X-Git-Url: http://demsky.eecs.uci.edu/git/?a=blobdiff_plain;f=include%2Fllvm%2FADT%2FDenseMap.h;h=cbcf7892c97004c01d0cd6263b1bd3ed9d16682c;hb=75eac5f0ebff4d0ffe10ce6bc8f2867c5f15315b;hp=9d55435c91f94ed4397d7bd04c8e13f6679ec7ca;hpb=7c78afefe96669cc3eb886308291213415d9d7b0;p=oota-llvm.git

diff --git a/include/llvm/ADT/DenseMap.h b/include/llvm/ADT/DenseMap.h
index 9d55435c91f..cbcf7892c97 100644
--- a/include/llvm/ADT/DenseMap.h
+++ b/include/llvm/ADT/DenseMap.h
@@ -1,63 +1,1039 @@
-//===- DenseMap.h - A dense map implmentation -------------------*- C++ -*-===//
-// 
+//===- llvm/ADT/DenseMap.h - Dense probed hash table ------------*- C++ -*-===//
+//
 //                     The LLVM Compiler Infrastructure
 //
-// This file was developed by the LLVM research group and is distributed under
-// the University of Illinois Open Source License. See LICENSE.TXT for details.
-// 
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
 //===----------------------------------------------------------------------===//
 //
-// This file implements a dense map. A dense map template takes two
-// types. The first is the mapped type and the second is a functor
-// that maps its argument to a size_t. On instantiation a "null" value
-// can be provided to be used as a "does not exist" indicator in the
-// map. A member function grow() is provided that given the value of
-// the maximally indexed key (the argument of the functor) makes sure
-// the map has enough space for it.
+// This file defines the DenseMap class.
 //
 //===----------------------------------------------------------------------===//
 
-#ifndef SUPPORT_DENSEMAP_H
-#define SUPPORT_DENSEMAP_H
+#ifndef LLVM_ADT_DENSEMAP_H
+#define LLVM_ADT_DENSEMAP_H
 
-#include <vector>
+#include "llvm/Support/Compiler.h"
+#include "llvm/Support/AlignOf.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>
 
 namespace llvm {
 
-template <typename T, typename ToIndexT>
-class DenseMap {
-    typedef typename ToIndexT::argument_type IndexT;
-    typedef std::vector<T> StorageT;
-    StorageT storage_;
-    T nullVal_;
-    ToIndexT toIndex_;
+template<typename KeyT, typename ValueT,
+         typename KeyInfoT = DenseMapInfo<KeyT>,
+         bool IsConst = false>
+class DenseMapIterator;
+
+template<typename DerivedT,
+         typename KeyT, typename ValueT, typename KeyInfoT>
+class DenseMapBase {
+protected:
+  typedef std::pair<KeyT, ValueT> BucketT;
+
+public:
+  typedef KeyT key_type;
+  typedef ValueT mapped_type;
+  typedef BucketT value_type;
+
+  typedef DenseMapIterator<KeyT, ValueT, KeyInfoT> iterator;
+  typedef DenseMapIterator<KeyT, ValueT,
+                           KeyInfoT, true> const_iterator;
+  inline iterator begin() {
+    // When the map is empty, avoid the overhead of AdvancePastEmptyBuckets().
+    return empty() ? end() : iterator(getBuckets(), getBucketsEnd());
+  }
+  inline iterator end() {
+    return iterator(getBucketsEnd(), getBucketsEnd(), true);
+  }
+  inline const_iterator begin() const {
+    return empty() ? end() : const_iterator(getBuckets(), getBucketsEnd());
+  }
+  inline const_iterator end() const {
+    return const_iterator(getBucketsEnd(), getBucketsEnd(), true);
+  }
+
+  bool 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) {
+    if (Size > getNumBuckets())
+      grow(Size);
+  }
+
+  void clear() {
+    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();
+    for (BucketT *P = getBuckets(), *E = getBucketsEnd(); P != E; ++P) {
+      if (!KeyInfoT::isEqual(P->first, EmptyKey)) {
+        if (!KeyInfoT::isEqual(P->first, TombstoneKey)) {
+          P->second.~ValueT();
+          decrementNumEntries();
+        }
+        P->first = EmptyKey;
+      }
+    }
+    assert(getNumEntries() == 0 && "Node count imbalance!");
+    setNumTombstones(0);
+  }
+
+  /// count - Return true if the specified key is in the map.
+  bool count(const KeyT &Val) const {
+    const BucketT *TheBucket;
+    return LookupBucketFor(Val, TheBucket);
+  }
+
+  iterator find(const KeyT &Val) {
+    BucketT *TheBucket;
+    if (LookupBucketFor(Val, TheBucket))
+      return iterator(TheBucket, getBucketsEnd(), true);
+    return end();
+  }
+  const_iterator find(const KeyT &Val) const {
+    const BucketT *TheBucket;
+    if (LookupBucketFor(Val, TheBucket))
+      return const_iterator(TheBucket, getBucketsEnd(), 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 iterator(TheBucket, getBucketsEnd(), 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(), 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 {
+    const BucketT *TheBucket;
+    if (LookupBucketFor(Val, TheBucket))
+      return TheBucket->second;
+    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) {
+    BucketT *TheBucket;
+    if (LookupBucketFor(KV.first, TheBucket))
+      return std::make_pair(iterator(TheBucket, getBucketsEnd(), true),
+                            false); // Already in map.
+
+    // Otherwise, insert the new element.
+    TheBucket = InsertIntoBucket(KV.first, KV.second, TheBucket);
+    return std::make_pair(iterator(TheBucket, getBucketsEnd(), 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->second.~ValueT();
+    TheBucket->first = getTombstoneKey();
+    decrementNumEntries();
+    incrementNumTombstones();
+    return true;
+  }
+  void erase(iterator I) {
+    BucketT *TheBucket = &*I;
+    TheBucket->second.~ValueT();
+    TheBucket->first = getTombstoneKey();
+    decrementNumEntries();
+    incrementNumTombstones();
+  }
+
+  value_type& FindAndConstruct(const KeyT &Key) {
+    BucketT *TheBucket;
+    if (LookupBucketFor(Key, TheBucket))
+      return *TheBucket;
+
+    return *InsertIntoBucket(Key, ValueT(), TheBucket);
+  }
+
+  ValueT &operator[](const KeyT &Key) {
+    return FindAndConstruct(Key).second;
+  }
+
+#if LLVM_USE_RVALUE_REFERENCES
+  value_type& FindAndConstruct(KeyT &&Key) {
+    BucketT *TheBucket;
+    if (LookupBucketFor(Key, TheBucket))
+      return *TheBucket;
+
+    return *InsertIntoBucket(Key, ValueT(), TheBucket);
+  }
+
+  ValueT &operator[](KeyT &&Key) {
+    return FindAndConstruct(Key).second;
+  }
+#endif
+
+  /// 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() {}
+
+  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->first, EmptyKey) &&
+          !KeyInfoT::isEqual(P->first, TombstoneKey))
+        P->second.~ValueT();
+      P->first.~KeyT();
+    }
+
+#ifndef NDEBUG
+    memset((void*)getBuckets(), 0x5a, sizeof(BucketT)*getNumBuckets());
+#endif
+  }
+
+  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->first) 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->first, EmptyKey) &&
+          !KeyInfoT::isEqual(B->first, TombstoneKey)) {
+        // Insert the key/value into the new table.
+        BucketT *DestBucket;
+        bool FoundVal = LookupBucketFor(B->first, DestBucket);
+        (void)FoundVal; // silence warning.
+        assert(!FoundVal && "Key already in new map?");
+        DestBucket->first = llvm_move(B->first);
+        new (&DestBucket->second) ValueT(llvm_move(B->second));
+        incrementNumEntries();
+
+        // Free the value.
+        B->second.~ValueT();
+      }
+      B->first.~KeyT();
+    }
+
+#ifndef NDEBUG
+    if (OldBucketsBegin != OldBucketsEnd)
+      memset((void*)OldBucketsBegin, 0x5a,
+             sizeof(BucketT) * (OldBucketsEnd - OldBucketsBegin));
+#endif
+  }
+
+  template <typename OtherBaseT>
+  void copyFrom(const DenseMapBase<OtherBaseT, KeyT, ValueT, KeyInfoT>& other) {
+    assert(getNumBuckets() == other.getNumBuckets());
+
+    setNumEntries(other.getNumEntries());
+    setNumTombstones(other.getNumTombstones());
+
+    if (isPodLike<KeyT>::value && isPodLike<ValueT>::value)
+      memcpy(getBuckets(), other.getBuckets(),
+             getNumBuckets() * sizeof(BucketT));
+    else
+      for (size_t i = 0; i < getNumBuckets(); ++i) {
+        new (&getBuckets()[i].first) KeyT(other.getBuckets()[i].first);
+        if (!KeyInfoT::isEqual(getBuckets()[i].first, getEmptyKey()) &&
+            !KeyInfoT::isEqual(getBuckets()[i].first, getTombstoneKey()))
+          new (&getBuckets()[i].second) ValueT(other.getBuckets()[i].second);
+      }
+  }
+
+  void swap(DenseMapBase& RHS) {
+    std::swap(getNumEntries(), RHS.getNumEntries());
+    std::swap(getNumTombstones(), RHS.getNumTombstones());
+  }
+
+  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->first = Key;
+    new (&TheBucket->second) ValueT(Value);
+    return TheBucket;
+  }
+
+#if LLVM_USE_RVALUE_REFERENCES
+  BucketT *InsertIntoBucket(const KeyT &Key, ValueT &&Value,
+                            BucketT *TheBucket) {
+    TheBucket = InsertIntoBucketImpl(Key, TheBucket);
+
+    TheBucket->first = Key;
+    new (&TheBucket->second) ValueT(std::move(Value));
+    return TheBucket;
+  }
+
+  BucketT *InsertIntoBucket(KeyT &&Key, ValueT &&Value, BucketT *TheBucket) {
+    TheBucket = InsertIntoBucketImpl(Key, TheBucket);
+
+    TheBucket->first = std::move(Key);
+    new (&TheBucket->second) ValueT(std::move(Value));
+    return TheBucket;
+  }
+#endif
+
+  BucketT *InsertIntoBucketImpl(const KeyT &Key, BucketT *TheBucket) {
+    // 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 (NewNumEntries*4 >= NumBuckets*3) {
+      this->grow(NumBuckets * 2);
+      LookupBucketFor(Key, TheBucket);
+      NumBuckets = getNumBuckets();
+    }
+    if (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()))
+      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 = 0;
+      return false;
+    }
+
+    // FoundTombstone - Keep track of whether we find a tombstone while probing.
+    const BucketT *FoundTombstone = 0;
+    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) {
+      const BucketT *ThisBucket = BucketsPtr + BucketNo;
+      // Found Val's bucket?  If so, return it.
+      if (KeyInfoT::isEqual(Val, ThisBucket->first)) {
+        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 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)
+        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> >
+class DenseMap
+    : public DenseMapBase<DenseMap<KeyT, ValueT, KeyInfoT>,
+                          KeyT, ValueT, KeyInfoT> {
+  // Lift some types from the dependent base class into this class for
+  // simplicity of referring to them.
+  typedef DenseMapBase<DenseMap, KeyT, ValueT, KeyInfoT> BaseT;
+  typedef typename BaseT::BucketT BucketT;
+  friend class DenseMapBase<DenseMap, KeyT, ValueT, KeyInfoT>;
+
+  BucketT *Buckets;
+  unsigned NumEntries;
+  unsigned NumTombstones;
+  unsigned NumBuckets;
 
 public:
-    DenseMap() : nullVal_(T()) { }
+  explicit DenseMap(unsigned NumInitBuckets = 0) {
+    init(NumInitBuckets);
+  }
+
+  DenseMap(const DenseMap &other) {
+    init(0);
+    copyFrom(other);
+  }
+
+#if LLVM_USE_RVALUE_REFERENCES
+  DenseMap(DenseMap &&other) {
+    init(0);
+    swap(other);
+  }
+#endif
+
+  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);
+  }
 
-    explicit DenseMap(const T& val) : nullVal_(val) { }
+  void swap(DenseMap& RHS) {
+    std::swap(Buckets, RHS.Buckets);
+    std::swap(NumEntries, RHS.NumEntries);
+    std::swap(NumTombstones, RHS.NumTombstones);
+    std::swap(NumBuckets, RHS.NumBuckets);
+  }
 
-    typename StorageT::reference operator[](IndexT n) {
-        assert(toIndex_(n) < storage_.size() && "index out of bounds!");
-        return storage_[toIndex_(n)];
+  DenseMap& operator=(const DenseMap& other) {
+    copyFrom(other);
+    return *this;
+  }
+
+#if LLVM_USE_RVALUE_REFERENCES
+  DenseMap& operator=(DenseMap &&other) {
+    this->destroyAll();
+    operator delete(Buckets);
+    init(0);
+    swap(other);
+    return *this;
+  }
+#endif
+
+  void copyFrom(const DenseMap& other) {
+    this->destroyAll();
+    operator delete(Buckets);
+    if (allocateBuckets(other.NumBuckets)) {
+      this->BaseT::copyFrom(other);
+    } else {
+      NumEntries = 0;
+      NumTombstones = 0;
     }
+  }
 
-    typename StorageT::const_reference operator[](IndexT n) const {
-        assert(toIndex_(n) < storage_.size() && "index out of bounds!");
-        return storage_[toIndex_(n)];
+  void init(unsigned InitBuckets) {
+    if (allocateBuckets(InitBuckets)) {
+      this->BaseT::initEmpty();
+    } else {
+      NumEntries = 0;
+      NumTombstones = 0;
     }
+  }
 
-    void clear() {
-        storage_.clear();
+  void grow(unsigned AtLeast) {
+    unsigned OldNumBuckets = NumBuckets;
+    BucketT *OldBuckets = Buckets;
+
+    allocateBuckets(std::max<unsigned>(64, NextPowerOf2(AtLeast)));
+    assert(Buckets);
+    if (!OldBuckets) {
+      this->BaseT::initEmpty();
+      return;
     }
 
-    void grow(IndexT n) {
-        unsigned NewSize = toIndex_(n) + 1;
-        if (NewSize > storage_.size())
-            storage_.resize(NewSize, nullVal_);
+    this->moveFromOldBuckets(OldBuckets, OldBuckets+OldNumBuckets);
+
+    // Free the old table.
+    operator delete(OldBuckets);
+  }
+
+  void shrink_and_clear() {
+    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;
+    }
+
+    operator delete(Buckets);
+    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 = 0;
+      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> >
+class SmallDenseMap
+    : public DenseMapBase<SmallDenseMap<KeyT, ValueT, InlineBuckets, KeyInfoT>,
+                          KeyT, ValueT, KeyInfoT> {
+  // Lift some types from the dependent base class into this class for
+  // simplicity of referring to them.
+  typedef DenseMapBase<SmallDenseMap, KeyT, ValueT, KeyInfoT> BaseT;
+  typedef typename BaseT::BucketT BucketT;
+  friend class DenseMapBase<SmallDenseMap, KeyT, ValueT, KeyInfoT>;
+
+  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) {
+    init(0);
+    copyFrom(other);
+  }
+
+#if LLVM_USE_RVALUE_REFERENCES
+  SmallDenseMap(SmallDenseMap &&other) {
+    init(0);
+    swap(other);
+  }
+#endif
+
+  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->first, EmptyKey) &&
+                            !KeyInfoT::isEqual(LHSB->first, TombstoneKey));
+        bool hasRHSValue = (!KeyInfoT::isEqual(RHSB->first, EmptyKey) &&
+                            !KeyInfoT::isEqual(RHSB->first, TombstoneKey));
+        if (hasLHSValue && hasRHSValue) {
+          // Swap together if we can...
+          std::swap(*LHSB, *RHSB);
+          continue;
+        }
+        // Swap separately and handle any assymetry.
+        std::swap(LHSB->first, RHSB->first);
+        if (hasLHSValue) {
+          new (&RHSB->second) ValueT(llvm_move(LHSB->second));
+          LHSB->second.~ValueT();
+        } else if (hasRHSValue) {
+          new (&LHSB->second) ValueT(llvm_move(RHSB->second));
+          RHSB->second.~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 = llvm_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->first) KeyT(llvm_move(OldB->first));
+      OldB->first.~KeyT();
+      if (!KeyInfoT::isEqual(NewB->first, EmptyKey) &&
+          !KeyInfoT::isEqual(NewB->first, TombstoneKey)) {
+        new (&NewB->second) ValueT(llvm_move(OldB->second));
+        OldB->second.~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(llvm_move(TmpRep));
+  }
+
+  SmallDenseMap& operator=(const SmallDenseMap& other) {
+    copyFrom(other);
+    return *this;
+  }
+
+#if LLVM_USE_RVALUE_REFERENCES
+  SmallDenseMap& operator=(SmallDenseMap &&other) {
+    this->destroyAll();
+    deallocateBuckets();
+    init(0);
+    swap(other);
+    return *this;
+  }
+#endif
+
+  void copyFrom(const SmallDenseMap& other) {
+    this->destroyAll();
+    deallocateBuckets();
+    Small = true;
+    if (other.getNumBuckets() > InlineBuckets) {
+      Small = false;
+      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));
+
+    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->first, EmptyKey) &&
+            !KeyInfoT::isEqual(P->first, TombstoneKey)) {
+          assert(size_t(TmpEnd - TmpBegin) < InlineBuckets &&
+                 "Too many inline buckets!");
+          new (&TmpEnd->first) KeyT(llvm_move(P->first));
+          new (&TmpEnd->second) ValueT(llvm_move(P->second));
+          ++TmpEnd;
+          P->second.~ValueT();
+        }
+        P->first.~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 = llvm_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(OldRep.Buckets);
+  }
+
+  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) {
+    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, bool IsConst>
+class DenseMapIterator {
+  typedef std::pair<KeyT, ValueT> Bucket;
+  typedef DenseMapIterator<KeyT, ValueT,
+                           KeyInfoT, true> ConstIterator;
+  friend class DenseMapIterator<KeyT, ValueT, KeyInfoT, true>;
+public:
+  typedef ptrdiff_t difference_type;
+  typedef typename 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(pointer Pos, pointer E, bool NoAdvance = false)
+    : Ptr(Pos), End(E) {
+    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, false>& I)
+    : Ptr(I.Ptr), End(I.End) {}
+
+  reference operator*() const {
+    return *Ptr;
+  }
+  pointer operator->() const {
+    return Ptr;
+  }
+
+  bool operator==(const ConstIterator &RHS) const {
+    return Ptr == RHS.operator->();
+  }
+  bool operator!=(const ConstIterator &RHS) const {
+    return Ptr != RHS.operator->();
+  }
+
+  inline DenseMapIterator& operator++() {  // Preincrement
+    ++Ptr;
+    AdvancePastEmptyBuckets();
+    return *this;
+  }
+  DenseMapIterator operator++(int) {  // Postincrement
+    DenseMapIterator tmp = *this; ++*this; return tmp;
+  }
+
+private:
+  void AdvancePastEmptyBuckets() {
+    const KeyT Empty = KeyInfoT::getEmptyKey();
+    const KeyT Tombstone = KeyInfoT::getTombstoneKey();
+
+    while (Ptr != End &&
+           (KeyInfoT::isEqual(Ptr->first, Empty) ||
+            KeyInfoT::isEqual(Ptr->first, 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 llvm namespace
+} // end namespace llvm
 
 #endif