Export clang-format16 via ydblib project

6e6be3a95868fde888d801b7590af4044049563f

3 files changed, 1780 insertions, 0 deletions

diff --git a/contrib/libs/llvm16/include/llvm/ADT/ImmutableList.h b/contrib/libs/llvm16/include/llvm/ADT/ImmutableList.h
new file mode 100644
index 0000000000..182670e455
--- /dev/null
+++ b/contrib/libs/llvm16/include/llvm/ADT/ImmutableList.h
@@ -0,0 +1,257 @@
+#pragma once
+
+#ifdef __GNUC__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wunused-parameter"
+#endif
+
+//==--- ImmutableList.h - Immutable (functional) list interface --*- 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 the ImmutableList class.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ADT_IMMUTABLELIST_H
+#define LLVM_ADT_IMMUTABLELIST_H
+
+#include "llvm/ADT/FoldingSet.h"
+#include "llvm/Support/Allocator.h"
+#include <cassert>
+#include <cstdint>
+#include <new>
+
+namespace llvm {
+
+template <typename T> class ImmutableListFactory;
+
+template <typename T>
+class ImmutableListImpl : public FoldingSetNode {
+  friend class ImmutableListFactory<T>;
+
+  T Head;
+  const ImmutableListImpl* Tail;
+
+  template <typename ElemT>
+  ImmutableListImpl(ElemT &&head, const ImmutableListImpl *tail = nullptr)
+    : Head(std::forward<ElemT>(head)), Tail(tail) {}
+
+public:
+  ImmutableListImpl(const ImmutableListImpl &) = delete;
+  ImmutableListImpl &operator=(const ImmutableListImpl &) = delete;
+
+  const T& getHead() const { return Head; }
+  const ImmutableListImpl* getTail() const { return Tail; }
+
+  static inline void Profile(FoldingSetNodeID& ID, const T& H,
+                             const ImmutableListImpl* L){
+    ID.AddPointer(L);
+    ID.Add(H);
+  }
+
+  void Profile(FoldingSetNodeID& ID) {
+    Profile(ID, Head, Tail);
+  }
+};
+
+/// ImmutableList - This class represents an immutable (functional) list.
+///  It is implemented as a smart pointer (wraps ImmutableListImpl), so it
+///  it is intended to always be copied by value as if it were a pointer.
+///  This interface matches ImmutableSet and ImmutableMap.  ImmutableList
+///  objects should almost never be created directly, and instead should
+///  be created by ImmutableListFactory objects that manage the lifetime
+///  of a group of lists.  When the factory object is reclaimed, all lists
+///  created by that factory are released as well.
+template <typename T>
+class ImmutableList {
+public:
+  using value_type = T;
+  using Factory = ImmutableListFactory<T>;
+
+  static_assert(std::is_trivially_destructible<T>::value,
+                "T must be trivially destructible!");
+
+private:
+  const ImmutableListImpl<T>* X;
+
+public:
+  // This constructor should normally only be called by ImmutableListFactory<T>.
+  // There may be cases, however, when one needs to extract the internal pointer
+  // and reconstruct a list object from that pointer.
+  ImmutableList(const ImmutableListImpl<T>* x = nullptr) : X(x) {}
+
+  const ImmutableListImpl<T>* getInternalPointer() const {
+    return X;
+  }
+
+  class iterator {
+    const ImmutableListImpl<T>* L = nullptr;
+
+  public:
+    iterator() = default;
+    iterator(ImmutableList l) : L(l.getInternalPointer()) {}
+
+    iterator& operator++() { L = L->getTail(); return *this; }
+    bool operator==(const iterator& I) const { return L == I.L; }
+    bool operator!=(const iterator& I) const { return L != I.L; }
+    const value_type& operator*() const { return L->getHead(); }
+    const std::remove_reference_t<value_type> *operator->() const {
+      return &L->getHead();
+    }
+
+    ImmutableList getList() const { return L; }
+  };
+
+  /// begin - Returns an iterator referring to the head of the list, or
+  ///  an iterator denoting the end of the list if the list is empty.
+  iterator begin() const { return iterator(X); }
+
+  /// end - Returns an iterator denoting the end of the list.  This iterator
+  ///  does not refer to a valid list element.
+  iterator end() const { return iterator(); }
+
+  /// isEmpty - Returns true if the list is empty.
+  bool isEmpty() const { return !X; }
+
+  bool contains(const T& V) const {
+    for (iterator I = begin(), E = end(); I != E; ++I) {
+      if (*I == V)
+        return true;
+    }
+    return false;
+  }
+
+  /// isEqual - Returns true if two lists are equal.  Because all lists created
+  ///  from the same ImmutableListFactory are uniqued, this has O(1) complexity
+  ///  because it the contents of the list do not need to be compared.  Note
+  ///  that you should only compare two lists created from the same
+  ///  ImmutableListFactory.
+  bool isEqual(const ImmutableList& L) const { return X == L.X; }
+
+  bool operator==(const ImmutableList& L) const { return isEqual(L); }
+
+  /// getHead - Returns the head of the list.
+  const T& getHead() const {
+    assert(!isEmpty() && "Cannot get the head of an empty list.");
+    return X->getHead();
+  }
+
+  /// getTail - Returns the tail of the list, which is another (possibly empty)
+  ///  ImmutableList.
+  ImmutableList getTail() const {
+    return X ? X->getTail() : nullptr;
+  }
+
+  void Profile(FoldingSetNodeID& ID) const {
+    ID.AddPointer(X);
+  }
+};
+
+template <typename T>
+class ImmutableListFactory {
+  using ListTy = ImmutableListImpl<T>;
+  using CacheTy = FoldingSet<ListTy>;
+
+  CacheTy Cache;
+  uintptr_t Allocator;
+
+  bool ownsAllocator() const {
+    return (Allocator & 0x1) == 0;
+  }
+
+  BumpPtrAllocator& getAllocator() const {
+    return *reinterpret_cast<BumpPtrAllocator*>(Allocator & ~0x1);
+  }
+
+public:
+  ImmutableListFactory()
+    : Allocator(reinterpret_cast<uintptr_t>(new BumpPtrAllocator())) {}
+
+  ImmutableListFactory(BumpPtrAllocator& Alloc)
+  : Allocator(reinterpret_cast<uintptr_t>(&Alloc) | 0x1) {}
+
+  ~ImmutableListFactory() {
+    if (ownsAllocator()) delete &getAllocator();
+  }
+
+  template <typename ElemT>
+  [[nodiscard]] ImmutableList<T> concat(ElemT &&Head, ImmutableList<T> Tail) {
+    // Profile the new list to see if it already exists in our cache.
+    FoldingSetNodeID ID;
+    void* InsertPos;
+
+    const ListTy* TailImpl = Tail.getInternalPointer();
+    ListTy::Profile(ID, Head, TailImpl);
+    ListTy* L = Cache.FindNodeOrInsertPos(ID, InsertPos);
+
+    if (!L) {
+      // The list does not exist in our cache.  Create it.
+      BumpPtrAllocator& A = getAllocator();
+      L = (ListTy*) A.Allocate<ListTy>();
+      new (L) ListTy(std::forward<ElemT>(Head), TailImpl);
+
+      // Insert the new list into the cache.
+      Cache.InsertNode(L, InsertPos);
+    }
+
+    return L;
+  }
+
+  template <typename ElemT>
+  [[nodiscard]] ImmutableList<T> add(ElemT &&Data, ImmutableList<T> L) {
+    return concat(std::forward<ElemT>(Data), L);
+  }
+
+  template <typename... CtorArgs>
+  [[nodiscard]] ImmutableList<T> emplace(ImmutableList<T> Tail,
+                                         CtorArgs &&...Args) {
+    return concat(T(std::forward<CtorArgs>(Args)...), Tail);
+  }
+
+  ImmutableList<T> getEmptyList() const {
+    return ImmutableList<T>(nullptr);
+  }
+
+  template <typename ElemT>
+  ImmutableList<T> create(ElemT &&Data) {
+    return concat(std::forward<ElemT>(Data), getEmptyList());
+  }
+};
+
+//===----------------------------------------------------------------------===//
+// Partially-specialized Traits.
+//===----------------------------------------------------------------------===//
+
+template <typename T> struct DenseMapInfo<ImmutableList<T>, void> {
+  static inline ImmutableList<T> getEmptyKey() {
+    return reinterpret_cast<ImmutableListImpl<T>*>(-1);
+  }
+
+  static inline ImmutableList<T> getTombstoneKey() {
+    return reinterpret_cast<ImmutableListImpl<T>*>(-2);
+  }
+
+  static unsigned getHashValue(ImmutableList<T> X) {
+    uintptr_t PtrVal = reinterpret_cast<uintptr_t>(X.getInternalPointer());
+    return (unsigned((uintptr_t)PtrVal) >> 4) ^
+           (unsigned((uintptr_t)PtrVal) >> 9);
+  }
+
+  static bool isEqual(ImmutableList<T> X1, ImmutableList<T> X2) {
+    return X1 == X2;
+  }
+};
+
+} // end namespace llvm
+
+#endif // LLVM_ADT_IMMUTABLELIST_H
+
+#ifdef __GNUC__
+#pragma GCC diagnostic pop
+#endif
diff --git a/contrib/libs/llvm16/include/llvm/ADT/ImmutableMap.h b/contrib/libs/llvm16/include/llvm/ADT/ImmutableMap.h
new file mode 100644
index 0000000000..50396cdeb0
--- /dev/null
+++ b/contrib/libs/llvm16/include/llvm/ADT/ImmutableMap.h
@@ -0,0 +1,341 @@
+#pragma once
+
+#ifdef __GNUC__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wunused-parameter"
+#endif
+
+//===--- ImmutableMap.h - Immutable (functional) map interface --*- 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 the ImmutableMap class.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ADT_IMMUTABLEMAP_H
+#define LLVM_ADT_IMMUTABLEMAP_H
+
+#include "llvm/ADT/FoldingSet.h"
+#include "llvm/ADT/ImmutableSet.h"
+#include "llvm/Support/Allocator.h"
+#include <utility>
+
+namespace llvm {
+
+/// ImutKeyValueInfo -Traits class used by ImmutableMap.  While both the first
+/// and second elements in a pair are used to generate profile information,
+/// only the first element (the key) is used by isEqual and isLess.
+template <typename T, typename S>
+struct ImutKeyValueInfo {
+  using value_type = const std::pair<T,S>;
+  using value_type_ref = const value_type&;
+  using key_type = const T;
+  using key_type_ref = const T&;
+  using data_type = const S;
+  using data_type_ref = const S&;
+
+  static inline key_type_ref KeyOfValue(value_type_ref V) {
+    return V.first;
+  }
+
+  static inline data_type_ref DataOfValue(value_type_ref V) {
+    return V.second;
+  }
+
+  static inline bool isEqual(key_type_ref L, key_type_ref R) {
+    return ImutContainerInfo<T>::isEqual(L,R);
+  }
+  static inline bool isLess(key_type_ref L, key_type_ref R) {
+    return ImutContainerInfo<T>::isLess(L,R);
+  }
+
+  static inline bool isDataEqual(data_type_ref L, data_type_ref R) {
+    return ImutContainerInfo<S>::isEqual(L,R);
+  }
+
+  static inline void Profile(FoldingSetNodeID& ID, value_type_ref V) {
+    ImutContainerInfo<T>::Profile(ID, V.first);
+    ImutContainerInfo<S>::Profile(ID, V.second);
+  }
+};
+
+template <typename KeyT, typename ValT,
+          typename ValInfo = ImutKeyValueInfo<KeyT,ValT>>
+class ImmutableMap {
+public:
+  using value_type = typename ValInfo::value_type;
+  using value_type_ref = typename ValInfo::value_type_ref;
+  using key_type = typename ValInfo::key_type;
+  using key_type_ref = typename ValInfo::key_type_ref;
+  using data_type = typename ValInfo::data_type;
+  using data_type_ref = typename ValInfo::data_type_ref;
+  using TreeTy = ImutAVLTree<ValInfo>;
+
+protected:
+  IntrusiveRefCntPtr<TreeTy> Root;
+
+public:
+  /// Constructs a map from a pointer to a tree root.  In general one
+  /// should use a Factory object to create maps instead of directly
+  /// invoking the constructor, but there are cases where make this
+  /// constructor public is useful.
+  explicit ImmutableMap(const TreeTy *R) : Root(const_cast<TreeTy *>(R)) {}
+
+  class Factory {
+    typename TreeTy::Factory F;
+    const bool Canonicalize;
+
+  public:
+    Factory(bool canonicalize = true) : Canonicalize(canonicalize) {}
+
+    Factory(BumpPtrAllocator &Alloc, bool canonicalize = true)
+        : F(Alloc), Canonicalize(canonicalize) {}
+
+    Factory(const Factory &) = delete;
+    Factory &operator=(const Factory &) = delete;
+
+    ImmutableMap getEmptyMap() { return ImmutableMap(F.getEmptyTree()); }
+
+    [[nodiscard]] ImmutableMap add(ImmutableMap Old, key_type_ref K,
+                                   data_type_ref D) {
+      TreeTy *T = F.add(Old.Root.get(), std::pair<key_type, data_type>(K, D));
+      return ImmutableMap(Canonicalize ? F.getCanonicalTree(T): T);
+    }
+
+    [[nodiscard]] ImmutableMap remove(ImmutableMap Old, key_type_ref K) {
+      TreeTy *T = F.remove(Old.Root.get(), K);
+      return ImmutableMap(Canonicalize ? F.getCanonicalTree(T): T);
+    }
+
+    typename TreeTy::Factory *getTreeFactory() const {
+      return const_cast<typename TreeTy::Factory *>(&F);
+    }
+  };
+
+  bool contains(key_type_ref K) const {
+    return Root ? Root->contains(K) : false;
+  }
+
+  bool operator==(const ImmutableMap &RHS) const {
+    return Root && RHS.Root ? Root->isEqual(*RHS.Root.get()) : Root == RHS.Root;
+  }
+
+  bool operator!=(const ImmutableMap &RHS) const {
+    return Root && RHS.Root ? Root->isNotEqual(*RHS.Root.get())
+                            : Root != RHS.Root;
+  }
+
+  TreeTy *getRoot() const {
+    if (Root) { Root->retain(); }
+    return Root.get();
+  }
+
+  TreeTy *getRootWithoutRetain() const { return Root.get(); }
+
+  void manualRetain() {
+    if (Root) Root->retain();
+  }
+
+  void manualRelease() {
+    if (Root) Root->release();
+  }
+
+  bool isEmpty() const { return !Root; }
+
+public:
+  //===--------------------------------------------------===//
+  // For testing.
+  //===--------------------------------------------------===//
+
+  void verify() const { if (Root) Root->verify(); }
+
+  //===--------------------------------------------------===//
+  // Iterators.
+  //===--------------------------------------------------===//
+
+  class iterator : public ImutAVLValueIterator<ImmutableMap> {
+    friend class ImmutableMap;
+
+    iterator() = default;
+    explicit iterator(TreeTy *Tree) : iterator::ImutAVLValueIterator(Tree) {}
+
+  public:
+    key_type_ref getKey() const { return (*this)->first; }
+    data_type_ref getData() const { return (*this)->second; }
+  };
+
+  iterator begin() const { return iterator(Root.get()); }
+  iterator end() const { return iterator(); }
+
+  data_type* lookup(key_type_ref K) const {
+    if (Root) {
+      TreeTy* T = Root->find(K);
+      if (T) return &T->getValue().second;
+    }
+
+    return nullptr;
+  }
+
+  /// getMaxElement - Returns the <key,value> pair in the ImmutableMap for
+  ///  which key is the highest in the ordering of keys in the map.  This
+  ///  method returns NULL if the map is empty.
+  value_type* getMaxElement() const {
+    return Root ? &(Root->getMaxElement()->getValue()) : nullptr;
+  }
+
+  //===--------------------------------------------------===//
+  // Utility methods.
+  //===--------------------------------------------------===//
+
+  unsigned getHeight() const { return Root ? Root->getHeight() : 0; }
+
+  static inline void Profile(FoldingSetNodeID& ID, const ImmutableMap& M) {
+    ID.AddPointer(M.Root.get());
+  }
+
+  inline void Profile(FoldingSetNodeID& ID) const {
+    return Profile(ID,*this);
+  }
+};
+
+// NOTE: This will possibly become the new implementation of ImmutableMap some day.
+template <typename KeyT, typename ValT,
+typename ValInfo = ImutKeyValueInfo<KeyT,ValT>>
+class ImmutableMapRef {
+public:
+  using value_type = typename ValInfo::value_type;
+  using value_type_ref = typename ValInfo::value_type_ref;
+  using key_type = typename ValInfo::key_type;
+  using key_type_ref = typename ValInfo::key_type_ref;
+  using data_type = typename ValInfo::data_type;
+  using data_type_ref = typename ValInfo::data_type_ref;
+  using TreeTy = ImutAVLTree<ValInfo>;
+  using FactoryTy = typename TreeTy::Factory;
+
+protected:
+  IntrusiveRefCntPtr<TreeTy> Root;
+  FactoryTy *Factory;
+
+public:
+  /// Constructs a map from a pointer to a tree root.  In general one
+  /// should use a Factory object to create maps instead of directly
+  /// invoking the constructor, but there are cases where make this
+  /// constructor public is useful.
+  ImmutableMapRef(const TreeTy *R, FactoryTy *F)
+      : Root(const_cast<TreeTy *>(R)), Factory(F) {}
+
+  ImmutableMapRef(const ImmutableMap<KeyT, ValT> &X,
+                  typename ImmutableMap<KeyT, ValT>::Factory &F)
+      : Root(X.getRootWithoutRetain()), Factory(F.getTreeFactory()) {}
+
+  static inline ImmutableMapRef getEmptyMap(FactoryTy *F) {
+    return ImmutableMapRef(nullptr, F);
+  }
+
+  void manualRetain() {
+    if (Root) Root->retain();
+  }
+
+  void manualRelease() {
+    if (Root) Root->release();
+  }
+
+  ImmutableMapRef add(key_type_ref K, data_type_ref D) const {
+    TreeTy *NewT =
+        Factory->add(Root.get(), std::pair<key_type, data_type>(K, D));
+    return ImmutableMapRef(NewT, Factory);
+  }
+
+  ImmutableMapRef remove(key_type_ref K) const {
+    TreeTy *NewT = Factory->remove(Root.get(), K);
+    return ImmutableMapRef(NewT, Factory);
+  }
+
+  bool contains(key_type_ref K) const {
+    return Root ? Root->contains(K) : false;
+  }
+
+  ImmutableMap<KeyT, ValT> asImmutableMap() const {
+    return ImmutableMap<KeyT, ValT>(Factory->getCanonicalTree(Root.get()));
+  }
+
+  bool operator==(const ImmutableMapRef &RHS) const {
+    return Root && RHS.Root ? Root->isEqual(*RHS.Root.get()) : Root == RHS.Root;
+  }
+
+  bool operator!=(const ImmutableMapRef &RHS) const {
+    return Root && RHS.Root ? Root->isNotEqual(*RHS.Root.get())
+                            : Root != RHS.Root;
+  }
+
+  bool isEmpty() const { return !Root; }
+
+  //===--------------------------------------------------===//
+  // For testing.
+  //===--------------------------------------------------===//
+
+  void verify() const {
+    if (Root)
+      Root->verify();
+  }
+
+  //===--------------------------------------------------===//
+  // Iterators.
+  //===--------------------------------------------------===//
+
+  class iterator : public ImutAVLValueIterator<ImmutableMapRef> {
+    friend class ImmutableMapRef;
+
+    iterator() = default;
+    explicit iterator(TreeTy *Tree) : iterator::ImutAVLValueIterator(Tree) {}
+
+  public:
+    key_type_ref getKey() const { return (*this)->first; }
+    data_type_ref getData() const { return (*this)->second; }
+  };
+
+  iterator begin() const { return iterator(Root.get()); }
+  iterator end() const { return iterator(); }
+
+  data_type *lookup(key_type_ref K) const {
+    if (Root) {
+      TreeTy* T = Root->find(K);
+      if (T) return &T->getValue().second;
+    }
+
+    return nullptr;
+  }
+
+  /// getMaxElement - Returns the <key,value> pair in the ImmutableMap for
+  ///  which key is the highest in the ordering of keys in the map.  This
+  ///  method returns NULL if the map is empty.
+  value_type* getMaxElement() const {
+    return Root ? &(Root->getMaxElement()->getValue()) : nullptr;
+  }
+
+  //===--------------------------------------------------===//
+  // Utility methods.
+  //===--------------------------------------------------===//
+
+  unsigned getHeight() const { return Root ? Root->getHeight() : 0; }
+
+  static inline void Profile(FoldingSetNodeID &ID, const ImmutableMapRef &M) {
+    ID.AddPointer(M.Root.get());
+  }
+
+  inline void Profile(FoldingSetNodeID &ID) const { return Profile(ID, *this); }
+};
+
+} // end namespace llvm
+
+#endif // LLVM_ADT_IMMUTABLEMAP_H
+
+#ifdef __GNUC__
+#pragma GCC diagnostic pop
+#endif
diff --git a/contrib/libs/llvm16/include/llvm/ADT/ImmutableSet.h b/contrib/libs/llvm16/include/llvm/ADT/ImmutableSet.h
new file mode 100644
index 0000000000..be64a514a9
--- /dev/null
+++ b/contrib/libs/llvm16/include/llvm/ADT/ImmutableSet.h
@@ -0,0 +1,1182 @@
+#pragma once
+
+#ifdef __GNUC__
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wunused-parameter"
+#endif
+
+//===--- ImmutableSet.h - Immutable (functional) set interface --*- 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 the ImutAVLTree and ImmutableSet classes.
+///
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ADT_IMMUTABLESET_H
+#define LLVM_ADT_IMMUTABLESET_H
+
+#include "llvm/ADT/DenseMap.h"
+#include "llvm/ADT/FoldingSet.h"
+#include "llvm/ADT/IntrusiveRefCntPtr.h"
+#include "llvm/ADT/SmallVector.h"
+#include "llvm/ADT/iterator.h"
+#include "llvm/Support/Allocator.h"
+#include "llvm/Support/ErrorHandling.h"
+#include <cassert>
+#include <cstdint>
+#include <functional>
+#include <iterator>
+#include <new>
+#include <vector>
+
+namespace llvm {
+
+//===----------------------------------------------------------------------===//
+// Immutable AVL-Tree Definition.
+//===----------------------------------------------------------------------===//
+
+template <typename ImutInfo> class ImutAVLFactory;
+template <typename ImutInfo> class ImutIntervalAVLFactory;
+template <typename ImutInfo> class ImutAVLTreeInOrderIterator;
+template <typename ImutInfo> class ImutAVLTreeGenericIterator;
+
+template <typename ImutInfo >
+class ImutAVLTree {
+public:
+  using key_type_ref = typename ImutInfo::key_type_ref;
+  using value_type = typename ImutInfo::value_type;
+  using value_type_ref = typename ImutInfo::value_type_ref;
+  using Factory = ImutAVLFactory<ImutInfo>;
+  using iterator = ImutAVLTreeInOrderIterator<ImutInfo>;
+
+  friend class ImutAVLFactory<ImutInfo>;
+  friend class ImutIntervalAVLFactory<ImutInfo>;
+  friend class ImutAVLTreeGenericIterator<ImutInfo>;
+
+  //===----------------------------------------------------===//
+  // Public Interface.
+  //===----------------------------------------------------===//
+
+  /// Return a pointer to the left subtree.  This value
+  ///  is NULL if there is no left subtree.
+  ImutAVLTree *getLeft() const { return left; }
+
+  /// Return a pointer to the right subtree.  This value is
+  ///  NULL if there is no right subtree.
+  ImutAVLTree *getRight() const { return right; }
+
+  /// getHeight - Returns the height of the tree.  A tree with no subtrees
+  ///  has a height of 1.
+  unsigned getHeight() const { return height; }
+
+  /// getValue - Returns the data value associated with the tree node.
+  const value_type& getValue() const { return value; }
+
+  /// find - Finds the subtree associated with the specified key value.
+  ///  This method returns NULL if no matching subtree is found.
+  ImutAVLTree* find(key_type_ref K) {
+    ImutAVLTree *T = this;
+    while (T) {
+      key_type_ref CurrentKey = ImutInfo::KeyOfValue(T->getValue());
+      if (ImutInfo::isEqual(K,CurrentKey))
+        return T;
+      else if (ImutInfo::isLess(K,CurrentKey))
+        T = T->getLeft();
+      else
+        T = T->getRight();
+    }
+    return nullptr;
+  }
+
+  /// getMaxElement - Find the subtree associated with the highest ranged
+  ///  key value.
+  ImutAVLTree* getMaxElement() {
+    ImutAVLTree *T = this;
+    ImutAVLTree *Right = T->getRight();
+    while (Right) { T = Right; Right = T->getRight(); }
+    return T;
+  }
+
+  /// size - Returns the number of nodes in the tree, which includes
+  ///  both leaves and non-leaf nodes.
+  unsigned size() const {
+    unsigned n = 1;
+    if (const ImutAVLTree* L = getLeft())
+      n += L->size();
+    if (const ImutAVLTree* R = getRight())
+      n += R->size();
+    return n;
+  }
+
+  /// begin - Returns an iterator that iterates over the nodes of the tree
+  ///  in an inorder traversal.  The returned iterator thus refers to the
+  ///  the tree node with the minimum data element.
+  iterator begin() const { return iterator(this); }
+
+  /// end - Returns an iterator for the tree that denotes the end of an
+  ///  inorder traversal.
+  iterator end() const { return iterator(); }
+
+  bool isElementEqual(value_type_ref V) const {
+    // Compare the keys.
+    if (!ImutInfo::isEqual(ImutInfo::KeyOfValue(getValue()),
+                           ImutInfo::KeyOfValue(V)))
+      return false;
+
+    // Also compare the data values.
+    if (!ImutInfo::isDataEqual(ImutInfo::DataOfValue(getValue()),
+                               ImutInfo::DataOfValue(V)))
+      return false;
+
+    return true;
+  }
+
+  bool isElementEqual(const ImutAVLTree* RHS) const {
+    return isElementEqual(RHS->getValue());
+  }
+
+  /// isEqual - Compares two trees for structural equality and returns true
+  ///   if they are equal.  This worst case performance of this operation is
+  //    linear in the sizes of the trees.
+  bool isEqual(const ImutAVLTree& RHS) const {
+    if (&RHS == this)
+      return true;
+
+    iterator LItr = begin(), LEnd = end();
+    iterator RItr = RHS.begin(), REnd = RHS.end();
+
+    while (LItr != LEnd && RItr != REnd) {
+      if (&*LItr == &*RItr) {
+        LItr.skipSubTree();
+        RItr.skipSubTree();
+        continue;
+      }
+
+      if (!LItr->isElementEqual(&*RItr))
+        return false;
+
+      ++LItr;
+      ++RItr;
+    }
+
+    return LItr == LEnd && RItr == REnd;
+  }
+
+  /// isNotEqual - Compares two trees for structural inequality.  Performance
+  ///  is the same is isEqual.
+  bool isNotEqual(const ImutAVLTree& RHS) const { return !isEqual(RHS); }
+
+  /// contains - Returns true if this tree contains a subtree (node) that
+  ///  has an data element that matches the specified key.  Complexity
+  ///  is logarithmic in the size of the tree.
+  bool contains(key_type_ref K) { return (bool) find(K); }
+
+  /// validateTree - A utility method that checks that the balancing and
+  ///  ordering invariants of the tree are satisfied.  It is a recursive
+  ///  method that returns the height of the tree, which is then consumed
+  ///  by the enclosing validateTree call.  External callers should ignore the
+  ///  return value.  An invalid tree will cause an assertion to fire in
+  ///  a debug build.
+  unsigned validateTree() const {
+    unsigned HL = getLeft() ? getLeft()->validateTree() : 0;
+    unsigned HR = getRight() ? getRight()->validateTree() : 0;
+    (void) HL;
+    (void) HR;
+
+    assert(getHeight() == ( HL > HR ? HL : HR ) + 1
+            && "Height calculation wrong");
+
+    assert((HL > HR ? HL-HR : HR-HL) <= 2
+           && "Balancing invariant violated");
+
+    assert((!getLeft() ||
+            ImutInfo::isLess(ImutInfo::KeyOfValue(getLeft()->getValue()),
+                             ImutInfo::KeyOfValue(getValue()))) &&
+           "Value in left child is not less that current value");
+
+    assert((!getRight() ||
+             ImutInfo::isLess(ImutInfo::KeyOfValue(getValue()),
+                              ImutInfo::KeyOfValue(getRight()->getValue()))) &&
+           "Current value is not less that value of right child");
+
+    return getHeight();
+  }
+
+  //===----------------------------------------------------===//
+  // Internal values.
+  //===----------------------------------------------------===//
+
+private:
+  Factory *factory;
+  ImutAVLTree *left;
+  ImutAVLTree *right;
+  ImutAVLTree *prev = nullptr;
+  ImutAVLTree *next = nullptr;
+
+  unsigned height : 28;
+  bool IsMutable : 1;
+  bool IsDigestCached : 1;
+  bool IsCanonicalized : 1;
+
+  value_type value;
+  uint32_t digest = 0;
+  uint32_t refCount = 0;
+
+  //===----------------------------------------------------===//
+  // Internal methods (node manipulation; used by Factory).
+  //===----------------------------------------------------===//
+
+private:
+  /// ImutAVLTree - Internal constructor that is only called by
+  ///   ImutAVLFactory.
+  ImutAVLTree(Factory *f, ImutAVLTree* l, ImutAVLTree* r, value_type_ref v,
+              unsigned height)
+    : factory(f), left(l), right(r), height(height), IsMutable(true),
+      IsDigestCached(false), IsCanonicalized(false), value(v)
+  {
+    if (left) left->retain();
+    if (right) right->retain();
+  }
+
+  /// isMutable - Returns true if the left and right subtree references
+  ///  (as well as height) can be changed.  If this method returns false,
+  ///  the tree is truly immutable.  Trees returned from an ImutAVLFactory
+  ///  object should always have this method return true.  Further, if this
+  ///  method returns false for an instance of ImutAVLTree, all subtrees
+  ///  will also have this method return false.  The converse is not true.
+  bool isMutable() const { return IsMutable; }
+
+  /// hasCachedDigest - Returns true if the digest for this tree is cached.
+  ///  This can only be true if the tree is immutable.
+  bool hasCachedDigest() const { return IsDigestCached; }
+
+  //===----------------------------------------------------===//
+  // Mutating operations.  A tree root can be manipulated as
+  // long as its reference has not "escaped" from internal
+  // methods of a factory object (see below).  When a tree
+  // pointer is externally viewable by client code, the
+  // internal "mutable bit" is cleared to mark the tree
+  // immutable.  Note that a tree that still has its mutable
+  // bit set may have children (subtrees) that are themselves
+  // immutable.
+  //===----------------------------------------------------===//
+
+  /// markImmutable - Clears the mutable flag for a tree.  After this happens,
+  ///   it is an error to call setLeft(), setRight(), and setHeight().
+  void markImmutable() {
+    assert(isMutable() && "Mutable flag already removed.");
+    IsMutable = false;
+  }
+
+  /// markedCachedDigest - Clears the NoCachedDigest flag for a tree.
+  void markedCachedDigest() {
+    assert(!hasCachedDigest() && "NoCachedDigest flag already removed.");
+    IsDigestCached = true;
+  }
+
+  /// setHeight - Changes the height of the tree.  Used internally by
+  ///  ImutAVLFactory.
+  void setHeight(unsigned h) {
+    assert(isMutable() && "Only a mutable tree can have its height changed.");
+    height = h;
+  }
+
+  static uint32_t computeDigest(ImutAVLTree *L, ImutAVLTree *R,
+                                value_type_ref V) {
+    uint32_t digest = 0;
+
+    if (L)
+      digest += L->computeDigest();
+
+    // Compute digest of stored data.
+    FoldingSetNodeID ID;
+    ImutInfo::Profile(ID,V);
+    digest += ID.ComputeHash();
+
+    if (R)
+      digest += R->computeDigest();
+
+    return digest;
+  }
+
+  uint32_t computeDigest() {
+    // Check the lowest bit to determine if digest has actually been
+    // pre-computed.
+    if (hasCachedDigest())
+      return digest;
+
+    uint32_t X = computeDigest(getLeft(), getRight(), getValue());
+    digest = X;
+    markedCachedDigest();
+    return X;
+  }
+
+  //===----------------------------------------------------===//
+  // Reference count operations.
+  //===----------------------------------------------------===//
+
+public:
+  void retain() { ++refCount; }
+
+  void release() {
+    assert(refCount > 0);
+    if (--refCount == 0)
+      destroy();
+  }
+
+  void destroy() {
+    if (left)
+      left->release();
+    if (right)
+      right->release();
+    if (IsCanonicalized) {
+      if (next)
+        next->prev = prev;
+
+      if (prev)
+        prev->next = next;
+      else
+        factory->Cache[factory->maskCacheIndex(computeDigest())] = next;
+    }
+
+    // We need to clear the mutability bit in case we are
+    // destroying the node as part of a sweep in ImutAVLFactory::recoverNodes().
+    IsMutable = false;
+    factory->freeNodes.push_back(this);
+  }
+};
+
+template <typename ImutInfo>
+struct IntrusiveRefCntPtrInfo<ImutAVLTree<ImutInfo>> {
+  static void retain(ImutAVLTree<ImutInfo> *Tree) { Tree->retain(); }
+  static void release(ImutAVLTree<ImutInfo> *Tree) { Tree->release(); }
+};
+
+//===----------------------------------------------------------------------===//
+// Immutable AVL-Tree Factory class.
+//===----------------------------------------------------------------------===//
+
+template <typename ImutInfo >
+class ImutAVLFactory {
+  friend class ImutAVLTree<ImutInfo>;
+
+  using TreeTy = ImutAVLTree<ImutInfo>;
+  using value_type_ref = typename TreeTy::value_type_ref;
+  using key_type_ref = typename TreeTy::key_type_ref;
+  using CacheTy = DenseMap<unsigned, TreeTy*>;
+
+  CacheTy Cache;
+  uintptr_t Allocator;
+  std::vector<TreeTy*> createdNodes;
+  std::vector<TreeTy*> freeNodes;
+
+  bool ownsAllocator() const {
+    return (Allocator & 0x1) == 0;
+  }
+
+  BumpPtrAllocator& getAllocator() const {
+    return *reinterpret_cast<BumpPtrAllocator*>(Allocator & ~0x1);
+  }
+
+  //===--------------------------------------------------===//
+  // Public interface.
+  //===--------------------------------------------------===//
+
+public:
+  ImutAVLFactory()
+    : Allocator(reinterpret_cast<uintptr_t>(new BumpPtrAllocator())) {}
+
+  ImutAVLFactory(BumpPtrAllocator& Alloc)
+    : Allocator(reinterpret_cast<uintptr_t>(&Alloc) | 0x1) {}
+
+  ~ImutAVLFactory() {
+    if (ownsAllocator()) delete &getAllocator();
+  }
+
+  TreeTy* add(TreeTy* T, value_type_ref V) {
+    T = add_internal(V,T);
+    markImmutable(T);
+    recoverNodes();
+    return T;
+  }
+
+  TreeTy* remove(TreeTy* T, key_type_ref V) {
+    T = remove_internal(V,T);
+    markImmutable(T);
+    recoverNodes();
+    return T;
+  }
+
+  TreeTy* getEmptyTree() const { return nullptr; }
+
+protected:
+  //===--------------------------------------------------===//
+  // A bunch of quick helper functions used for reasoning
+  // about the properties of trees and their children.
+  // These have succinct names so that the balancing code
+  // is as terse (and readable) as possible.
+  //===--------------------------------------------------===//
+
+  bool            isEmpty(TreeTy* T) const { return !T; }
+  unsigned        getHeight(TreeTy* T) const { return T ? T->getHeight() : 0; }
+  TreeTy*         getLeft(TreeTy* T) const { return T->getLeft(); }
+  TreeTy*         getRight(TreeTy* T) const { return T->getRight(); }
+  value_type_ref  getValue(TreeTy* T) const { return T->value; }
+
+  // Make sure the index is not the Tombstone or Entry key of the DenseMap.
+  static unsigned maskCacheIndex(unsigned I) { return (I & ~0x02); }
+
+  unsigned incrementHeight(TreeTy* L, TreeTy* R) const {
+    unsigned hl = getHeight(L);
+    unsigned hr = getHeight(R);
+    return (hl > hr ? hl : hr) + 1;
+  }
+
+  static bool compareTreeWithSection(TreeTy* T,
+                                     typename TreeTy::iterator& TI,
+                                     typename TreeTy::iterator& TE) {
+    typename TreeTy::iterator I = T->begin(), E = T->end();
+    for ( ; I!=E ; ++I, ++TI) {
+      if (TI == TE || !I->isElementEqual(&*TI))
+        return false;
+    }
+    return true;
+  }
+
+  //===--------------------------------------------------===//
+  // "createNode" is used to generate new tree roots that link
+  // to other trees.  The function may also simply move links
+  // in an existing root if that root is still marked mutable.
+  // This is necessary because otherwise our balancing code
+  // would leak memory as it would create nodes that are
+  // then discarded later before the finished tree is
+  // returned to the caller.
+  //===--------------------------------------------------===//
+
+  TreeTy* createNode(TreeTy* L, value_type_ref V, TreeTy* R) {
+    BumpPtrAllocator& A = getAllocator();
+    TreeTy* T;
+    if (!freeNodes.empty()) {
+      T = freeNodes.back();
+      freeNodes.pop_back();
+      assert(T != L);
+      assert(T != R);
+    } else {
+      T = (TreeTy*) A.Allocate<TreeTy>();
+    }
+    new (T) TreeTy(this, L, R, V, incrementHeight(L,R));
+    createdNodes.push_back(T);
+    return T;
+  }
+
+  TreeTy* createNode(TreeTy* newLeft, TreeTy* oldTree, TreeTy* newRight) {
+    return createNode(newLeft, getValue(oldTree), newRight);
+  }
+
+  void recoverNodes() {
+    for (unsigned i = 0, n = createdNodes.size(); i < n; ++i) {
+      TreeTy *N = createdNodes[i];
+      if (N->isMutable() && N->refCount == 0)
+        N->destroy();
+    }
+    createdNodes.clear();
+  }
+
+  /// balanceTree - Used by add_internal and remove_internal to
+  ///  balance a newly created tree.
+  TreeTy* balanceTree(TreeTy* L, value_type_ref V, TreeTy* R) {
+    unsigned hl = getHeight(L);
+    unsigned hr = getHeight(R);
+
+    if (hl > hr + 2) {
+      assert(!isEmpty(L) && "Left tree cannot be empty to have a height >= 2");
+
+      TreeTy *LL = getLeft(L);
+      TreeTy *LR = getRight(L);
+
+      if (getHeight(LL) >= getHeight(LR))
+        return createNode(LL, L, createNode(LR,V,R));
+
+      assert(!isEmpty(LR) && "LR cannot be empty because it has a height >= 1");
+
+      TreeTy *LRL = getLeft(LR);
+      TreeTy *LRR = getRight(LR);
+
+      return createNode(createNode(LL,L,LRL), LR, createNode(LRR,V,R));
+    }
+
+    if (hr > hl + 2) {
+      assert(!isEmpty(R) && "Right tree cannot be empty to have a height >= 2");
+
+      TreeTy *RL = getLeft(R);
+      TreeTy *RR = getRight(R);
+
+      if (getHeight(RR) >= getHeight(RL))
+        return createNode(createNode(L,V,RL), R, RR);
+
+      assert(!isEmpty(RL) && "RL cannot be empty because it has a height >= 1");
+
+      TreeTy *RLL = getLeft(RL);
+      TreeTy *RLR = getRight(RL);
+
+      return createNode(createNode(L,V,RLL), RL, createNode(RLR,R,RR));
+    }
+
+    return createNode(L,V,R);
+  }
+
+  /// add_internal - Creates a new tree that includes the specified
+  ///  data and the data from the original tree.  If the original tree
+  ///  already contained the data item, the original tree is returned.
+  TreeTy* add_internal(value_type_ref V, TreeTy* T) {
+    if (isEmpty(T))
+      return createNode(T, V, T);
+    assert(!T->isMutable());
+
+    key_type_ref K = ImutInfo::KeyOfValue(V);
+    key_type_ref KCurrent = ImutInfo::KeyOfValue(getValue(T));
+
+    if (ImutInfo::isEqual(K,KCurrent))
+      return createNode(getLeft(T), V, getRight(T));
+    else if (ImutInfo::isLess(K,KCurrent))
+      return balanceTree(add_internal(V, getLeft(T)), getValue(T), getRight(T));
+    else
+      return balanceTree(getLeft(T), getValue(T), add_internal(V, getRight(T)));
+  }
+
+  /// remove_internal - Creates a new tree that includes all the data
+  ///  from the original tree except the specified data.  If the
+  ///  specified data did not exist in the original tree, the original
+  ///  tree is returned.
+  TreeTy* remove_internal(key_type_ref K, TreeTy* T) {
+    if (isEmpty(T))
+      return T;
+
+    assert(!T->isMutable());
+
+    key_type_ref KCurrent = ImutInfo::KeyOfValue(getValue(T));
+
+    if (ImutInfo::isEqual(K,KCurrent)) {
+      return combineTrees(getLeft(T), getRight(T));
+    } else if (ImutInfo::isLess(K,KCurrent)) {
+      return balanceTree(remove_internal(K, getLeft(T)),
+                                            getValue(T), getRight(T));
+    } else {
+      return balanceTree(getLeft(T), getValue(T),
+                         remove_internal(K, getRight(T)));
+    }
+  }
+
+  TreeTy* combineTrees(TreeTy* L, TreeTy* R) {
+    if (isEmpty(L))
+      return R;
+    if (isEmpty(R))
+      return L;
+    TreeTy* OldNode;
+    TreeTy* newRight = removeMinBinding(R,OldNode);
+    return balanceTree(L, getValue(OldNode), newRight);
+  }
+
+  TreeTy* removeMinBinding(TreeTy* T, TreeTy*& Noderemoved) {
+    assert(!isEmpty(T));
+    if (isEmpty(getLeft(T))) {
+      Noderemoved = T;
+      return getRight(T);
+    }
+    return balanceTree(removeMinBinding(getLeft(T), Noderemoved),
+                       getValue(T), getRight(T));
+  }
+
+  /// markImmutable - Clears the mutable bits of a root and all of its
+  ///  descendants.
+  void markImmutable(TreeTy* T) {
+    if (!T || !T->isMutable())
+      return;
+    T->markImmutable();
+    markImmutable(getLeft(T));
+    markImmutable(getRight(T));
+  }
+
+public:
+  TreeTy *getCanonicalTree(TreeTy *TNew) {
+    if (!TNew)
+      return nullptr;
+
+    if (TNew->IsCanonicalized)
+      return TNew;
+
+    // Search the hashtable for another tree with the same digest, and
+    // if find a collision compare those trees by their contents.
+    unsigned digest = TNew->computeDigest();
+    TreeTy *&entry = Cache[maskCacheIndex(digest)];
+    do {
+      if (!entry)
+        break;
+      for (TreeTy *T = entry ; T != nullptr; T = T->next) {
+        // Compare the Contents('T') with Contents('TNew')
+        typename TreeTy::iterator TI = T->begin(), TE = T->end();
+        if (!compareTreeWithSection(TNew, TI, TE))
+          continue;
+        if (TI != TE)
+          continue; // T has more contents than TNew.
+        // Trees did match!  Return 'T'.
+        if (TNew->refCount == 0)
+          TNew->destroy();
+        return T;
+      }
+      entry->prev = TNew;
+      TNew->next = entry;
+    }
+    while (false);
+
+    entry = TNew;
+    TNew->IsCanonicalized = true;
+    return TNew;
+  }
+};
+
+//===----------------------------------------------------------------------===//
+// Immutable AVL-Tree Iterators.
+//===----------------------------------------------------------------------===//
+
+template <typename ImutInfo> class ImutAVLTreeGenericIterator {
+  SmallVector<uintptr_t,20> stack;
+
+public:
+  using iterator_category = std::bidirectional_iterator_tag;
+  using value_type = ImutAVLTree<ImutInfo>;
+  using difference_type = std::ptrdiff_t;
+  using pointer = value_type *;
+  using reference = value_type &;
+
+  enum VisitFlag { VisitedNone=0x0, VisitedLeft=0x1, VisitedRight=0x3,
+                   Flags=0x3 };
+
+  using TreeTy = ImutAVLTree<ImutInfo>;
+
+  ImutAVLTreeGenericIterator() = default;
+  ImutAVLTreeGenericIterator(const TreeTy *Root) {
+    if (Root) stack.push_back(reinterpret_cast<uintptr_t>(Root));
+  }
+
+  TreeTy &operator*() const {
+    assert(!stack.empty());
+    return *reinterpret_cast<TreeTy *>(stack.back() & ~Flags);
+  }
+  TreeTy *operator->() const { return &*this; }
+
+  uintptr_t getVisitState() const {
+    assert(!stack.empty());
+    return stack.back() & Flags;
+  }
+
+  bool atEnd() const { return stack.empty(); }
+
+  bool atBeginning() const {
+    return stack.size() == 1 && getVisitState() == VisitedNone;
+  }
+
+  void skipToParent() {
+    assert(!stack.empty());
+    stack.pop_back();
+    if (stack.empty())
+      return;
+    switch (getVisitState()) {
+      case VisitedNone:
+        stack.back() |= VisitedLeft;
+        break;
+      case VisitedLeft:
+        stack.back() |= VisitedRight;
+        break;
+      default:
+        llvm_unreachable("Unreachable.");
+    }
+  }
+
+  bool operator==(const ImutAVLTreeGenericIterator &x) const {
+    return stack == x.stack;
+  }
+
+  bool operator!=(const ImutAVLTreeGenericIterator &x) const {
+    return !(*this == x);
+  }
+
+  ImutAVLTreeGenericIterator &operator++() {
+    assert(!stack.empty());
+    TreeTy* Current = reinterpret_cast<TreeTy*>(stack.back() & ~Flags);
+    assert(Current);
+    switch (getVisitState()) {
+      case VisitedNone:
+        if (TreeTy* L = Current->getLeft())
+          stack.push_back(reinterpret_cast<uintptr_t>(L));
+        else
+          stack.back() |= VisitedLeft;
+        break;
+      case VisitedLeft:
+        if (TreeTy* R = Current->getRight())
+          stack.push_back(reinterpret_cast<uintptr_t>(R));
+        else
+          stack.back() |= VisitedRight;
+        break;
+      case VisitedRight:
+        skipToParent();
+        break;
+      default:
+        llvm_unreachable("Unreachable.");
+    }
+    return *this;
+  }
+
+  ImutAVLTreeGenericIterator &operator--() {
+    assert(!stack.empty());
+    TreeTy* Current = reinterpret_cast<TreeTy*>(stack.back() & ~Flags);
+    assert(Current);
+    switch (getVisitState()) {
+      case VisitedNone:
+        stack.pop_back();
+        break;
+      case VisitedLeft:
+        stack.back() &= ~Flags; // Set state to "VisitedNone."
+        if (TreeTy* L = Current->getLeft())
+          stack.push_back(reinterpret_cast<uintptr_t>(L) | VisitedRight);
+        break;
+      case VisitedRight:
+        stack.back() &= ~Flags;
+        stack.back() |= VisitedLeft;
+        if (TreeTy* R = Current->getRight())
+          stack.push_back(reinterpret_cast<uintptr_t>(R) | VisitedRight);
+        break;
+      default:
+        llvm_unreachable("Unreachable.");
+    }
+    return *this;
+  }
+};
+
+template <typename ImutInfo> class ImutAVLTreeInOrderIterator {
+  using InternalIteratorTy = ImutAVLTreeGenericIterator<ImutInfo>;
+
+  InternalIteratorTy InternalItr;
+
+public:
+  using iterator_category = std::bidirectional_iterator_tag;
+  using value_type = ImutAVLTree<ImutInfo>;
+  using difference_type = std::ptrdiff_t;
+  using pointer = value_type *;
+  using reference = value_type &;
+
+  using TreeTy = ImutAVLTree<ImutInfo>;
+
+  ImutAVLTreeInOrderIterator(const TreeTy* Root) : InternalItr(Root) {
+    if (Root)
+      ++*this; // Advance to first element.
+  }
+
+  ImutAVLTreeInOrderIterator() : InternalItr() {}
+
+  bool operator==(const ImutAVLTreeInOrderIterator &x) const {
+    return InternalItr == x.InternalItr;
+  }
+
+  bool operator!=(const ImutAVLTreeInOrderIterator &x) const {
+    return !(*this == x);
+  }
+
+  TreeTy &operator*() const { return *InternalItr; }
+  TreeTy *operator->() const { return &*InternalItr; }
+
+  ImutAVLTreeInOrderIterator &operator++() {
+    do ++InternalItr;
+    while (!InternalItr.atEnd() &&
+           InternalItr.getVisitState() != InternalIteratorTy::VisitedLeft);
+
+    return *this;
+  }
+
+  ImutAVLTreeInOrderIterator &operator--() {
+    do --InternalItr;
+    while (!InternalItr.atBeginning() &&
+           InternalItr.getVisitState() != InternalIteratorTy::VisitedLeft);
+
+    return *this;
+  }
+
+  void skipSubTree() {
+    InternalItr.skipToParent();
+
+    while (!InternalItr.atEnd() &&
+           InternalItr.getVisitState() != InternalIteratorTy::VisitedLeft)
+      ++InternalItr;
+  }
+};
+
+/// Generic iterator that wraps a T::TreeTy::iterator and exposes
+/// iterator::getValue() on dereference.
+template <typename T>
+struct ImutAVLValueIterator
+    : iterator_adaptor_base<
+          ImutAVLValueIterator<T>, typename T::TreeTy::iterator,
+          typename std::iterator_traits<
+              typename T::TreeTy::iterator>::iterator_category,
+          const typename T::value_type> {
+  ImutAVLValueIterator() = default;
+  explicit ImutAVLValueIterator(typename T::TreeTy *Tree)
+      : ImutAVLValueIterator::iterator_adaptor_base(Tree) {}
+
+  typename ImutAVLValueIterator::reference operator*() const {
+    return this->I->getValue();
+  }
+};
+
+//===----------------------------------------------------------------------===//
+// Trait classes for Profile information.
+//===----------------------------------------------------------------------===//
+
+/// Generic profile template.  The default behavior is to invoke the
+/// profile method of an object.  Specializations for primitive integers
+/// and generic handling of pointers is done below.
+template <typename T>
+struct ImutProfileInfo {
+  using value_type = const T;
+  using value_type_ref = const T&;
+
+  static void Profile(FoldingSetNodeID &ID, value_type_ref X) {
+    FoldingSetTrait<T>::Profile(X,ID);
+  }
+};
+
+/// Profile traits for integers.
+template <typename T>
+struct ImutProfileInteger {
+  using value_type = const T;
+  using value_type_ref = const T&;
+
+  static void Profile(FoldingSetNodeID &ID, value_type_ref X) {
+    ID.AddInteger(X);
+  }
+};
+
+#define PROFILE_INTEGER_INFO(X)\
+template<> struct ImutProfileInfo<X> : ImutProfileInteger<X> {};
+
+PROFILE_INTEGER_INFO(char)
+PROFILE_INTEGER_INFO(unsigned char)
+PROFILE_INTEGER_INFO(short)
+PROFILE_INTEGER_INFO(unsigned short)
+PROFILE_INTEGER_INFO(unsigned)
+PROFILE_INTEGER_INFO(signed)
+PROFILE_INTEGER_INFO(long)
+PROFILE_INTEGER_INFO(unsigned long)
+PROFILE_INTEGER_INFO(long long)
+PROFILE_INTEGER_INFO(unsigned long long)
+
+#undef PROFILE_INTEGER_INFO
+
+/// Profile traits for booleans.
+template <>
+struct ImutProfileInfo<bool> {
+  using value_type = const bool;
+  using value_type_ref = const bool&;
+
+  static void Profile(FoldingSetNodeID &ID, value_type_ref X) {
+    ID.AddBoolean(X);
+  }
+};
+
+/// Generic profile trait for pointer types.  We treat pointers as
+/// references to unique objects.
+template <typename T>
+struct ImutProfileInfo<T*> {
+  using value_type = const T*;
+  using value_type_ref = value_type;
+
+  static void Profile(FoldingSetNodeID &ID, value_type_ref X) {
+    ID.AddPointer(X);
+  }
+};
+
+//===----------------------------------------------------------------------===//
+// Trait classes that contain element comparison operators and type
+//  definitions used by ImutAVLTree, ImmutableSet, and ImmutableMap.  These
+//  inherit from the profile traits (ImutProfileInfo) to include operations
+//  for element profiling.
+//===----------------------------------------------------------------------===//
+
+/// ImutContainerInfo - Generic definition of comparison operations for
+///   elements of immutable containers that defaults to using
+///   std::equal_to<> and std::less<> to perform comparison of elements.
+template <typename T>
+struct ImutContainerInfo : public ImutProfileInfo<T> {
+  using value_type = typename ImutProfileInfo<T>::value_type;
+  using value_type_ref = typename ImutProfileInfo<T>::value_type_ref;
+  using key_type = value_type;
+  using key_type_ref = value_type_ref;
+  using data_type = bool;
+  using data_type_ref = bool;
+
+  static key_type_ref KeyOfValue(value_type_ref D) { return D; }
+  static data_type_ref DataOfValue(value_type_ref) { return true; }
+
+  static bool isEqual(key_type_ref LHS, key_type_ref RHS) {
+    return std::equal_to<key_type>()(LHS,RHS);
+  }
+
+  static bool isLess(key_type_ref LHS, key_type_ref RHS) {
+    return std::less<key_type>()(LHS,RHS);
+  }
+
+  static bool isDataEqual(data_type_ref, data_type_ref) { return true; }
+};
+
+/// ImutContainerInfo - Specialization for pointer values to treat pointers
+///  as references to unique objects.  Pointers are thus compared by
+///  their addresses.
+template <typename T>
+struct ImutContainerInfo<T*> : public ImutProfileInfo<T*> {
+  using value_type = typename ImutProfileInfo<T*>::value_type;
+  using value_type_ref = typename ImutProfileInfo<T*>::value_type_ref;
+  using key_type = value_type;
+  using key_type_ref = value_type_ref;
+  using data_type = bool;
+  using data_type_ref = bool;
+
+  static key_type_ref KeyOfValue(value_type_ref D) { return D; }
+  static data_type_ref DataOfValue(value_type_ref) { return true; }
+
+  static bool isEqual(key_type_ref LHS, key_type_ref RHS) { return LHS == RHS; }
+
+  static bool isLess(key_type_ref LHS, key_type_ref RHS) { return LHS < RHS; }
+
+  static bool isDataEqual(data_type_ref, data_type_ref) { return true; }
+};
+
+//===----------------------------------------------------------------------===//
+// Immutable Set
+//===----------------------------------------------------------------------===//
+
+template <typename ValT, typename ValInfo = ImutContainerInfo<ValT>>
+class ImmutableSet {
+public:
+  using value_type = typename ValInfo::value_type;
+  using value_type_ref = typename ValInfo::value_type_ref;
+  using TreeTy = ImutAVLTree<ValInfo>;
+
+private:
+  IntrusiveRefCntPtr<TreeTy> Root;
+
+public:
+  /// Constructs a set from a pointer to a tree root.  In general one
+  /// should use a Factory object to create sets instead of directly
+  /// invoking the constructor, but there are cases where make this
+  /// constructor public is useful.
+  explicit ImmutableSet(TreeTy *R) : Root(R) {}
+
+  class Factory {
+    typename TreeTy::Factory F;
+    const bool Canonicalize;
+
+  public:
+    Factory(bool canonicalize = true)
+      : Canonicalize(canonicalize) {}
+
+    Factory(BumpPtrAllocator& Alloc, bool canonicalize = true)
+      : F(Alloc), Canonicalize(canonicalize) {}
+
+    Factory(const Factory& RHS) = delete;
+    void operator=(const Factory& RHS) = delete;
+
+    /// getEmptySet - Returns an immutable set that contains no elements.
+    ImmutableSet getEmptySet() {
+      return ImmutableSet(F.getEmptyTree());
+    }
+
+    /// add - Creates a new immutable set that contains all of the values
+    ///  of the original set with the addition of the specified value.  If
+    ///  the original set already included the value, then the original set is
+    ///  returned and no memory is allocated.  The time and space complexity
+    ///  of this operation is logarithmic in the size of the original set.
+    ///  The memory allocated to represent the set is released when the
+    ///  factory object that created the set is destroyed.
+    [[nodiscard]] ImmutableSet add(ImmutableSet Old, value_type_ref V) {
+      TreeTy *NewT = F.add(Old.Root.get(), V);
+      return ImmutableSet(Canonicalize ? F.getCanonicalTree(NewT) : NewT);
+    }
+
+    /// remove - Creates a new immutable set that contains all of the values
+    ///  of the original set with the exception of the specified value.  If
+    ///  the original set did not contain the value, the original set is
+    ///  returned and no memory is allocated.  The time and space complexity
+    ///  of this operation is logarithmic in the size of the original set.
+    ///  The memory allocated to represent the set is released when the
+    ///  factory object that created the set is destroyed.
+    [[nodiscard]] ImmutableSet remove(ImmutableSet Old, value_type_ref V) {
+      TreeTy *NewT = F.remove(Old.Root.get(), V);
+      return ImmutableSet(Canonicalize ? F.getCanonicalTree(NewT) : NewT);
+    }
+
+    BumpPtrAllocator& getAllocator() { return F.getAllocator(); }
+
+    typename TreeTy::Factory *getTreeFactory() const {
+      return const_cast<typename TreeTy::Factory *>(&F);
+    }
+  };
+
+  friend class Factory;
+
+  /// Returns true if the set contains the specified value.
+  bool contains(value_type_ref V) const {
+    return Root ? Root->contains(V) : false;
+  }
+
+  bool operator==(const ImmutableSet &RHS) const {
+    return Root && RHS.Root ? Root->isEqual(*RHS.Root.get()) : Root == RHS.Root;
+  }
+
+  bool operator!=(const ImmutableSet &RHS) const {
+    return Root && RHS.Root ? Root->isNotEqual(*RHS.Root.get())
+                            : Root != RHS.Root;
+  }
+
+  TreeTy *getRoot() {
+    if (Root) { Root->retain(); }
+    return Root.get();
+  }
+
+  TreeTy *getRootWithoutRetain() const { return Root.get(); }
+
+  /// isEmpty - Return true if the set contains no elements.
+  bool isEmpty() const { return !Root; }
+
+  /// isSingleton - Return true if the set contains exactly one element.
+  ///   This method runs in constant time.
+  bool isSingleton() const { return getHeight() == 1; }
+
+  //===--------------------------------------------------===//
+  // Iterators.
+  //===--------------------------------------------------===//
+
+  using iterator = ImutAVLValueIterator<ImmutableSet>;
+
+  iterator begin() const { return iterator(Root.get()); }
+  iterator end() const { return iterator(); }
+
+  //===--------------------------------------------------===//
+  // Utility methods.
+  //===--------------------------------------------------===//
+
+  unsigned getHeight() const { return Root ? Root->getHeight() : 0; }
+
+  static void Profile(FoldingSetNodeID &ID, const ImmutableSet &S) {
+    ID.AddPointer(S.Root.get());
+  }
+
+  void Profile(FoldingSetNodeID &ID) const { return Profile(ID, *this); }
+
+  //===--------------------------------------------------===//
+  // For testing.
+  //===--------------------------------------------------===//
+
+  void validateTree() const { if (Root) Root->validateTree(); }
+};
+
+// NOTE: This may some day replace the current ImmutableSet.
+template <typename ValT, typename ValInfo = ImutContainerInfo<ValT>>
+class ImmutableSetRef {
+public:
+  using value_type = typename ValInfo::value_type;
+  using value_type_ref = typename ValInfo::value_type_ref;
+  using TreeTy = ImutAVLTree<ValInfo>;
+  using FactoryTy = typename TreeTy::Factory;
+
+private:
+  IntrusiveRefCntPtr<TreeTy> Root;
+  FactoryTy *Factory;
+
+public:
+  /// Constructs a set from a pointer to a tree root.  In general one
+  /// should use a Factory object to create sets instead of directly
+  /// invoking the constructor, but there are cases where make this
+  /// constructor public is useful.
+  ImmutableSetRef(TreeTy *R, FactoryTy *F) : Root(R), Factory(F) {}
+
+  static ImmutableSetRef getEmptySet(FactoryTy *F) {
+    return ImmutableSetRef(0, F);
+  }
+
+  ImmutableSetRef add(value_type_ref V) {
+    return ImmutableSetRef(Factory->add(Root.get(), V), Factory);
+  }
+
+  ImmutableSetRef remove(value_type_ref V) {
+    return ImmutableSetRef(Factory->remove(Root.get(), V), Factory);
+  }
+
+  /// Returns true if the set contains the specified value.
+  bool contains(value_type_ref V) const {
+    return Root ? Root->contains(V) : false;
+  }
+
+  ImmutableSet<ValT> asImmutableSet(bool canonicalize = true) const {
+    return ImmutableSet<ValT>(
+        canonicalize ? Factory->getCanonicalTree(Root.get()) : Root.get());
+  }
+
+  TreeTy *getRootWithoutRetain() const { return Root.get(); }
+
+  bool operator==(const ImmutableSetRef &RHS) const {
+    return Root && RHS.Root ? Root->isEqual(*RHS.Root.get()) : Root == RHS.Root;
+  }
+
+  bool operator!=(const ImmutableSetRef &RHS) const {
+    return Root && RHS.Root ? Root->isNotEqual(*RHS.Root.get())
+                            : Root != RHS.Root;
+  }
+
+  /// isEmpty - Return true if the set contains no elements.
+  bool isEmpty() const { return !Root; }
+
+  /// isSingleton - Return true if the set contains exactly one element.
+  ///   This method runs in constant time.
+  bool isSingleton() const { return getHeight() == 1; }
+
+  //===--------------------------------------------------===//
+  // Iterators.
+  //===--------------------------------------------------===//
+
+  using iterator = ImutAVLValueIterator<ImmutableSetRef>;
+
+  iterator begin() const { return iterator(Root.get()); }
+  iterator end() const { return iterator(); }
+
+  //===--------------------------------------------------===//
+  // Utility methods.
+  //===--------------------------------------------------===//
+
+  unsigned getHeight() const { return Root ? Root->getHeight() : 0; }
+
+  static void Profile(FoldingSetNodeID &ID, const ImmutableSetRef &S) {
+    ID.AddPointer(S.Root.get());
+  }
+
+  void Profile(FoldingSetNodeID &ID) const { return Profile(ID, *this); }
+
+  //===--------------------------------------------------===//
+  // For testing.
+  //===--------------------------------------------------===//
+
+  void validateTree() const { if (Root) Root->validateTree(); }
+};
+
+} // end namespace llvm
+
+#endif // LLVM_ADT_IMMUTABLESET_H
+
+#ifdef __GNUC__
+#pragma GCC diagnostic pop
+#endif