[NFC][sanitizer] Add unchanged DenseMap

[vitalybuka]

Summary

It's just a copy even without reformatting.

[vitalybuka]

noop

compiler-rt/lib/sanitizer_common/sanitizer_dense_map.h

+//===- llvm/ADT/DenseMap.h - Dense probed hash table ------------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the DenseMap class.
+//
+//===----------------------------------------------------------------------===//
+
+#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/MemAlloc.h"
+#include "llvm/Support/ReverseIteration.h"
+#include "llvm/Support/type_traits.h"
+#include <algorithm>
+#include <cassert>
+#include <cstddef>
+#include <cstring>
+#include <initializer_list>
+#include <iterator>
+#include <new>
+#include <type_traits>
+#include <utility>
+
+namespace llvm {
+
+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> {
+  using std::pair<KeyT, ValueT>::pair;
+
+  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; }
+};
+
+} // end namespace detail
+
+template <typename KeyT, typename ValueT,
+          typename KeyInfoT = DenseMapInfo<KeyT>,
+          typename Bucket = llvm::detail::DenseMapPair<KeyT, ValueT>,
+          bool IsConst = false>
+class DenseMapIterator;
+
+template <typename DerivedT, typename KeyT, typename ValueT, typename KeyInfoT,
+          typename BucketT>
+class DenseMapBase : public DebugEpochBase {
+  template <typename T>
+  using const_arg_type_t = typename const_pointer_or_const_ref<T>::type;
+
+public:
+  using size_type = unsigned;
+  using key_type = KeyT;
+  using mapped_type = ValueT;
+  using value_type = BucketT;
+
+  using iterator = DenseMapIterator<KeyT, ValueT, KeyInfoT, BucketT>;
+  using const_iterator =
+      DenseMapIterator<KeyT, ValueT, KeyInfoT, BucketT, true>;
+
+  inline iterator begin() {
+    // When the map is empty, avoid the overhead of advancing/retreating past
+    // empty buckets.
+    if (empty())
+      return end();
+    if (shouldReverseIterate<KeyT>())
+      return makeIterator(getBucketsEnd() - 1, getBuckets(), *this);
+    return makeIterator(getBuckets(), getBucketsEnd(), *this);
+  }
+  inline iterator end() {
+    return makeIterator(getBucketsEnd(), getBucketsEnd(), *this, true);
+  }
+  inline const_iterator begin() const {
+    if (empty())
+      return end();
+    if (shouldReverseIterate<KeyT>())
+      return makeConstIterator(getBucketsEnd() - 1, getBuckets(), *this);
+    return makeConstIterator(getBuckets(), getBucketsEnd(), *this);
+  }
+  inline const_iterator end() const {
+    return makeConstIterator(getBucketsEnd(), getBucketsEnd(), *this, true);
+  }
+
+  LLVM_NODISCARD bool empty() const {
+    return getNumEntries() == 0;
+  }
+  unsigned size() const { return getNumEntries(); }
+
+  /// Grow the densemap so that it can contain at least \p NumEntries items
+  /// before resizing again.
+  void reserve(size_type NumEntries) {
+    auto NumBuckets = getMinBucketToReserveForEntries(NumEntries);
+    incrementEpoch();
+    if (NumBuckets > getNumBuckets())
+      grow(NumBuckets);
+  }
+
+  void clear() {
+    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 (getNumEntries() * 4 < getNumBuckets() && getNumBuckets() > 64) {
+      shrink_and_clear();
+      return;
+    }
+
+    const KeyT EmptyKey = getEmptyKey(), TombstoneKey = getTombstoneKey();
+    if (std::is_trivially_destructible<ValueT>::value) {
+      // Use a simpler loop when values don't need destruction.
+      for (BucketT *P = getBuckets(), *E = getBucketsEnd(); P != E; ++P)
+        P->getFirst() = EmptyKey;
+    } else {
+      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->getFirst() = EmptyKey;
+        }
+      }
+      assert(NumEntries == 0 && "Node count imbalance!");
+    }
+    setNumEntries(0);
+    setNumTombstones(0);
+  }
+
+  /// Return 1 if the specified key is in the map, 0 otherwise.
+  size_type count(const_arg_type_t<KeyT> Val) const {
+    const BucketT *TheBucket;
+    return LookupBucketFor(Val, TheBucket) ? 1 : 0;
+  }
+
+  iterator find(const_arg_type_t<KeyT> Val) {
+    BucketT *TheBucket;
+    if (LookupBucketFor(Val, TheBucket))
+      return makeIterator(TheBucket,
+                          shouldReverseIterate<KeyT>() ? getBuckets()
+                                                       : getBucketsEnd(),
+                          *this, true);
+    return end();
+  }
+  const_iterator find(const_arg_type_t<KeyT> Val) const {
+    const BucketT *TheBucket;
+    if (LookupBucketFor(Val, TheBucket))
+      return makeConstIterator(TheBucket,
+                               shouldReverseIterate<KeyT>() ? getBuckets()
+                                                            : 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 makeIterator(TheBucket,
+                          shouldReverseIterate<KeyT>() ? getBuckets()
+                                                       : getBucketsEnd(),
+                          *this, true);
+    return end();
+  }
+  template<class LookupKeyT>
+  const_iterator find_as(const LookupKeyT &Val) const {
+    const BucketT *TheBucket;
+    if (LookupBucketFor(Val, TheBucket))
+      return makeConstIterator(TheBucket,
+                               shouldReverseIterate<KeyT>() ? getBuckets()
+                                                            : 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_arg_type_t<KeyT> Val) const {
+    const BucketT *TheBucket;
+    if (LookupBucketFor(Val, TheBucket))
+      return TheBucket->getSecond();
+    return ValueT();
+  }
+
+  // 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(const std::pair<KeyT, ValueT> &KV) {
+    return try_emplace(KV.first, KV.second);
+  }
+
+  // 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) {
+    return try_emplace(std::move(KV.first), std::move(KV.second));
+  }
+
+  // Inserts key,value pair into the map if the key isn't already in the map.
+  // The value is constructed in-place if the key is not in the map, otherwise
+  // it is not moved.
+  template <typename... Ts>
+  std::pair<iterator, bool> try_emplace(KeyT &&Key, Ts &&... Args) {
+    BucketT *TheBucket;
+    if (LookupBucketFor(Key, TheBucket))
+      return std::make_pair(makeIterator(TheBucket,
+                                         shouldReverseIterate<KeyT>()
+                                             ? getBuckets()
+                                             : getBucketsEnd(),
+                                         *this, true),
+                            false); // Already in map.
+
+    // Otherwise, insert the new element.
+    TheBucket =
+        InsertIntoBucket(TheBucket, std::move(Key), std::forward<Ts>(Args)...);
+    return std::make_pair(makeIterator(TheBucket,
+                                       shouldReverseIterate<KeyT>()
+                                           ? getBuckets()
+                                           : getBucketsEnd(),
+                                       *this, true),
+                          true);
+  }
+
+  // Inserts key,value pair into the map if the key isn't already in the map.
+  // The value is constructed in-place if the key is not in the map, otherwise
+  // it is not moved.
+  template <typename... Ts>
+  std::pair<iterator, bool> try_emplace(const KeyT &Key, Ts &&... Args) {
+    BucketT *TheBucket;
+    if (LookupBucketFor(Key, TheBucket))
+      return std::make_pair(makeIterator(TheBucket,
+                                         shouldReverseIterate<KeyT>()
+                                             ? getBuckets()
+                                             : getBucketsEnd(),
+                                         *this, true),
+                            false); // Already in map.
+
+    // Otherwise, insert the new element.
+    TheBucket = InsertIntoBucket(TheBucket, Key, std::forward<Ts>(Args)...);
+    return std::make_pair(makeIterator(TheBucket,
+                                       shouldReverseIterate<KeyT>()
+                                           ? getBuckets()
+                                           : getBucketsEnd(),
+                                       *this, true),
+                          true);
+  }
+
+  /// Alternate version of insert() 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 <typename LookupKeyT>
+  std::pair<iterator, bool> insert_as(std::pair<KeyT, ValueT> &&KV,
+                                      const LookupKeyT &Val) {
+    BucketT *TheBucket;
+    if (LookupBucketFor(Val, TheBucket))
+      return std::make_pair(makeIterator(TheBucket,
+                                         shouldReverseIterate<KeyT>()
+                                             ? getBuckets()
+                                             : getBucketsEnd(),
+                                         *this, true),
+                            false); // Already in map.
+
+    // Otherwise, insert the new element.
+    TheBucket = InsertIntoBucketWithLookup(TheBucket, std::move(KV.first),
+                                           std::move(KV.second), Val);
+    return std::make_pair(makeIterator(TheBucket,
+                                       shouldReverseIterate<KeyT>()
+                                           ? getBuckets()
+                                           : getBucketsEnd(),
+                                       *this, true),
+                          true);
+  }
+
+  /// insert - Range insertion of pairs.
+  template<typename InputIt>
+  void insert(InputIt I, InputIt E) {
+    for (; I != E; ++I)
+      insert(*I);
+  }
+
+  bool erase(const KeyT &Val) {
+    BucketT *TheBucket;
+    if (!LookupBucketFor(Val, TheBucket))
+      return false; // not in map.
+
+    TheBucket->getSecond().~ValueT();
+    TheBucket->getFirst() = getTombstoneKey();
+    decrementNumEntries();
+    incrementNumTombstones();
+    return true;
+  }
+  void erase(iterator I) {
+    BucketT *TheBucket = &*I;
+    TheBucket->getSecond().~ValueT();
+    TheBucket->getFirst() = getTombstoneKey();
+    decrementNumEntries();
+    incrementNumTombstones();
+  }
+
+  value_type& FindAndConstruct(const KeyT &Key) {
+    BucketT *TheBucket;
+    if (LookupBucketFor(Key, TheBucket))
+      return *TheBucket;
+
+    return *InsertIntoBucket(TheBucket, Key);
+  }
+
+  ValueT &operator[](const KeyT &Key) {
+    return FindAndConstruct(Key).second;
+  }
+
+  value_type& FindAndConstruct(KeyT &&Key) {
+    BucketT *TheBucket;
+    if (LookupBucketFor(Key, TheBucket))
+      return *TheBucket;
+
+    return *InsertIntoBucket(TheBucket, std::move(Key));
+  }
+
+  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 >= 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 getBuckets(); }
+
+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();
+    }
+  }
+
+  void initEmpty() {
+    setNumEntries(0);
+    setNumTombstones(0);
+
+    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);
+  }
+
+  /// Returns the number of buckets to allocate to ensure that the DenseMap can
+  /// accommodate \p NumEntries without need to grow().
+  unsigned getMinBucketToReserveForEntries(unsigned NumEntries) {
+    // Ensure that "NumEntries * 4 < NumBuckets * 3"
+    if (NumEntries == 0)
+      return 0;
+    // +1 is required because of the strict equality.
+    // For example if NumEntries is 48, we need to return 401.
+    return NextPowerOf2(NumEntries * 4 / 3 + 1);
+  }
+
+  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();
+    }
+  }
+
+  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 (std::is_trivially_copyable<KeyT>::value &&
+        std::is_trivially_copyable<ValueT>::value)
+      memcpy(reinterpret_cast<void *>(getBuckets()), other.getBuckets(),
+             getNumBuckets() * sizeof(BucketT));
+    else
+      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());
+      }
+  }
+
+  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() {
+    static_assert(std::is_base_of<DenseMapBase, DerivedT>::value,
+                  "Must pass the derived type to this template!");
+    return KeyInfoT::getEmptyKey();
+  }
+
+  static const KeyT getTombstoneKey() {
+    return KeyInfoT::getTombstoneKey();
+  }
+
+private:
+  iterator makeIterator(BucketT *P, BucketT *E,
+                        DebugEpochBase &Epoch,
+                        bool NoAdvance=false) {
+    if (shouldReverseIterate<KeyT>()) {
+      BucketT *B = P == getBucketsEnd() ? getBuckets() : P + 1;
+      return iterator(B, E, Epoch, NoAdvance);
+    }
+    return iterator(P, E, Epoch, NoAdvance);
+  }
+
+  const_iterator makeConstIterator(const BucketT *P, const BucketT *E,
+                                   const DebugEpochBase &Epoch,
+                                   const bool NoAdvance=false) const {
+    if (shouldReverseIterate<KeyT>()) {
+      const BucketT *B = P == getBucketsEnd() ? getBuckets() : P + 1;
+      return const_iterator(B, E, Epoch, NoAdvance);
+    }
+    return const_iterator(P, E, Epoch, NoAdvance);
+  }
+
+  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();
+  }
+
+  template <typename KeyArg, typename... ValueArgs>
+  BucketT *InsertIntoBucket(BucketT *TheBucket, KeyArg &&Key,
+                            ValueArgs &&... Values) {
+    TheBucket = InsertIntoBucketImpl(Key, Key, TheBucket);
+
+    TheBucket->getFirst() = std::forward<KeyArg>(Key);
+    ::new (&TheBucket->getSecond()) ValueT(std::forward<ValueArgs>(Values)...);
+    return TheBucket;
+  }
+
+  template <typename LookupKeyT>
+  BucketT *InsertIntoBucketWithLookup(BucketT *TheBucket, KeyT &&Key,
+                                      ValueT &&Value, LookupKeyT &Lookup) {
+    TheBucket = InsertIntoBucketImpl(Key, Lookup, TheBucket);
+
+    TheBucket->getFirst() = std::move(Key);
+    ::new (&TheBucket->getSecond()) ValueT(std::move(Value));
+    return TheBucket;
+  }
+
+  template <typename LookupKeyT>
+  BucketT *InsertIntoBucketImpl(const KeyT &Key, const LookupKeyT &Lookup,
+                                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.
+    //
+    // The later case is tricky.  For example, if we had one empty bucket with
+    // tons of tombstones, failing lookups (e.g. for insertion) would have to
+    // 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.
+    unsigned NewNumEntries = getNumEntries() + 1;
+    unsigned NumBuckets = getNumBuckets();
+    if (LLVM_UNLIKELY(NewNumEntries * 4 >= NumBuckets * 3)) {
+      this->grow(NumBuckets * 2);
+      LookupBucketFor(Lookup, TheBucket);
+      NumBuckets = getNumBuckets();
+    } else if (LLVM_UNLIKELY(NumBuckets-(NewNumEntries+getNumTombstones()) <=
+                             NumBuckets/8)) {
+      this->grow(NumBuckets);
+      LookupBucketFor(Lookup, 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.
+    const KeyT EmptyKey = getEmptyKey();
+    if (!KeyInfoT::isEqual(TheBucket->getFirst(), EmptyKey))
+      decrementNumTombstones();
+
+    return TheBucket;
+  }
+
+  /// 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.
+  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.
+    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 (true) {
+      const BucketT *ThisBucket = BucketsPtr + BucketNo;
+      // Found Val's bucket?  If so, return it.
+      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 (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.
+        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->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);
+  }
+};
+
+/// Equality comparison for DenseMap.
+///
+/// Iterates over elements of LHS confirming that each (key, value) pair in LHS
+/// is also in RHS, and that no additional pairs are in RHS.
+/// Equivalent to N calls to RHS.find and N value comparisons. Amortized
+/// complexity is linear, worst case is O(N^2) (if every hash collides).
+template <typename DerivedT, typename KeyT, typename ValueT, typename KeyInfoT,
+          typename BucketT>
+bool operator==(
+    const DenseMapBase<DerivedT, KeyT, ValueT, KeyInfoT, BucketT> &LHS,
+    const DenseMapBase<DerivedT, KeyT, ValueT, KeyInfoT, BucketT> &RHS) {
+  if (LHS.size() != RHS.size())
+    return false;
+
+  for (auto &KV : LHS) {
+    auto I = RHS.find(KV.first);
+    if (I == RHS.end() || I->second != KV.second)
+      return false;
+  }
+
+  return true;
+}
+
+/// Inequality comparison for DenseMap.
+///
+/// Equivalent to !(LHS == RHS). See operator== for performance notes.
+template <typename DerivedT, typename KeyT, typename ValueT, typename KeyInfoT,
+          typename BucketT>
+bool operator!=(
+    const DenseMapBase<DerivedT, KeyT, ValueT, KeyInfoT, BucketT> &LHS,
+    const DenseMapBase<DerivedT, KeyT, ValueT, KeyInfoT, BucketT> &RHS) {
+  return !(LHS == RHS);
+}
+
+template <typename KeyT, typename ValueT,
+          typename KeyInfoT = DenseMapInfo<KeyT>,
+          typename BucketT = llvm::detail::DenseMapPair<KeyT, ValueT>>
+class DenseMap : public DenseMapBase<DenseMap<KeyT, ValueT, KeyInfoT, BucketT>,
+                                     KeyT, ValueT, KeyInfoT, BucketT> {
+  friend class DenseMapBase<DenseMap, KeyT, ValueT, KeyInfoT, BucketT>;
+
+  // Lift some types from the dependent base class into this class for
+  // simplicity of referring to them.
+  using BaseT = DenseMapBase<DenseMap, KeyT, ValueT, KeyInfoT, BucketT>;
+
+  BucketT *Buckets;
+  unsigned NumEntries;
+  unsigned NumTombstones;
+  unsigned NumBuckets;
+
+public:
+  /// Create a DenseMap with an optional \p InitialReserve that guarantee that
+  /// this number of elements can be inserted in the map without grow()
+  explicit DenseMap(unsigned InitialReserve = 0) { init(InitialReserve); }
+
+  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(std::distance(I, E));
+    this->insert(I, E);
+  }
+
+  DenseMap(std::initializer_list<typename BaseT::value_type> Vals) {
+    init(Vals.size());
+    this->insert(Vals.begin(), Vals.end());
+  }
+
+  ~DenseMap() {
+    this->destroyAll();
+    deallocate_buffer(Buckets, sizeof(BucketT) * NumBuckets, alignof(BucketT));
+  }
+
+  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();
+    deallocate_buffer(Buckets, sizeof(BucketT) * NumBuckets, alignof(BucketT));
+    init(0);
+    swap(other);
+    return *this;
+  }
+
+  void copyFrom(const DenseMap& other) {
+    this->destroyAll();
+    deallocate_buffer(Buckets, sizeof(BucketT) * NumBuckets, alignof(BucketT));
+    if (allocateBuckets(other.NumBuckets)) {
+      this->BaseT::copyFrom(other);
+    } else {
+      NumEntries = 0;
+      NumTombstones = 0;
+    }
+  }
+
+  void init(unsigned InitNumEntries) {
+    auto InitBuckets = BaseT::getMinBucketToReserveForEntries(InitNumEntries);
+    if (allocateBuckets(InitBuckets)) {
+      this->BaseT::initEmpty();
+    } else {
+      NumEntries = 0;
+      NumTombstones = 0;
+    }
+  }
+
+  void grow(unsigned AtLeast) {
+    unsigned OldNumBuckets = NumBuckets;
+    BucketT *OldBuckets = Buckets;
+
+    allocateBuckets(std::max<unsigned>(64, static_cast<unsigned>(NextPowerOf2(AtLeast-1))));
+    assert(Buckets);
+    if (!OldBuckets) {
+      this->BaseT::initEmpty();
+      return;
+    }
+
+    this->moveFromOldBuckets(OldBuckets, OldBuckets+OldNumBuckets);
+
+    // Free the old table.
+    deallocate_buffer(OldBuckets, sizeof(BucketT) * OldNumBuckets,
+                      alignof(BucketT));
+  }
+
+  void shrink_and_clear() {
+    unsigned OldNumBuckets = NumBuckets;
+    unsigned OldNumEntries = NumEntries;
+    this->destroyAll();
+
+    // Reduce the number of buckets.
+    unsigned NewNumBuckets = 0;
+    if (OldNumEntries)
+      NewNumBuckets = std::max(64, 1 << (Log2_32_Ceil(OldNumEntries) + 1));
+    if (NewNumBuckets == NumBuckets) {
+      this->BaseT::initEmpty();
+      return;
+    }
+
+    deallocate_buffer(Buckets, sizeof(BucketT) * OldNumBuckets,
+                      alignof(BucketT));
+    init(NewNumBuckets);
+  }
+
+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 *>(
+        allocate_buffer(sizeof(BucketT) * NumBuckets, alignof(BucketT)));
+    return true;
+  }
+};
+
+template <typename KeyT, typename ValueT, unsigned InlineBuckets = 4,
+          typename KeyInfoT = DenseMapInfo<KeyT>,
+          typename BucketT = llvm::detail::DenseMapPair<KeyT, ValueT>>
+class SmallDenseMap
+    : public DenseMapBase<
+          SmallDenseMap<KeyT, ValueT, InlineBuckets, KeyInfoT, BucketT>, KeyT,
+          ValueT, KeyInfoT, BucketT> {
+  friend class DenseMapBase<SmallDenseMap, KeyT, ValueT, KeyInfoT, BucketT>;
+
+  // Lift some types from the dependent base class into this class for
+  // simplicity of referring to them.
+  using BaseT = DenseMapBase<SmallDenseMap, KeyT, ValueT, KeyInfoT, BucketT>;
+
+  static_assert(isPowerOf2_64(InlineBuckets),
+                "InlineBuckets must be a power of 2.");
+
+  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(std::initializer_list<typename BaseT::value_type> Vals)
+      : SmallDenseMap(Vals.begin(), Vals.end()) {}
+
+  ~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 asymmetry.
+        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();
+        }
+      }
+      return;
+    }
+    if (!Small && !RHS.Small) {
+      std::swap(getLargeRep()->Buckets, RHS.getLargeRep()->Buckets);
+      std::swap(getLargeRep()->NumBuckets, RHS.getLargeRep()->NumBuckets);
+      return;
+    }
+
+    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) {
+      // First move the inline buckets into a temporary storage.
+      AlignedCharArrayUnion<BucketT[InlineBuckets]> TmpStorage;
+      BucketT *TmpBegin = reinterpret_cast<BucketT *>(&TmpStorage);
+      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();
+      }
+
+      // AtLeast == InlineBuckets can happen if there are many tombstones,
+      // and grow() is used to remove them. Usually we always switch to the
+      // large rep here.
+      if (AtLeast > InlineBuckets) {
+        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.
+    deallocate_buffer(OldRep.Buckets, sizeof(BucketT) * OldRep.NumBuckets,
+                      alignof(BucketT));
+  }
+
+  void shrink_and_clear() {
+    unsigned OldSize = this->size();
+    this->destroyAll();
+
+    // 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) {
+    // NumEntries is hardcoded to be 31 bits wide.
+    assert(Num < (1U << 31) && "Cannot support more than 1<<31 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' is a POD containing a char buffer.
+    return reinterpret_cast<const BucketT *>(&storage);
+  }
+
+  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);
+  }
+
+  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;
+
+    deallocate_buffer(getLargeRep()->Buckets,
+                      sizeof(BucketT) * getLargeRep()->NumBuckets,
+                      alignof(BucketT));
+    getLargeRep()->~LargeRep();
+  }
+
+  LargeRep allocateBuckets(unsigned Num) {
+    assert(Num > InlineBuckets && "Must allocate more buckets than are inline");
+    LargeRep Rep = {static_cast<BucketT *>(allocate_buffer(
+                        sizeof(BucketT) * Num, alignof(BucketT))),
+                    Num};
+    return Rep;
+  }
+};
+
+template <typename KeyT, typename ValueT, typename KeyInfoT, typename Bucket,
+          bool IsConst>
+class DenseMapIterator : DebugEpochBase::HandleBase {
+  friend class DenseMapIterator<KeyT, ValueT, KeyInfoT, Bucket, true>;
+  friend class DenseMapIterator<KeyT, ValueT, KeyInfoT, Bucket, false>;
+
+public:
+  using difference_type = ptrdiff_t;
+  using value_type =
+      typename std::conditional<IsConst, const Bucket, Bucket>::type;
+  using pointer = value_type *;
+  using reference = value_type &;
+  using iterator_category = std::forward_iterator_tag;
+
+private:
+  pointer Ptr = nullptr;
+  pointer End = nullptr;
+
+public:
+  DenseMapIterator() = default;
+
+  DenseMapIterator(pointer Pos, pointer E, const DebugEpochBase &Epoch,
+                   bool NoAdvance = false)
+      : DebugEpochBase::HandleBase(&Epoch), Ptr(Pos), End(E) {
+    assert(isHandleInSync() && "invalid construction!");
+
+    if (NoAdvance) return;
+    if (shouldReverseIterate<KeyT>()) {
+      RetreatPastEmptyBuckets();
+      return;
+    }
+    AdvancePastEmptyBuckets();
+  }
+
+  // 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 = std::enable_if_t<!IsConstSrc && IsConst>>
+  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!");
+    assert(Ptr != End && "dereferencing end() iterator");
+    if (shouldReverseIterate<KeyT>())
+      return Ptr[-1];
+    return *Ptr;
+  }
+  pointer operator->() const {
+    assert(isHandleInSync() && "invalid iterator access!");
+    assert(Ptr != End && "dereferencing end() iterator");
+    if (shouldReverseIterate<KeyT>())
+      return &(Ptr[-1]);
+    return Ptr;
+  }
+
+  friend bool operator==(const DenseMapIterator &LHS,
+                         const DenseMapIterator &RHS) {
+    assert((!LHS.Ptr || LHS.isHandleInSync()) && "handle not in sync!");
+    assert((!RHS.Ptr || RHS.isHandleInSync()) && "handle not in sync!");
+    assert(LHS.getEpochAddress() == RHS.getEpochAddress() &&
+           "comparing incomparable iterators!");
+    return LHS.Ptr == RHS.Ptr;
+  }
+
+  friend bool operator!=(const DenseMapIterator &LHS,
+                         const DenseMapIterator &RHS) {
+    return !(LHS == RHS);
+  }
+
+  inline DenseMapIterator& operator++() {  // Preincrement
+    assert(isHandleInSync() && "invalid iterator access!");
+    assert(Ptr != End && "incrementing end() iterator");
+    if (shouldReverseIterate<KeyT>()) {
+      --Ptr;
+      RetreatPastEmptyBuckets();
+      return *this;
+    }
+    ++Ptr;
+    AdvancePastEmptyBuckets();
+    return *this;
+  }
+  DenseMapIterator operator++(int) {  // Postincrement
+    assert(isHandleInSync() && "invalid iterator access!");
+    DenseMapIterator tmp = *this; ++*this; return tmp;
+  }
+
+private:
+  void AdvancePastEmptyBuckets() {
+    assert(Ptr <= End);
+    const KeyT Empty = KeyInfoT::getEmptyKey();
+    const KeyT Tombstone = KeyInfoT::getTombstoneKey();
+
+    while (Ptr != End && (KeyInfoT::isEqual(Ptr->getFirst(), Empty) ||
+                          KeyInfoT::isEqual(Ptr->getFirst(), Tombstone)))
+      ++Ptr;
+  }
+
+  void RetreatPastEmptyBuckets() {
+    assert(Ptr >= End);
+    const KeyT Empty = KeyInfoT::getEmptyKey();
+    const KeyT Tombstone = KeyInfoT::getTombstoneKey();
+
+    while (Ptr != End && (KeyInfoT::isEqual(Ptr[-1].getFirst(), Empty) ||
+                          KeyInfoT::isEqual(Ptr[-1].getFirst(), Tombstone)))
+      --Ptr;
+  }
+};
+
+template <typename KeyT, typename ValueT, typename KeyInfoT>
+inline size_t capacity_in_bytes(const DenseMap<KeyT, ValueT, KeyInfoT> &X) {
+  return X.getMemorySize();
+}
+
+} // end namespace llvm
+
+#endif // LLVM_ADT_DENSEMAP_H

compiler-rt/lib/sanitizer_common/sanitizer_dense_map_info.h

+//===- llvm/ADT/DenseMapInfo.h - Type traits for DenseMap -------*- C++ -*-===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines DenseMapInfo traits for DenseMap.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ADT_DENSEMAPINFO_H
+#define LLVM_ADT_DENSEMAPINFO_H
+
+#include <cassert>
+#include <cstddef>
+#include <cstdint>
+#include <tuple>
+#include <utility>
+
+namespace llvm {
+
+namespace detail {
+
+/// Simplistic combination of 32-bit hash values into 32-bit hash values.
+static inline unsigned combineHashValue(unsigned a, unsigned b) {
+  uint64_t key = (uint64_t)a << 32 | (uint64_t)b;
+  key += ~(key << 32);
+  key ^= (key >> 22);
+  key += ~(key << 13);
+  key ^= (key >> 8);
+  key += (key << 3);
+  key ^= (key >> 15);
+  key += ~(key << 27);
+  key ^= (key >> 31);
+  return (unsigned)key;
+}
+
+} // end namespace detail
+
+template<typename T>
+struct DenseMapInfo {
+  //static inline T getEmptyKey();
+  //static inline T getTombstoneKey();
+  //static unsigned getHashValue(const T &Val);
+  //static bool isEqual(const T &LHS, const T &RHS);
+};
+
+// Provide DenseMapInfo for all pointers. Come up with sentinel pointer values
+// that are aligned to alignof(T) bytes, but try to avoid requiring T to be
+// complete. This allows clients to instantiate DenseMap<T*, ...> with forward
+// declared key types. Assume that no pointer key type requires more than 4096
+// bytes of alignment.
+template<typename T>
+struct DenseMapInfo<T*> {
+  // The following should hold, but it would require T to be complete:
+  // static_assert(alignof(T) <= (1 << Log2MaxAlign),
+  //               "DenseMap does not support pointer keys requiring more than "
+  //               "Log2MaxAlign bits of alignment");
+  static constexpr uintptr_t Log2MaxAlign = 12;
+
+  static inline T* getEmptyKey() {
+    uintptr_t Val = static_cast<uintptr_t>(-1);
+    Val <<= Log2MaxAlign;
+    return reinterpret_cast<T*>(Val);
+  }
+
+  static inline T* getTombstoneKey() {
+    uintptr_t Val = static_cast<uintptr_t>(-2);
+    Val <<= Log2MaxAlign;
+    return reinterpret_cast<T*>(Val);
+  }
+
+  static unsigned getHashValue(const T *PtrVal) {
+    return (unsigned((uintptr_t)PtrVal) >> 4) ^
+           (unsigned((uintptr_t)PtrVal) >> 9);
+  }
+
+  static bool isEqual(const T *LHS, const T *RHS) { return LHS == RHS; }
+};
+
+// Provide DenseMapInfo for chars.
+template<> struct DenseMapInfo<char> {
+  static inline char getEmptyKey() { return ~0; }
+  static inline char getTombstoneKey() { return ~0 - 1; }
+  static unsigned getHashValue(const char& Val) { return Val * 37U; }
+
+  static bool isEqual(const char &LHS, const char &RHS) {
+    return LHS == RHS;
+  }
+};
+
+// Provide DenseMapInfo for unsigned chars.
+template <> struct DenseMapInfo<unsigned char> {
+  static inline unsigned char getEmptyKey() { return ~0; }
+  static inline unsigned char getTombstoneKey() { return ~0 - 1; }
+  static unsigned getHashValue(const unsigned char &Val) { return Val * 37U; }
+
+  static bool isEqual(const unsigned char &LHS, const unsigned char &RHS) {
+    return LHS == RHS;
+  }
+};
+
+// Provide DenseMapInfo for unsigned shorts.
+template <> struct DenseMapInfo<unsigned short> {
+  static inline unsigned short getEmptyKey() { return 0xFFFF; }
+  static inline unsigned short getTombstoneKey() { return 0xFFFF - 1; }
+  static unsigned getHashValue(const unsigned short &Val) { return Val * 37U; }
+
+  static bool isEqual(const unsigned short &LHS, const unsigned short &RHS) {
+    return LHS == RHS;
+  }
+};
+
+// Provide DenseMapInfo for unsigned ints.
+template<> struct DenseMapInfo<unsigned> {
+  static inline unsigned getEmptyKey() { return ~0U; }
+  static inline unsigned getTombstoneKey() { return ~0U - 1; }
+  static unsigned getHashValue(const unsigned& Val) { return Val * 37U; }
+
+  static bool isEqual(const unsigned& LHS, const unsigned& RHS) {
+    return LHS == RHS;
+  }
+};
+
+// Provide DenseMapInfo for unsigned longs.
+template<> struct DenseMapInfo<unsigned long> {
+  static inline unsigned long getEmptyKey() { return ~0UL; }
+  static inline unsigned long getTombstoneKey() { return ~0UL - 1L; }
+
+  static unsigned getHashValue(const unsigned long& Val) {
+    return (unsigned)(Val * 37UL);
+  }
+
+  static bool isEqual(const unsigned long& LHS, const unsigned long& RHS) {
+    return LHS == RHS;
+  }
+};
+
+// Provide DenseMapInfo for unsigned long longs.
+template<> struct DenseMapInfo<unsigned long long> {
+  static inline unsigned long long getEmptyKey() { return ~0ULL; }
+  static inline unsigned long long getTombstoneKey() { return ~0ULL - 1ULL; }
+
+  static unsigned getHashValue(const unsigned long long& Val) {
+    return (unsigned)(Val * 37ULL);
+  }
+
+  static bool isEqual(const unsigned long long& LHS,
+                      const unsigned long long& RHS) {
+    return LHS == RHS;
+  }
+};
+
+// Provide DenseMapInfo for shorts.
+template <> struct DenseMapInfo<short> {
+  static inline short getEmptyKey() { return 0x7FFF; }
+  static inline short getTombstoneKey() { return -0x7FFF - 1; }
+  static unsigned getHashValue(const short &Val) { return Val * 37U; }
+  static bool isEqual(const short &LHS, const short &RHS) { return LHS == RHS; }
+};
+
+// Provide DenseMapInfo for ints.
+template<> struct DenseMapInfo<int> {
+  static inline int getEmptyKey() { return 0x7fffffff; }
+  static inline int getTombstoneKey() { return -0x7fffffff - 1; }
+  static unsigned getHashValue(const int& Val) { return (unsigned)(Val * 37U); }
+
+  static bool isEqual(const int& LHS, const int& RHS) {
+    return LHS == RHS;
+  }
+};
+
+// Provide DenseMapInfo for longs.
+template<> struct DenseMapInfo<long> {
+  static inline long getEmptyKey() {
+    return (1UL << (sizeof(long) * 8 - 1)) - 1UL;
+  }
+
+  static inline long getTombstoneKey() { return getEmptyKey() - 1L; }
+
+  static unsigned getHashValue(const long& Val) {
+    return (unsigned)(Val * 37UL);
+  }
+
+  static bool isEqual(const long& LHS, const long& RHS) {
+    return LHS == RHS;
+  }
+};
+
+// Provide DenseMapInfo for long longs.
+template<> struct DenseMapInfo<long long> {
+  static inline long long getEmptyKey() { return 0x7fffffffffffffffLL; }
+  static inline long long getTombstoneKey() { return -0x7fffffffffffffffLL-1; }
+
+  static unsigned getHashValue(const long long& Val) {
+    return (unsigned)(Val * 37ULL);
+  }
+
+  static bool isEqual(const long long& LHS,
+                      const long long& RHS) {
+    return LHS == RHS;
+  }
+};
+
+// Provide DenseMapInfo for all pairs whose members have info.
+template<typename T, typename U>
+struct DenseMapInfo<std::pair<T, U>> {
+  using Pair = std::pair<T, U>;
+  using FirstInfo = DenseMapInfo<T>;
+  using SecondInfo = DenseMapInfo<U>;
+
+  static inline Pair getEmptyKey() {
+    return std::make_pair(FirstInfo::getEmptyKey(),
+                          SecondInfo::getEmptyKey());
+  }
+
+  static inline Pair getTombstoneKey() {
+    return std::make_pair(FirstInfo::getTombstoneKey(),
+                          SecondInfo::getTombstoneKey());
+  }
+
+  static unsigned getHashValue(const Pair& PairVal) {
+    return detail::combineHashValue(FirstInfo::getHashValue(PairVal.first),
+                                    SecondInfo::getHashValue(PairVal.second));
+  }
+
+  static bool isEqual(const Pair &LHS, const Pair &RHS) {
+    return FirstInfo::isEqual(LHS.first, RHS.first) &&
+           SecondInfo::isEqual(LHS.second, RHS.second);
+  }
+};
+
+// Provide DenseMapInfo for all tuples whose members have info.
+template <typename... Ts> struct DenseMapInfo<std::tuple<Ts...>> {
+  using Tuple = std::tuple<Ts...>;
+
+  static inline Tuple getEmptyKey() {
+    return Tuple(DenseMapInfo<Ts>::getEmptyKey()...);
+  }
+
+  static inline Tuple getTombstoneKey() {
+    return Tuple(DenseMapInfo<Ts>::getTombstoneKey()...);
+  }
+
+  template <unsigned I>
+  static unsigned getHashValueImpl(const Tuple &values, std::false_type) {
+    using EltType = typename std::tuple_element<I, Tuple>::type;
+    std::integral_constant<bool, I + 1 == sizeof...(Ts)> atEnd;
+    return detail::combineHashValue(
+        DenseMapInfo<EltType>::getHashValue(std::get<I>(values)),
+        getHashValueImpl<I + 1>(values, atEnd));
+  }
+
+  template <unsigned I>
+  static unsigned getHashValueImpl(const Tuple &, std::true_type) {
+    return 0;
+  }
+
+  static unsigned getHashValue(const std::tuple<Ts...> &values) {
+    std::integral_constant<bool, 0 == sizeof...(Ts)> atEnd;
+    return getHashValueImpl<0>(values, atEnd);
+  }
+
+  template <unsigned I>
+  static bool isEqualImpl(const Tuple &lhs, const Tuple &rhs, std::false_type) {
+    using EltType = typename std::tuple_element<I, Tuple>::type;
+    std::integral_constant<bool, I + 1 == sizeof...(Ts)> atEnd;
+    return DenseMapInfo<EltType>::isEqual(std::get<I>(lhs), std::get<I>(rhs)) &&
+           isEqualImpl<I + 1>(lhs, rhs, atEnd);
+  }
+
+  template <unsigned I>
+  static bool isEqualImpl(const Tuple &, const Tuple &, std::true_type) {
+    return true;
+  }
+
+  static bool isEqual(const Tuple &lhs, const Tuple &rhs) {
+    std::integral_constant<bool, 0 == sizeof...(Ts)> atEnd;
+    return isEqualImpl<0>(lhs, rhs, atEnd);
+  }
+};
+
+} // end namespace llvm
+
+#endif // LLVM_ADT_DENSEMAPINFO_H

compiler-rt/lib/sanitizer_common/tests/sanitizer_dense_map_test.cpp

+//===- llvm/unittest/ADT/DenseMapMap.cpp - DenseMap unit tests --*- 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
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/DenseMap.h"
+#include "gtest/gtest.h"
+#include <map>
+#include <set>
+
+using namespace llvm;
+
+namespace {
+
+uint32_t getTestKey(int i, uint32_t *) { return i; }
+uint32_t getTestValue(int i, uint32_t *) { return 42 + i; }
+
+uint32_t *getTestKey(int i, uint32_t **) {
+  static uint32_t dummy_arr1[8192];
+  assert(i < 8192 && "Only support 8192 dummy keys.");
+  return &dummy_arr1[i];
+}
+uint32_t *getTestValue(int i, uint32_t **) {
+  static uint32_t dummy_arr1[8192];
+  assert(i < 8192 && "Only support 8192 dummy keys.");
+  return &dummy_arr1[i];
+}
+
+/// A test class that tries to check that construction and destruction
+/// occur correctly.
+class CtorTester {
+  static std::set<CtorTester *> Constructed;
+  int Value;
+
+public:
+  explicit CtorTester(int Value = 0) : Value(Value) {
+    EXPECT_TRUE(Constructed.insert(this).second);
+  }
+  CtorTester(uint32_t Value) : Value(Value) {
+    EXPECT_TRUE(Constructed.insert(this).second);
+  }
+  CtorTester(const CtorTester &Arg) : Value(Arg.Value) {
+    EXPECT_TRUE(Constructed.insert(this).second);
+  }
+  CtorTester &operator=(const CtorTester &) = default;
+  ~CtorTester() {
+    EXPECT_EQ(1u, Constructed.erase(this));
+  }
+  operator uint32_t() const { return Value; }
+
+  int getValue() const { return Value; }
+  bool operator==(const CtorTester &RHS) const { return Value == RHS.Value; }
+};
+
+std::set<CtorTester *> CtorTester::Constructed;
+
+struct CtorTesterMapInfo {
+  static inline CtorTester getEmptyKey() { return CtorTester(-1); }
+  static inline CtorTester getTombstoneKey() { return CtorTester(-2); }
+  static unsigned getHashValue(const CtorTester &Val) {
+    return Val.getValue() * 37u;
+  }
+  static bool isEqual(const CtorTester &LHS, const CtorTester &RHS) {
+    return LHS == RHS;
+  }
+};
+
+CtorTester getTestKey(int i, CtorTester *) { return CtorTester(i); }
+CtorTester getTestValue(int i, CtorTester *) { return CtorTester(42 + i); }
+
+// Test fixture, with helper functions implemented by forwarding to global
+// function overloads selected by component types of the type parameter. This
+// allows all of the map implementations to be tested with shared
+// implementations of helper routines.
+template <typename T>
+class DenseMapTest : public ::testing::Test {
+protected:
+  T Map;
+
+  static typename T::key_type *const dummy_key_ptr;
+  static typename T::mapped_type *const dummy_value_ptr;
+
+  typename T::key_type getKey(int i = 0) {
+    return getTestKey(i, dummy_key_ptr);
+  }
+  typename T::mapped_type getValue(int i = 0) {
+    return getTestValue(i, dummy_value_ptr);
+  }
+};
+
+template <typename T>
+typename T::key_type *const DenseMapTest<T>::dummy_key_ptr = nullptr;
+template <typename T>
+typename T::mapped_type *const DenseMapTest<T>::dummy_value_ptr = nullptr;
+
+// Register these types for testing.
+typedef ::testing::Types<DenseMap<uint32_t, uint32_t>,
+                         DenseMap<uint32_t *, uint32_t *>,
+                         DenseMap<CtorTester, CtorTester, CtorTesterMapInfo>,
+                         SmallDenseMap<uint32_t, uint32_t>,
+                         SmallDenseMap<uint32_t *, uint32_t *>,
+                         SmallDenseMap<CtorTester, CtorTester, 4,
+                                       CtorTesterMapInfo>
+                         > DenseMapTestTypes;
+TYPED_TEST_SUITE(DenseMapTest, DenseMapTestTypes, );
+
+// Empty map tests
+TYPED_TEST(DenseMapTest, EmptyIntMapTest) {
+  // Size tests
+  EXPECT_EQ(0u, this->Map.size());
+  EXPECT_TRUE(this->Map.empty());
+
+  // Iterator tests
+  EXPECT_TRUE(this->Map.begin() == this->Map.end());
+
+  // Lookup tests
+  EXPECT_FALSE(this->Map.count(this->getKey()));
+  EXPECT_TRUE(this->Map.find(this->getKey()) == this->Map.end());
+  EXPECT_EQ(typename TypeParam::mapped_type(),
+            this->Map.lookup(this->getKey()));
+}
+
+// Constant map tests
+TYPED_TEST(DenseMapTest, ConstEmptyMapTest) {
+  const TypeParam &ConstMap = this->Map;
+  EXPECT_EQ(0u, ConstMap.size());
+  EXPECT_TRUE(ConstMap.empty());
+  EXPECT_TRUE(ConstMap.begin() == ConstMap.end());
+}
+
+// A map with a single entry
+TYPED_TEST(DenseMapTest, SingleEntryMapTest) {
+  this->Map[this->getKey()] = this->getValue();
+
+  // Size tests
+  EXPECT_EQ(1u, this->Map.size());
+  EXPECT_FALSE(this->Map.begin() == this->Map.end());
+  EXPECT_FALSE(this->Map.empty());
+
+  // Iterator tests
+  typename TypeParam::iterator it = this->Map.begin();
+  EXPECT_EQ(this->getKey(), it->first);
+  EXPECT_EQ(this->getValue(), it->second);
+  ++it;
+  EXPECT_TRUE(it == this->Map.end());
+
+  // Lookup tests
+  EXPECT_TRUE(this->Map.count(this->getKey()));
+  EXPECT_TRUE(this->Map.find(this->getKey()) == this->Map.begin());
+  EXPECT_EQ(this->getValue(), this->Map.lookup(this->getKey()));
+  EXPECT_EQ(this->getValue(), this->Map[this->getKey()]);
+}
+
+// Test clear() method
+TYPED_TEST(DenseMapTest, ClearTest) {
+  this->Map[this->getKey()] = this->getValue();
+  this->Map.clear();
+
+  EXPECT_EQ(0u, this->Map.size());
+  EXPECT_TRUE(this->Map.empty());
+  EXPECT_TRUE(this->Map.begin() == this->Map.end());
+}
+
+// Test erase(iterator) method
+TYPED_TEST(DenseMapTest, EraseTest) {
+  this->Map[this->getKey()] = this->getValue();
+  this->Map.erase(this->Map.begin());
+
+  EXPECT_EQ(0u, this->Map.size());
+  EXPECT_TRUE(this->Map.empty());
+  EXPECT_TRUE(this->Map.begin() == this->Map.end());
+}
+
+// Test erase(value) method
+TYPED_TEST(DenseMapTest, EraseTest2) {
+  this->Map[this->getKey()] = this->getValue();
+  this->Map.erase(this->getKey());
+
+  EXPECT_EQ(0u, this->Map.size());
+  EXPECT_TRUE(this->Map.empty());
+  EXPECT_TRUE(this->Map.begin() == this->Map.end());
+}
+
+// Test insert() method
+TYPED_TEST(DenseMapTest, InsertTest) {
+  this->Map.insert(std::make_pair(this->getKey(), this->getValue()));
+  EXPECT_EQ(1u, this->Map.size());
+  EXPECT_EQ(this->getValue(), this->Map[this->getKey()]);
+}
+
+// Test copy constructor method
+TYPED_TEST(DenseMapTest, CopyConstructorTest) {
+  this->Map[this->getKey()] = this->getValue();
+  TypeParam copyMap(this->Map);
+
+  EXPECT_EQ(1u, copyMap.size());
+  EXPECT_EQ(this->getValue(), copyMap[this->getKey()]);
+}
+
+// Test copy constructor method where SmallDenseMap isn't small.
+TYPED_TEST(DenseMapTest, CopyConstructorNotSmallTest) {
+  for (int Key = 0; Key < 5; ++Key)
+    this->Map[this->getKey(Key)] = this->getValue(Key);
+  TypeParam copyMap(this->Map);
+
+  EXPECT_EQ(5u, copyMap.size());
+  for (int Key = 0; Key < 5; ++Key)
+    EXPECT_EQ(this->getValue(Key), copyMap[this->getKey(Key)]);
+}
+
+// Test copying from a default-constructed map.
+TYPED_TEST(DenseMapTest, CopyConstructorFromDefaultTest) {
+  TypeParam copyMap(this->Map);
+
+  EXPECT_TRUE(copyMap.empty());
+}
+
+// Test copying from an empty map where SmallDenseMap isn't small.
+TYPED_TEST(DenseMapTest, CopyConstructorFromEmptyTest) {
+  for (int Key = 0; Key < 5; ++Key)
+    this->Map[this->getKey(Key)] = this->getValue(Key);
+  this->Map.clear();
+  TypeParam copyMap(this->Map);
+
+  EXPECT_TRUE(copyMap.empty());
+}
+
+// Test assignment operator method
+TYPED_TEST(DenseMapTest, AssignmentTest) {
+  this->Map[this->getKey()] = this->getValue();
+  TypeParam copyMap = this->Map;
+
+  EXPECT_EQ(1u, copyMap.size());
+  EXPECT_EQ(this->getValue(), copyMap[this->getKey()]);
+
+  // test self-assignment.
+  copyMap = static_cast<TypeParam &>(copyMap);
+  EXPECT_EQ(1u, copyMap.size());
+  EXPECT_EQ(this->getValue(), copyMap[this->getKey()]);
+}
+
+TYPED_TEST(DenseMapTest, AssignmentTestNotSmall) {
+  for (int Key = 0; Key < 5; ++Key)
+    this->Map[this->getKey(Key)] = this->getValue(Key);
+  TypeParam copyMap = this->Map;
+
+  EXPECT_EQ(5u, copyMap.size());
+  for (int Key = 0; Key < 5; ++Key)
+    EXPECT_EQ(this->getValue(Key), copyMap[this->getKey(Key)]);
+
+  // test self-assignment.
+  copyMap = static_cast<TypeParam &>(copyMap);
+  EXPECT_EQ(5u, copyMap.size());
+  for (int Key = 0; Key < 5; ++Key)
+    EXPECT_EQ(this->getValue(Key), copyMap[this->getKey(Key)]);
+}
+
+// Test swap method
+TYPED_TEST(DenseMapTest, SwapTest) {
+  this->Map[this->getKey()] = this->getValue();
+  TypeParam otherMap;
+
+  this->Map.swap(otherMap);
+  EXPECT_EQ(0u, this->Map.size());
+  EXPECT_TRUE(this->Map.empty());
+  EXPECT_EQ(1u, otherMap.size());
+  EXPECT_EQ(this->getValue(), otherMap[this->getKey()]);
+
+  this->Map.swap(otherMap);
+  EXPECT_EQ(0u, otherMap.size());
+  EXPECT_TRUE(otherMap.empty());
+  EXPECT_EQ(1u, this->Map.size());
+  EXPECT_EQ(this->getValue(), this->Map[this->getKey()]);
+
+  // Make this more interesting by inserting 100 numbers into the map.
+  for (int i = 0; i < 100; ++i)
+    this->Map[this->getKey(i)] = this->getValue(i);
+
+  this->Map.swap(otherMap);
+  EXPECT_EQ(0u, this->Map.size());
+  EXPECT_TRUE(this->Map.empty());
+  EXPECT_EQ(100u, otherMap.size());
+  for (int i = 0; i < 100; ++i)
+    EXPECT_EQ(this->getValue(i), otherMap[this->getKey(i)]);
+
+  this->Map.swap(otherMap);
+  EXPECT_EQ(0u, otherMap.size());
+  EXPECT_TRUE(otherMap.empty());
+  EXPECT_EQ(100u, this->Map.size());
+  for (int i = 0; i < 100; ++i)
+    EXPECT_EQ(this->getValue(i), this->Map[this->getKey(i)]);
+}
+
+// A more complex iteration test
+TYPED_TEST(DenseMapTest, IterationTest) {
+  bool visited[100];
+  std::map<typename TypeParam::key_type, unsigned> visitedIndex;
+
+  // Insert 100 numbers into the map
+  for (int i = 0; i < 100; ++i) {
+    visited[i] = false;
+    visitedIndex[this->getKey(i)] = i;
+
+    this->Map[this->getKey(i)] = this->getValue(i);
+  }
+
+  // Iterate over all numbers and mark each one found.
+  for (typename TypeParam::iterator it = this->Map.begin();
+       it != this->Map.end(); ++it)
+    visited[visitedIndex[it->first]] = true;
+
+  // Ensure every number was visited.
+  for (int i = 0; i < 100; ++i)
+    ASSERT_TRUE(visited[i]) << "Entry #" << i << " was never visited";
+}
+
+// const_iterator test
+TYPED_TEST(DenseMapTest, ConstIteratorTest) {
+  // Check conversion from iterator to const_iterator.
+  typename TypeParam::iterator it = this->Map.begin();
+  typename TypeParam::const_iterator cit(it);
+  EXPECT_TRUE(it == cit);
+
+  // Check copying of const_iterators.
+  typename TypeParam::const_iterator cit2(cit);
+  EXPECT_TRUE(cit == cit2);
+}
+
+namespace {
+// Simple class that counts how many moves and copy happens when growing a map
+struct CountCopyAndMove {
+  static int Move;
+  static int Copy;
+  CountCopyAndMove() {}
+
+  CountCopyAndMove(const CountCopyAndMove &) { Copy++; }
+  CountCopyAndMove &operator=(const CountCopyAndMove &) {
+    Copy++;
+    return *this;
+  }
+  CountCopyAndMove(CountCopyAndMove &&) { Move++; }
+  CountCopyAndMove &operator=(const CountCopyAndMove &&) {
+    Move++;
+    return *this;
+  }
+};
+int CountCopyAndMove::Copy = 0;
+int CountCopyAndMove::Move = 0;
+
+} // anonymous namespace
+
+// Test initializer list construction.
+TEST(DenseMapCustomTest, InitializerList) {
+  DenseMap<int, int> M({{0, 0}, {0, 1}, {1, 2}});
+  EXPECT_EQ(2u, M.size());
+  EXPECT_EQ(1u, M.count(0));
+  EXPECT_EQ(0, M[0]);
+  EXPECT_EQ(1u, M.count(1));
+  EXPECT_EQ(2, M[1]);
+}
+
+// Test initializer list construction.
+TEST(DenseMapCustomTest, EqualityComparison) {
+  DenseMap<int, int> M1({{0, 0}, {1, 2}});
+  DenseMap<int, int> M2({{0, 0}, {1, 2}});
+  DenseMap<int, int> M3({{0, 0}, {1, 3}});
+
+  EXPECT_EQ(M1, M2);
+  EXPECT_NE(M1, M3);
+}
+
+// Test for the default minimum size of a DenseMap
+TEST(DenseMapCustomTest, DefaultMinReservedSizeTest) {
+  // IF THIS VALUE CHANGE, please update InitialSizeTest, InitFromIterator, and
+  // ReserveTest as well!
+  const int ExpectedInitialBucketCount = 64;
+  // Formula from DenseMap::getMinBucketToReserveForEntries()
+  const int ExpectedMaxInitialEntries = ExpectedInitialBucketCount * 3 / 4 - 1;
+
+  DenseMap<int, CountCopyAndMove> Map;
+  // Will allocate 64 buckets
+  Map.reserve(1);
+  unsigned MemorySize = Map.getMemorySize();
+  CountCopyAndMove::Copy = 0;
+  CountCopyAndMove::Move = 0;
+  for (int i = 0; i < ExpectedMaxInitialEntries; ++i)
+    Map.insert(std::pair<int, CountCopyAndMove>(std::piecewise_construct,
+                                                std::forward_as_tuple(i),
+                                                std::forward_as_tuple()));
+  // Check that we didn't grow
+  EXPECT_EQ(MemorySize, Map.getMemorySize());
+  // Check that move was called the expected number of times
+  EXPECT_EQ(ExpectedMaxInitialEntries, CountCopyAndMove::Move);
+  // Check that no copy occurred
+  EXPECT_EQ(0, CountCopyAndMove::Copy);
+
+  // Adding one extra element should grow the map
+  Map.insert(std::pair<int, CountCopyAndMove>(
+      std::piecewise_construct,
+      std::forward_as_tuple(ExpectedMaxInitialEntries),
+      std::forward_as_tuple()));
+  // Check that we grew
+  EXPECT_NE(MemorySize, Map.getMemorySize());
+  // Check that move was called the expected number of times
+  //  This relies on move-construction elision, and cannot be reliably tested.
+  //   EXPECT_EQ(ExpectedMaxInitialEntries + 2, CountCopyAndMove::Move);
+  // Check that no copy occurred
+  EXPECT_EQ(0, CountCopyAndMove::Copy);
+}
+
+// Make sure creating the map with an initial size of N actually gives us enough
+// buckets to insert N items without increasing allocation size.
+TEST(DenseMapCustomTest, InitialSizeTest) {
+  // Test a few different sizes, 48 is *not* a random choice: we need a value
+  // that is 2/3 of a power of two to stress the grow() condition, and the power
+  // of two has to be at least 64 because of minimum size allocation in the
+  // DenseMap (see DefaultMinReservedSizeTest). 66 is a value just above the
+  // 64 default init.
+  for (auto Size : {1, 2, 48, 66}) {
+    DenseMap<int, CountCopyAndMove> Map(Size);
+    unsigned MemorySize = Map.getMemorySize();
+    CountCopyAndMove::Copy = 0;
+    CountCopyAndMove::Move = 0;
+    for (int i = 0; i < Size; ++i)
+      Map.insert(std::pair<int, CountCopyAndMove>(std::piecewise_construct,
+                                                  std::forward_as_tuple(i),
+                                                  std::forward_as_tuple()));
+    // Check that we didn't grow
+    EXPECT_EQ(MemorySize, Map.getMemorySize());
+    // Check that move was called the expected number of times
+    EXPECT_EQ(Size, CountCopyAndMove::Move);
+    // Check that no copy occurred
+    EXPECT_EQ(0, CountCopyAndMove::Copy);
+  }
+}
+
+// Make sure creating the map with a iterator range does not trigger grow()
+TEST(DenseMapCustomTest, InitFromIterator) {
+  std::vector<std::pair<int, CountCopyAndMove>> Values;
+  // The size is a random value greater than 64 (hardcoded DenseMap min init)
+  const int Count = 65;
+  for (int i = 0; i < Count; i++)
+    Values.emplace_back(i, CountCopyAndMove());
+
+  CountCopyAndMove::Move = 0;
+  CountCopyAndMove::Copy = 0;
+  DenseMap<int, CountCopyAndMove> Map(Values.begin(), Values.end());
+  // Check that no move occurred
+  EXPECT_EQ(0, CountCopyAndMove::Move);
+  // Check that copy was called the expected number of times
+  EXPECT_EQ(Count, CountCopyAndMove::Copy);
+}
+
+// Make sure reserve actually gives us enough buckets to insert N items
+// without increasing allocation size.
+TEST(DenseMapCustomTest, ReserveTest) {
+  // Test a few different size, 48 is *not* a random choice: we need a value
+  // that is 2/3 of a power of two to stress the grow() condition, and the power
+  // of two has to be at least 64 because of minimum size allocation in the
+  // DenseMap (see DefaultMinReservedSizeTest). 66 is a value just above the
+  // 64 default init.
+  for (auto Size : {1, 2, 48, 66}) {
+    DenseMap<int, CountCopyAndMove> Map;
+    Map.reserve(Size);
+    unsigned MemorySize = Map.getMemorySize();
+    CountCopyAndMove::Copy = 0;
+    CountCopyAndMove::Move = 0;
+    for (int i = 0; i < Size; ++i)
+      Map.insert(std::pair<int, CountCopyAndMove>(std::piecewise_construct,
+                                                  std::forward_as_tuple(i),
+                                                  std::forward_as_tuple()));
+    // Check that we didn't grow
+    EXPECT_EQ(MemorySize, Map.getMemorySize());
+    // Check that move was called the expected number of times
+    EXPECT_EQ(Size, CountCopyAndMove::Move);
+    // Check that no copy occurred
+    EXPECT_EQ(0, CountCopyAndMove::Copy);
+  }
+}
+
+// Make sure DenseMap works with StringRef keys.
+TEST(DenseMapCustomTest, StringRefTest) {
+  DenseMap<StringRef, int> M;
+
+  M["a"] = 1;
+  M["b"] = 2;
+  M["c"] = 3;
+
+  EXPECT_EQ(3u, M.size());
+  EXPECT_EQ(1, M.lookup("a"));
+  EXPECT_EQ(2, M.lookup("b"));
+  EXPECT_EQ(3, M.lookup("c"));
+
+  EXPECT_EQ(0, M.lookup("q"));
+
+  // Test the empty string, spelled various ways.
+  EXPECT_EQ(0, M.lookup(""));
+  EXPECT_EQ(0, M.lookup(StringRef()));
+  EXPECT_EQ(0, M.lookup(StringRef("a", 0)));
+  M[""] = 42;
+  EXPECT_EQ(42, M.lookup(""));
+  EXPECT_EQ(42, M.lookup(StringRef()));
+  EXPECT_EQ(42, M.lookup(StringRef("a", 0)));
+}
+
+// Key traits that allows lookup with either an unsigned or char* key;
+// In the latter case, "a" == 0, "b" == 1 and so on.
+struct TestDenseMapInfo {
+  static inline unsigned getEmptyKey() { return ~0; }
+  static inline unsigned getTombstoneKey() { return ~0U - 1; }
+  static unsigned getHashValue(const unsigned& Val) { return Val * 37U; }
+  static unsigned getHashValue(const char* Val) {
+    return (unsigned)(Val[0] - 'a') * 37U;
+  }
+  static bool isEqual(const unsigned& LHS, const unsigned& RHS) {
+    return LHS == RHS;
+  }
+  static bool isEqual(const char* LHS, const unsigned& RHS) {
+    return (unsigned)(LHS[0] - 'a') == RHS;
+  }
+};
+
+// find_as() tests
+TEST(DenseMapCustomTest, FindAsTest) {
+  DenseMap<unsigned, unsigned, TestDenseMapInfo> map;
+  map[0] = 1;
+  map[1] = 2;
+  map[2] = 3;
+
+  // Size tests
+  EXPECT_EQ(3u, map.size());
+
+  // Normal lookup tests
+  EXPECT_EQ(1u, map.count(1));
+  EXPECT_EQ(1u, map.find(0)->second);
+  EXPECT_EQ(2u, map.find(1)->second);
+  EXPECT_EQ(3u, map.find(2)->second);
+  EXPECT_TRUE(map.find(3) == map.end());
+
+  // find_as() tests
+  EXPECT_EQ(1u, map.find_as("a")->second);
+  EXPECT_EQ(2u, map.find_as("b")->second);
+  EXPECT_EQ(3u, map.find_as("c")->second);
+  EXPECT_TRUE(map.find_as("d") == map.end());
+}
+
+TEST(DenseMapCustomTest, SmallDenseMapInitializerList) {
+  SmallDenseMap<int, int> M = {{0, 0}, {0, 1}, {1, 2}};
+  EXPECT_EQ(2u, M.size());
+  EXPECT_EQ(1u, M.count(0));
+  EXPECT_EQ(0, M[0]);
+  EXPECT_EQ(1u, M.count(1));
+  EXPECT_EQ(2, M[1]);
+}
+
+struct ContiguousDenseMapInfo {
+  static inline unsigned getEmptyKey() { return ~0; }
+  static inline unsigned getTombstoneKey() { return ~0U - 1; }
+  static unsigned getHashValue(const unsigned& Val) { return Val; }
+  static bool isEqual(const unsigned& LHS, const unsigned& RHS) {
+    return LHS == RHS;
+  }
+};
+
+// Test that filling a small dense map with exactly the number of elements in
+// the map grows to have enough space for an empty bucket.
+TEST(DenseMapCustomTest, SmallDenseMapGrowTest) {
+  SmallDenseMap<unsigned, unsigned, 32, ContiguousDenseMapInfo> map;
+  // Add some number of elements, then delete a few to leave us some tombstones.
+  // If we just filled the map with 32 elements we'd grow because of not enough
+  // tombstones which masks the issue here.
+  for (unsigned i = 0; i < 20; ++i)
+    map[i] = i + 1;
+  for (unsigned i = 0; i < 10; ++i)
+    map.erase(i);
+  for (unsigned i = 20; i < 32; ++i)
+    map[i] = i + 1;
+
+  // Size tests
+  EXPECT_EQ(22u, map.size());
+
+  // Try to find an element which doesn't exist.  There was a bug in
+  // SmallDenseMap which led to a map with num elements == small capacity not
+  // having an empty bucket any more.  Finding an element not in the map would
+  // therefore never terminate.
+  EXPECT_TRUE(map.find(32) == map.end());
+}
+
+TEST(DenseMapCustomTest, LargeSmallDenseMapCompaction) {
+  SmallDenseMap<unsigned, unsigned, 128, ContiguousDenseMapInfo> map;
+  // Fill to < 3/4 load.
+  for (unsigned i = 0; i < 95; ++i)
+    map[i] = i;
+  // And erase, leaving behind tombstones.
+  for (unsigned i = 0; i < 95; ++i)
+    map.erase(i);
+  // Fill further, so that less than 1/8 are empty, but still below 3/4 load.
+  for (unsigned i = 95; i < 128; ++i)
+    map[i] = i;
+
+  EXPECT_EQ(33u, map.size());
+  // Similar to the previous test, check for a non-existing element, as an
+  // indirect check that tombstones have been removed.
+  EXPECT_TRUE(map.find(0) == map.end());
+}
+
+TEST(DenseMapCustomTest, TryEmplaceTest) {
+  DenseMap<int, std::unique_ptr<int>> Map;
+  std::unique_ptr<int> P(new int(2));
+  auto Try1 = Map.try_emplace(0, new int(1));
+  EXPECT_TRUE(Try1.second);
+  auto Try2 = Map.try_emplace(0, std::move(P));
+  EXPECT_FALSE(Try2.second);
+  EXPECT_EQ(Try1.first, Try2.first);
+  EXPECT_NE(nullptr, P);
+}
+
+TEST(DenseMapCustomTest, ConstTest) {
+  // Test that const pointers work okay for count and find, even when the
+  // underlying map is a non-const pointer.
+  DenseMap<int *, int> Map;
+  int A;
+  int *B = &A;
+  const int *C = &A;
+  Map.insert({B, 0});
+  EXPECT_EQ(Map.count(B), 1u);
+  EXPECT_EQ(Map.count(C), 1u);
+  EXPECT_NE(Map.find(B), Map.end());
+  EXPECT_NE(Map.find(C), Map.end());
+}
+
+struct IncompleteStruct;
+
+TEST(DenseMapCustomTest, OpaquePointerKey) {
+  // Test that we can use a pointer to an incomplete type as a DenseMap key.
+  // This is an important build time optimization, since many classes have
+  // DenseMap members.
+  DenseMap<IncompleteStruct *, int> Map;
+  int Keys[3] = {0, 0, 0};
+  IncompleteStruct *K1 = reinterpret_cast<IncompleteStruct *>(&Keys[0]);
+  IncompleteStruct *K2 = reinterpret_cast<IncompleteStruct *>(&Keys[1]);
+  IncompleteStruct *K3 = reinterpret_cast<IncompleteStruct *>(&Keys[2]);
+  Map.insert({K1, 1});
+  Map.insert({K2, 2});
+  Map.insert({K3, 3});
+  EXPECT_EQ(Map.count(K1), 1u);
+  EXPECT_EQ(Map[K1], 1);
+  EXPECT_EQ(Map[K2], 2);
+  EXPECT_EQ(Map[K3], 3);
+  Map.clear();
+  EXPECT_EQ(Map.find(K1), Map.end());
+  EXPECT_EQ(Map.find(K2), Map.end());
+  EXPECT_EQ(Map.find(K3), Map.end());
+}
+}