5 files changed, 804 insertions, 91 deletions

diff --git a/include/llvm/ADT/SparseMultiSet.h b/include/llvm/ADT/SparseMultiSet.h
new file mode 100644
index 0000000000..749b5c0e21
--- /dev/null
+++ b/include/llvm/ADT/SparseMultiSet.h
@@ -0,0 +1,526 @@
+//===--- llvm/ADT/SparseMultiSet.h - Sparse multiset ------------*- 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 SparseMultiSet class, which adds multiset behavior to
+// the SparseSet.
+//
+// A sparse multiset holds a small number of objects identified by integer keys
+// from a moderately sized universe. The sparse multiset uses more memory than
+// other containers in order to provide faster operations. Any key can map to
+// multiple values. A SparseMultiSetNode class is provided, which serves as a
+// convenient base class for the contents of a SparseMultiSet.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ADT_SPARSEMULTISET_H
+#define LLVM_ADT_SPARSEMULTISET_H
+
+#include "llvm/ADT/SparseSet.h"
+
+namespace llvm {
+
+/// Fast multiset implementation for objects that can be identified by small
+/// unsigned keys.
+///
+/// SparseMultiSet allocates memory proportional to the size of the key
+/// universe, so it is not recommended for building composite data structures.
+/// It is useful for algorithms that require a single set with fast operations.
+///
+/// Compared to DenseSet and DenseMap, SparseMultiSet provides constant-time
+/// fast clear() as fast as a vector.  The find(), insert(), and erase()
+/// operations are all constant time, and typically faster than a hash table.
+/// The iteration order doesn't depend on numerical key values, it only depends
+/// on the order of insert() and erase() operations.  Iteration order is the
+/// insertion order. Iteration is only provided over elements of equivalent
+/// keys, but iterators are bidirectional.
+///
+/// Compared to BitVector, SparseMultiSet<unsigned> uses 8x-40x more memory, but
+/// offers constant-time clear() and size() operations as well as fast iteration
+/// independent on the size of the universe.
+///
+/// SparseMultiSet contains a dense vector holding all the objects and a sparse
+/// array holding indexes into the dense vector.  Most of the memory is used by
+/// the sparse array which is the size of the key universe. The SparseT template
+/// parameter provides a space/speed tradeoff for sets holding many elements.
+///
+/// When SparseT is uint32_t, find() only touches up to 3 cache lines, but the
+/// sparse array uses 4 x Universe bytes.
+///
+/// When SparseT is uint8_t (the default), find() touches up to 3+[N/256] cache
+/// lines, but the sparse array is 4x smaller.  N is the number of elements in
+/// the set.
+///
+/// For sets that may grow to thousands of elements, SparseT should be set to
+/// uint16_t or uint32_t.
+///
+/// Multiset behavior is provided by providing doubly linked lists for values
+/// that are inlined in the dense vector. SparseMultiSet is a good choice when
+/// one desires a growable number of entries per key, as it will retain the
+/// SparseSet algorithmic properties despite being growable. Thus, it is often a
+/// better choice than a SparseSet of growable containers or a vector of
+/// vectors. SparseMultiSet also keeps iterators valid after erasure (provided
+/// the iterators don't point to the element erased), allowing for more
+/// intuitive and fast removal.
+///
+/// @tparam ValueT      The type of objects in the set.
+/// @tparam KeyFunctorT A functor that computes an unsigned index from KeyT.
+/// @tparam SparseT     An unsigned integer type. See above.
+///
+template<typename ValueT,
+         typename KeyFunctorT = llvm::identity<unsigned>,
+         typename SparseT = uint8_t>
+class SparseMultiSet {
+  /// The actual data that's stored, as a doubly-linked list implemented via
+  /// indices into the DenseVector.  The doubly linked list is implemented
+  /// circular in Prev indices, and INVALID-terminated in Next indices. This
+  /// provides efficient access to list tails. These nodes can also be
+  /// tombstones, in which case they are actually nodes in a single-linked
+  /// freelist of recyclable slots.
+  struct SMSNode {
+    static const unsigned INVALID = ~0U;
+
+    ValueT Data;
+    unsigned Prev;
+    unsigned Next;
+
+    SMSNode(ValueT D, unsigned P, unsigned N) : Data(D), Prev(P), Next(N) { }
+
+    /// List tails have invalid Nexts.
+    bool isTail() const {
+      return Next == INVALID;
+    }
+
+    /// Whether this node is a tombstone node, and thus is in our freelist.
+    bool isTombstone() const {
+      return Prev == INVALID;
+    }
+
+    /// Since the list is circular in Prev, all non-tombstone nodes have a valid
+    /// Prev.
+    bool isValid() const { return Prev != INVALID; }
+  };
+
+  typedef typename KeyFunctorT::argument_type KeyT;
+  typedef SmallVector<SMSNode, 8> DenseT;
+  DenseT Dense;
+  SparseT *Sparse;
+  unsigned Universe;
+  KeyFunctorT KeyIndexOf;
+  SparseSetValFunctor<KeyT, ValueT, KeyFunctorT> ValIndexOf;
+
+  /// We have a built-in recycler for reusing tombstone slots. This recycler
+  /// puts a singly-linked free list into tombstone slots, allowing us quick
+  /// erasure, iterator preservation, and dense size.
+  unsigned FreelistIdx;
+  unsigned NumFree;
+
+  unsigned sparseIndex(const ValueT &Val) const {
+    assert(ValIndexOf(Val) < Universe &&
+           "Invalid key in set. Did object mutate?");
+    return ValIndexOf(Val);
+  }
+  unsigned sparseIndex(const SMSNode &N) const { return sparseIndex(N.Data); }
+
+  // Disable copy construction and assignment.
+  // This data structure is not meant to be used that way.
+  SparseMultiSet(const SparseMultiSet&) LLVM_DELETED_FUNCTION;
+  SparseMultiSet &operator=(const SparseMultiSet&) LLVM_DELETED_FUNCTION;
+
+  /// Whether the given entry is the head of the list. List heads's previous
+  /// pointers are to the tail of the list, allowing for efficient access to the
+  /// list tail. D must be a valid entry node.
+  bool isHead(const SMSNode &D) const {
+    assert(D.isValid() && "Invalid node for head");
+    return Dense[D.Prev].isTail();
+  }
+
+  /// Whether the given entry is a singleton entry, i.e. the only entry with
+  /// that key.
+  bool isSingleton(const SMSNode &N) const {
+    assert(N.isValid() && "Invalid node for singleton");
+    // Is N its own predecessor?
+    return &Dense[N.Prev] == &N;
+  }
+
+  /// Add in the given SMSNode. Uses a free entry in our freelist if
+  /// available. Returns the index of the added node.
+  unsigned addValue(const ValueT& V, unsigned Prev, unsigned Next) {
+    if (NumFree == 0) {
+      Dense.push_back(SMSNode(V, Prev, Next));
+      return Dense.size() - 1;
+    }
+
+    // Peel off a free slot
+    unsigned Idx = FreelistIdx;
+    unsigned NextFree = Dense[Idx].Next;
+    assert(Dense[Idx].isTombstone() && "Non-tombstone free?");
+
+    Dense[Idx] = SMSNode(V, Prev, Next);
+    FreelistIdx = NextFree;
+    --NumFree;
+    return Idx;
+  }
+
+  /// Make the current index a new tombstone. Pushes it onto the freelist.
+  void makeTombstone(unsigned Idx) {
+    Dense[Idx].Prev = SMSNode::INVALID;
+    Dense[Idx].Next = FreelistIdx;
+    FreelistIdx = Idx;
+    ++NumFree;
+  }
+
+public:
+  typedef ValueT value_type;
+  typedef ValueT &reference;
+  typedef const ValueT &const_reference;
+  typedef ValueT *pointer;
+  typedef const ValueT *const_pointer;
+
+  SparseMultiSet()
+    : Sparse(0), Universe(0), FreelistIdx(SMSNode::INVALID), NumFree(0) { }
+
+  ~SparseMultiSet() { free(Sparse); }
+
+  /// Set the universe size which determines the largest key the set can hold.
+  /// The universe must be sized before any elements can be added.
+  ///
+  /// @param U Universe size. All object keys must be less than U.
+  ///
+  void setUniverse(unsigned U) {
+    // It's not hard to resize the universe on a non-empty set, but it doesn't
+    // seem like a likely use case, so we can add that code when we need it.
+    assert(empty() && "Can only resize universe on an empty map");
+    // Hysteresis prevents needless reallocations.
+    if (U >= Universe/4 && U <= Universe)
+      return;
+    free(Sparse);
+    // The Sparse array doesn't actually need to be initialized, so malloc
+    // would be enough here, but that will cause tools like valgrind to
+    // complain about branching on uninitialized data.
+    Sparse = reinterpret_cast<SparseT*>(calloc(U, sizeof(SparseT)));
+    Universe = U;
+  }
+
+  /// Our iterators are iterators over the collection of objects that share a
+  /// key.
+  template<typename SMSPtrTy>
+  class iterator_base : public std::iterator<std::bidirectional_iterator_tag,
+                                             ValueT> {
+    friend class SparseMultiSet;
+    SMSPtrTy SMS;
+    unsigned Idx;
+    unsigned SparseIdx;
+
+    iterator_base(SMSPtrTy P, unsigned I, unsigned SI)
+      : SMS(P), Idx(I), SparseIdx(SI) { }
+
+    /// Whether our iterator has fallen outside our dense vector.
+    bool isEnd() const {
+      if (Idx == SMSNode::INVALID)
+        return true;
+
+      assert(Idx < SMS->Dense.size() && "Out of range, non-INVALID Idx?");
+      return false;
+    }
+
+    /// Whether our iterator is properly keyed, i.e. the SparseIdx is valid
+    bool isKeyed() const { return SparseIdx < SMS->Universe; }
+
+    unsigned Prev() const { return SMS->Dense[Idx].Prev; }
+    unsigned Next() const { return SMS->Dense[Idx].Next; }
+
+    void setPrev(unsigned P) { SMS->Dense[Idx].Prev = P; }
+    void setNext(unsigned N) { SMS->Dense[Idx].Next = N; }
+
+  public:
+    typedef std::iterator<std::bidirectional_iterator_tag, ValueT> super;
+    typedef typename super::value_type value_type;
+    typedef typename super::difference_type difference_type;
+    typedef typename super::pointer pointer;
+    typedef typename super::reference reference;
+
+    iterator_base(const iterator_base &RHS)
+      : SMS(RHS.SMS), Idx(RHS.Idx), SparseIdx(RHS.SparseIdx) { }
+
+    const iterator_base &operator=(const iterator_base &RHS) {
+      SMS = RHS.SMS;
+      Idx = RHS.Idx;
+      SparseIdx = RHS.SparseIdx;
+      return *this;
+    }
+
+    reference operator*() const {
+      assert(isKeyed() && SMS->sparseIndex(SMS->Dense[Idx].Data) == SparseIdx &&
+             "Dereferencing iterator of invalid key or index");
+
+      return SMS->Dense[Idx].Data;
+    }
+    pointer operator->() const { return &operator*(); }
+
+    /// Comparison operators
+    bool operator==(const iterator_base &RHS) const {
+      // end compares equal
+      if (SMS == RHS.SMS && Idx == RHS.Idx) {
+        assert(isEnd() || SparseIdx == RHS.SparseIdx &&
+               "Same dense entry, but different keys?");
+        return true;
+      }
+
+      return false;
+    }
+
+    bool operator!=(const iterator_base &RHS) const {
+      return !operator==(RHS);
+    }
+
+    /// Increment and decrement operators
+    iterator_base &operator--() { // predecrement - Back up
+      assert(isKeyed() && "Decrementing an invalid iterator");
+      assert(isEnd() || !SMS->isHead(SMS->Dense[Idx]) &&
+             "Decrementing head of list");
+
+      // If we're at the end, then issue a new find()
+      if (isEnd())
+        Idx = SMS->findIndex(SparseIdx).Prev();
+      else
+        Idx = Prev();
+
+      return *this;
+    }
+    iterator_base &operator++() { // preincrement - Advance
+      assert(!isEnd() && isKeyed() && "Incrementing an invalid/end iterator");
+      Idx = Next();
+      return *this;
+    }
+    iterator_base operator--(int) { // postdecrement
+      iterator_base I(*this);
+      --*this;
+      return I;
+    }
+    iterator_base operator++(int) { // postincrement
+      iterator_base I(*this);
+      ++*this;
+      return I;
+    }
+  };
+  typedef iterator_base<SparseMultiSet *> iterator;
+  typedef iterator_base<const SparseMultiSet *> const_iterator;
+
+  // Convenience types
+  typedef std::pair<iterator, iterator> RangePair;
+
+  /// Returns an iterator past this container. Note that such an iterator cannot
+  /// be decremented, but will compare equal to other end iterators.
+  iterator end() { return iterator(this, SMSNode::INVALID, SMSNode::INVALID); }
+  const_iterator end() const {
+    return const_iterator(this, SMSNode::INVALID, SMSNode::INVALID);
+  }
+
+  /// Returns true if the set is empty.
+  ///
+  /// This is not the same as BitVector::empty().
+  ///
+  bool empty() const { return size() == 0; }
+
+  /// Returns the number of elements in the set.
+  ///
+  /// This is not the same as BitVector::size() which returns the size of the
+  /// universe.
+  ///
+  unsigned size() const {
+    assert(NumFree <= Dense.size() && "Out-of-bounds free entries");
+    return Dense.size() - NumFree;
+  }
+
+  /// Clears the set.  This is a very fast constant time operation.
+  ///
+  void clear() {
+    // Sparse does not need to be cleared, see find().
+    Dense.clear();
+    NumFree = 0;
+    FreelistIdx = SMSNode::INVALID;
+  }
+
+  /// Find an element by its index.
+  ///
+  /// @param   Idx A valid index to find.
+  /// @returns An iterator to the element identified by key, or end().
+  ///
+  iterator findIndex(unsigned Idx) {
+    assert(Idx < Universe && "Key out of range");
+    assert(std::numeric_limits<SparseT>::is_integer &&
+           !std::numeric_limits<SparseT>::is_signed &&
+           "SparseT must be an unsigned integer type");
+    const unsigned Stride = std::numeric_limits<SparseT>::max() + 1u;
+    for (unsigned i = Sparse[Idx], e = Dense.size(); i < e; i += Stride) {
+      const unsigned FoundIdx = sparseIndex(Dense[i]);
+      // Check that we're pointing at the correct entry and that it is the head
+      // of a valid list.
+      if (Idx == FoundIdx && Dense[i].isValid() && isHead(Dense[i]))
+        return iterator(this, i, Idx);
+      // Stride is 0 when SparseT >= unsigned.  We don't need to loop.
+      if (!Stride)
+        break;
+    }
+    return end();
+  }
+
+  /// Find an element by its key.
+  ///
+  /// @param   Key A valid key to find.
+  /// @returns An iterator to the element identified by key, or end().
+  ///
+  iterator find(const KeyT &Key) {
+    return findIndex(KeyIndexOf(Key));
+  }
+
+  const_iterator find(const KeyT &Key) const {
+    iterator I = const_cast<SparseMultiSet*>(this)->findIndex(KeyIndexOf(Key));
+    return const_iterator(I.SMS, I.Idx, KeyIndexOf(Key));
+  }
+
+  /// Returns the number of elements identified by Key. This will be linear in
+  /// the number of elements of that key.
+  unsigned count(const KeyT &Key) const {
+    unsigned Ret = 0;
+    for (const_iterator It = find(Key); It != end(); ++It)
+      ++Ret;
+
+    return Ret;
+  }
+
+  /// Returns true if this set contains an element identified by Key.
+  bool contains(const KeyT &Key) const {
+    return find(Key) != end();
+  }
+
+  /// Return the head and tail of the subset's list, otherwise returns end().
+  iterator getHead(const KeyT &Key) { return find(Key); }
+  iterator getTail(const KeyT &Key) {
+    iterator I = find(Key);
+    if (I != end())
+      I = iterator(this, I.Prev(), KeyIndexOf(Key));
+    return I;
+  }
+
+  /// The bounds of the range of items sharing Key K. First member is the head
+  /// of the list, and the second member is a decrementable end iterator for
+  /// that key.
+  RangePair equal_range(const KeyT &K) {
+    iterator B = find(K);
+    iterator E = iterator(this, SMSNode::INVALID, B.SparseIdx);
+    return make_pair(B, E);
+  }
+
+  /// Insert a new element at the tail of the subset list. Returns an iterator
+  /// to the newly added entry.
+  iterator insert(const ValueT &Val) {
+    unsigned Idx = sparseIndex(Val);
+    iterator I = findIndex(Idx);
+
+    unsigned NodeIdx = addValue(Val, SMSNode::INVALID, SMSNode::INVALID);
+
+    if (I == end()) {
+      // Make a singleton list
+      Sparse[Idx] = NodeIdx;
+      Dense[NodeIdx].Prev = NodeIdx;
+      return iterator(this, NodeIdx, Idx);
+    }
+
+    // Stick it at the end.
+    unsigned HeadIdx = I.Idx;
+    unsigned TailIdx = I.Prev();
+    Dense[TailIdx].Next = NodeIdx;
+    Dense[HeadIdx].Prev = NodeIdx;
+    Dense[NodeIdx].Prev = TailIdx;
+
+    return iterator(this, NodeIdx, Idx);
+  }
+
+  /// Erases an existing element identified by a valid iterator.
+  ///
+  /// This invalidates iterators pointing at the same entry, but erase() returns
+  /// an iterator pointing to the next element in the subset's list. This makes
+  /// it possible to erase selected elements while iterating over the subset:
+  ///
+  ///   tie(I, E) = Set.equal_range(Key);
+  ///   while (I != E)
+  ///     if (test(*I))
+  ///       I = Set.erase(I);
+  ///     else
+  ///       ++I;
+  ///
+  /// Note that if the last element in the subset list is erased, this will
+  /// return an end iterator which can be decremented to get the new tail (if it
+  /// exists):
+  ///
+  ///  tie(B, I) = Set.equal_range(Key);
+  ///  for (bool isBegin = B == I; !isBegin; /* empty */) {
+  ///    isBegin = (--I) == B;
+  ///    if (test(I))
+  ///      break;
+  ///    I = erase(I);
+  ///  }
+  iterator erase(iterator I) {
+    assert(I.isKeyed() && !I.isEnd() && !Dense[I.Idx].isTombstone() &&
+           "erasing invalid/end/tombstone iterator");
+
+    // First, unlink the node from its list. Then swap the node out with the
+    // dense vector's last entry
+    iterator NextI = unlink(Dense[I.Idx]);
+
+    // Put in a tombstone.
+    makeTombstone(I.Idx);
+
+    return NextI;
+  }
+
+  /// Erase all elements with the given key. This invalidates all
+  /// iterators of that key.
+  void eraseAll(const KeyT &K) {
+    for (iterator I = find(K); I != end(); /* empty */)
+      I = erase(I);
+  }
+
+private:
+  /// Unlink the node from its list. Returns the next node in the list.
+  iterator unlink(const SMSNode &N) {
+    if (isSingleton(N)) {
+      // Singleton is already unlinked
+      assert(N.Next == SMSNode::INVALID && "Singleton has next?");
+      return iterator(this, SMSNode::INVALID, ValIndexOf(N.Data));
+    }
+
+    if (isHead(N)) {
+      // If we're the head, then update the sparse array and our next.
+      Sparse[sparseIndex(N)] = N.Next;
+      Dense[N.Next].Prev = N.Prev;
+      return iterator(this, N.Next, ValIndexOf(N.Data));
+    }
+
+    if (N.isTail()) {
+      // If we're the tail, then update our head and our previous.
+      findIndex(sparseIndex(N)).setPrev(N.Prev);
+      Dense[N.Prev].Next = N.Next;
+
+      // Give back an end iterator that can be decremented
+      iterator I(this, N.Prev, ValIndexOf(N.Data));
+      return ++I;
+    }
+
+    // Otherwise, just drop us
+    Dense[N.Next].Prev = N.Prev;
+    Dense[N.Prev].Next = N.Next;
+    return iterator(this, N.Next, ValIndexOf(N.Data));
+  }
+};
+
+} // end namespace llvm
+
+#endif
diff --git a/include/llvm/CodeGen/ScheduleDAGInstrs.h b/include/llvm/CodeGen/ScheduleDAGInstrs.h
index 8b841e20cd..94abec2002 100644
--- a/include/llvm/CodeGen/ScheduleDAGInstrs.h
+++ b/include/llvm/CodeGen/ScheduleDAGInstrs.h
@@ -17,6 +17,7 @@
 
 #include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/SparseSet.h"
+#include "llvm/ADT/SparseMultiSet.h"
 #include "llvm/CodeGen/MachineDominators.h"
 #include "llvm/CodeGen/MachineLoopInfo.h"
 #include "llvm/CodeGen/ScheduleDAG.h"
@@ -48,56 +49,18 @@ namespace llvm {
   struct PhysRegSUOper {
     SUnit *SU;
     int OpIdx;
+    unsigned Reg;
 
-    PhysRegSUOper(SUnit *su, int op): SU(su), OpIdx(op) {}
-  };
-
-  /// Combine a SparseSet with a 1x1 vector to track physical registers.
-  /// The SparseSet allows iterating over the (few) live registers for quickly
-  /// comparing against a regmask or clearing the set.
-  ///
-  /// Storage for the map is allocated once for the pass. The map can be
-  /// cleared between scheduling regions without freeing unused entries.
-  class Reg2SUnitsMap {
-    SparseSet<unsigned> PhysRegSet;
-    std::vector<std::vector<PhysRegSUOper> > SUnits;
-  public:
-    typedef SparseSet<unsigned>::const_iterator const_iterator;
-
-    // Allow iteration over register numbers (keys) in the map. If needed, we
-    // can provide an iterator over SUnits (values) as well.
-    const_iterator reg_begin() const { return PhysRegSet.begin(); }
-    const_iterator reg_end() const { return PhysRegSet.end(); }
-
-    /// Initialize the map with the number of registers.
-    /// If the map is already large enough, no allocation occurs.
-    /// For simplicity we expect the map to be empty().
-    void setRegLimit(unsigned Limit);
-
-    /// Returns true if the map is empty.
-    bool empty() const { return PhysRegSet.empty(); }
+    PhysRegSUOper(SUnit *su, int op, unsigned R): SU(su), OpIdx(op), Reg(R) {}
 
-    /// Clear the map without deallocating storage.
-    void clear();
-
-    bool contains(unsigned Reg) const { return PhysRegSet.count(Reg); }
-
-    /// If this register is mapped, return its existing SUnits vector.
-    /// Otherwise map the register and return an empty SUnits vector.
-    std::vector<PhysRegSUOper> &operator[](unsigned Reg) {
-      bool New = PhysRegSet.insert(Reg).second;
-      assert((!New || SUnits[Reg].empty()) && "stale SUnits vector");
-      (void)New;
-      return SUnits[Reg];
-    }
-
-    /// Erase an existing element without freeing memory.
-    void erase(unsigned Reg) {
-      PhysRegSet.erase(Reg);
-      SUnits[Reg].clear();
-    }
+    unsigned getSparseSetIndex() const { return Reg; }
   };
 
+  /// Use a SparseMultiSet to track physical registers. Storage is only
+  /// allocated once for the pass. It can be cleared in constant time and reused
+  /// without any frees.
+  typedef SparseMultiSet<PhysRegSUOper, llvm::identity<unsigned>, uint16_t> Reg2SUnitsMap;
+
   /// Use SparseSet as a SparseMap by relying on the fact that it never
   /// compares ValueT's, only unsigned keys. This allows the set to be cleared
   /// between scheduling regions in constant time as long as ValueT does not
diff --git a/lib/CodeGen/ScheduleDAGInstrs.cpp b/lib/CodeGen/ScheduleDAGInstrs.cpp
index 662fc0e6d1..411c46b8f5 100644
--- a/lib/CodeGen/ScheduleDAGInstrs.cpp
+++ b/lib/CodeGen/ScheduleDAGInstrs.cpp
@@ -168,20 +168,6 @@ void ScheduleDAGInstrs::finishBlock() {
   BB = 0;
 }
 
-/// Initialize the map with the number of registers.
-void Reg2SUnitsMap::setRegLimit(unsigned Limit) {
-  PhysRegSet.setUniverse(Limit);
-  SUnits.resize(Limit);
-}
-
-/// Clear the map without deallocating storage.
-void Reg2SUnitsMap::clear() {
-  for (const_iterator I = reg_begin(), E = reg_end(); I != E; ++I) {
-    SUnits[*I].clear();
-  }
-  PhysRegSet.clear();
-}
-
 /// Initialize the DAG and common scheduler state for the current scheduling
 /// region. This does not actually create the DAG, only clears it. The
 /// scheduling driver may call BuildSchedGraph multiple times per scheduling
@@ -228,7 +214,7 @@ void ScheduleDAGInstrs::addSchedBarrierDeps() {
       if (Reg == 0) continue;
 
       if (TRI->isPhysicalRegister(Reg))
-        Uses[Reg].push_back(PhysRegSUOper(&ExitSU, -1));
+        Uses.insert(PhysRegSUOper(&ExitSU, -1, Reg));
       else {
         assert(!IsPostRA && "Virtual register encountered after regalloc.");
         if (MO.readsReg()) // ignore undef operands
@@ -245,7 +231,7 @@ void ScheduleDAGInstrs::addSchedBarrierDeps() {
              E = (*SI)->livein_end(); I != E; ++I) {
         unsigned Reg = *I;
         if (!Uses.contains(Reg))
-          Uses[Reg].push_back(PhysRegSUOper(&ExitSU, -1));
+          Uses.insert(PhysRegSUOper(&ExitSU, -1, Reg));
       }
   }
 }
@@ -263,15 +249,14 @@ void ScheduleDAGInstrs::addPhysRegDataDeps(SUnit *SU, unsigned OperIdx) {
        Alias.isValid(); ++Alias) {
     if (!Uses.contains(*Alias))
       continue;
-    std::vector<PhysRegSUOper> &UseList = Uses[*Alias];
-    for (unsigned i = 0, e = UseList.size(); i != e; ++i) {
-      SUnit *UseSU = UseList[i].SU;
+    for (Reg2SUnitsMap::iterator I = Uses.find(*Alias); I != Uses.end(); ++I) {
+      SUnit *UseSU = I->SU;
       if (UseSU == SU)
         continue;
 
       // Adjust the dependence latency using operand def/use information,
       // then allow the target to perform its own adjustments.
-      int UseOp = UseList[i].OpIdx;
+      int UseOp = I->OpIdx;
       MachineInstr *RegUse = 0;
       SDep Dep;
       if (UseOp < 0)
@@ -311,9 +296,8 @@ void ScheduleDAGInstrs::addPhysRegDeps(SUnit *SU, unsigned OperIdx) {
        Alias.isValid(); ++Alias) {
     if (!Defs.contains(*Alias))
       continue;
-    std::vector<PhysRegSUOper> &DefList = Defs[*Alias];
-    for (unsigned i = 0, e = DefList.size(); i != e; ++i) {
-      SUnit *DefSU = DefList[i].SU;
+    for (Reg2SUnitsMap::iterator I = Defs.find(*Alias); I != Defs.end(); ++I) {
+      SUnit *DefSU = I->SU;
       if (DefSU == &ExitSU)
         continue;
       if (DefSU != SU &&
@@ -337,33 +321,37 @@ void ScheduleDAGInstrs::addPhysRegDeps(SUnit *SU, unsigned OperIdx) {
     // Either insert a new Reg2SUnits entry with an empty SUnits list, or
     // retrieve the existing SUnits list for this register's uses.
     // Push this SUnit on the use list.
-    Uses[MO.getReg()].push_back(PhysRegSUOper(SU, OperIdx));
+    Uses.insert(PhysRegSUOper(SU, OperIdx, MO.getReg()));
   }
   else {
     addPhysRegDataDeps(SU, OperIdx);
-
-    // Either insert a new Reg2SUnits entry with an empty SUnits list, or
-    // retrieve the existing SUnits list for this register's defs.
-    std::vector<PhysRegSUOper> &DefList = Defs[MO.getReg()];
+    unsigned Reg = MO.getReg();
 
     // clear this register's use list
-    if (Uses.contains(MO.getReg()))
-      Uses[MO.getReg()].clear();
-
-    if (!MO.isDead())
-      DefList.clear();
-
-    // Calls will not be reordered because of chain dependencies (see
-    // below). Since call operands are dead, calls may continue to be added
-    // to the DefList making dependence checking quadratic in the size of
-    // the block. Instead, we leave only one call at the back of the
-    // DefList.
-    if (SU->isCall) {
-      while (!DefList.empty() && DefList.back().SU->isCall)
-        DefList.pop_back();
+    if (Uses.contains(Reg))
+      Uses.eraseAll(Reg);
+
+    if (!MO.isDead()) {
+      Defs.eraseAll(Reg);
+    } else if (SU->isCall) {
+      // Calls will not be reordered because of chain dependencies (see
+      // below). Since call operands are dead, calls may continue to be added
+      // to the DefList making dependence checking quadratic in the size of
+      // the block. Instead, we leave only one call at the back of the
+      // DefList.
+      Reg2SUnitsMap::RangePair P = Defs.equal_range(Reg);
+      Reg2SUnitsMap::iterator B = P.first;
+      Reg2SUnitsMap::iterator I = P.second;
+      for (bool isBegin = I == B; !isBegin; /* empty */) {
+        isBegin = (--I) == B;
+        if (!I->SU->isCall)
+          break;
+        I = Defs.erase(I);
+      }
     }
+
     // Defs are pushed in the order they are visited and never reordered.
-    DefList.push_back(PhysRegSUOper(SU, OperIdx));
+    Defs.insert(PhysRegSUOper(SU, OperIdx, Reg));
   }
 }
 
@@ -726,8 +714,8 @@ void ScheduleDAGInstrs::buildSchedGraph(AliasAnalysis *AA,
 
   assert(Defs.empty() && Uses.empty() &&
          "Only BuildGraph should update Defs/Uses");
-  Defs.setRegLimit(TRI->getNumRegs());
-  Uses.setRegLimit(TRI->getNumRegs());
+  Defs.setUniverse(TRI->getNumRegs());
+  Uses.setUniverse(TRI->getNumRegs());
 
   assert(VRegDefs.empty() && "Only BuildSchedGraph may access VRegDefs");
   // FIXME: Allow SparseSet to reserve space for the creation of virtual
diff --git a/unittests/ADT/CMakeLists.txt b/unittests/ADT/CMakeLists.txt
index 94f7fda2a9..09ca89944b 100644
--- a/unittests/ADT/CMakeLists.txt
+++ b/unittests/ADT/CMakeLists.txt
@@ -24,6 +24,7 @@ set(ADTSources
   SmallStringTest.cpp
   SmallVectorTest.cpp
   SparseBitVectorTest.cpp
+  SparseMultiSetTest.cpp
   SparseSetTest.cpp
   StringMapTest.cpp
   StringRefTest.cpp
diff --git a/unittests/ADT/SparseMultiSetTest.cpp b/unittests/ADT/SparseMultiSetTest.cpp
new file mode 100644
index 0000000000..4ac0388063
--- /dev/null
+++ b/unittests/ADT/SparseMultiSetTest.cpp
@@ -0,0 +1,235 @@
+//===------ ADT/SparseSetTest.cpp - SparseSet unit tests -  -----*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+#include "llvm/ADT/SparseMultiSet.h"
+#include "gtest/gtest.h"
+
+using namespace llvm;
+
+namespace {
+
+typedef SparseMultiSet<unsigned> USet;
+
+// Empty set tests.
+TEST(SparseMultiSetTest, EmptySet) {
+  USet Set;
+  EXPECT_TRUE(Set.empty());
+  EXPECT_EQ(0u, Set.size());
+
+  Set.setUniverse(10);
+
+  // Lookups on empty set.
+  EXPECT_TRUE(Set.find(0) == Set.end());
+  EXPECT_TRUE(Set.find(9) == Set.end());
+
+  // Same thing on a const reference.
+  const USet &CSet = Set;
+  EXPECT_TRUE(CSet.empty());
+  EXPECT_EQ(0u, CSet.size());
+  EXPECT_TRUE(CSet.find(0) == CSet.end());
+  USet::const_iterator I = CSet.find(5);
+  EXPECT_TRUE(I == CSet.end());
+}
+
+// Single entry set tests.
+TEST(SparseMultiSetTest, SingleEntrySet) {
+  USet Set;
+  Set.setUniverse(10);
+  USet::iterator I = Set.insert(5);
+  EXPECT_TRUE(I != Set.end());
+  EXPECT_TRUE(*I == 5);
+
+  EXPECT_FALSE(Set.empty());
+  EXPECT_EQ(1u, Set.size());
+
+  EXPECT_TRUE(Set.find(0) == Set.end());
+  EXPECT_TRUE(Set.find(9) == Set.end());
+
+  EXPECT_FALSE(Set.contains(0));
+  EXPECT_TRUE(Set.contains(5));
+
+  // Extra insert.
+  I = Set.insert(5);
+  EXPECT_TRUE(I != Set.end());
+  EXPECT_TRUE(I == ++Set.find(5));
+  I--;
+  EXPECT_TRUE(I == Set.find(5));
+
+  // Erase non-existent element.
+  I = Set.find(1);
+  EXPECT_TRUE(I == Set.end());
+  EXPECT_EQ(2u, Set.size());
+  EXPECT_EQ(5u, *Set.find(5));
+
+  // Erase iterator.
+  I = Set.find(5);
+  EXPECT_TRUE(I != Set.end());
+  I = Set.erase(I);
+  EXPECT_TRUE(I != Set.end());
+  I = Set.erase(I);
+  EXPECT_TRUE(I == Set.end());
+  EXPECT_TRUE(Set.empty());
+}
+
+// Multiple entry set tests.
+TEST(SparseMultiSetTest, MultipleEntrySet) {
+  USet Set;
+  Set.setUniverse(10);
+
+  Set.insert(5);
+  Set.insert(5);
+  Set.insert(5);
+  Set.insert(3);
+  Set.insert(2);
+  Set.insert(1);
+  Set.insert(4);
+  EXPECT_EQ(7u, Set.size());
+
+  // Erase last element by key.
+  EXPECT_TRUE(Set.erase(Set.find(4)) == Set.end());
+  EXPECT_EQ(6u, Set.size());
+  EXPECT_FALSE(Set.contains(4));
+  EXPECT_TRUE(Set.find(4) == Set.end());
+
+  // Erase first element by key.
+  EXPECT_EQ(3u, Set.count(5));
+  EXPECT_TRUE(Set.find(5) != Set.end());
+  EXPECT_TRUE(Set.erase(Set.find(5)) != Set.end());
+  EXPECT_EQ(5u, Set.size());
+  EXPECT_EQ(2u, Set.count(5));
+
+  Set.insert(6);
+  Set.insert(7);
+  EXPECT_EQ(7u, Set.size());
+
+  // Erase tail by iterator.
+  EXPECT_TRUE(Set.getTail(6) == Set.getHead(6));
+  USet::iterator I = Set.erase(Set.find(6));
+  EXPECT_TRUE(I == Set.end());
+  EXPECT_EQ(6u, Set.size());
+
+  // Erase tails by iterator.
+  EXPECT_EQ(2u, Set.count(5));
+  I = Set.getTail(5);
+  I = Set.erase(I);
+  EXPECT_TRUE(I == Set.end());
+  --I;
+  EXPECT_EQ(1u, Set.count(5));
+  EXPECT_EQ(5u, *I);
+  I = Set.erase(I);
+  EXPECT_TRUE(I == Set.end());
+  EXPECT_EQ(0u, Set.count(5));
+
+  Set.insert(8);
+  Set.insert(8);
+  Set.insert(8);
+  Set.insert(8);
+  Set.insert(8);
+
+  // Erase all the 8s
+  EXPECT_EQ(5u, std::distance(Set.getHead(8), Set.end()));
+  Set.eraseAll(8);
+  EXPECT_EQ(0u, std::distance(Set.getHead(8), Set.end()));
+
+  // Clear and resize the universe.
+  Set.clear();
+  EXPECT_EQ(0u, Set.size());
+  EXPECT_FALSE(Set.contains(3));
+  Set.setUniverse(1000);
+
+  // Add more than 256 elements.
+  for (unsigned i = 100; i != 800; ++i)
+    Set.insert(i);
+
+  for (unsigned i = 0; i != 10; ++i)
+    Set.eraseAll(i);
+
+  for (unsigned i = 100; i != 800; ++i)
+    EXPECT_EQ(1u, Set.count(i));
+
+  EXPECT_FALSE(Set.contains(99));
+  EXPECT_FALSE(Set.contains(800));
+  EXPECT_EQ(700u, Set.size());
+}
+
+// Test out iterators
+TEST(SparseMultiSetTest, Iterators) {
+  USet Set;
+  Set.setUniverse(100);
+
+  Set.insert(0);
+  Set.insert(1);
+  Set.insert(2);
+  Set.insert(0);
+  Set.insert(1);
+  Set.insert(0);
+
+  USet::RangePair RangePair = Set.equal_range(0);
+  USet::iterator B = RangePair.first;
+  USet::iterator E = RangePair.second;
+
+  // Move the iterators around, going to end and coming back.
+  EXPECT_EQ(3u, std::distance(B, E));
+  EXPECT_EQ(B, --(--(--E)));
+  EXPECT_EQ(++(++(++E)), Set.end());
+  EXPECT_EQ(B, --(--(--E)));
+  EXPECT_EQ(++(++(++E)), Set.end());
+
+  // Insert into the tail, and move around again
+  Set.insert(0);
+  EXPECT_EQ(B, --(--(--(--E))));
+  EXPECT_EQ(++(++(++(++E))), Set.end());
+  EXPECT_EQ(B, --(--(--(--E))));
+  EXPECT_EQ(++(++(++(++E))), Set.end());
+
+  // Erase a tail, and move around again
+  USet::iterator Erased = Set.erase(Set.getTail(0));
+  EXPECT_EQ(Erased, E);
+  EXPECT_EQ(B, --(--(--E)));
+
+  USet Set2;
+  Set2.setUniverse(11);
+  Set2.insert(3);
+  EXPECT_TRUE(!Set2.contains(0));
+  EXPECT_TRUE(!Set.contains(3));
+
+  EXPECT_EQ(Set2.getHead(3), Set2.getTail(3));
+  EXPECT_EQ(Set2.getHead(0), Set2.getTail(0));
+  B = Set2.find(3);
+  EXPECT_EQ(Set2.find(3), --(++B));
+}
+
+struct Alt {
+  unsigned Value;
+  explicit Alt(unsigned x) : Value(x) {}
+  unsigned getSparseSetIndex() const { return Value - 1000; }
+};
+
+TEST(SparseMultiSetTest, AltStructSet) {
+  typedef SparseMultiSet<Alt> ASet;
+  ASet Set;
+  Set.setUnivers