Import LLVM, at r72732.

1 files changed, 1070 insertions, 0 deletions

diff --git a/include/llvm/ADT/ImmutableSet.h b/include/llvm/ADT/ImmutableSet.h
new file mode 100644
index 0000000..be274db
--- /dev/null
+++ b/include/llvm/ADT/ImmutableSet.h
@@ -0,0 +1,1070 @@
+//===--- ImmutableSet.h - Immutable (functional) set interface --*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the ImutAVLTree and ImmutableSet classes.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ADT_IMSET_H
+#define LLVM_ADT_IMSET_H
+
+#include "llvm/Support/Allocator.h"
+#include "llvm/ADT/FoldingSet.h"
+#include "llvm/Support/DataTypes.h"
+#include <cassert>
+#include <functional>
+
+namespace llvm {
+
+//===----------------------------------------------------------------------===//
+// Immutable AVL-Tree Definition.
+//===----------------------------------------------------------------------===//
+
+template <typename ImutInfo> class ImutAVLFactory;
+template <typename ImutInfo> class ImutAVLTreeInOrderIterator;
+template <typename ImutInfo> class ImutAVLTreeGenericIterator;
+
+template <typename ImutInfo >
+class ImutAVLTree : public FoldingSetNode {
+public:
+  typedef typename ImutInfo::key_type_ref   key_type_ref;
+  typedef typename ImutInfo::value_type     value_type;
+  typedef typename ImutInfo::value_type_ref value_type_ref;
+
+  typedef ImutAVLFactory<ImutInfo>          Factory;
+  friend class ImutAVLFactory<ImutInfo>;
+
+  friend class ImutAVLTreeGenericIterator<ImutInfo>;
+  friend class FoldingSet<ImutAVLTree>;
+
+  typedef ImutAVLTreeInOrderIterator<ImutInfo>  iterator;
+
+  //===----------------------------------------------------===//
+  // Public Interface.
+  //===----------------------------------------------------===//
+
+  /// getLeft - Returns a pointer to the left subtree.  This value
+  ///  is NULL if there is no left subtree.
+  ImutAVLTree* getLeft() const {
+    assert (!isMutable() && "Node is incorrectly marked mutable.");
+
+    return reinterpret_cast<ImutAVLTree*>(Left);
+  }
+
+  /// getRight - Returns 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 NULL;
+  }
+  
+  /// 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 ElementEqual(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 ElementEqual(const ImutAVLTree* RHS) const {
+    return ElementEqual(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->ElementEqual(*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(const key_type_ref K) { return (bool) find(K); }
+
+  /// foreach - A member template the accepts invokes operator() on a functor
+  ///  object (specifed by Callback) for every node/subtree in the tree.
+  ///  Nodes are visited using an inorder traversal.
+  template <typename Callback>
+  void foreach(Callback& C) {
+    if (ImutAVLTree* L = getLeft()) L->foreach(C);
+
+    C(Value);
+
+    if (ImutAVLTree* R = getRight()) R->foreach(C);
+  }
+
+  /// verify - A utility method that checks that the balancing and
+  ///  ordering invariants of the tree are satisifed.  It is a recursive
+  ///  method that returns the height of the tree, which is then consumed
+  ///  by the enclosing verify call.  External callers should ignore the
+  ///  return value.  An invalid tree will cause an assertion to fire in
+  ///  a debug build.
+  unsigned verify() const {
+    unsigned HL = getLeft() ? getLeft()->verify() : 0;
+    unsigned HR = getRight() ? getRight()->verify() : 0;
+
+    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();
+  }
+
+  /// Profile - Profiling for ImutAVLTree.
+  void Profile(llvm::FoldingSetNodeID& ID) {
+    ID.AddInteger(ComputeDigest());
+  }
+
+  //===----------------------------------------------------===//
+  // Internal Values.
+  //===----------------------------------------------------===//
+
+private:
+  uintptr_t        Left;
+  ImutAVLTree*     Right;
+  unsigned         Height;
+  value_type       Value;
+  unsigned         Digest;
+
+  //===----------------------------------------------------===//
+  // Internal methods (node manipulation; used by Factory).
+  //===----------------------------------------------------===//
+
+private:
+
+  enum { Mutable = 0x1 };
+
+  /// ImutAVLTree - Internal constructor that is only called by
+  ///   ImutAVLFactory.
+  ImutAVLTree(ImutAVLTree* l, ImutAVLTree* r, value_type_ref v, unsigned height)
+  : Left(reinterpret_cast<uintptr_t>(l) | Mutable),
+    Right(r), Height(height), Value(v), Digest(0) {}
+
+
+  /// 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 Left & Mutable; }
+
+  /// getSafeLeft - Returns the pointer to the left tree by always masking
+  ///  out the mutable bit.  This is used internally by ImutAVLFactory,
+  ///  as no trees returned to the client should have the mutable flag set.
+  ImutAVLTree* getSafeLeft() const {
+    return reinterpret_cast<ImutAVLTree*>(Left & ~Mutable);
+  }
+
+  //===----------------------------------------------------===//
+  // 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().  It
+  ///   is also then safe to call getLeft() instead of getSafeLeft().
+  void MarkImmutable() {
+    assert (isMutable() && "Mutable flag already removed.");
+    Left &= ~Mutable;
+  }
+
+  /// setLeft - Changes the reference of the left subtree.  Used internally
+  ///   by ImutAVLFactory.
+  void setLeft(ImutAVLTree* NewLeft) {
+    assert (isMutable() &&
+            "Only a mutable tree can have its left subtree changed.");
+
+    Left = reinterpret_cast<uintptr_t>(NewLeft) | Mutable;
+  }
+
+  /// setRight - Changes the reference of the right subtree.  Used internally
+  ///  by ImutAVLFactory.
+  void setRight(ImutAVLTree* NewRight) {
+    assert (isMutable() &&
+            "Only a mutable tree can have its right subtree changed.");
+
+    Right = NewRight;
+  }
+
+  /// 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 inline
+  unsigned ComputeDigest(ImutAVLTree* L, ImutAVLTree* R, value_type_ref V) {
+    unsigned 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;
+  }
+
+  inline unsigned ComputeDigest() {
+    if (Digest) return Digest;
+
+    unsigned X = ComputeDigest(getSafeLeft(), getRight(), getValue());
+    if (!isMutable()) Digest = X;
+
+    return X;
+  }
+};
+
+//===----------------------------------------------------------------------===//
+// Immutable AVL-Tree Factory class.
+//===----------------------------------------------------------------------===//
+
+template <typename ImutInfo >
+class ImutAVLFactory {
+  typedef ImutAVLTree<ImutInfo> TreeTy;
+  typedef typename TreeTy::value_type_ref value_type_ref;
+  typedef typename TreeTy::key_type_ref   key_type_ref;
+
+  typedef FoldingSet<TreeTy> CacheTy;
+
+  CacheTy Cache;
+  uintptr_t Allocator;
+
+  bool ownsAllocator() const {
+    return Allocator & 0x1 ? false : true;
+  }
+
+  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);
+    return T;
+  }
+
+  TreeTy* Remove(TreeTy* T, key_type_ref V) {
+    T = Remove_internal(V,T);
+    MarkImmutable(T);
+    return T;
+  }
+
+  TreeTy* GetEmptyTree() const { return NULL; }
+
+  //===--------------------------------------------------===//
+  // 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.
+  //===--------------------------------------------------===//
+private:
+
+  bool           isEmpty(TreeTy* T) const { return !T; }
+  unsigned        Height(TreeTy* T) const { return T ? T->getHeight() : 0; }
+  TreeTy*           Left(TreeTy* T) const { return T->getSafeLeft(); }
+  TreeTy*          Right(TreeTy* T) const { return T->getRight(); }
+  value_type_ref   Value(TreeTy* T) const { return T->Value; }
+
+  unsigned IncrementHeight(TreeTy* L, TreeTy* R) const {
+    unsigned hl = Height(L);
+    unsigned hr = Height(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->ElementEqual(*TI))
+        return false;
+
+    return true;
+  }
+
+  //===--------------------------------------------------===//
+  // "CreateNode" is used to generate new tree roots that link
+  // to other trees.  The functon 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) {
+    // Search the FoldingSet bucket for a Tree with the same digest.
+    FoldingSetNodeID ID;
+    unsigned digest = TreeTy::ComputeDigest(L, R, V);
+    ID.AddInteger(digest);
+    unsigned hash = ID.ComputeHash();
+
+    typename CacheTy::bucket_iterator I = Cache.bucket_begin(hash);
+    typename CacheTy::bucket_iterator E = Cache.bucket_end(hash);
+
+    for (; I != E; ++I) {
+      TreeTy* T = &*I;
+
+      if (T->ComputeDigest() != digest)
+        continue;
+
+      // We found a collision.  Perform a comparison of Contents('T')
+      // with Contents('L')+'V'+Contents('R').
+
+      typename TreeTy::iterator TI = T->begin(), TE = T->end();
+
+      // First compare Contents('L') with the (initial) contents of T.
+      if (!CompareTreeWithSection(L, TI, TE))
+        continue;
+
+      // Now compare the new data element.
+      if (TI == TE || !TI->ElementEqual(V))
+        continue;
+
+      ++TI;
+
+      // Now compare the remainder of 'T' with 'R'.
+      if (!CompareTreeWithSection(R, TI, TE))
+        continue;
+
+      if (TI != TE) // Contents('R') did not match suffix of 'T'.
+        continue;
+
+      // Trees did match!  Return 'T'.
+      return T;
+    }
+
+    // No tree with the contents: Contents('L')+'V'+Contents('R').
+    // Create it.
+
+    // Allocate the new tree node and insert it into the cache.
+    BumpPtrAllocator& A = getAllocator();
+    TreeTy* T = (TreeTy*) A.Allocate<TreeTy>();
+    new (T) TreeTy(L,R,V,IncrementHeight(L,R));
+
+    // We do not insert 'T' into the FoldingSet here.  This is because
+    // this tree is still mutable and things may get rebalanced.
+    // Because our digest is associative and based on the contents of
+    // the set, this should hopefully not cause any strange bugs.
+    // 'T' is inserted by 'MarkImmutable'.
+
+    return T;
+  }
+
+  TreeTy* CreateNode(TreeTy* L, TreeTy* OldTree, TreeTy* R) {
+    assert (!isEmpty(OldTree));
+
+    if (OldTree->isMutable()) {
+      OldTree->setLeft(L);
+      OldTree->setRight(R);
+      OldTree->setHeight(IncrementHeight(L,R));
+      return OldTree;
+    }
+    else return CreateNode(L, Value(OldTree), R);
+  }
+
+  /// Balance - Used by Add_internal and Remove_internal to
+  ///  balance a newly created tree.
+  TreeTy* Balance(TreeTy* L, value_type_ref V, TreeTy* R) {
+
+    unsigned hl = Height(L);
+    unsigned hr = Height(R);
+
+    if (hl > hr + 2) {
+      assert (!isEmpty(L) &&
+              "Left tree cannot be empty to have a height >= 2.");
+
+      TreeTy* LL = Left(L);
+      TreeTy* LR = Right(L);
+
+      if (Height(LL) >= Height(LR))
+        return CreateNode(LL, L, CreateNode(LR,V,R));
+
+      assert (!isEmpty(LR) &&
+              "LR cannot be empty because it has a height >= 1.");
+
+      TreeTy* LRL = Left(LR);
+      TreeTy* LRR = Right(LR);
+
+      return CreateNode(CreateNode(LL,L,LRL), LR, CreateNode(LRR,V,R));
+    }
+    else if (hr > hl + 2) {
+      assert (!isEmpty(R) &&
+              "Right tree cannot be empty to have a height >= 2.");
+
+      TreeTy* RL = Left(R);
+      TreeTy* RR = Right(R);
+
+      if (Height(RR) >= Height(RL))
+        return CreateNode(CreateNode(L,V,RL), R, RR);
+
+      assert (!isEmpty(RL) &&
+              "RL cannot be empty because it has a height >= 1.");
+
+      TreeTy* RLL = Left(RL);
+      TreeTy* RLR = Right(RL);
+
+      return CreateNode(CreateNode(L,V,RLL), RL, CreateNode(RLR,R,RR));
+    }
+    else
+      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(Value(T));
+
+    if (ImutInfo::isEqual(K,KCurrent))
+      return CreateNode(Left(T), V, Right(T));
+    else if (ImutInfo::isLess(K,KCurrent))
+      return Balance(Add_internal(V,Left(T)), Value(T), Right(T));
+    else
+      return Balance(Left(T), Value(T), Add_internal(V,Right(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(Value(T));
+
+    if (ImutInfo::isEqual(K,KCurrent))
+      return CombineLeftRightTrees(Left(T),Right(T));
+    else if (ImutInfo::isLess(K,KCurrent))
+      return Balance(Remove_internal(K,Left(T)), Value(T), Right(T));
+    else
+      return Balance(Left(T), Value(T), Remove_internal(K,Right(T)));
+  }
+
+  TreeTy* CombineLeftRightTrees(TreeTy* L, TreeTy* R) {
+    if (isEmpty(L)) return R;
+    if (isEmpty(R)) return L;
+
+    TreeTy* OldNode;
+    TreeTy* NewRight = RemoveMinBinding(R,OldNode);
+    return Balance(L,Value(OldNode),NewRight);
+  }
+
+  TreeTy* RemoveMinBinding(TreeTy* T, TreeTy*& NodeRemoved) {
+    assert (!isEmpty(T));
+
+    if (isEmpty(Left(T))) {
+      NodeRemoved = T;
+      return Right(T);
+    }
+
+    return Balance(RemoveMinBinding(Left(T),NodeRemoved),Value(T),Right(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(Left(T));
+    MarkImmutable(Right(T));
+
+    // Now that the node is immutable it can safely be inserted
+    // into the node cache.
+    llvm::FoldingSetNodeID ID;
+    ID.AddInteger(T->ComputeDigest());
+    Cache.InsertNode(T, (void*) &*Cache.bucket_end(ID.ComputeHash()));
+  }
+};
+
+
+//===----------------------------------------------------------------------===//
+// Immutable AVL-Tree Iterators.
+//===----------------------------------------------------------------------===//
+
+template <typename ImutInfo>
+class ImutAVLTreeGenericIterator {
+  SmallVector<uintptr_t,20> stack;
+public:
+  enum VisitFlag { VisitedNone=0x0, VisitedLeft=0x1, VisitedRight=0x3,
+                   Flags=0x3 };
+
+  typedef ImutAVLTree<ImutInfo> TreeTy;
+  typedef ImutAVLTreeGenericIterator<ImutInfo> _Self;
+
+  inline ImutAVLTreeGenericIterator() {}
+  inline 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);
+  }
+
+  uintptr_t getVisitState() {
+    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:
+        assert (false && "Unreachable.");
+    }
+  }
+
+  inline bool operator==(const _Self& x) const {
+    if (stack.size() != x.stack.size())
+      return false;
+
+    for (unsigned i = 0 ; i < stack.size(); i++)
+      if (stack[i] != x.stack[i])
+        return false;
+
+    return true;
+  }
+
+  inline bool operator!=(const _Self& x) const { return !operator==(x); }
+
+  _Self& operator++() {
+    assert (!stack.empty());
+
+    TreeTy* Current = reinterpret_cast<TreeTy*>(stack.back() & ~Flags);
+    assert (Current);
+
+    switch (getVisitState()) {
+      case VisitedNone:
+        if (TreeTy* L = Current->getSafeLeft())
+          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:
+        assert (false && "Unreachable.");
+    }
+
+    return *this;
+  }
+
+  _Self& 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:
+        assert (false && "Unreachable.");
+    }
+
+    return *this;
+  }
+};
+
+template <typename ImutInfo>
+class ImutAVLTreeInOrderIterator {
+  typedef ImutAVLTreeGenericIterator<ImutInfo> InternalIteratorTy;
+  InternalIteratorTy InternalItr;
+
+public:
+  typedef ImutAVLTree<ImutInfo> TreeTy;
+  typedef ImutAVLTreeInOrderIterator<ImutInfo> _Self;
+
+  ImutAVLTreeInOrderIterator(const TreeTy* Root) : InternalItr(Root) {
+    if (Root) operator++(); // Advance to first element.
+  }
+
+  ImutAVLTreeInOrderIterator() : InternalItr() {}
+
+  inline bool operator==(const _Self& x) const {
+    return InternalItr == x.InternalItr;
+  }
+
+  inline bool operator!=(const _Self& x) const { return !operator==(x); }
+
+  inline TreeTy* operator*() const { return *InternalItr; }
+  inline TreeTy* operator->() const { return *InternalItr; }
+
+  inline _Self& operator++() {
+    do ++InternalItr;
+    while (!InternalItr.AtEnd() &&
+           InternalItr.getVisitState() != InternalIteratorTy::VisitedLeft);
+
+    return *this;
+  }
+
+  inline _Self& operator--() {
+    do --InternalItr;
+    while (!InternalItr.AtBeginning() &&
+           InternalItr.getVisitState() != InternalIteratorTy::VisitedLeft);
+
+    return *this;
+  }
+
+  inline void SkipSubTree() {
+    InternalItr.SkipToParent();
+
+    while (!InternalItr.AtEnd() &&
+           InternalItr.getVisitState() != InternalIteratorTy::VisitedLeft)
+      ++InternalItr;
+  }
+};
+
+//===----------------------------------------------------------------------===//
+// 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 {
+  typedef const T  value_type;
+  typedef const T& value_type_ref;
+
+  static inline void Profile(FoldingSetNodeID& ID, value_type_ref X) {
+    FoldingSetTrait<T>::Profile(X,ID);
+  }
+};
+
+/// Profile traits for integers.
+template <typename T>
+struct ImutProfileInteger {
+  typedef const T  value_type;
+  typedef const T& value_type_ref;
+
+  static inline 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
+
+/// Generic profile trait for pointer types.  We treat pointers as
+/// references to unique objects.
+template <typename T>
+struct ImutProfileInfo<T*> {
+  typedef const T*   value_type;
+  typedef value_type value_type_ref;
+
+  static inline 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> {
+  typedef typename ImutProfileInfo<T>::value_type      value_type;
+  typedef typename ImutProfileInfo<T>::value_type_ref  value_type_ref;
+  typedef value_type      key_type;
+  typedef value_type_ref  key_type_ref;
+  typedef bool            data_type;
+  typedef bool            data_type_ref;
+
+  static inline key_type_ref KeyOfValue(value_type_ref D) { return D; }
+  static inline data_type_ref DataOfValue(value_type_ref) { return true; }
+
+  static inline bool isEqual(key_type_ref LHS, key_type_ref RHS) {
+    return std::equal_to<key_type>()(LHS,RHS);
+  }
+
+  static inline bool isLess(key_type_ref LHS, key_type_ref RHS) {
+    return std::less<key_type>()(LHS,RHS);
+  }
+
+  static inline 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*> {
+  typedef typename ImutProfileInfo<T*>::value_type      value_type;
+  typedef typename ImutProfileInfo<T*>::value_type_ref  value_type_ref;
+  typedef value_type      key_type;
+  typedef value_type_ref  key_type_ref;
+  typedef bool            data_type;
+  typedef bool            data_type_ref;
+
+  static inline key_type_ref KeyOfValue(value_type_ref D) { return D; }
+  static inline data_type_ref DataOfValue(value_type_ref) { return true; }
+
+  static inline bool isEqual(key_type_ref LHS, key_type_ref RHS) {
+    return LHS == RHS;
+  }
+
+  static inline bool isLess(key_type_ref LHS, key_type_ref RHS) {
+    return LHS < RHS;
+  }
+
+  static inline bool isDataEqual(data_type_ref,data_type_ref) { return true; }
+};
+
+//===----------------------------------------------------------------------===//
+// Immutable Set
+//===----------------------------------------------------------------------===//
+
+template <typename ValT, typename ValInfo = ImutContainerInfo<ValT> >
+class ImmutableSet {
+public:
+  typedef typename ValInfo::value_type      value_type;
+  typedef typename ValInfo::value_type_ref  value_type_ref;
+  typedef ImutAVLTree<ValInfo> TreeTy;
+
+private:
+  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;
+
+  public:
+    Factory() {}
+
+    Factory(BumpPtrAllocator& Alloc)
+      : F(Alloc) {}
+
+    /// 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.
+    ImmutableSet Add(ImmutableSet Old, value_type_ref V) {
+      return ImmutableSet(F.Add(Old.Root,V));
+    }
+
+    /// 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.
+    ImmutableSet Remove(ImmutableSet Old, value_type_ref V) {
+      return ImmutableSet(F.Remove(Old.Root,V));
+    }
+
+    BumpPtrAllocator& getAllocator() { return F.getAllocator(); }
+
+  private:
+    Factory(const Factory& RHS) {};
+    void operator=(const Factory& RHS) {};
+  };
+
+  friend class Factory;
+
+  /// contains - Returns true if the set contains the specified value.
+  bool contains(const value_type_ref V) const {
+    return Root ? Root->contains(V) : false;
+  }
+
+  bool operator==(ImmutableSet RHS) const {
+    return Root && RHS.Root ? Root->isEqual(*RHS.Root) : Root == RHS.Root;
+  }
+
+  bool operator!=(ImmutableSet RHS) const {
+    return Root && RHS.Root ? Root->isNotEqual(*RHS.Root) : Root != RHS.Root;
+  }
+
+  TreeTy* getRoot() const { return 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; }
+
+  template <typename Callback>
+  void foreach(Callback& C) { if (Root) Root->foreach(C); }
+
+  template <typename Callback>
+  void foreach() { if (Root) { Callback C; Root->foreach(C); } }
+
+  //===--------------------------------------------------===//
+  // Iterators.
+  //===--------------------------------------------------===//
+
+  class iterator {
+    typename TreeTy::iterator itr;
+
+    iterator() {}
+    iterator(TreeTy* t) : itr(t) {}
+    friend class ImmutableSet<ValT,ValInfo>;
+  public:
+    inline value_type_ref operator*() const { return itr->getValue(); }
+    inline iterator& operator++() { ++itr; return *this; }
+    inline iterator  operator++(int) { iterator tmp(*this); ++itr; return tmp; }
+    inline iterator& operator--() { --itr; return *this; }
+    inline iterator  operator--(int) { iterator tmp(*this); --itr; return tmp; }
+    inline bool operator==(const iterator& RHS) const { return RHS.itr == itr; }
+    inline bool operator!=(const iterator& RHS) const { return RHS.itr != itr; }
+    inline value_type *operator->() const { return &(operator*()); }
+  };
+
+  iterator begin() const { return iterator(Root); }
+  iterator end() const { return iterator(); }
+
+  //===--------------------------------------------------===//
+  // Utility methods.
+  //===--------------------------------------------------===//
+
+  inline unsigned getHeight() const { return Root ? Root->getHeight() : 0; }
+
+  static inline void Profile(FoldingSetNodeID& ID, const ImmutableSet& S) {
+    ID.AddPointer(S.Root);
+  }
+
+  inline void Profile(FoldingSetNodeID& ID) const {
+    return Profile(ID,*this);
+  }
+
+  //===--------------------------------------------------===//
+  // For testing.
+  //===--------------------------------------------------===//
+
+  void verify() const { if (Root) Root->verify(); }
+};
+
+} // end namespace llvm
+
+#endif