  /// getFunctionNames - Return a space separated list of the name of the
  /// functions in this graph (if any)
  ///
  std::string getFunctionNames() const;

  /// addNode - Add a new node to the graph.
  ///
  void addNode(DSNode *N) { Nodes.push_back(N); }
  void unlinkNode(DSNode *N) { Nodes.remove(N); }

  /// getScalarMap - Get a map that describes what the nodes the scalars in this
  /// function point to...
  ///
  ScalarMapTy &getScalarMap() { return ScalarMap; }
  const ScalarMapTy &getScalarMap() const { return ScalarMap; }

  /// getFunctionCalls - Return the list of call sites in the original local
  /// graph...
  ///
  const FunctionListTy &getFunctionCalls() const { return FunctionCalls;}
  FunctionListTy &getFunctionCalls() { return FunctionCalls;}

  /// getAuxFunctionCalls - Get the call sites as modified by whatever passes
  /// have been run.
  ///
  FunctionListTy &getAuxFunctionCalls() { return AuxFunctionCalls; }
  const FunctionListTy &getAuxFunctionCalls() const {
    return AuxFunctionCalls;
  }

  // addAuxFunctionCall - Add a call site to the AuxFunctionCallList
  void addAuxFunctionCall(DSCallSite D) { AuxFunctionCalls.push_back(D); }

  void buildCallGraph(DSCallGraph& DCG, std::vector<const Function*> &GlobalFunctionList, bool filter) const;
  void buildCompleteCallGraph(DSCallGraph& DCG, std::vector<const Function*> &GlobalFunctionList, bool filter) const;

  /// removeFunction - Specify that all call sites to the function have been
  /// fully specified by a pass such as StdLibPass.
  void removeFunctionCalls(Function& F);

  // Function Call iteration
  typedef FunctionListTy::const_iterator fc_iterator;
  fc_iterator fc_begin() const { return FunctionCalls.begin(); }
  fc_iterator fc_end() const { return FunctionCalls.end(); }


  // Aux Function Call iteration
  typedef FunctionListTy::iterator afc_iterator;
  afc_iterator afc_begin() { return AuxFunctionCalls.begin(); }
  afc_iterator afc_end() { return AuxFunctionCalls.end(); }
  typedef FunctionListTy::const_iterator afc_const_iterator;
  afc_const_iterator afc_begin() const { return AuxFunctionCalls.begin(); }
  afc_const_iterator afc_end() const { return AuxFunctionCalls.end(); }

  /// getNodeForValue - Given a value that is used or defined in the body of the
  /// current function, return the DSNode that it points to.
  ///
  DSNodeHandle &getNodeForValue(const Value *V) { return ScalarMap[V]; }

  const DSNodeHandle &getNodeForValue(const Value *V) const {
    ScalarMapTy::const_iterator I = ScalarMap.find(V);
    assert(I != ScalarMap.end() &&
           "Use non-const lookup function if node may not be in the map");
    return I->second;
  }

  bool hasNodeForValue(const Value* V) const {
    ScalarMapTy::const_iterator I = ScalarMap.find(V);
    return I != ScalarMap.end();
  }

  void eraseNodeForValue(const Value* V) {
    ScalarMap.erase(V);
  }

  /// retnodes_* iterator methods: expose iteration over return nodes in the
  /// graph, which are also the set of functions incorporated in this graph.
  typedef ReturnNodesTy::const_iterator retnodes_iterator;
  retnodes_iterator retnodes_begin() const { return ReturnNodes.begin(); }
  retnodes_iterator retnodes_end() const { return ReturnNodes.end(); }
  
  typedef VANodesTy::const_iterator vanodes_iterator;
  vanodes_iterator vanodes_begin() const { return VANodes.begin(); }
  vanodes_iterator vanodes_end() const { return VANodes.end(); }


  /// getReturnNodes - Return the mapping of functions to their return nodes for
  /// this graph.
  ///
  const ReturnNodesTy &getReturnNodes() const { return ReturnNodes; }
        ReturnNodesTy &getReturnNodes()       { return ReturnNodes; }

  /// getReturnNodeFor - Return the return node for the specified function.
  ///
  DSNodeHandle &getReturnNodeFor(const Function &F) {
    ReturnNodesTy::iterator I = ReturnNodes.find(&F);
    assert(I != ReturnNodes.end() && "F not in this DSGraph!");
    return I->second;
  }

  const DSNodeHandle &getReturnNodeFor(const Function &F) const {
    ReturnNodesTy::const_iterator I = ReturnNodes.find(&F);
    assert(I != ReturnNodes.end() && "F not in this DSGraph!");
    return I->second;
  }

  /// getVANodes - Return the mapping of functions to their var-arg nodes for
  /// this graph.
  ///
  const VANodesTy &getVANodes() const { return VANodes; }
        VANodesTy &getVANodes()       { return VANodes; }

  /// getVANodeFor - Return the var-arg node for the specified function.
  ///
  DSNodeHandle &getVANodeFor(const Function &F) {
    VANodesTy::iterator I = VANodes.find(&F);
    assert(I != VANodes.end() && "Var-arg info for F not in this graph!");
    return I->second;
  }

  const DSNodeHandle &getVANodeFor(const Function &F) const {
    VANodesTy::const_iterator I = VANodes.find(&F);
    assert(I != VANodes.end() && "Var-arg info for F not in this graph!");
    return I->second;
  }

  DSNodeHandle& getOrCreateReturnNodeFor(const Function& F) {
    return ReturnNodes[&F];
  }

  DSNodeHandle& getOrCreateVANodeFor(const Function& F) {
    return VANodes[&F];
  }

  /// containsFunction - Return true if this DSGraph contains information for
  /// the specified function.
  bool containsFunction(const Function *F) const {
    return ReturnNodes.count(F);
  }

  /// getGraphSize - Return the number of nodes in this graph.
  ///
  unsigned getGraphSize() const {
    return Nodes.size();
  }

  /// addObjectToGraph - This method can be used to add global, stack, and heap
  /// objects to the graph.  This can be used when updating DSGraphs due to the
  /// introduction of new temporary objects.  The new object is not pointed to
  /// and does not point to any other objects in the graph.  Note that this
  /// method initializes the type of the DSNode to the declared type of the
  /// object if UseDeclaredType is true, otherwise it leaves the node type as
  /// void.
  DSNode *addObjectToGraph(Value *Ptr, bool UseDeclaredType = true);


  /// print - Print a dot graph to the specified ostream...
  ///
  void print(llvm::raw_ostream &O) const;

  /// dump - call print(cerr), for use from the debugger...
  ///
  void dump() const;

  /// viewGraph - Emit a dot graph, run 'dot', run gv on the postscript file,
  /// then cleanup.  For use from the debugger.
  ///
  void viewGraph() const;

  void writeGraphToFile(llvm::raw_ostream &O, const std::string &GraphName) const;

  /// maskNodeTypes - Apply a mask to all of the node types in the graph.  This
  /// is useful for clearing out markers like Incomplete.
  ///
  void maskNodeTypes(unsigned Mask) {
    for (node_iterator I = node_begin(), E = node_end(); I != E; ++I)
      I->maskNodeTypes(Mask);
  }
  void maskIncompleteMarkers() { maskNodeTypes(~DSNode::IncompleteNode); }

  // markIncompleteNodes - Traverse the graph, identifying nodes that may be
  // modified by other functions that have not been resolved yet.  This marks
  // nodes that are reachable through three sources of "unknownness":
  //   Global Variables, Function Calls, and Incoming Arguments
  //
  // For any node that may have unknown components (because something outside
  // the scope of current analysis may have modified it), the 'Incomplete' flag
  // is added to the NodeType.
  //
  enum MarkIncompleteFlags {
    MarkFormalArgs = 1, IgnoreFormalArgs = 0,
    IgnoreGlobals = 2, MarkGlobalsIncomplete = 0,
    MarkVAStart = 4
  };
  void markIncompleteNodes(unsigned Flags);
  
  // Mark nodes that have overlapping Int and Pointer types.
  void computeIntPtrFlags();

  // Mark all reachable from external as external.
  enum ComputeExternalFlags {
    MarkFormalsExternal = 1, DontMarkFormalsExternal = 0,
    ProcessCallSites = 2, IgnoreCallSites = 0,
    ResetExternal = 4, DontResetExternal = 0
  };
  void computeExternalFlags(unsigned Flags);

  // removeDeadNodes - Use a reachability analysis to eliminate subgraphs that
  // are unreachable.  This often occurs because the data structure doesn't
  // "escape" into it's caller, and thus should be eliminated from the caller's
  // graph entirely.  This is only appropriate to use when inlining graphs.
  //
  enum RemoveDeadNodesFlags {
    RemoveUnreachableGlobals = 1, KeepUnreachableGlobals = 0
  };
  void removeDeadNodes(unsigned Flags);

  /// CloneFlags enum - Bits that may be passed into the cloneInto method to
  /// specify how to clone the function graph.
  enum CloneFlags {
    StripAllocaBit        = 1 << 0, KeepAllocaBit     = 0,
    DontCloneCallNodes    = 1 << 1, CloneCallNodes    = 0,
    DontCloneAuxCallNodes = 1 << 2, CloneAuxCallNodes = 0,
    StripModRefBits       = 1 << 3, KeepModRefBits    = 0,
    StripIncompleteBit    = 1 << 4, KeepIncompleteBit = 0
  };

  void updateFromGlobalGraph();

  /// computeNodeMapping - Given roots in two different DSGraphs, traverse the
  /// nodes reachable from the two graphs, computing the mapping of nodes from
  /// the first to the second graph.
  ///
  static void computeNodeMapping(const DSNodeHandle &NH1,
                                 const DSNodeHandle &NH2, NodeMapTy &NodeMap,
                                 bool StrictChecking = true);

  /// computeGToGGMapping - Compute the mapping of nodes in the graph to nodes
  /// in the globals graph.
  void computeGToGGMapping(NodeMapTy &NodeMap);

  /// computeGGToGMapping - Compute the mapping of nodes in the global
  /// graph to nodes in this graph.
  void computeGGToGMapping(InvNodeMapTy &InvNodeMap);

  /// computeCalleeCallerMapping - Given a call from a function in the current
  /// graph to the 'Callee' function (which lives in 'CalleeGraph'), compute the
  /// mapping of nodes from the callee to nodes in the caller.
  void computeCalleeCallerMapping(DSCallSite CS, const Function &Callee,
                                  DSGraph &CalleeGraph, NodeMapTy &NodeMap);

  /// spliceFrom - Logically perform the operation of cloning the RHS graph into
  /// this graph, then clearing the RHS graph.  Instead of performing this as
  /// two seperate operations, do it as a single, much faster, one.
  ///
  void spliceFrom(DSGraph* RHS);

  /// cloneInto - Clone the specified DSGraph into the current graph.
  ///
  /// The CloneFlags member controls various aspects of the cloning process.
  ///
  void cloneInto(DSGraph* G, unsigned CloneFlags = 0);

  /// getFunctionArgumentsForCall - Given a function that is currently in this
  /// graph, return the DSNodeHandles that correspond to the pointer-compatible
  /// function arguments.  The vector is filled in with the return value (or
  /// null if it is not pointer compatible), followed by all of the
  /// pointer-compatible arguments.
  void getFunctionArgumentsForCall(const Function *F,
                                   std::vector<DSNodeHandle> &Args) const;

  /// mergeInGraph - This graph merges in the minimal number of
  /// nodes from G2 into 'this' graph, merging the bindings specified by the
  /// call site (in this graph) with the bindings specified by the vector in G2.
  /// If the StripAlloca's argument is 'StripAllocaBit' then Alloca markers are
  /// removed from nodes.
  ///
  void mergeInGraph(const DSCallSite &CS, std::vector<DSNodeHandle> &Args,
                    const DSGraph &G2, unsigned CloneFlags);

  /// mergeInGraph - This method is the same as the above method, but the
  /// argument bindings are provided by using the formal arguments of F.
  ///
  void mergeInGraph(const DSCallSite &CS, const Function &F, 
                    const DSGraph &Graph, unsigned CloneFlags);

  /// getCallSiteForArguments - Get the arguments and return value bindings for
  /// the specified function in the current graph.
  ///
  DSCallSite getCallSiteForArguments(const Function &F) const;

  /// getDSCallSiteForCallSite - Given an LLVM CallSite object that is live in
  /// the context of this graph, return the DSCallSite for it.
  DSCallSite getDSCallSiteForCallSite(CallSite CS) const;

  // Methods for checking to make sure graphs are well formed...
  void AssertNodeInGraph(const DSNode *N) const {
    assert((!N || N->getParentGraph() == this) &&
           "AssertNodeInGraph: Node is not in graph!");
  }
  void AssertNodeContainsGlobal(const DSNode *N, const GlobalValue *GV) const;

  void AssertCallSiteInGraph(const DSCallSite &CS) const;
  void AssertCallNodesInGraph() const;
  void AssertAuxCallNodesInGraph() const;

  void AssertGraphOK() const;

  /// removeTriviallyDeadNodes - After the graph has been constructed, this
  /// method removes all unreachable nodes that are created because they got
  /// merged with other nodes in the graph.  This is used as the first step of
  /// removeDeadNodes.
  ///
  void removeTriviallyDeadNodes();
};


/// ReachabilityCloner - This class is used to incrementally clone and merge
/// nodes from a non-changing source graph into a potentially mutating
/// destination graph.  Nodes are only cloned over on demand, either in
/// responds to a merge() or getClonedNH() call.  When a node is cloned over,
/// all of the nodes reachable from it are automatically brought over as well.
///
class ReachabilityCloner {
  DSGraph* Dest;
  const DSGraph* Src;

  /// BitsToKeep - These bits are retained from the source node when the
  /// source nodes are merged into the destination graph.
  unsigned BitsToKeep;
  unsigned CloneFlags;

  bool createDest;

  // NodeMap - A mapping from nodes in the source graph to the nodes that
  // represent them in the destination graph.
  // We cannot use a densemap here as references into it are not stable across
  // insertion
  typedef std::map<const DSNode*, DSNodeHandle> RCNodeMap;
  RCNodeMap NodeMap;

public:
  ReachabilityCloner(DSGraph* dest, const DSGraph* src, unsigned cloneFlags,
                     bool _createDest = true)
    : Dest(dest), Src(src), CloneFlags(cloneFlags), createDest(_createDest) {
    assert(Dest != Src && "Cannot clone from graph to same graph!");
    BitsToKeep = ~DSNode::DeadNode;
    if (CloneFlags & DSGraph::StripAllocaBit)
      BitsToKeep &= ~DSNode::AllocaNode;
    if (CloneFlags & DSGraph::StripModRefBits)
      BitsToKeep &= ~(DSNode::ModifiedNode | DSNode::ReadNode);
    if (CloneFlags & DSGraph::StripIncompleteBit)
      BitsToKeep &= ~DSNode::IncompleteNode;
  }

  DSNodeHandle getClonedNH(const DSNodeHandle &SrcNH);

  void merge(const DSNodeHandle &NH, const DSNodeHandle &SrcNH);

  /// mergeCallSite - Merge the nodes reachable from the specified src call
  /// site into the nodes reachable from DestCS.
  ///
  void mergeCallSite(DSCallSite &DestCS, const DSCallSite &SrcCS);

  DSCallSite cloneCallSite(const DSCallSite& SrcCS);

  bool clonedAnyNodes() const { return !NodeMap.empty(); }

  /// hasClonedNode - Return true if the specified node has been cloned from
  /// the source graph into the destination graph.
  bool hasClonedNode(const DSNode *N) {
    return NodeMap.count(N);
  }

  void destroy() { NodeMap.clear(); }
};

//
// Function: functionIsCallable()
//
// Description:
//  Determine whether the specified function can be a target of the specified
//  call site.  We allow the user to configure what we consider to be
//  uncallable at an indirect function call site.
//
// Inputs:
//  CS - The call site which calls the function.
//  F  - The function that is potentially called by CS.
//
// Return value:
//  true  - The function F can be called by the call site.
//  false - The function F cannot be called by the call site.
//
bool
functionIsCallable (ImmutableCallSite CS, const Function* F);

} // End llvm namespace

#endif