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+//===- llvm/ADT/SparseBitVector.h - Efficient Sparse BitVector --*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file defines the SparseBitVector class.  See the doxygen comment for
+// SparseBitVector for more details on the algorithm used.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ADT_SPARSEBITVECTOR_H
+#define LLVM_ADT_SPARSEBITVECTOR_H
+
+#include "llvm/Support/ErrorHandling.h"
+#include "llvm/Support/MathExtras.h"
+#include "llvm/Support/raw_ostream.h"
+#include <cassert>
+#include <climits>
+#include <cstring>
+#include <iterator>
+#include <list>
+
+namespace llvm {
+
+/// SparseBitVector is an implementation of a bitvector that is sparse by only
+/// storing the elements that have non-zero bits set.  In order to make this
+/// fast for the most common cases, SparseBitVector is implemented as a linked
+/// list of SparseBitVectorElements.  We maintain a pointer to the last
+/// SparseBitVectorElement accessed (in the form of a list iterator), in order
+/// to make multiple in-order test/set constant time after the first one is
+/// executed.  Note that using vectors to store SparseBitVectorElement's does
+/// not work out very well because it causes insertion in the middle to take
+/// enormous amounts of time with a large amount of bits.  Other structures that
+/// have better worst cases for insertion in the middle (various balanced trees,
+/// etc) do not perform as well in practice as a linked list with this iterator
+/// kept up to date.  They are also significantly more memory intensive.
+
+template <unsigned ElementSize = 128> struct SparseBitVectorElement {
+public:
+  using BitWord = unsigned long;
+  using size_type = unsigned;
+  enum {
+    BITWORD_SIZE = sizeof(BitWord) * CHAR_BIT,
+    BITWORDS_PER_ELEMENT = (ElementSize + BITWORD_SIZE - 1) / BITWORD_SIZE,
+    BITS_PER_ELEMENT = ElementSize
+  };
+
+private:
+  // Index of Element in terms of where first bit starts.
+  unsigned ElementIndex;
+  BitWord Bits[BITWORDS_PER_ELEMENT];
+
+  SparseBitVectorElement() {
+    ElementIndex = ~0U;
+    memset(&Bits[0], 0, sizeof (BitWord) * BITWORDS_PER_ELEMENT);
+  }
+
+public:
+  explicit SparseBitVectorElement(unsigned Idx) {
+    ElementIndex = Idx;
+    memset(&Bits[0], 0, sizeof (BitWord) * BITWORDS_PER_ELEMENT);
+  }
+
+  // Comparison.
+  bool operator==(const SparseBitVectorElement &RHS) const {
+    if (ElementIndex != RHS.ElementIndex)
+      return false;
+    for (unsigned i = 0; i < BITWORDS_PER_ELEMENT; ++i)
+      if (Bits[i] != RHS.Bits[i])
+        return false;
+    return true;
+  }
+
+  bool operator!=(const SparseBitVectorElement &RHS) const {
+    return !(*this == RHS);
+  }
+
+  // Return the bits that make up word Idx in our element.
+  BitWord word(unsigned Idx) const {
+    assert(Idx < BITWORDS_PER_ELEMENT);
+    return Bits[Idx];
+  }
+
+  unsigned index() const {
+    return ElementIndex;
+  }
+
+  bool empty() const {
+    for (unsigned i = 0; i < BITWORDS_PER_ELEMENT; ++i)
+      if (Bits[i])
+        return false;
+    return true;
+  }
+
+  void set(unsigned Idx) {
+    Bits[Idx / BITWORD_SIZE] |= 1L << (Idx % BITWORD_SIZE);
+  }
+
+  bool test_and_set(unsigned Idx) {
+    bool old = test(Idx);
+    if (!old) {
+      set(Idx);
+      return true;
+    }
+    return false;
+  }
+
+  void reset(unsigned Idx) {
+    Bits[Idx / BITWORD_SIZE] &= ~(1L << (Idx % BITWORD_SIZE));
+  }
+
+  bool test(unsigned Idx) const {
+    return Bits[Idx / BITWORD_SIZE] & (1L << (Idx % BITWORD_SIZE));
+  }
+
+  size_type count() const {
+    unsigned NumBits = 0;
+    for (unsigned i = 0; i < BITWORDS_PER_ELEMENT; ++i)
+      NumBits += countPopulation(Bits[i]);
+    return NumBits;
+  }
+
+  /// find_first - Returns the index of the first set bit.
+  int find_first() const {
+    for (unsigned i = 0; i < BITWORDS_PER_ELEMENT; ++i)
+      if (Bits[i] != 0)
+        return i * BITWORD_SIZE + countTrailingZeros(Bits[i]);
+    llvm_unreachable("Illegal empty element");
+  }
+
+  /// find_last - Returns the index of the last set bit.
+  int find_last() const {
+    for (unsigned I = 0; I < BITWORDS_PER_ELEMENT; ++I) {
+      unsigned Idx = BITWORDS_PER_ELEMENT - I - 1;
+      if (Bits[Idx] != 0)
+        return Idx * BITWORD_SIZE + BITWORD_SIZE -
+               countLeadingZeros(Bits[Idx]) - 1;
+    }
+    llvm_unreachable("Illegal empty element");
+  }
+
+  /// find_next - Returns the index of the next set bit starting from the
+  /// "Curr" bit. Returns -1 if the next set bit is not found.
+  int find_next(unsigned Curr) const {
+    if (Curr >= BITS_PER_ELEMENT)
+      return -1;
+
+    unsigned WordPos = Curr / BITWORD_SIZE;
+    unsigned BitPos = Curr % BITWORD_SIZE;
+    BitWord Copy = Bits[WordPos];
+    assert(WordPos <= BITWORDS_PER_ELEMENT
+           && "Word Position outside of element");
+
+    // Mask off previous bits.
+    Copy &= ~0UL << BitPos;
+
+    if (Copy != 0)
+      return WordPos * BITWORD_SIZE + countTrailingZeros(Copy);
+
+    // Check subsequent words.
+    for (unsigned i = WordPos+1; i < BITWORDS_PER_ELEMENT; ++i)
+      if (Bits[i] != 0)
+        return i * BITWORD_SIZE + countTrailingZeros(Bits[i]);
+    return -1;
+  }
+
+  // Union this element with RHS and return true if this one changed.
+  bool unionWith(const SparseBitVectorElement &RHS) {
+    bool changed = false;
+    for (unsigned i = 0; i < BITWORDS_PER_ELEMENT; ++i) {
+      BitWord old = changed ? 0 : Bits[i];
+
+      Bits[i] |= RHS.Bits[i];
+      if (!changed && old != Bits[i])
+        changed = true;
+    }
+    return changed;
+  }
+
+  // Return true if we have any bits in common with RHS
+  bool intersects(const SparseBitVectorElement &RHS) const {
+    for (unsigned i = 0; i < BITWORDS_PER_ELEMENT; ++i) {
+      if (RHS.Bits[i] & Bits[i])
+        return true;
+    }
+    return false;
+  }
+
+  // Intersect this Element with RHS and return true if this one changed.
+  // BecameZero is set to true if this element became all-zero bits.
+  bool intersectWith(const SparseBitVectorElement &RHS,
+                     bool &BecameZero) {
+    bool changed = false;
+    bool allzero = true;
+
+    BecameZero = false;
+    for (unsigned i = 0; i < BITWORDS_PER_ELEMENT; ++i) {
+      BitWord old = changed ? 0 : Bits[i];
+
+      Bits[i] &= RHS.Bits[i];
+      if (Bits[i] != 0)
+        allzero = false;
+
+      if (!changed && old != Bits[i])
+        changed = true;
+    }
+    BecameZero = allzero;
+    return changed;
+  }
+
+  // Intersect this Element with the complement of RHS and return true if this
+  // one changed.  BecameZero is set to true if this element became all-zero
+  // bits.
+  bool intersectWithComplement(const SparseBitVectorElement &RHS,
+                               bool &BecameZero) {
+    bool changed = false;
+    bool allzero = true;
+
+    BecameZero = false;
+    for (unsigned i = 0; i < BITWORDS_PER_ELEMENT; ++i) {
+      BitWord old = changed ? 0 : Bits[i];
+
+      Bits[i] &= ~RHS.Bits[i];
+      if (Bits[i] != 0)
+        allzero = false;
+
+      if (!changed && old != Bits[i])
+        changed = true;
+    }
+    BecameZero = allzero;
+    return changed;
+  }
+
+  // Three argument version of intersectWithComplement that intersects
+  // RHS1 & ~RHS2 into this element
+  void intersectWithComplement(const SparseBitVectorElement &RHS1,
+                               const SparseBitVectorElement &RHS2,
+                               bool &BecameZero) {
+    bool allzero = true;
+
+    BecameZero = false;
+    for (unsigned i = 0; i < BITWORDS_PER_ELEMENT; ++i) {
+      Bits[i] = RHS1.Bits[i] & ~RHS2.Bits[i];
+      if (Bits[i] != 0)
+        allzero = false;
+    }
+    BecameZero = allzero;
+  }
+};
+
+template <unsigned ElementSize = 128>
+class SparseBitVector {
+  using ElementList = std::list<SparseBitVectorElement<ElementSize>>;
+  using ElementListIter = typename ElementList::iterator;
+  using ElementListConstIter = typename ElementList::const_iterator;
+  enum {
+    BITWORD_SIZE = SparseBitVectorElement<ElementSize>::BITWORD_SIZE
+  };
+
+  // Pointer to our current Element.
+  ElementListIter CurrElementIter;
+  ElementList Elements;
+
+  // This is like std::lower_bound, except we do linear searching from the
+  // current position.
+  ElementListIter FindLowerBound(unsigned ElementIndex) {
+
+    if (Elements.empty()) {
+      CurrElementIter = Elements.begin();
+      return Elements.begin();
+    }
+
+    // Make sure our current iterator is valid.
+    if (CurrElementIter == Elements.end())
+      --CurrElementIter;
+
+    // Search from our current iterator, either backwards or forwards,
+    // depending on what element we are looking for.
+    ElementListIter ElementIter = CurrElementIter;
+    if (CurrElementIter->index() == ElementIndex) {
+      return ElementIter;
+    } else if (CurrElementIter->index() > ElementIndex) {
+      while (ElementIter != Elements.begin()
+             && ElementIter->index() > ElementIndex)
+        --ElementIter;
+    } else {
+      while (ElementIter != Elements.end() &&
+             ElementIter->index() < ElementIndex)
+        ++ElementIter;
+    }
+    CurrElementIter = ElementIter;
+    return ElementIter;
+  }
+
+  // Iterator to walk set bits in the bitmap.  This iterator is a lot uglier
+  // than it would be, in order to be efficient.
+  class SparseBitVectorIterator {
+  private:
+    bool AtEnd;
+
+    const SparseBitVector<ElementSize> *BitVector = nullptr;
+
+    // Current element inside of bitmap.
+    ElementListConstIter Iter;
+
+    // Current bit number inside of our bitmap.
+    unsigned BitNumber;
+
+    // Current word number inside of our element.
+    unsigned WordNumber;
+
+    // Current bits from the element.
+    typename SparseBitVectorElement<ElementSize>::BitWord Bits;
+
+    // Move our iterator to the first non-zero bit in the bitmap.
+    void AdvanceToFirstNonZero() {
+      if (AtEnd)
+        return;
+      if (BitVector->Elements.empty()) {
+        AtEnd = true;
+        return;
+      }
+      Iter = BitVector->Elements.begin();
+      BitNumber = Iter->index() * ElementSize;
+      unsigned BitPos = Iter->find_first();
+      BitNumber += BitPos;
+      WordNumber = (BitNumber % ElementSize) / BITWORD_SIZE;
+      Bits = Iter->word(WordNumber);
+      Bits >>= BitPos % BITWORD_SIZE;
+    }
+
+    // Move our iterator to the next non-zero bit.
+    void AdvanceToNextNonZero() {
+      if (AtEnd)
+        return;
+
+      while (Bits && !(Bits & 1)) {
+        Bits >>= 1;
+        BitNumber += 1;
+      }
+
+      // See if we ran out of Bits in this word.
+      if (!Bits) {
+        int NextSetBitNumber = Iter->find_next(BitNumber % ElementSize) ;
+        // If we ran out of set bits in this element, move to next element.
+        if (NextSetBitNumber == -1 || (BitNumber % ElementSize == 0)) {
+          ++Iter;
+          WordNumber = 0;
+
+          // We may run out of elements in the bitmap.
+          if (Iter == BitVector->Elements.end()) {
+            AtEnd = true;
+            return;
+          }
+          // Set up for next non-zero word in bitmap.
+          BitNumber = Iter->index() * ElementSize;
+          NextSetBitNumber = Iter->find_first();
+          BitNumber += NextSetBitNumber;
+          WordNumber = (BitNumber % ElementSize) / BITWORD_SIZE;
+          Bits = Iter->word(WordNumber);
+          Bits >>= NextSetBitNumber % BITWORD_SIZE;
+        } else {
+          WordNumber = (NextSetBitNumber % ElementSize) / BITWORD_SIZE;
+          Bits = Iter->word(WordNumber);
+          Bits >>= NextSetBitNumber % BITWORD_SIZE;
+          BitNumber = Iter->index() * ElementSize;
+          BitNumber += NextSetBitNumber;
+        }
+      }
+    }
+
+  public:
+    SparseBitVectorIterator() = default;
+
+    SparseBitVectorIterator(const SparseBitVector<ElementSize> *RHS,
+                            bool end = false):BitVector(RHS) {
+      Iter = BitVector->Elements.begin();
+      BitNumber = 0;
+      Bits = 0;
+      WordNumber = ~0;
+      AtEnd = end;
+      AdvanceToFirstNonZero();
+    }
+
+    // Preincrement.
+    inline SparseBitVectorIterator& operator++() {
+      ++BitNumber;
+      Bits >>= 1;
+      AdvanceToNextNonZero();
+      return *this;
+    }
+
+    // Postincrement.
+    inline SparseBitVectorIterator operator++(int) {
+      SparseBitVectorIterator tmp = *this;
+      ++*this;
+      return tmp;
+    }
+
+    // Return the current set bit number.
+    unsigned operator*() const {
+      return BitNumber;
+    }
+
+    bool operator==(const SparseBitVectorIterator &RHS) const {
+      // If they are both at the end, ignore the rest of the fields.
+      if (AtEnd && RHS.AtEnd)
+        return true;
+      // Otherwise they are the same if they have the same bit number and
+      // bitmap.
+      return AtEnd == RHS.AtEnd && RHS.BitNumber == BitNumber;
+    }
+
+    bool operator!=(const SparseBitVectorIterator &RHS) const {
+      return !(*this == RHS);
+    }
+  };
+
+public:
+  using iterator = SparseBitVectorIterator;
+
+  SparseBitVector() {
+    CurrElementIter = Elements.begin();
+  }
+
+  // SparseBitVector copy ctor.
+  SparseBitVector(const SparseBitVector &RHS) {
+    ElementListConstIter ElementIter = RHS.Elements.begin();
+    while (ElementIter != RHS.Elements.end()) {
+      Elements.push_back(SparseBitVectorElement<ElementSize>(*ElementIter));
+      ++ElementIter;
+    }
+
+    CurrElementIter = Elements.begin ();
+  }
+
+  ~SparseBitVector() = default;
+
+  // Clear.
+  void clear() {
+    Elements.clear();
+  }
+
+  // Assignment
+  SparseBitVector& operator=(const SparseBitVector& RHS) {
+    if (this == &RHS)
+      return *this;
+
+    Elements.clear();
+
+    ElementListConstIter ElementIter = RHS.Elements.begin();
+    while (ElementIter != RHS.Elements.end()) {
+      Elements.push_back(SparseBitVectorElement<ElementSize>(*ElementIter));
+      ++ElementIter;
+    }
+
+    CurrElementIter = Elements.begin ();
+
+    return *this;
+  }
+
+  // Test, Reset, and Set a bit in the bitmap.
+  bool test(unsigned Idx) {
+    if (Elements.empty())
+      return false;
+
+    unsigned ElementIndex = Idx / ElementSize;
+    ElementListIter ElementIter = FindLowerBound(ElementIndex);
+
+    // If we can't find an element that is supposed to contain this bit, there
+    // is nothing more to do.
+    if (ElementIter == Elements.end() ||
+        ElementIter->index() != ElementIndex)
+      return false;
+    return ElementIter->test(Idx % ElementSize);
+  }
+
+  void reset(unsigned Idx) {
+    if (Elements.empty())
+      return;
+
+    unsigned ElementIndex = Idx / ElementSize;
+    ElementListIter ElementIter = FindLowerBound(ElementIndex);
+
+    // If we can't find an element that is supposed to contain this bit, there
+    // is nothing more to do.
+    if (ElementIter == Elements.end() ||
+        ElementIter->index() != ElementIndex)
+      return;
+    ElementIter->reset(Idx % ElementSize);
+
+    // When the element is zeroed out, delete it.
+    if (ElementIter->empty()) {
+      ++CurrElementIter;
+      Elements.erase(ElementIter);
+    }
+  }
+
+  void set(unsigned Idx) {
+    unsigned ElementIndex = Idx / ElementSize;
+    ElementListIter ElementIter;
+    if (Elements.empty()) {
+      ElementIter = Elements.emplace(Elements.end(), ElementIndex);
+    } else {
+      ElementIter = FindLowerBound(ElementIndex);
+
+      if (ElementIter == Elements.end() ||
+          ElementIter->index() != ElementIndex) {
+        // We may have hit the beginning of our SparseBitVector, in which case,
+        // we may need to insert right after this element, which requires moving
+        // the current iterator forward one, because insert does insert before.
+        if (ElementIter != Elements.end() &&
+            ElementIter->index() < ElementIndex)
+          ++ElementIter;
+        ElementIter = Elements.emplace(ElementIter, ElementIndex);
+      }
+    }
+    CurrElementIter = ElementIter;
+
+    ElementIter->set(Idx % ElementSize);
+  }
+
+  bool test_and_set(unsigned Idx) {
+    bool old = test(Idx);
+    if (!old) {
+      set(Idx);
+      return true;
+    }
+    return false;
+  }
+
+  bool operator!=(const SparseBitVector &RHS) const {
+    return !(*this == RHS);
+  }
+
+  bool operator==(const SparseBitVector &RHS) const {
+    ElementListConstIter Iter1 = Elements.begin();
+    ElementListConstIter Iter2 = RHS.Elements.begin();
+
+    for (; Iter1 != Elements.end() && Iter2 != RHS.Elements.end();
+         ++Iter1, ++Iter2) {
+      if (*Iter1 != *Iter2)
+        return false;
+    }
+    return Iter1 == Elements.end() && Iter2 == RHS.Elements.end();
+  }
+
+  // Union our bitmap with the RHS and return true if we changed.
+  bool operator|=(const SparseBitVector &RHS) {
+    if (this == &RHS)
+      return false;
+
+    bool changed = false;
+    ElementListIter Iter1 = Elements.begin();
+    ElementListConstIter Iter2 = RHS.Elements.begin();
+
+    // If RHS is empty, we are done
+    if (RHS.Elements.empty())
+      return false;
+
+    while (Iter2 != RHS.Elements.end()) {
+      if (Iter1 == Elements.end() || Iter1->index() > Iter2->index()) {
+        Elements.insert(Iter1, *Iter2);
+        ++Iter2;
+        changed = true;
+      } else if (Iter1->index() == Iter2->index()) {
+        changed |= Iter1->unionWith(*Iter2);
+        ++Iter1;
+        ++Iter2;
+      } else {
+        ++Iter1;
+      }
+    }
+    CurrElementIter = Elements.begin();
+    return changed;
+  }
+
+  // Intersect our bitmap with the RHS and return true if ours changed.
+  bool operator&=(const SparseBitVector &RHS) {
+    if (this == &RHS)
+      return false;
+
+    bool changed = false;
+    ElementListIter Iter1 = Elements.begin();
+    ElementListConstIter Iter2 = RHS.Elements.begin();
+
+    // Check if both bitmaps are empty.
+    if (Elements.empty() && RHS.Elements.empty())
+      return false;
+
+    // Loop through, intersecting as we go, erasing elements when necessary.
+    while (Iter2 != RHS.Elements.end()) {
+      if (Iter1 == Elements.end()) {
+        CurrElementIter = Elements.begin();
+        return changed;
+      }
+
+      if (Iter1->index() > Iter2->index()) {
+        ++Iter2;
+      } else if (Iter1->index() == Iter2->index()) {
+        bool BecameZero;
+        changed |= Iter1->intersectWith(*Iter2, BecameZero);
+        if (BecameZero) {
+          ElementListIter IterTmp = Iter1;
+          ++Iter1;
+          Elements.erase(IterTmp);
+        } else {
+          ++Iter1;
+        }
+        ++Iter2;
+      } else {
+        ElementListIter IterTmp = Iter1;
+        ++Iter1;
+        Elements.erase(IterTmp);
+        changed = true;
+      }
+    }
+    if (Iter1 != Elements.end()) {
+      Elements.erase(Iter1, Elements.end());
+      changed = true;
+    }
+    CurrElementIter = Elements.begin();
+    return changed;
+  }
+
+  // Intersect our bitmap with the complement of the RHS and return true
+  // if ours changed.
+  bool intersectWithComplement(const SparseBitVector &RHS) {
+    if (this == &RHS) {
+      if (!empty()) {
+        clear();
+        return true;
+      }
+      return false;
+    }
+
+    bool changed = false;
+    ElementListIter Iter1 = Elements.begin();
+    ElementListConstIter Iter2 = RHS.Elements.begin();
+
+    // If either our bitmap or RHS is empty, we are done
+    if (Elements.empty() || RHS.Elements.empty())
+      return false;
+
+    // Loop through, intersecting as we go, erasing elements when necessary.
+    while (Iter2 != RHS.Elements.end()) {
+      if (Iter1 == Elements.end()) {
+        CurrElementIter = Elements.begin();
+        return changed;
+      }
+
+      if (Iter1->index() > Iter2->index()) {
+        ++Iter2;
+      } else if (Iter1->index() == Iter2->index()) {
+        bool BecameZero;
+        changed |= Iter1->intersectWithComplement(*Iter2, BecameZero);
+        if (BecameZero) {
+          ElementListIter IterTmp = Iter1;
+          ++Iter1;
+          Elements.erase(IterTmp);
+        } else {
+          ++Iter1;
+        }
+        ++Iter2;
+      } else {
+        ++Iter1;
+      }
+    }
+    CurrElementIter = Elements.begin();
+    return changed;
+  }
+
+  bool intersectWithComplement(const SparseBitVector<ElementSize> *RHS) const {
+    return intersectWithComplement(*RHS);
+  }
+
+  //  Three argument version of intersectWithComplement.
+  //  Result of RHS1 & ~RHS2 is stored into this bitmap.
+  void intersectWithComplement(const SparseBitVector<ElementSize> &RHS1,
+                               const SparseBitVector<ElementSize> &RHS2)
+  {
+    if (this == &RHS1) {
+      intersectWithComplement(RHS2);
+      return;
+    } else if (this == &RHS2) {
+      SparseBitVector RHS2Copy(RHS2);
+      intersectWithComplement(RHS1, RHS2Copy);
+      return;
+    }
+
+    Elements.clear();
+    CurrElementIter = Elements.begin();
+    ElementListConstIter Iter1 = RHS1.Elements.begin();
+    ElementListConstIter Iter2 = RHS2.Elements.begin();
+
+    // If RHS1 is empty, we are done
+    // If RHS2 is empty, we still have to copy RHS1
+    if (RHS1.Elements.empty())
+      return;
+
+    // Loop through, intersecting as we go, erasing elements when necessary.
+    while (Iter2 != RHS2.Elements.end()) {
+      if (Iter1 == RHS1.Elements.end())
+        return;
+
+      if (Iter1->index() > Iter2->index()) {
+        ++Iter2;
+      } else if (Iter1->index() == Iter2->index()) {
+        bool BecameZero = false;
+        Elements.emplace_back(Iter1->index());
+        Elements.back().intersectWithComplement(*Iter1, *Iter2, BecameZero);
+        if (BecameZero)
+          Elements.pop_back();
+        ++Iter1;
+        ++Iter2;
+      } else {
+        Elements.push_back(*Iter1++);
+      }
+    }
+
+    // copy the remaining elements
+    std::copy(Iter1, RHS1.Elements.end(), std::back_inserter(Elements));
+  }
+
+  void intersectWithComplement(const SparseBitVector<ElementSize> *RHS1,
+                               const SparseBitVector<ElementSize> *RHS2) {
+    intersectWithComplement(*RHS1, *RHS2);
+  }
+
+  bool intersects(const SparseBitVector<ElementSize> *RHS) const {
+    return intersects(*RHS);
+  }
+
+  // Return true if we share any bits in common with RHS
+  bool intersects(const SparseBitVector<ElementSize> &RHS) const {
+    ElementListConstIter Iter1 = Elements.begin();
+    ElementListConstIter Iter2 = RHS.Elements.begin();
+
+    // Check if both bitmaps are empty.
+    if (Elements.empty() && RHS.Elements.empty())
+      return false;
+
+    // Loop through, intersecting stopping when we hit bits in common.
+    while (Iter2 != RHS.Elements.end()) {
+      if (Iter1 == Elements.end())
+        return false;
+
+      if (Iter1->index() > Iter2->index()) {
+        ++Iter2;
+      } else if (Iter1->index() == Iter2->index()) {
+        if (Iter1->intersects(*Iter2))
+          return true;
+        ++Iter1;
+        ++Iter2;
+      } else {
+        ++Iter1;
+      }
+    }
+    return false;
+  }
+
+  // Return true iff all bits set in this SparseBitVector are
+  // also set in RHS.
+  bool contains(const SparseBitVector<ElementSize> &RHS) const {
+    SparseBitVector<ElementSize> Result(*this);
+    Result &= RHS;
+    return (Result == RHS);
+  }
+
+  // Return the first set bit in the bitmap.  Return -1 if no bits are set.
+  int find_first() const {
+    if (Elements.empty())
+      return -1;
+    const SparseBitVectorElement<ElementSize> &First = *(Elements.begin());
+    return (First.index() * ElementSize) + First.find_first();
+  }
+
+  // Return the last set bit in the bitmap.  Return -1 if no bits are set.
+  int find_last() const {
+    if (Elements.empty())
+      return -1;
+    const SparseBitVectorElement<ElementSize> &Last = *(Elements.rbegin());
+    return (Last.index() * ElementSize) + Last.find_last();
+  }
+
+  // Return true if the SparseBitVector is empty
+  bool empty() const {
+    return Elements.empty();
+  }
+
+  unsigned count() const {
+    unsigned BitCount = 0;
+    for (ElementListConstIter Iter = Elements.begin();
+         Iter != Elements.end();
+         ++Iter)
+      BitCount += Iter->count();
+
+    return BitCount;
+  }
+
+  iterator begin() const {
+    return iterator(this);
+  }
+
+  iterator end() const {
+    return iterator(this, true);
+  }
+};
+
+// Convenience functions to allow Or and And without dereferencing in the user
+// code.
+
+template <unsigned ElementSize>
+inline bool operator |=(SparseBitVector<ElementSize> &LHS,
+                        const SparseBitVector<ElementSize> *RHS) {
+  return LHS |= *RHS;
+}
+
+template <unsigned ElementSize>
+inline bool operator |=(SparseBitVector<ElementSize> *LHS,
+                        const SparseBitVector<ElementSize> &RHS) {
+  return LHS->operator|=(RHS);
+}
+
+template <unsigned ElementSize>
+inline bool operator &=(SparseBitVector<ElementSize> *LHS,
+                        const SparseBitVector<ElementSize> &RHS) {
+  return LHS->operator&=(RHS);
+}
+
+template <unsigned ElementSize>
+inline bool operator &=(SparseBitVector<ElementSize> &LHS,
+                        const SparseBitVector<ElementSize> *RHS) {
+  return LHS &= *RHS;
+}
+
+// Convenience functions for infix union, intersection, difference operators.
+
+template <unsigned ElementSize>
+inline SparseBitVector<ElementSize>
+operator|(const SparseBitVector<ElementSize> &LHS,
+          const SparseBitVector<ElementSize> &RHS) {
+  SparseBitVector<ElementSize> Result(LHS);
+  Result |= RHS;
+  return Result;
+}
+
+template <unsigned ElementSize>
+inline SparseBitVector<ElementSize>
+operator&(const SparseBitVector<ElementSize> &LHS,
+          const SparseBitVector<ElementSize> &RHS) {
+  SparseBitVector<ElementSize> Result(LHS);
+  Result &= RHS;
+  return Result;
+}
+
+template <unsigned ElementSize>
+inline SparseBitVector<ElementSize>
+operator-(const SparseBitVector<ElementSize> &LHS,
+          const SparseBitVector<ElementSize> &RHS) {
+  SparseBitVector<ElementSize> Result;
+  Result.intersectWithComplement(LHS, RHS);
+  return Result;
+}
+
+// Dump a SparseBitVector to a stream
+template <unsigned ElementSize>
+void dump(const SparseBitVector<ElementSize> &LHS, raw_ostream &out) {
+  out << "[";
+
+  typename SparseBitVector<ElementSize>::iterator bi = LHS.begin(),
+    be = LHS.end();
+  if (bi != be) {
+    out << *bi;
+    for (++bi; bi != be; ++bi) {
+      out << " " << *bi;
+    }
+  }
+  out << "]\n";
+}
+
+} // end namespace llvm
+
+#endif // LLVM_ADT_SPARSEBITVECTOR_H