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 //===- 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
 //
 //===----------------------------------------------------------------------===//
 ///
 /// \file
 /// 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/Hashing.h"
 #include "llvm/ADT/STLForwardCompat.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/iterator.h"
 #include "llvm/Support/Allocator.h"
 #include "llvm/Support/xxhash.h"
 #include <cassert>
 #include <cstddef>
 #include <cstdint>
 #include <type_traits>
 #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, typename Enable = void>
 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) {}
 
   // Compute a strong hash value used to lookup the node in the FoldingSetBase.
   // The hash value is not guaranteed to be deterministic across processes.
   unsigned ComputeHash() const {
     return static_cast<unsigned>(hash_combine_range(Data, Data + Size));
   }
 
   // Compute a deterministic hash value across processes that is suitable for
   // on-disk serialization.
   unsigned computeStableHash() const {
     return static_cast<unsigned>(xxh3_64bits(ArrayRef(
         reinterpret_cast<const uint8_t *>(Data), sizeof(unsigned) * Size)));
   }
 
   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) {
     // Note: this adds pointers to the hash using sizes and endianness that
     // depend on the host. It doesn't matter, however, because hashing on
     // pointer values is inherently unstable. Nothing should depend on the
     // ordering of nodes in the folding set.
     static_assert(sizeof(uintptr_t) <= sizeof(unsigned long long),
                   "unexpected pointer size");
     AddInteger(reinterpret_cast<uintptr_t>(Ptr));
   }
   void AddInteger(signed I) { Bits.push_back(I); }
   void AddInteger(unsigned I) { Bits.push_back(I); }
   void AddInteger(long I) { AddInteger((unsigned long)I); }
   void AddInteger(unsigned long I) {
     if (sizeof(long) == sizeof(int))
       AddInteger(unsigned(I));
     else if (sizeof(long) == sizeof(long long)) {
       AddInteger((unsigned long long)I);
     } else {
       llvm_unreachable("unexpected sizeof(long)");
     }
   }
   void AddInteger(long long I) { AddInteger((unsigned long long)I); }
   void AddInteger(unsigned long long I) {
     AddInteger(unsigned(I));
     AddInteger(unsigned(I >> 32));
   }
 
   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(); }
 
   // Compute a strong hash value for this FoldingSetNodeID, used to lookup the
   // node in the FoldingSetBase. The hash value is not guaranteed to be
   // deterministic across processes.
   unsigned ComputeHash() const {
     return FoldingSetNodeIDRef(Bits.data(), Bits.size()).ComputeHash();
   }
 
   // Compute a deterministic hash value across processes that is suitable for
   // on-disk serialization.
   unsigned computeStableHash() const {
     return FoldingSetNodeIDRef(Bits.data(), Bits.size()).computeStableHash();
   }
 
   /// 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);
   }
 };
 
 template <typename T>
 struct FoldingSetTrait<T, std::enable_if_t<std::is_enum<T>::value>> {
   static void Profile(const T &X, FoldingSetNodeID &ID) {
     ID.AddInteger(llvm::to_underlying(X));
   }
 };
 
 } // end namespace llvm
 
 #endif // LLVM_ADT_FOLDINGSET_H

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