X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=include%2Fllvm%2FADT%2FDenseMap.h;h=27f73157a29f38cd39e3fa8c3afab85bec7ff61f;hb=116832190dc04f511dacff847742733cc957d46a;hp=f9f37b81a31ed3cfcf5eb74cc773fc463facae59;hpb=476b242fe7a61e5f9ac6214b0bc5c680d24f152e;p=oota-llvm.git

diff --git a/include/llvm/ADT/DenseMap.h b/include/llvm/ADT/DenseMap.h
index f9f37b81a31..27f73157a29 100644
--- a/include/llvm/ADT/DenseMap.h
+++ b/include/llvm/ADT/DenseMap.h
@@ -14,141 +14,152 @@
 #ifndef LLVM_ADT_DENSEMAP_H
 #define LLVM_ADT_DENSEMAP_H
 
+#include "llvm/ADT/DenseMapInfo.h"
+#include "llvm/ADT/EpochTracker.h"
+#include "llvm/Support/AlignOf.h"
+#include "llvm/Support/Compiler.h"
 #include "llvm/Support/MathExtras.h"
 #include "llvm/Support/PointerLikeTypeTraits.h"
 #include "llvm/Support/type_traits.h"
-#include "llvm/ADT/DenseMapInfo.h"
 #include <algorithm>
-#include <iterator>
-#include <new>
-#include <utility>
 #include <cassert>
+#include <climits>
 #include <cstddef>
 #include <cstring>
+#include <iterator>
+#include <new>
+#include <utility>
 
 namespace llvm {
 
-template<typename KeyT, typename ValueT,
-         typename KeyInfoT = DenseMapInfo<KeyT>,
-         typename ValueInfoT = DenseMapInfo<ValueT>, bool IsConst = false>
-class DenseMapIterator;
+namespace detail {
+// We extend a pair to allow users to override the bucket type with their own
+// implementation without requiring two members.
+template <typename KeyT, typename ValueT>
+struct DenseMapPair : public std::pair<KeyT, ValueT> {
+  KeyT &getFirst() { return std::pair<KeyT, ValueT>::first; }
+  const KeyT &getFirst() const { return std::pair<KeyT, ValueT>::first; }
+  ValueT &getSecond() { return std::pair<KeyT, ValueT>::second; }
+  const ValueT &getSecond() const { return std::pair<KeyT, ValueT>::second; }
+};
+}
 
-template<typename KeyT, typename ValueT,
-         typename KeyInfoT = DenseMapInfo<KeyT>,
-         typename ValueInfoT = DenseMapInfo<ValueT> >
-class DenseMap {
-  typedef std::pair<KeyT, ValueT> BucketT;
-  unsigned NumBuckets;
-  BucketT *Buckets;
+template <
+    typename KeyT, typename ValueT, typename KeyInfoT = DenseMapInfo<KeyT>,
+    typename Bucket = detail::DenseMapPair<KeyT, ValueT>, bool IsConst = false>
+class DenseMapIterator;
 
-  unsigned NumEntries;
-  unsigned NumTombstones;
+template <typename DerivedT, typename KeyT, typename ValueT, typename KeyInfoT,
+          typename BucketT>
+class DenseMapBase : public DebugEpochBase {
 public:
+  typedef unsigned size_type;
   typedef KeyT key_type;
   typedef ValueT mapped_type;
   typedef BucketT value_type;
 
-  DenseMap(const DenseMap &other) {
-    NumBuckets = 0;
-    CopyFrom(other);
-  }
-
-  explicit DenseMap(unsigned NumInitBuckets = 64) {
-    init(NumInitBuckets);
-  }
-
-  template<typename InputIt>
-  DenseMap(const InputIt &I, const InputIt &E) {
-    init(64);
-    insert(I, E);
-  }
-  
-  ~DenseMap() {
-    const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
-    for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
-      if (!KeyInfoT::isEqual(P->first, EmptyKey) &&
-          !KeyInfoT::isEqual(P->first, TombstoneKey))
-        P->second.~ValueT();
-      P->first.~KeyT();
-    }
-#ifndef NDEBUG
-    memset(Buckets, 0x5a, sizeof(BucketT)*NumBuckets);
-#endif
-    operator delete(Buckets);
-  }
-
-  typedef DenseMapIterator<KeyT, ValueT, KeyInfoT> iterator;
-  typedef DenseMapIterator<KeyT, ValueT,
-                           KeyInfoT, ValueInfoT, true> const_iterator;
+  typedef DenseMapIterator<KeyT, ValueT, KeyInfoT, BucketT> iterator;
+  typedef DenseMapIterator<KeyT, ValueT, KeyInfoT, BucketT, true>
+      const_iterator;
   inline iterator begin() {
     // When the map is empty, avoid the overhead of AdvancePastEmptyBuckets().
-    return empty() ? end() : iterator(Buckets, Buckets+NumBuckets);
+    return empty() ? end() : iterator(getBuckets(), getBucketsEnd(), *this);
   }
   inline iterator end() {
-    return iterator(Buckets+NumBuckets, Buckets+NumBuckets);
+    return iterator(getBucketsEnd(), getBucketsEnd(), *this, true);
   }
   inline const_iterator begin() const {
-    return empty() ? end() : const_iterator(Buckets, Buckets+NumBuckets);
+    return empty() ? end()
+                   : const_iterator(getBuckets(), getBucketsEnd(), *this);
   }
   inline const_iterator end() const {
-    return const_iterator(Buckets+NumBuckets, Buckets+NumBuckets);
+    return const_iterator(getBucketsEnd(), getBucketsEnd(), *this, true);
   }
 
-  bool empty() const { return NumEntries == 0; }
-  unsigned size() const { return NumEntries; }
+  bool LLVM_ATTRIBUTE_UNUSED_RESULT empty() const {
+    return getNumEntries() == 0;
+  }
+  unsigned size() const { return getNumEntries(); }
 
   /// Grow the densemap so that it has at least Size buckets. Does not shrink
-  void resize(size_t Size) { grow(Size); }
+  void resize(size_type Size) {
+    incrementEpoch();
+    if (Size > getNumBuckets())
+      grow(Size);
+  }
 
   void clear() {
-    if (NumEntries == 0 && NumTombstones == 0) return;
-    
+    incrementEpoch();
+    if (getNumEntries() == 0 && getNumTombstones() == 0) return;
+
     // If the capacity of the array is huge, and the # elements used is small,
     // shrink the array.
-    if (NumEntries * 4 < NumBuckets && NumBuckets > 64) {
+    if (getNumEntries() * 4 < getNumBuckets() && getNumBuckets() > 64) {
       shrink_and_clear();
       return;
     }
 
     const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
-    for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
-      if (!KeyInfoT::isEqual(P->first, EmptyKey)) {
-        if (!KeyInfoT::isEqual(P->first, TombstoneKey)) {
-          P->second.~ValueT();
+    unsigned NumEntries = getNumEntries();
+    for (BucketT *P = getBuckets(), *E = getBucketsEnd(); P != E; ++P) {
+      if (!KeyInfoT::isEqual(P->getFirst(), EmptyKey)) {
+        if (!KeyInfoT::isEqual(P->getFirst(), TombstoneKey)) {
+          P->getSecond().~ValueT();
           --NumEntries;
         }
-        P->first = EmptyKey;
+        P->getFirst() = EmptyKey;
       }
     }
     assert(NumEntries == 0 && "Node count imbalance!");
-    NumTombstones = 0;
+    setNumEntries(0);
+    setNumTombstones(0);
   }
 
-  /// count - Return true if the specified key is in the map.
-  bool count(const KeyT &Val) const {
-    BucketT *TheBucket;
-    return LookupBucketFor(Val, TheBucket);
+  /// Return 1 if the specified key is in the map, 0 otherwise.
+  size_type count(const KeyT &Val) const {
+    const BucketT *TheBucket;
+    return LookupBucketFor(Val, TheBucket) ? 1 : 0;
   }
 
   iterator find(const KeyT &Val) {
     BucketT *TheBucket;
     if (LookupBucketFor(Val, TheBucket))
-      return iterator(TheBucket, Buckets+NumBuckets);
+      return iterator(TheBucket, getBucketsEnd(), *this, true);
     return end();
   }
   const_iterator find(const KeyT &Val) const {
+    const BucketT *TheBucket;
+    if (LookupBucketFor(Val, TheBucket))
+      return const_iterator(TheBucket, getBucketsEnd(), *this, true);
+    return end();
+  }
+
+  /// Alternate version of find() which allows a different, and possibly
+  /// less expensive, key type.
+  /// The DenseMapInfo is responsible for supplying methods
+  /// getHashValue(LookupKeyT) and isEqual(LookupKeyT, KeyT) for each key
+  /// type used.
+  template<class LookupKeyT>
+  iterator find_as(const LookupKeyT &Val) {
     BucketT *TheBucket;
     if (LookupBucketFor(Val, TheBucket))
-      return const_iterator(TheBucket, Buckets+NumBuckets);
+      return iterator(TheBucket, getBucketsEnd(), *this, true);
+    return end();
+  }
+  template<class LookupKeyT>
+  const_iterator find_as(const LookupKeyT &Val) const {
+    const BucketT *TheBucket;
+    if (LookupBucketFor(Val, TheBucket))
+      return const_iterator(TheBucket, getBucketsEnd(), *this, true);
     return end();
   }
 
   /// lookup - Return the entry for the specified key, or a default
   /// constructed value if no such entry exists.
   ValueT lookup(const KeyT &Val) const {
-    BucketT *TheBucket;
+    const BucketT *TheBucket;
     if (LookupBucketFor(Val, TheBucket))
-      return TheBucket->second;
+      return TheBucket->getSecond();
     return ValueT();
   }
 
@@ -158,12 +169,29 @@ public:
   std::pair<iterator, bool> insert(const std::pair<KeyT, ValueT> &KV) {
     BucketT *TheBucket;
     if (LookupBucketFor(KV.first, TheBucket))
-      return std::make_pair(iterator(TheBucket, Buckets+NumBuckets),
+      return std::make_pair(iterator(TheBucket, getBucketsEnd(), *this, true),
                             false); // Already in map.
 
     // Otherwise, insert the new element.
     TheBucket = InsertIntoBucket(KV.first, KV.second, TheBucket);
-    return std::make_pair(iterator(TheBucket, Buckets+NumBuckets),
+    return std::make_pair(iterator(TheBucket, getBucketsEnd(), *this, true),
+                          true);
+  }
+
+  // Inserts key,value pair into the map if the key isn't already in the map.
+  // If the key is already in the map, it returns false and doesn't update the
+  // value.
+  std::pair<iterator, bool> insert(std::pair<KeyT, ValueT> &&KV) {
+    BucketT *TheBucket;
+    if (LookupBucketFor(KV.first, TheBucket))
+      return std::make_pair(iterator(TheBucket, getBucketsEnd(), *this, true),
+                            false); // Already in map.
+
+    // Otherwise, insert the new element.
+    TheBucket = InsertIntoBucket(std::move(KV.first),
+                                 std::move(KV.second),
+                                 TheBucket);
+    return std::make_pair(iterator(TheBucket, getBucketsEnd(), *this, true),
                           true);
   }
 
@@ -180,25 +208,18 @@ public:
     if (!LookupBucketFor(Val, TheBucket))
       return false; // not in map.
 
-    TheBucket->second.~ValueT();
-    TheBucket->first = getTombstoneKey();
-    --NumEntries;
-    ++NumTombstones;
+    TheBucket->getSecond().~ValueT();
+    TheBucket->getFirst() = getTombstoneKey();
+    decrementNumEntries();
+    incrementNumTombstones();
     return true;
   }
   void erase(iterator I) {
     BucketT *TheBucket = &*I;
-    TheBucket->second.~ValueT();
-    TheBucket->first = getTombstoneKey();
-    --NumEntries;
-    ++NumTombstones;
-  }
-
-  void swap(DenseMap& RHS) {
-    std::swap(NumBuckets, RHS.NumBuckets);
-    std::swap(Buckets, RHS.Buckets);
-    std::swap(NumEntries, RHS.NumEntries);
-    std::swap(NumTombstones, RHS.NumTombstones);
+    TheBucket->getSecond().~ValueT();
+    TheBucket->getFirst() = getTombstoneKey();
+    decrementNumEntries();
+    incrementNumTombstones();
   }
 
   value_type& FindAndConstruct(const KeyT &Key) {
@@ -213,62 +234,198 @@ public:
     return FindAndConstruct(Key).second;
   }
 
-  DenseMap& operator=(const DenseMap& other) {
-    CopyFrom(other);
-    return *this;
+  value_type& FindAndConstruct(KeyT &&Key) {
+    BucketT *TheBucket;
+    if (LookupBucketFor(Key, TheBucket))
+      return *TheBucket;
+
+    return *InsertIntoBucket(std::move(Key), ValueT(), TheBucket);
+  }
+
+  ValueT &operator[](KeyT &&Key) {
+    return FindAndConstruct(std::move(Key)).second;
   }
 
   /// isPointerIntoBucketsArray - Return true if the specified pointer points
   /// somewhere into the DenseMap's array of buckets (i.e. either to a key or
   /// value in the DenseMap).
   bool isPointerIntoBucketsArray(const void *Ptr) const {
-    return Ptr >= Buckets && Ptr < Buckets+NumBuckets;
+    return Ptr >= getBuckets() && Ptr < getBucketsEnd();
   }
 
   /// getPointerIntoBucketsArray() - Return an opaque pointer into the buckets
   /// array.  In conjunction with the previous method, this can be used to
   /// determine whether an insertion caused the DenseMap to reallocate.
-  const void *getPointerIntoBucketsArray() const { return Buckets; }
+  const void *getPointerIntoBucketsArray() const { return getBuckets(); }
 
-private:
-  void CopyFrom(const DenseMap& other) {
-    if (NumBuckets != 0 &&
-        (!isPodLike<KeyInfoT>::value || !isPodLike<ValueInfoT>::value)) {
-      const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
-      for (BucketT *P = Buckets, *E = Buckets+NumBuckets; P != E; ++P) {
-        if (!KeyInfoT::isEqual(P->first, EmptyKey) &&
-            !KeyInfoT::isEqual(P->first, TombstoneKey))
-          P->second.~ValueT();
-        P->first.~KeyT();
-      }
+protected:
+  DenseMapBase() = default;
+
+  void destroyAll() {
+    if (getNumBuckets() == 0) // Nothing to do.
+      return;
+
+    const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
+    for (BucketT *P = getBuckets(), *E = getBucketsEnd(); P != E; ++P) {
+      if (!KeyInfoT::isEqual(P->getFirst(), EmptyKey) &&
+          !KeyInfoT::isEqual(P->getFirst(), TombstoneKey))
+        P->getSecond().~ValueT();
+      P->getFirst().~KeyT();
     }
+  }
 
-    NumEntries = other.NumEntries;
-    NumTombstones = other.NumTombstones;
+  void initEmpty() {
+    setNumEntries(0);
+    setNumTombstones(0);
 
-    if (NumBuckets) {
-#ifndef NDEBUG
-      memset(Buckets, 0x5a, sizeof(BucketT)*NumBuckets);
-#endif
-      operator delete(Buckets);
+    assert((getNumBuckets() & (getNumBuckets()-1)) == 0 &&
+           "# initial buckets must be a power of two!");
+    const KeyT EmptyKey = getEmptyKey();
+    for (BucketT *B = getBuckets(), *E = getBucketsEnd(); B != E; ++B)
+      new (&B->getFirst()) KeyT(EmptyKey);
+  }
+
+  void moveFromOldBuckets(BucketT *OldBucketsBegin, BucketT *OldBucketsEnd) {
+    initEmpty();
+
+    // Insert all the old elements.
+    const KeyT EmptyKey = getEmptyKey();
+    const KeyT TombstoneKey = getTombstoneKey();
+    for (BucketT *B = OldBucketsBegin, *E = OldBucketsEnd; B != E; ++B) {
+      if (!KeyInfoT::isEqual(B->getFirst(), EmptyKey) &&
+          !KeyInfoT::isEqual(B->getFirst(), TombstoneKey)) {
+        // Insert the key/value into the new table.
+        BucketT *DestBucket;
+        bool FoundVal = LookupBucketFor(B->getFirst(), DestBucket);
+        (void)FoundVal; // silence warning.
+        assert(!FoundVal && "Key already in new map?");
+        DestBucket->getFirst() = std::move(B->getFirst());
+        new (&DestBucket->getSecond()) ValueT(std::move(B->getSecond()));
+        incrementNumEntries();
+
+        // Free the value.
+        B->getSecond().~ValueT();
+      }
+      B->getFirst().~KeyT();
     }
-    Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT) *
-                                                 other.NumBuckets));
+  }
+
+  template <typename OtherBaseT>
+  void copyFrom(
+      const DenseMapBase<OtherBaseT, KeyT, ValueT, KeyInfoT, BucketT> &other) {
+    assert(&other != this);
+    assert(getNumBuckets() == other.getNumBuckets());
+
+    setNumEntries(other.getNumEntries());
+    setNumTombstones(other.getNumTombstones());
 
-    if (isPodLike<KeyInfoT>::value && isPodLike<ValueInfoT>::value)
-      memcpy(Buckets, other.Buckets, other.NumBuckets * sizeof(BucketT));
+    if (isPodLike<KeyT>::value && isPodLike<ValueT>::value)
+      memcpy(getBuckets(), other.getBuckets(),
+             getNumBuckets() * sizeof(BucketT));
     else
-      for (size_t i = 0; i < other.NumBuckets; ++i) {
-        new (&Buckets[i].first) KeyT(other.Buckets[i].first);
-        if (!KeyInfoT::isEqual(Buckets[i].first, getEmptyKey()) &&
-            !KeyInfoT::isEqual(Buckets[i].first, getTombstoneKey()))
-          new (&Buckets[i].second) ValueT(other.Buckets[i].second);
+      for (size_t i = 0; i < getNumBuckets(); ++i) {
+        new (&getBuckets()[i].getFirst())
+            KeyT(other.getBuckets()[i].getFirst());
+        if (!KeyInfoT::isEqual(getBuckets()[i].getFirst(), getEmptyKey()) &&
+            !KeyInfoT::isEqual(getBuckets()[i].getFirst(), getTombstoneKey()))
+          new (&getBuckets()[i].getSecond())
+              ValueT(other.getBuckets()[i].getSecond());
       }
-    NumBuckets = other.NumBuckets;
   }
 
+  static unsigned getHashValue(const KeyT &Val) {
+    return KeyInfoT::getHashValue(Val);
+  }
+  template<typename LookupKeyT>
+  static unsigned getHashValue(const LookupKeyT &Val) {
+    return KeyInfoT::getHashValue(Val);
+  }
+  static const KeyT getEmptyKey() {
+    return KeyInfoT::getEmptyKey();
+  }
+  static const KeyT getTombstoneKey() {
+    return KeyInfoT::getTombstoneKey();
+  }
+
+private:
+  unsigned getNumEntries() const {
+    return static_cast<const DerivedT *>(this)->getNumEntries();
+  }
+  void setNumEntries(unsigned Num) {
+    static_cast<DerivedT *>(this)->setNumEntries(Num);
+  }
+  void incrementNumEntries() {
+    setNumEntries(getNumEntries() + 1);
+  }
+  void decrementNumEntries() {
+    setNumEntries(getNumEntries() - 1);
+  }
+  unsigned getNumTombstones() const {
+    return static_cast<const DerivedT *>(this)->getNumTombstones();
+  }
+  void setNumTombstones(unsigned Num) {
+    static_cast<DerivedT *>(this)->setNumTombstones(Num);
+  }
+  void incrementNumTombstones() {
+    setNumTombstones(getNumTombstones() + 1);
+  }
+  void decrementNumTombstones() {
+    setNumTombstones(getNumTombstones() - 1);
+  }
+  const BucketT *getBuckets() const {
+    return static_cast<const DerivedT *>(this)->getBuckets();
+  }
+  BucketT *getBuckets() {
+    return static_cast<DerivedT *>(this)->getBuckets();
+  }
+  unsigned getNumBuckets() const {
+    return static_cast<const DerivedT *>(this)->getNumBuckets();
+  }
+  BucketT *getBucketsEnd() {
+    return getBuckets() + getNumBuckets();
+  }
+  const BucketT *getBucketsEnd() const {
+    return getBuckets() + getNumBuckets();
+  }
+
+  void grow(unsigned AtLeast) {
+    static_cast<DerivedT *>(this)->grow(AtLeast);
+  }
+
+  void shrink_and_clear() {
+    static_cast<DerivedT *>(this)->shrink_and_clear();
+  }
+
+
   BucketT *InsertIntoBucket(const KeyT &Key, const ValueT &Value,
                             BucketT *TheBucket) {
+    TheBucket = InsertIntoBucketImpl(Key, TheBucket);
+
+    TheBucket->getFirst() = Key;
+    new (&TheBucket->getSecond()) ValueT(Value);
+    return TheBucket;
+  }
+
+  BucketT *InsertIntoBucket(const KeyT &Key, ValueT &&Value,
+                            BucketT *TheBucket) {
+    TheBucket = InsertIntoBucketImpl(Key, TheBucket);
+
+    TheBucket->getFirst() = Key;
+    new (&TheBucket->getSecond()) ValueT(std::move(Value));
+    return TheBucket;
+  }
+
+  BucketT *InsertIntoBucket(KeyT &&Key, ValueT &&Value, BucketT *TheBucket) {
+    TheBucket = InsertIntoBucketImpl(Key, TheBucket);
+
+    TheBucket->getFirst() = std::move(Key);
+    new (&TheBucket->getSecond()) ValueT(std::move(Value));
+    return TheBucket;
+  }
+
+  BucketT *InsertIntoBucketImpl(const KeyT &Key, BucketT *TheBucket) {
+    incrementEpoch();
+
     // If the load of the hash table is more than 3/4, or if fewer than 1/8 of
     // the buckets are empty (meaning that many are filled with tombstones),
     // grow the table.
@@ -278,217 +435,620 @@ private:
     // probe almost the entire table until it found the empty bucket.  If the
     // table completely filled with tombstones, no lookup would ever succeed,
     // causing infinite loops in lookup.
-    ++NumEntries;
-    if (NumEntries*4 >= NumBuckets*3 ||
-        NumBuckets-(NumEntries+NumTombstones) < NumBuckets/8) {
+    unsigned NewNumEntries = getNumEntries() + 1;
+    unsigned NumBuckets = getNumBuckets();
+    if (LLVM_UNLIKELY(NewNumEntries * 4 >= NumBuckets * 3)) {
       this->grow(NumBuckets * 2);
       LookupBucketFor(Key, TheBucket);
+      NumBuckets = getNumBuckets();
+    } else if (LLVM_UNLIKELY(NumBuckets-(NewNumEntries+getNumTombstones()) <=
+                             NumBuckets/8)) {
+      this->grow(NumBuckets);
+      LookupBucketFor(Key, TheBucket);
     }
+    assert(TheBucket);
+
+    // Only update the state after we've grown our bucket space appropriately
+    // so that when growing buckets we have self-consistent entry count.
+    incrementNumEntries();
 
     // If we are writing over a tombstone, remember this.
-    if (!KeyInfoT::isEqual(TheBucket->first, getEmptyKey()))
-      --NumTombstones;
+    const KeyT EmptyKey = getEmptyKey();
+    if (!KeyInfoT::isEqual(TheBucket->getFirst(), EmptyKey))
+      decrementNumTombstones();
 
-    TheBucket->first = Key;
-    new (&TheBucket->second) ValueT(Value);
     return TheBucket;
   }
 
-  static unsigned getHashValue(const KeyT &Val) {
-    return KeyInfoT::getHashValue(Val);
-  }
-  static const KeyT getEmptyKey() {
-    return KeyInfoT::getEmptyKey();
-  }
-  static const KeyT getTombstoneKey() {
-    return KeyInfoT::getTombstoneKey();
-  }
-
   /// LookupBucketFor - Lookup the appropriate bucket for Val, returning it in
   /// FoundBucket.  If the bucket contains the key and a value, this returns
   /// true, otherwise it returns a bucket with an empty marker or tombstone and
   /// returns false.
-  bool LookupBucketFor(const KeyT &Val, BucketT *&FoundBucket) const {
-    unsigned BucketNo = getHashValue(Val);
-    unsigned ProbeAmt = 1;
-    BucketT *BucketsPtr = Buckets;
+  template<typename LookupKeyT>
+  bool LookupBucketFor(const LookupKeyT &Val,
+                       const BucketT *&FoundBucket) const {
+    const BucketT *BucketsPtr = getBuckets();
+    const unsigned NumBuckets = getNumBuckets();
+
+    if (NumBuckets == 0) {
+      FoundBucket = nullptr;
+      return false;
+    }
 
     // FoundTombstone - Keep track of whether we find a tombstone while probing.
-    BucketT *FoundTombstone = 0;
+    const BucketT *FoundTombstone = nullptr;
     const KeyT EmptyKey = getEmptyKey();
     const KeyT TombstoneKey = getTombstoneKey();
     assert(!KeyInfoT::isEqual(Val, EmptyKey) &&
            !KeyInfoT::isEqual(Val, TombstoneKey) &&
            "Empty/Tombstone value shouldn't be inserted into map!");
 
+    unsigned BucketNo = getHashValue(Val) & (NumBuckets-1);
+    unsigned ProbeAmt = 1;
     while (1) {
-      BucketT *ThisBucket = BucketsPtr + (BucketNo & (NumBuckets-1));
+      const BucketT *ThisBucket = BucketsPtr + BucketNo;
       // Found Val's bucket?  If so, return it.
-      if (KeyInfoT::isEqual(ThisBucket->first, Val)) {
+      if (LLVM_LIKELY(KeyInfoT::isEqual(Val, ThisBucket->getFirst()))) {
         FoundBucket = ThisBucket;
         return true;
       }
 
       // If we found an empty bucket, the key doesn't exist in the set.
       // Insert it and return the default value.
-      if (KeyInfoT::isEqual(ThisBucket->first, EmptyKey)) {
+      if (LLVM_LIKELY(KeyInfoT::isEqual(ThisBucket->getFirst(), EmptyKey))) {
         // If we've already seen a tombstone while probing, fill it in instead
         // of the empty bucket we eventually probed to.
-        if (FoundTombstone) ThisBucket = FoundTombstone;
         FoundBucket = FoundTombstone ? FoundTombstone : ThisBucket;
         return false;
       }
 
       // If this is a tombstone, remember it.  If Val ends up not in the map, we
       // prefer to return it than something that would require more probing.
-      if (KeyInfoT::isEqual(ThisBucket->first, TombstoneKey) && !FoundTombstone)
+      if (KeyInfoT::isEqual(ThisBucket->getFirst(), TombstoneKey) &&
+          !FoundTombstone)
         FoundTombstone = ThisBucket;  // Remember the first tombstone found.
 
       // Otherwise, it's a hash collision or a tombstone, continue quadratic
       // probing.
       BucketNo += ProbeAmt++;
+      BucketNo &= (NumBuckets-1);
+    }
+  }
+
+  template <typename LookupKeyT>
+  bool LookupBucketFor(const LookupKeyT &Val, BucketT *&FoundBucket) {
+    const BucketT *ConstFoundBucket;
+    bool Result = const_cast<const DenseMapBase *>(this)
+      ->LookupBucketFor(Val, ConstFoundBucket);
+    FoundBucket = const_cast<BucketT *>(ConstFoundBucket);
+    return Result;
+  }
+
+public:
+  /// Return the approximate size (in bytes) of the actual map.
+  /// This is just the raw memory used by DenseMap.
+  /// If entries are pointers to objects, the size of the referenced objects
+  /// are not included.
+  size_t getMemorySize() const {
+    return getNumBuckets() * sizeof(BucketT);
+  }
+};
+
+template <typename KeyT, typename ValueT,
+          typename KeyInfoT = DenseMapInfo<KeyT>,
+          typename BucketT = detail::DenseMapPair<KeyT, ValueT>>
+class DenseMap : public DenseMapBase<DenseMap<KeyT, ValueT, KeyInfoT, BucketT>,
+                                     KeyT, ValueT, KeyInfoT, BucketT> {
+  // Lift some types from the dependent base class into this class for
+  // simplicity of referring to them.
+  typedef DenseMapBase<DenseMap, KeyT, ValueT, KeyInfoT, BucketT> BaseT;
+  friend class DenseMapBase<DenseMap, KeyT, ValueT, KeyInfoT, BucketT>;
+
+  BucketT *Buckets;
+  unsigned NumEntries;
+  unsigned NumTombstones;
+  unsigned NumBuckets;
+
+public:
+  explicit DenseMap(unsigned NumInitBuckets = 0) {
+    init(NumInitBuckets);
+  }
+
+  DenseMap(const DenseMap &other) : BaseT() {
+    init(0);
+    copyFrom(other);
+  }
+
+  DenseMap(DenseMap &&other) : BaseT() {
+    init(0);
+    swap(other);
+  }
+
+  template<typename InputIt>
+  DenseMap(const InputIt &I, const InputIt &E) {
+    init(NextPowerOf2(std::distance(I, E)));
+    this->insert(I, E);
+  }
+
+  ~DenseMap() {
+    this->destroyAll();
+    operator delete(Buckets);
+  }
+
+  void swap(DenseMap& RHS) {
+    this->incrementEpoch();
+    RHS.incrementEpoch();
+    std::swap(Buckets, RHS.Buckets);
+    std::swap(NumEntries, RHS.NumEntries);
+    std::swap(NumTombstones, RHS.NumTombstones);
+    std::swap(NumBuckets, RHS.NumBuckets);
+  }
+
+  DenseMap& operator=(const DenseMap& other) {
+    if (&other != this)
+      copyFrom(other);
+    return *this;
+  }
+
+  DenseMap& operator=(DenseMap &&other) {
+    this->destroyAll();
+    operator delete(Buckets);
+    init(0);
+    swap(other);
+    return *this;
+  }
+
+  void copyFrom(const DenseMap& other) {
+    this->destroyAll();
+    operator delete(Buckets);
+    if (allocateBuckets(other.NumBuckets)) {
+      this->BaseT::copyFrom(other);
+    } else {
+      NumEntries = 0;
+      NumTombstones = 0;
     }
   }
 
   void init(unsigned InitBuckets) {
-    NumEntries = 0;
-    NumTombstones = 0;
-    NumBuckets = InitBuckets;
-    assert(InitBuckets && (InitBuckets & (InitBuckets-1)) == 0 &&
-           "# initial buckets must be a power of two!");
-    Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT)*InitBuckets));
-    // Initialize all the keys to EmptyKey.
-    const KeyT EmptyKey = getEmptyKey();
-    for (unsigned i = 0; i != InitBuckets; ++i)
-      new (&Buckets[i].first) KeyT(EmptyKey);
+    if (allocateBuckets(InitBuckets)) {
+      this->BaseT::initEmpty();
+    } else {
+      NumEntries = 0;
+      NumTombstones = 0;
+    }
   }
 
   void grow(unsigned AtLeast) {
     unsigned OldNumBuckets = NumBuckets;
     BucketT *OldBuckets = Buckets;
 
-    // Double the number of buckets.
-    while (NumBuckets < AtLeast)
-      NumBuckets <<= 1;
-    NumTombstones = 0;
-    Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT)*NumBuckets));
-
-    // Initialize all the keys to EmptyKey.
-    const KeyT EmptyKey = getEmptyKey();
-    for (unsigned i = 0, e = NumBuckets; i != e; ++i)
-      new (&Buckets[i].first) KeyT(EmptyKey);
-
-    // Insert all the old elements.
-    const KeyT TombstoneKey = getTombstoneKey();
-    for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) {
-      if (!KeyInfoT::isEqual(B->first, EmptyKey) &&
-          !KeyInfoT::isEqual(B->first, TombstoneKey)) {
-        // Insert the key/value into the new table.
-        BucketT *DestBucket;
-        bool FoundVal = LookupBucketFor(B->first, DestBucket);
-        FoundVal = FoundVal; // silence warning.
-        assert(!FoundVal && "Key already in new map?");
-        DestBucket->first = B->first;
-        new (&DestBucket->second) ValueT(B->second);
-
-        // Free the value.
-        B->second.~ValueT();
-      }
-      B->first.~KeyT();
+    allocateBuckets(std::max<unsigned>(64, static_cast<unsigned>(NextPowerOf2(AtLeast-1))));
+    assert(Buckets);
+    if (!OldBuckets) {
+      this->BaseT::initEmpty();
+      return;
     }
 
-#ifndef NDEBUG
-    memset(OldBuckets, 0x5a, sizeof(BucketT)*OldNumBuckets);
-#endif
+    this->moveFromOldBuckets(OldBuckets, OldBuckets+OldNumBuckets);
+
     // Free the old table.
     operator delete(OldBuckets);
   }
 
   void shrink_and_clear() {
-    unsigned OldNumBuckets = NumBuckets;
-    BucketT *OldBuckets = Buckets;
+    unsigned OldNumEntries = NumEntries;
+    this->destroyAll();
 
     // Reduce the number of buckets.
-    NumBuckets = NumEntries > 32 ? 1 << (Log2_32_Ceil(NumEntries) + 1)
-                                 : 64;
-    NumTombstones = 0;
-    Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT)*NumBuckets));
+    unsigned NewNumBuckets = 0;
+    if (OldNumEntries)
+      NewNumBuckets = std::max(64, 1 << (Log2_32_Ceil(OldNumEntries) + 1));
+    if (NewNumBuckets == NumBuckets) {
+      this->BaseT::initEmpty();
+      return;
+    }
 
-    // Initialize all the keys to EmptyKey.
-    const KeyT EmptyKey = getEmptyKey();
-    for (unsigned i = 0, e = NumBuckets; i != e; ++i)
-      new (&Buckets[i].first) KeyT(EmptyKey);
+    operator delete(Buckets);
+    init(NewNumBuckets);
+  }
 
-    // Free the old buckets.
-    const KeyT TombstoneKey = getTombstoneKey();
-    for (BucketT *B = OldBuckets, *E = OldBuckets+OldNumBuckets; B != E; ++B) {
-      if (!KeyInfoT::isEqual(B->first, EmptyKey) &&
-          !KeyInfoT::isEqual(B->first, TombstoneKey)) {
-        // Free the value.
-        B->second.~ValueT();
+private:
+  unsigned getNumEntries() const {
+    return NumEntries;
+  }
+  void setNumEntries(unsigned Num) {
+    NumEntries = Num;
+  }
+
+  unsigned getNumTombstones() const {
+    return NumTombstones;
+  }
+  void setNumTombstones(unsigned Num) {
+    NumTombstones = Num;
+  }
+
+  BucketT *getBuckets() const {
+    return Buckets;
+  }
+
+  unsigned getNumBuckets() const {
+    return NumBuckets;
+  }
+
+  bool allocateBuckets(unsigned Num) {
+    NumBuckets = Num;
+    if (NumBuckets == 0) {
+      Buckets = nullptr;
+      return false;
+    }
+
+    Buckets = static_cast<BucketT*>(operator new(sizeof(BucketT) * NumBuckets));
+    return true;
+  }
+};
+
+template <typename KeyT, typename ValueT, unsigned InlineBuckets = 4,
+          typename KeyInfoT = DenseMapInfo<KeyT>,
+          typename BucketT = detail::DenseMapPair<KeyT, ValueT>>
+class SmallDenseMap
+    : public DenseMapBase<
+          SmallDenseMap<KeyT, ValueT, InlineBuckets, KeyInfoT, BucketT>, KeyT,
+          ValueT, KeyInfoT, BucketT> {
+  // Lift some types from the dependent base class into this class for
+  // simplicity of referring to them.
+  typedef DenseMapBase<SmallDenseMap, KeyT, ValueT, KeyInfoT, BucketT> BaseT;
+  friend class DenseMapBase<SmallDenseMap, KeyT, ValueT, KeyInfoT, BucketT>;
+
+  unsigned Small : 1;
+  unsigned NumEntries : 31;
+  unsigned NumTombstones;
+
+  struct LargeRep {
+    BucketT *Buckets;
+    unsigned NumBuckets;
+  };
+
+  /// A "union" of an inline bucket array and the struct representing
+  /// a large bucket. This union will be discriminated by the 'Small' bit.
+  AlignedCharArrayUnion<BucketT[InlineBuckets], LargeRep> storage;
+
+public:
+  explicit SmallDenseMap(unsigned NumInitBuckets = 0) {
+    init(NumInitBuckets);
+  }
+
+  SmallDenseMap(const SmallDenseMap &other) : BaseT() {
+    init(0);
+    copyFrom(other);
+  }
+
+  SmallDenseMap(SmallDenseMap &&other) : BaseT() {
+    init(0);
+    swap(other);
+  }
+
+  template<typename InputIt>
+  SmallDenseMap(const InputIt &I, const InputIt &E) {
+    init(NextPowerOf2(std::distance(I, E)));
+    this->insert(I, E);
+  }
+
+  ~SmallDenseMap() {
+    this->destroyAll();
+    deallocateBuckets();
+  }
+
+  void swap(SmallDenseMap& RHS) {
+    unsigned TmpNumEntries = RHS.NumEntries;
+    RHS.NumEntries = NumEntries;
+    NumEntries = TmpNumEntries;
+    std::swap(NumTombstones, RHS.NumTombstones);
+
+    const KeyT EmptyKey = this->getEmptyKey();
+    const KeyT TombstoneKey = this->getTombstoneKey();
+    if (Small && RHS.Small) {
+      // If we're swapping inline bucket arrays, we have to cope with some of
+      // the tricky bits of DenseMap's storage system: the buckets are not
+      // fully initialized. Thus we swap every key, but we may have
+      // a one-directional move of the value.
+      for (unsigned i = 0, e = InlineBuckets; i != e; ++i) {
+        BucketT *LHSB = &getInlineBuckets()[i],
+                *RHSB = &RHS.getInlineBuckets()[i];
+        bool hasLHSValue = (!KeyInfoT::isEqual(LHSB->getFirst(), EmptyKey) &&
+                            !KeyInfoT::isEqual(LHSB->getFirst(), TombstoneKey));
+        bool hasRHSValue = (!KeyInfoT::isEqual(RHSB->getFirst(), EmptyKey) &&
+                            !KeyInfoT::isEqual(RHSB->getFirst(), TombstoneKey));
+        if (hasLHSValue && hasRHSValue) {
+          // Swap together if we can...
+          std::swap(*LHSB, *RHSB);
+          continue;
+        }
+        // Swap separately and handle any assymetry.
+        std::swap(LHSB->getFirst(), RHSB->getFirst());
+        if (hasLHSValue) {
+          new (&RHSB->getSecond()) ValueT(std::move(LHSB->getSecond()));
+          LHSB->getSecond().~ValueT();
+        } else if (hasRHSValue) {
+          new (&LHSB->getSecond()) ValueT(std::move(RHSB->getSecond()));
+          RHSB->getSecond().~ValueT();
+        }
       }
-      B->first.~KeyT();
+      return;
+    }
+    if (!Small && !RHS.Small) {
+      std::swap(getLargeRep()->Buckets, RHS.getLargeRep()->Buckets);
+      std::swap(getLargeRep()->NumBuckets, RHS.getLargeRep()->NumBuckets);
+      return;
     }
 
-#ifndef NDEBUG
-    memset(OldBuckets, 0x5a, sizeof(BucketT)*OldNumBuckets);
-#endif
+    SmallDenseMap &SmallSide = Small ? *this : RHS;
+    SmallDenseMap &LargeSide = Small ? RHS : *this;
+
+    // First stash the large side's rep and move the small side across.
+    LargeRep TmpRep = std::move(*LargeSide.getLargeRep());
+    LargeSide.getLargeRep()->~LargeRep();
+    LargeSide.Small = true;
+    // This is similar to the standard move-from-old-buckets, but the bucket
+    // count hasn't actually rotated in this case. So we have to carefully
+    // move construct the keys and values into their new locations, but there
+    // is no need to re-hash things.
+    for (unsigned i = 0, e = InlineBuckets; i != e; ++i) {
+      BucketT *NewB = &LargeSide.getInlineBuckets()[i],
+              *OldB = &SmallSide.getInlineBuckets()[i];
+      new (&NewB->getFirst()) KeyT(std::move(OldB->getFirst()));
+      OldB->getFirst().~KeyT();
+      if (!KeyInfoT::isEqual(NewB->getFirst(), EmptyKey) &&
+          !KeyInfoT::isEqual(NewB->getFirst(), TombstoneKey)) {
+        new (&NewB->getSecond()) ValueT(std::move(OldB->getSecond()));
+        OldB->getSecond().~ValueT();
+      }
+    }
+
+    // The hard part of moving the small buckets across is done, just move
+    // the TmpRep into its new home.
+    SmallSide.Small = false;
+    new (SmallSide.getLargeRep()) LargeRep(std::move(TmpRep));
+  }
+
+  SmallDenseMap& operator=(const SmallDenseMap& other) {
+    if (&other != this)
+      copyFrom(other);
+    return *this;
+  }
+
+  SmallDenseMap& operator=(SmallDenseMap &&other) {
+    this->destroyAll();
+    deallocateBuckets();
+    init(0);
+    swap(other);
+    return *this;
+  }
+
+  void copyFrom(const SmallDenseMap& other) {
+    this->destroyAll();
+    deallocateBuckets();
+    Small = true;
+    if (other.getNumBuckets() > InlineBuckets) {
+      Small = false;
+      new (getLargeRep()) LargeRep(allocateBuckets(other.getNumBuckets()));
+    }
+    this->BaseT::copyFrom(other);
+  }
+
+  void init(unsigned InitBuckets) {
+    Small = true;
+    if (InitBuckets > InlineBuckets) {
+      Small = false;
+      new (getLargeRep()) LargeRep(allocateBuckets(InitBuckets));
+    }
+    this->BaseT::initEmpty();
+  }
+
+  void grow(unsigned AtLeast) {
+    if (AtLeast >= InlineBuckets)
+      AtLeast = std::max<unsigned>(64, NextPowerOf2(AtLeast-1));
+
+    if (Small) {
+      if (AtLeast < InlineBuckets)
+        return; // Nothing to do.
+
+      // First move the inline buckets into a temporary storage.
+      AlignedCharArrayUnion<BucketT[InlineBuckets]> TmpStorage;
+      BucketT *TmpBegin = reinterpret_cast<BucketT *>(TmpStorage.buffer);
+      BucketT *TmpEnd = TmpBegin;
+
+      // Loop over the buckets, moving non-empty, non-tombstones into the
+      // temporary storage. Have the loop move the TmpEnd forward as it goes.
+      const KeyT EmptyKey = this->getEmptyKey();
+      const KeyT TombstoneKey = this->getTombstoneKey();
+      for (BucketT *P = getBuckets(), *E = P + InlineBuckets; P != E; ++P) {
+        if (!KeyInfoT::isEqual(P->getFirst(), EmptyKey) &&
+            !KeyInfoT::isEqual(P->getFirst(), TombstoneKey)) {
+          assert(size_t(TmpEnd - TmpBegin) < InlineBuckets &&
+                 "Too many inline buckets!");
+          new (&TmpEnd->getFirst()) KeyT(std::move(P->getFirst()));
+          new (&TmpEnd->getSecond()) ValueT(std::move(P->getSecond()));
+          ++TmpEnd;
+          P->getSecond().~ValueT();
+        }
+        P->getFirst().~KeyT();
+      }
+
+      // Now make this map use the large rep, and move all the entries back
+      // into it.
+      Small = false;
+      new (getLargeRep()) LargeRep(allocateBuckets(AtLeast));
+      this->moveFromOldBuckets(TmpBegin, TmpEnd);
+      return;
+    }
+
+    LargeRep OldRep = std::move(*getLargeRep());
+    getLargeRep()->~LargeRep();
+    if (AtLeast <= InlineBuckets) {
+      Small = true;
+    } else {
+      new (getLargeRep()) LargeRep(allocateBuckets(AtLeast));
+    }
+
+    this->moveFromOldBuckets(OldRep.Buckets, OldRep.Buckets+OldRep.NumBuckets);
+
     // Free the old table.
-    operator delete(OldBuckets);
+    operator delete(OldRep.Buckets);
+  }
+
+  void shrink_and_clear() {
+    unsigned OldSize = this->size();
+    this->destroyAll();
 
-    NumEntries = 0;
+    // Reduce the number of buckets.
+    unsigned NewNumBuckets = 0;
+    if (OldSize) {
+      NewNumBuckets = 1 << (Log2_32_Ceil(OldSize) + 1);
+      if (NewNumBuckets > InlineBuckets && NewNumBuckets < 64u)
+        NewNumBuckets = 64;
+    }
+    if ((Small && NewNumBuckets <= InlineBuckets) ||
+        (!Small && NewNumBuckets == getLargeRep()->NumBuckets)) {
+      this->BaseT::initEmpty();
+      return;
+    }
+
+    deallocateBuckets();
+    init(NewNumBuckets);
+  }
+
+private:
+  unsigned getNumEntries() const {
+    return NumEntries;
+  }
+  void setNumEntries(unsigned Num) {
+    assert(Num < INT_MAX && "Cannot support more than INT_MAX entries");
+    NumEntries = Num;
+  }
+
+  unsigned getNumTombstones() const {
+    return NumTombstones;
+  }
+  void setNumTombstones(unsigned Num) {
+    NumTombstones = Num;
+  }
+
+  const BucketT *getInlineBuckets() const {
+    assert(Small);
+    // Note that this cast does not violate aliasing rules as we assert that
+    // the memory's dynamic type is the small, inline bucket buffer, and the
+    // 'storage.buffer' static type is 'char *'.
+    return reinterpret_cast<const BucketT *>(storage.buffer);
+  }
+  BucketT *getInlineBuckets() {
+    return const_cast<BucketT *>(
+      const_cast<const SmallDenseMap *>(this)->getInlineBuckets());
+  }
+  const LargeRep *getLargeRep() const {
+    assert(!Small);
+    // Note, same rule about aliasing as with getInlineBuckets.
+    return reinterpret_cast<const LargeRep *>(storage.buffer);
+  }
+  LargeRep *getLargeRep() {
+    return const_cast<LargeRep *>(
+      const_cast<const SmallDenseMap *>(this)->getLargeRep());
+  }
+
+  const BucketT *getBuckets() const {
+    return Small ? getInlineBuckets() : getLargeRep()->Buckets;
+  }
+  BucketT *getBuckets() {
+    return const_cast<BucketT *>(
+      const_cast<const SmallDenseMap *>(this)->getBuckets());
+  }
+  unsigned getNumBuckets() const {
+    return Small ? InlineBuckets : getLargeRep()->NumBuckets;
+  }
+
+  void deallocateBuckets() {
+    if (Small)
+      return;
+
+    operator delete(getLargeRep()->Buckets);
+    getLargeRep()->~LargeRep();
+  }
+
+  LargeRep allocateBuckets(unsigned Num) {
+    assert(Num > InlineBuckets && "Must allocate more buckets than are inline");
+    LargeRep Rep = {
+      static_cast<BucketT*>(operator new(sizeof(BucketT) * Num)), Num
+    };
+    return Rep;
   }
 };
 
-template<typename KeyT, typename ValueT,
-         typename KeyInfoT, typename ValueInfoT, bool IsConst>
-class DenseMapIterator {
-  typedef std::pair<KeyT, ValueT> Bucket;
-  typedef DenseMapIterator<KeyT, ValueT,
-                           KeyInfoT, ValueInfoT, true> ConstIterator;
-  friend class DenseMapIterator<KeyT, ValueT, KeyInfoT, ValueInfoT, true>;
+template <typename KeyT, typename ValueT, typename KeyInfoT, typename Bucket,
+          bool IsConst>
+class DenseMapIterator : DebugEpochBase::HandleBase {
+  typedef DenseMapIterator<KeyT, ValueT, KeyInfoT, Bucket, true> ConstIterator;
+  friend class DenseMapIterator<KeyT, ValueT, KeyInfoT, Bucket, true>;
+  friend class DenseMapIterator<KeyT, ValueT, KeyInfoT, Bucket, false>;
+
 public:
   typedef ptrdiff_t difference_type;
-  typedef typename conditional<IsConst, const Bucket, Bucket>::type value_type;
+  typedef typename std::conditional<IsConst, const Bucket, Bucket>::type
+  value_type;
   typedef value_type *pointer;
   typedef value_type &reference;
   typedef std::forward_iterator_tag iterator_category;
 private:
   pointer Ptr, End;
 public:
-  DenseMapIterator() : Ptr(0), End(0) {}
+  DenseMapIterator() : Ptr(nullptr), End(nullptr) {}
 
-  DenseMapIterator(pointer Pos, pointer E) : Ptr(Pos), End(E) {
-    AdvancePastEmptyBuckets();
+  DenseMapIterator(pointer Pos, pointer E, const DebugEpochBase &Epoch,
+                   bool NoAdvance = false)
+      : DebugEpochBase::HandleBase(&Epoch), Ptr(Pos), End(E) {
+    assert(isHandleInSync() && "invalid construction!");
+    if (!NoAdvance) AdvancePastEmptyBuckets();
   }
 
-  // If IsConst is true this is a converting constructor from iterator to
-  // const_iterator and the default copy constructor is used.
-  // Otherwise this is a copy constructor for iterator.
-  DenseMapIterator(const DenseMapIterator<KeyT, ValueT,
-                                          KeyInfoT, ValueInfoT, false>& I)
-    : Ptr(I.Ptr), End(I.End) {}
+  // Converting ctor from non-const iterators to const iterators. SFINAE'd out
+  // for const iterator destinations so it doesn't end up as a user defined copy
+  // constructor.
+  template <bool IsConstSrc,
+            typename = typename std::enable_if<!IsConstSrc && IsConst>::type>
+  DenseMapIterator(
+      const DenseMapIterator<KeyT, ValueT, KeyInfoT, Bucket, IsConstSrc> &I)
+      : DebugEpochBase::HandleBase(I), Ptr(I.Ptr), End(I.End) {}
 
   reference operator*() const {
+    assert(isHandleInSync() && "invalid iterator access!");
     return *Ptr;
   }
   pointer operator->() const {
+    assert(isHandleInSync() && "invalid iterator access!");
     return Ptr;
   }
 
   bool operator==(const ConstIterator &RHS) const {
-    return Ptr == RHS.operator->();
+    assert((!Ptr || isHandleInSync()) && "handle not in sync!");
+    assert((!RHS.Ptr || RHS.isHandleInSync()) && "handle not in sync!");
+    assert(getEpochAddress() == RHS.getEpochAddress() &&
+           "comparing incomparable iterators!");
+    return Ptr == RHS.Ptr;
   }
   bool operator!=(const ConstIterator &RHS) const {
-    return Ptr != RHS.operator->();
+    assert((!Ptr || isHandleInSync()) && "handle not in sync!");
+    assert((!RHS.Ptr || RHS.isHandleInSync()) && "handle not in sync!");
+    assert(getEpochAddress() == RHS.getEpochAddress() &&
+           "comparing incomparable iterators!");
+    return Ptr != RHS.Ptr;
   }
 
   inline DenseMapIterator& operator++() {  // Preincrement
+    assert(isHandleInSync() && "invalid iterator access!");
     ++Ptr;
     AdvancePastEmptyBuckets();
     return *this;
   }
   DenseMapIterator operator++(int) {  // Postincrement
+    assert(isHandleInSync() && "invalid iterator access!");
     DenseMapIterator tmp = *this; ++*this; return tmp;
   }
 
@@ -497,13 +1057,18 @@ private:
     const KeyT Empty = KeyInfoT::getEmptyKey();
     const KeyT Tombstone = KeyInfoT::getTombstoneKey();
 
-    while (Ptr != End &&
-           (KeyInfoT::isEqual(Ptr->first, Empty) ||
-            KeyInfoT::isEqual(Ptr->first, Tombstone)))
+    while (Ptr != End && (KeyInfoT::isEqual(Ptr->getFirst(), Empty) ||
+                          KeyInfoT::isEqual(Ptr->getFirst(), Tombstone)))
       ++Ptr;
   }
 };
 
+template<typename KeyT, typename ValueT, typename KeyInfoT>
+static inline size_t
+capacity_in_bytes(const DenseMap<KeyT, ValueT, KeyInfoT> &X) {
+  return X.getMemorySize();
+}
+
 } // end namespace llvm
 
 #endif