//===- llvm/ADT/FoldingSet.h - Uniquing Hash Set ----------------*- C++ -*-===//

//

// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.

// See https://llvm.org/LICENSE.txt for license information.

// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception

//

//===----------------------------------------------------------------------===//

//

// This file defines a hash set that can be used to remove duplication of nodes

// in a graph.  This code was originally created by Chris Lattner for use with

// SelectionDAGCSEMap, but was isolated to provide use across the llvm code set.

//

//===----------------------------------------------------------------------===//

#ifndef LLVM_ADT_FOLDINGSET_H

#define LLVM_ADT_FOLDINGSET_H

#include "llvm/ADT/SmallVector.h"

#include "llvm/ADT/iterator.h"

#include "llvm/Support/Allocator.h"

#include <cassert>

#include <cstddef>

#include <cstdint>

#include <utility>

namespace llvm {

/// This folding set used for two purposes:

///   1. Given information about a node we want to create, look up the unique

///      instance of the node in the set.  If the node already exists, return

///      it, otherwise return the bucket it should be inserted into.

///   2. Given a node that has already been created, remove it from the set.

///

/// This class is implemented as a single-link chained hash table, where the

/// "buckets" are actually the nodes themselves (the next pointer is in the

/// node).  The last node points back to the bucket to simplify node removal.

///

/// Any node that is to be included in the folding set must be a subclass of

/// FoldingSetNode.  The node class must also define a Profile method used to

/// establish the unique bits of data for the node.  The Profile method is

/// passed a FoldingSetNodeID object which is used to gather the bits.  Just

/// call one of the Add* functions defined in the FoldingSetBase::NodeID class.

/// NOTE: That the folding set does not own the nodes and it is the

/// responsibility of the user to dispose of the nodes.

///

/// Eg.

///    class MyNode : public FoldingSetNode {

///    private:

///      std::string Name;

///      unsigned Value;

///    public:

///      MyNode(const char *N, unsigned V) : Name(N), Value(V) {}

///       ...

///      void Profile(FoldingSetNodeID &ID) const {

///        ID.AddString(Name);

///        ID.AddInteger(Value);

///      }

///      ...

///    };

///

/// To define the folding set itself use the FoldingSet template;

///

/// Eg.

///    FoldingSet<MyNode> MyFoldingSet;

///

/// Four public methods are available to manipulate the folding set;

///

/// 1) If you have an existing node that you want add to the set but unsure

/// that the node might already exist then call;

///

///    MyNode *M = MyFoldingSet.GetOrInsertNode(N);

///

/// If The result is equal to the input then the node has been inserted.

/// Otherwise, the result is the node existing in the folding set, and the

/// input can be discarded (use the result instead.)

///

/// 2) If you are ready to construct a node but want to check if it already

/// exists, then call FindNodeOrInsertPos with a FoldingSetNodeID of the bits to

/// check;

///

///   FoldingSetNodeID ID;

///   ID.AddString(Name);

///   ID.AddInteger(Value);

///   void *InsertPoint;

///

///    MyNode *M = MyFoldingSet.FindNodeOrInsertPos(ID, InsertPoint);

///

/// If found then M will be non-NULL, else InsertPoint will point to where it

/// should be inserted using InsertNode.

///

/// 3) If you get a NULL result from FindNodeOrInsertPos then you can insert a

/// new node with InsertNode;

///

///    MyFoldingSet.InsertNode(M, InsertPoint);

///

/// 4) Finally, if you want to remove a node from the folding set call;

///

///    bool WasRemoved = MyFoldingSet.RemoveNode(M);

///

/// The result indicates whether the node existed in the folding set.

class FoldingSetNodeID;

class StringRef;

//===----------------------------------------------------------------------===//

/// FoldingSetBase - Implements the folding set functionality.  The main

/// structure is an array of buckets.  Each bucket is indexed by the hash of

/// the nodes it contains.  The bucket itself points to the nodes contained

/// in the bucket via a singly linked list.  The last node in the list points

/// back to the bucket to facilitate node removal.

///

class FoldingSetBase {

protected:

  /// Buckets - Array of bucket chains.

  void **Buckets;

  /// NumBuckets - Length of the Buckets array.  Always a power of 2.

  unsigned NumBuckets;

  /// NumNodes - Number of nodes in the folding set. Growth occurs when NumNodes

  /// is greater than twice the number of buckets.

  unsigned NumNodes;

  explicit FoldingSetBase(unsigned Log2InitSize = 6);

  FoldingSetBase(FoldingSetBase &&Arg);

  FoldingSetBase &operator=(FoldingSetBase &&RHS);

  ~FoldingSetBase();

public:

  //===--------------------------------------------------------------------===//

  /// Node - This class is used to maintain the singly linked bucket list in

  /// a folding set.

  class Node {

  private:

    // NextInFoldingSetBucket - next link in the bucket list.

    void *NextInFoldingSetBucket = nullptr;

  public:

    Node() = default;

    // Accessors

    void *getNextInBucket() const { return NextInFoldingSetBucket; }

    void SetNextInBucket(void *N) { NextInFoldingSetBucket = N; }

  };

  /// clear - Remove all nodes from the folding set.

  void clear();

  /// size - Returns the number of nodes in the folding set.

  unsigned size() const { return NumNodes; }

  /// empty - Returns true if there are no nodes in the folding set.

  bool empty() const { return NumNodes == 0; }

  /// capacity - Returns the number of nodes permitted in the folding set

  /// before a rebucket operation is performed.

  unsigned capacity() {

    // We allow a load factor of up to 2.0,

    // so that means our capacity is NumBuckets * 2

    return NumBuckets * 2;

  }

protected:

  /// Functions provided by the derived class to compute folding properties.

  /// This is effectively a vtable for FoldingSetBase, except that we don't

  /// actually store a pointer to it in the object.

  struct FoldingSetInfo {

    /// GetNodeProfile - Instantiations of the FoldingSet template implement

    /// this function to gather data bits for the given node.

    void (*GetNodeProfile)(const FoldingSetBase *Self, Node *N,

                           FoldingSetNodeID &ID);

    /// NodeEquals - Instantiations of the FoldingSet template implement

    /// this function to compare the given node with the given ID.

    bool (*NodeEquals)(const FoldingSetBase *Self, Node *N,

                       const FoldingSetNodeID &ID, unsigned IDHash,

                       FoldingSetNodeID &TempID);

    /// ComputeNodeHash - Instantiations of the FoldingSet template implement

    /// this function to compute a hash value for the given node.

    unsigned (*ComputeNodeHash)(const FoldingSetBase *Self, Node *N,

                                FoldingSetNodeID &TempID);

  };

private:

  /// GrowHashTable - Double the size of the hash table and rehash everything.

  void GrowHashTable(const FoldingSetInfo &Info);

  /// GrowBucketCount - resize the hash table and rehash everything.

  /// NewBucketCount must be a power of two, and must be greater than the old

  /// bucket count.

  void GrowBucketCount(unsigned NewBucketCount, const FoldingSetInfo &Info);

protected:

  // The below methods are protected to encourage subclasses to provide a more

  // type-safe API.

  /// reserve - Increase the number of buckets such that adding the

  /// EltCount-th node won't cause a rebucket operation. reserve is permitted

  /// to allocate more space than requested by EltCount.

  void reserve(unsigned EltCount, const FoldingSetInfo &Info);

  /// RemoveNode - Remove a node from the folding set, returning true if one

  /// was removed or false if the node was not in the folding set.

  bool RemoveNode(Node *N);

  /// GetOrInsertNode - If there is an existing simple Node exactly

  /// equal to the specified node, return it.  Otherwise, insert 'N' and return

  /// it instead.

  Node *GetOrInsertNode(Node *N, const FoldingSetInfo &Info);

  /// FindNodeOrInsertPos - Look up the node specified by ID.  If it exists,

  /// return it.  If not, return the insertion token that will make insertion

  /// faster.

  Node *FindNodeOrInsertPos(const FoldingSetNodeID &ID, void *&InsertPos,

                            const FoldingSetInfo &Info);

  /// InsertNode - Insert the specified node into the folding set, knowing that

  /// it is not already in the folding set.  InsertPos must be obtained from

  /// FindNodeOrInsertPos.

  void InsertNode(Node *N, void *InsertPos, const FoldingSetInfo &Info);

};

//===----------------------------------------------------------------------===//

/// DefaultFoldingSetTrait - This class provides default implementations

/// for FoldingSetTrait implementations.

template<typename T> struct DefaultFoldingSetTrait {

  static void Profile(const T &X, FoldingSetNodeID &ID) {

    X.Profile(ID);

  }

  static void Profile(T &X, FoldingSetNodeID &ID) {

    X.Profile(ID);

  }

  // Equals - Test if the profile for X would match ID, using TempID

  // to compute a temporary ID if necessary. The default implementation

  // just calls Profile and does a regular comparison. Implementations

  // can override this to provide more efficient implementations.

  static inline bool Equals(T &X, const FoldingSetNodeID &ID, unsigned IDHash,

                            FoldingSetNodeID &TempID);

  // ComputeHash - Compute a hash value for X, using TempID to

  // compute a temporary ID if necessary. The default implementation

  // just calls Profile and does a regular hash computation.

  // Implementations can override this to provide more efficient

  // implementations.

  static inline unsigned ComputeHash(T &X, FoldingSetNodeID &TempID);

};

/// FoldingSetTrait - This trait class is used to define behavior of how

/// to "profile" (in the FoldingSet parlance) an object of a given type.

/// The default behavior is to invoke a 'Profile' method on an object, but

/// through template specialization the behavior can be tailored for specific

/// types.  Combined with the FoldingSetNodeWrapper class, one can add objects

/// to FoldingSets that were not originally designed to have that behavior.

template<typename T> struct FoldingSetTrait

  : public DefaultFoldingSetTrait<T> {};

/// DefaultContextualFoldingSetTrait - Like DefaultFoldingSetTrait, but

/// for ContextualFoldingSets.

template<typename T, typename Ctx>

struct DefaultContextualFoldingSetTrait {

  static void Profile(T &X, FoldingSetNodeID &ID, Ctx Context) {

    X.Profile(ID, Context);

  }

  static inline bool Equals(T &X, const FoldingSetNodeID &ID, unsigned IDHash,

                            FoldingSetNodeID &TempID, Ctx Context);

  static inline unsigned ComputeHash(T &X, FoldingSetNodeID &TempID,

                                     Ctx Context);

};

/// ContextualFoldingSetTrait - Like FoldingSetTrait, but for

/// ContextualFoldingSets.

template<typename T, typename Ctx> struct ContextualFoldingSetTrait

  : public DefaultContextualFoldingSetTrait<T, Ctx> {};

//===--------------------------------------------------------------------===//

/// FoldingSetNodeIDRef - This class describes a reference to an interned

/// FoldingSetNodeID, which can be a useful to store node id data rather

/// than using plain FoldingSetNodeIDs, since the 32-element SmallVector

/// is often much larger than necessary, and the possibility of heap

/// allocation means it requires a non-trivial destructor call.

class FoldingSetNodeIDRef {

  const unsigned *Data = nullptr;

  size_t Size = 0;

public:

  FoldingSetNodeIDRef() = default;

  FoldingSetNodeIDRef(const unsigned *D, size_t S) : Data(D), Size(S) {}

  /// ComputeHash - Compute a strong hash value for this FoldingSetNodeIDRef,

  /// used to lookup the node in the FoldingSetBase.

  unsigned ComputeHash() const;

  bool operator==(FoldingSetNodeIDRef) const;

  bool operator!=(FoldingSetNodeIDRef RHS) const { return !(*this == RHS); }

  /// Used to compare the "ordering" of two nodes as defined by the

  /// profiled bits and their ordering defined by memcmp().

  bool operator<(FoldingSetNodeIDRef) const;

  const unsigned *getData() const { return Data; }

  size_t getSize() const { return Size; }

};

//===--------------------------------------------------------------------===//

/// FoldingSetNodeID - This class is used to gather all the unique data bits of

/// a node.  When all the bits are gathered this class is used to produce a

/// hash value for the node.

class FoldingSetNodeID {

  /// Bits - Vector of all the data bits that make the node unique.

  /// Use a SmallVector to avoid a heap allocation in the common case.

  SmallVector<unsigned, 32> Bits;

public:

  FoldingSetNodeID() = default;

  FoldingSetNodeID(FoldingSetNodeIDRef Ref)

    : Bits(Ref.getData(), Ref.getData() + Ref.getSize()) {}

  /// Add* - Add various data types to Bit data.

  void AddPointer(const void *Ptr);

  void AddInteger(signed I);

  void AddInteger(unsigned I);

  void AddInteger(long I);

  void AddInteger(unsigned long I);

  void AddInteger(long long I);

  void AddInteger(unsigned long long I);

  void AddBoolean(bool B) { AddInteger(B ? 1U : 0U); }

  void AddString(StringRef String);

  void AddNodeID(const FoldingSetNodeID &ID);

  template <typename T>

  inline void Add(const T &x) { FoldingSetTrait<T>::Profile(x, *this); }

  /// clear - Clear the accumulated profile, allowing this FoldingSetNodeID

  /// object to be used to compute a new profile.

  inline void clear() { Bits.clear(); }

  /// ComputeHash - Compute a strong hash value for this FoldingSetNodeID, used

  /// to lookup the node in the FoldingSetBase.

  unsigned ComputeHash() const;

  /// operator== - Used to compare two nodes to each other.

  bool operator==(const FoldingSetNodeID &RHS) const;

  bool operator==(const FoldingSetNodeIDRef RHS) const;

  bool operator!=(const FoldingSetNodeID &RHS) const { return !(*this == RHS); }

  bool operator!=(const FoldingSetNodeIDRef RHS) const { return !(*this ==RHS);}

  /// Used to compare the "ordering" of two nodes as defined by the

  /// profiled bits and their ordering defined by memcmp().

  bool operator<(const FoldingSetNodeID &RHS) const;

  bool operator<(const FoldingSetNodeIDRef RHS) const;

  /// Intern - Copy this node's data to a memory region allocated from the

  /// given allocator and return a FoldingSetNodeIDRef describing the

  /// interned data.

  FoldingSetNodeIDRef Intern(BumpPtrAllocator &Allocator) const;

};

// Convenience type to hide the implementation of the folding set.

using FoldingSetNode = FoldingSetBase::Node;

template<class T> class FoldingSetIterator;

template<class T> class FoldingSetBucketIterator;

// Definitions of FoldingSetTrait and ContextualFoldingSetTrait functions, which

// require the definition of FoldingSetNodeID.

template<typename T>

inline bool

DefaultFoldingSetTrait<T>::Equals(T &X, const FoldingSetNodeID &ID,

                                  unsigned /*IDHash*/,

                                  FoldingSetNodeID &TempID) {

  FoldingSetTrait<T>::Profile(X, TempID);

  return TempID == ID;

}

template<typename T>

inline unsigned

DefaultFoldingSetTrait<T>::ComputeHash(T &X, FoldingSetNodeID &TempID) {

  FoldingSetTrait<T>::Profile(X, TempID);

  return TempID.ComputeHash();

}

template<typename T, typename Ctx>

inline bool

DefaultContextualFoldingSetTrait<T, Ctx>::Equals(T &X,

                                                 const FoldingSetNodeID &ID,

                                                 unsigned /*IDHash*/,

                                                 FoldingSetNodeID &TempID,

                                                 Ctx Context) {

  ContextualFoldingSetTrait<T, Ctx>::Profile(X, TempID, Context);

  return TempID == ID;

}

template<typename T, typename Ctx>

inline unsigned

DefaultContextualFoldingSetTrait<T, Ctx>::ComputeHash(T &X,

                                                      FoldingSetNodeID &TempID,

                                                      Ctx Context) {

  ContextualFoldingSetTrait<T, Ctx>::Profile(X, TempID, Context);

  return TempID.ComputeHash();

}

//===----------------------------------------------------------------------===//

/// FoldingSetImpl - An implementation detail that lets us share code between

/// FoldingSet and ContextualFoldingSet.

template <class Derived, class T> class FoldingSetImpl : public FoldingSetBase {

protected:

  explicit FoldingSetImpl(unsigned Log2InitSize)

      : FoldingSetBase(Log2InitSize) {}

  FoldingSetImpl(FoldingSetImpl &&Arg) = default;

  FoldingSetImpl &operator=(FoldingSetImpl &&RHS) = default;

  ~FoldingSetImpl() = default;

public:

  using iterator = FoldingSetIterator<T>;

  iterator begin() { return iterator(Buckets); }

  iterator end() { return iterator(Buckets+NumBuckets); }

  using const_iterator = FoldingSetIterator<const T>;

  const_iterator begin() const { return const_iterator(Buckets); }

  const_iterator end() const { return const_iterator(Buckets+NumBuckets); }

  using bucket_iterator = FoldingSetBucketIterator<T>;

  bucket_iterator bucket_begin(unsigned hash) {

    return bucket_iterator(Buckets + (hash & (NumBuckets-1)));

  }

  bucket_iterator bucket_end(unsigned hash) {

    return bucket_iterator(Buckets + (hash & (NumBuckets-1)), true);

  }

  /// reserve - Increase the number of buckets such that adding the

  /// EltCount-th node won't cause a rebucket operation. reserve is permitted

  /// to allocate more space than requested by EltCount.

  void reserve(unsigned EltCount) {

    return FoldingSetBase::reserve(EltCount, Derived::getFoldingSetInfo());

  }

  /// RemoveNode - Remove a node from the folding set, returning true if one

  /// was removed or false if the node was not in the folding set.

  bool RemoveNode(T *N) {

    return FoldingSetBase::RemoveNode(N);

  }

  /// GetOrInsertNode - If there is an existing simple Node exactly

  /// equal to the specified node, return it.  Otherwise, insert 'N' and

  /// return it instead.

  T *GetOrInsertNode(T *N) {

    return static_cast<T *>(

        FoldingSetBase::GetOrInsertNode(N, Derived::getFoldingSetInfo()));

  }

  /// FindNodeOrInsertPos - Look up the node specified by ID.  If it exists,

  /// return it.  If not, return the insertion token that will make insertion

  /// faster.

  T *FindNodeOrInsertPos(const FoldingSetNodeID &ID, void *&InsertPos) {

    return static_cast<T *>(FoldingSetBase::FindNodeOrInsertPos(

        ID, InsertPos, Derived::getFoldingSetInfo()));

  }

  /// InsertNode - Insert the specified node into the folding set, knowing that

  /// it is not already in the folding set.  InsertPos must be obtained from

  /// FindNodeOrInsertPos.

  void InsertNode(T *N, void *InsertPos) {

    FoldingSetBase::InsertNode(N, InsertPos, Derived::getFoldingSetInfo());

  }

  /// InsertNode - Insert the specified node into the folding set, knowing that

  /// it is not already in the folding set.

  void InsertNode(T *N) {

    T *Inserted = GetOrInsertNode(N);

    (void)Inserted;

    assert(Inserted == N && "Node already inserted!");

  }

};

//===----------------------------------------------------------------------===//

/// FoldingSet - This template class is used to instantiate a specialized

/// implementation of the folding set to the node class T.  T must be a

/// subclass of FoldingSetNode and implement a Profile function.

///

/// Note that this set type is movable and move-assignable. However, its

/// moved-from state is not a valid state for anything other than

/// move-assigning and destroying. This is primarily to enable movable APIs

/// that incorporate these objects.

template <class T>

class FoldingSet : public FoldingSetImpl<FoldingSet<T>, T> {

  using Super = FoldingSetImpl<FoldingSet, T>;

  using Node = typename Super::Node;

  /// GetNodeProfile - Each instantiation of the FoldingSet needs to provide a

  /// way to convert nodes into a unique specifier.

  static void GetNodeProfile(const FoldingSetBase *, Node *N,

                             FoldingSetNodeID &ID) {

    T *TN = static_cast<T *>(N);

    FoldingSetTrait<T>::Profile(*TN, ID);

  }

  /// NodeEquals - Instantiations may optionally provide a way to compare a

  /// node with a specified ID.

  static bool NodeEquals(const FoldingSetBase *, Node *N,

                         const FoldingSetNodeID &ID, unsigned IDHash,

                         FoldingSetNodeID &TempID) {

    T *TN = static_cast<T *>(N);

    return FoldingSetTrait<T>::Equals(*TN, ID, IDHash, TempID);

  }

  /// ComputeNodeHash - Instantiations may optionally provide a way to compute a

  /// hash value directly from a node.

  static unsigned ComputeNodeHash(const FoldingSetBase *, Node *N,

                                  FoldingSetNodeID &TempID) {

    T *TN = static_cast<T *>(N);

    return FoldingSetTrait<T>::ComputeHash(*TN, TempID);

  }

  static const FoldingSetBase::FoldingSetInfo &getFoldingSetInfo() {

    static constexpr FoldingSetBase::FoldingSetInfo Info = {

        GetNodeProfile, NodeEquals, ComputeNodeHash};

    return Info;

  }

  friend Super;

public:

  explicit FoldingSet(unsigned Log2InitSize = 6) : Super(Log2InitSize) {}

  FoldingSet(FoldingSet &&Arg) = default;

  FoldingSet &operator=(FoldingSet &&RHS) = default;

};

//===----------------------------------------------------------------------===//

/// ContextualFoldingSet - This template class is a further refinement

/// of FoldingSet which provides a context argument when calling

/// Profile on its nodes.  Currently, that argument is fixed at

/// initialization time.

///

/// T must be a subclass of FoldingSetNode and implement a Profile

/// function with signature

///   void Profile(FoldingSetNodeID &, Ctx);

template <class T, class Ctx>

class ContextualFoldingSet

    : public FoldingSetImpl<ContextualFoldingSet<T, Ctx>, T> {

  // Unfortunately, this can't derive from FoldingSet<T> because the

  // construction of the vtable for FoldingSet<T> requires

  // FoldingSet<T>::GetNodeProfile to be instantiated, which in turn

  // requires a single-argument T::Profile().

  using Super = FoldingSetImpl<ContextualFoldingSet, T>;

  using Node = typename Super::Node;

  Ctx Context;

  static const Ctx &getContext(const FoldingSetBase *Base) {

    return static_cast<const ContextualFoldingSet*>(Base)->Context;

  }

  /// GetNodeProfile - Each instantiatation of the FoldingSet needs to provide a

  /// way to convert nodes into a unique specifier.

  static void GetNodeProfile(const FoldingSetBase *Base, Node *N,

                             FoldingSetNodeID &ID) {

    T *TN = static_cast<T *>(N);

    ContextualFoldingSetTrait<T, Ctx>::Profile(*TN, ID, getContext(Base));

  }

  static bool NodeEquals(const FoldingSetBase *Base, Node *N,

                         const FoldingSetNodeID &ID, unsigned IDHash,

                         FoldingSetNodeID &TempID) {

    T *TN = static_cast<T *>(N);

    return ContextualFoldingSetTrait<T, Ctx>::Equals(*TN, ID, IDHash, TempID,

                                                     getContext(Base));

  }

  static unsigned ComputeNodeHash(const FoldingSetBase *Base, Node *N,

                                  FoldingSetNodeID &TempID) {

    T *TN = static_cast<T *>(N);

    return ContextualFoldingSetTrait<T, Ctx>::ComputeHash(*TN, TempID,

                                                          getContext(Base));

  }

  static const FoldingSetBase::FoldingSetInfo &getFoldingSetInfo() {

    static constexpr FoldingSetBase::FoldingSetInfo Info = {

        GetNodeProfile, NodeEquals, ComputeNodeHash};

    return Info;

  }

  friend Super;

public:

  explicit ContextualFoldingSet(Ctx Context, unsigned Log2InitSize = 6)

      : Super(Log2InitSize), Context(Context) {}

  Ctx getContext() const { return Context; }

};

//===----------------------------------------------------------------------===//

/// FoldingSetVector - This template class combines a FoldingSet and a vector

/// to provide the interface of FoldingSet but with deterministic iteration

/// order based on the insertion order. T must be a subclass of FoldingSetNode

/// and implement a Profile function.

template <class T, class VectorT = SmallVector<T*, 8>>

class FoldingSetVector {

  FoldingSet<T> Set;

  VectorT Vector;

public:

  explicit FoldingSetVector(unsigned Log2InitSize = 6) : Set(Log2InitSize) {}

  using iterator = pointee_iterator<typename VectorT::iterator>;

  iterator begin() { return Vector.begin(); }

  iterator end()   { return Vector.end(); }

  using const_iterator = pointee_iterator<typename VectorT::const_iterator>;

  const_iterator begin() const { return Vector.begin(); }

  const_iterator end()   const { return Vector.end(); }

  /// clear - Remove all nodes from the folding set.

  void clear() { Set.clear(); Vector.clear(); }

  /// FindNodeOrInsertPos - Look up the node specified by ID.  If it exists,

  /// return it.  If not, return the insertion token that will make insertion

  /// faster.

  T *FindNodeOrInsertPos(const FoldingSetNodeID &ID, void *&InsertPos) {

    return Set.FindNodeOrInsertPos(ID, InsertPos);

  }

  /// GetOrInsertNode - If there is an existing simple Node exactly

  /// equal to the specified node, return it.  Otherwise, insert 'N' and

  /// return it instead.

  T *GetOrInsertNode(T *N) {

    T *Result = Set.GetOrInsertNode(N);

    if (Result == N) Vector.push_back(N);

    return Result;

  }

  /// InsertNode - Insert the specified node into the folding set, knowing that

  /// it is not already in the folding set.  InsertPos must be obtained from

  /// FindNodeOrInsertPos.

  void InsertNode(T *N, void *InsertPos) {

    Set.InsertNode(N, InsertPos);

    Vector.push_back(N);

  }

  /// InsertNode - Insert the specified node into the folding set, knowing that

  /// it is not already in the folding set.

  void InsertNode(T *N) {

    Set.InsertNode(N);

    Vector.push_back(N);

  }

  /// size - Returns the number of nodes in the folding set.

  unsigned size() const { return Set.size(); }

  /// empty - Returns true if there are no nodes in the folding set.

  bool empty() const { return Set.empty(); }

};

//===----------------------------------------------------------------------===//

/// FoldingSetIteratorImpl - This is the common iterator support shared by all

/// folding sets, which knows how to walk the folding set hash table.

class FoldingSetIteratorImpl {

protected:

  FoldingSetNode *NodePtr;

  FoldingSetIteratorImpl(void **Bucket);

  void advance();

public:

  bool operator==(const FoldingSetIteratorImpl &RHS) const {

    return NodePtr == RHS.NodePtr;

  }

  bool operator!=(const FoldingSetIteratorImpl &RHS) const {

    return NodePtr != RHS.NodePtr;

  }

};

template <class T> class FoldingSetIterator : public FoldingSetIteratorImpl {

public:

  explicit FoldingSetIterator(void **Bucket) : FoldingSetIteratorImpl(Bucket) {}

  T &operator*() const {

    return *static_cast<T*>(NodePtr);

  }

  T *operator->() const {

    return static_cast<T*>(NodePtr);

  }

  inline FoldingSetIterator &operator++() {          // Preincrement

    advance();

    return *this;

  }

  FoldingSetIterator operator++(int) {        // Postincrement

    FoldingSetIterator tmp = *this; ++*this; return tmp;

  }

};

//===----------------------------------------------------------------------===//

/// FoldingSetBucketIteratorImpl - This is the common bucket iterator support

/// shared by all folding sets, which knows how to walk a particular bucket

/// of a folding set hash table.

class FoldingSetBucketIteratorImpl {

protected:

  void *Ptr;

  explicit FoldingSetBucketIteratorImpl(void **Bucket);

  FoldingSetBucketIteratorImpl(void **Bucket, bool) : Ptr(Bucket) {}

  void advance() {

    void *Probe = static_cast<FoldingSetNode*>(Ptr)->getNextInBucket();

    uintptr_t x = reinterpret_cast<uintptr_t>(Probe) & ~0x1;

    Ptr = reinterpret_cast<void*>(x);

  }

public:

  bool operator==(const FoldingSetBucketIteratorImpl &RHS) const {

    return Ptr == RHS.Ptr;

  }

  bool operator!=(const FoldingSetBucketIteratorImpl &RHS) const {

    return Ptr != RHS.Ptr;

  }

};

template <class T>

class FoldingSetBucketIterator : public FoldingSetBucketIteratorImpl {

public:

  explicit FoldingSetBucketIterator(void **Bucket) :

    FoldingSetBucketIteratorImpl(Bucket) {}

  FoldingSetBucketIterator(void **Bucket, bool) :

    FoldingSetBucketIteratorImpl(Bucket, true) {}

  T &operator*() const { return *static_cast<T*>(Ptr); }

  T *operator->() const { return static_cast<T*>(Ptr); }

  inline FoldingSetBucketIterator &operator++() { // Preincrement

    advance();

    return *this;

  }

  FoldingSetBucketIterator operator++(int) {      // Postincrement

    FoldingSetBucketIterator tmp = *this; ++*this; return tmp;

  }

};

//===----------------------------------------------------------------------===//

/// FoldingSetNodeWrapper - This template class is used to "wrap" arbitrary

/// types in an enclosing object so that they can be inserted into FoldingSets.

template <typename T>

class FoldingSetNodeWrapper : public FoldingSetNode {

  T data;

public:

  template <typename... Ts>

  explicit FoldingSetNodeWrapper(Ts &&... Args)

      : data(std::forward<Ts>(Args)...) {}

  void Profile(FoldingSetNodeID &ID) { FoldingSetTrait<T>::Profile(data, ID); }

  T &getValue() { return data; }

  const T &getValue() const { return data; }

  operator T&() { return data; }

  operator const T&() const { return data; }

};

//===----------------------------------------------------------------------===//

/// FastFoldingSetNode - This is a subclass of FoldingSetNode which stores

/// a FoldingSetNodeID value rather than requiring the node to recompute it

/// each time it is needed. This trades space for speed (which can be

/// significant if the ID is long), and it also permits nodes to drop

/// information that would otherwise only be required for recomputing an ID.

class FastFoldingSetNode : public FoldingSetNode {

  FoldingSetNodeID FastID;

protected:

  explicit FastFoldingSetNode(const FoldingSetNodeID &ID) : FastID(ID) {}

public:

  void Profile(FoldingSetNodeID &ID) const { ID.AddNodeID(FastID); }

};

//===----------------------------------------------------------------------===//

// Partial specializations of FoldingSetTrait.

template<typename T> struct FoldingSetTrait<T*> {

  static inline void Profile(T *X, FoldingSetNodeID &ID) {

    ID.AddPointer(X);

  }

};

template <typename T1, typename T2>

struct FoldingSetTrait<std::pair<T1, T2>> {

  static inline void Profile(const std::pair<T1, T2> &P,

                             FoldingSetNodeID &ID) {

    ID.Add(P.first);

    ID.Add(P.second);

  }

};

} // end namespace llvm

#endif // LLVM_ADT_FOLDINGSET_H