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diff --git a/include/llvm/ADT/SmallPtrSet.h b/include/llvm/ADT/SmallPtrSet.h
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+//===- llvm/ADT/SmallPtrSet.h - 'Normally small' pointer set ----*- 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 SmallPtrSet class.  See the doxygen comment for
+// SmallPtrSetImpl for more details on the algorithm used.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_ADT_SMALLPTRSET_H
+#define LLVM_ADT_SMALLPTRSET_H
+
+#include <cassert>
+#include <cstring>
+#include "llvm/Support/DataTypes.h"
+#include "llvm/Support/PointerLikeTypeTraits.h"
+
+namespace llvm {
+
+class SmallPtrSetIteratorImpl;
+
+/// SmallPtrSetImpl - This is the common code shared among all the
+/// SmallPtrSet<>'s, which is almost everything.  SmallPtrSet has two modes, one
+/// for small and one for large sets.
+///
+/// Small sets use an array of pointers allocated in the SmallPtrSet object,
+/// which is treated as a simple array of pointers.  When a pointer is added to
+/// the set, the array is scanned to see if the element already exists, if not
+/// the element is 'pushed back' onto the array.  If we run out of space in the
+/// array, we grow into the 'large set' case.  SmallSet should be used when the
+/// sets are often small.  In this case, no memory allocation is used, and only
+/// light-weight and cache-efficient scanning is used.
+///
+/// Large sets use a classic exponentially-probed hash table.  Empty buckets are
+/// represented with an illegal pointer value (-1) to allow null pointers to be
+/// inserted.  Tombstones are represented with another illegal pointer value
+/// (-2), to allow deletion.  The hash table is resized when the table is 3/4 or
+/// more.  When this happens, the table is doubled in size.
+///
+class SmallPtrSetImpl {
+  friend class SmallPtrSetIteratorImpl;
+protected:
+  /// CurArray - This is the current set of buckets.  If it points to
+  /// SmallArray, then the set is in 'small mode'.
+  const void **CurArray;
+  /// CurArraySize - The allocated size of CurArray, always a power of two.
+  /// Note that CurArray points to an array that has CurArraySize+1 elements in
+  /// it, so that the end iterator actually points to valid memory.
+  unsigned CurArraySize;
+
+  // If small, this is # elts allocated consequtively
+  unsigned NumElements;
+  unsigned NumTombstones;
+  const void *SmallArray[1];  // Must be last ivar.
+
+  // Helper to copy construct a SmallPtrSet.
+  SmallPtrSetImpl(const SmallPtrSetImpl& that);
+  explicit SmallPtrSetImpl(unsigned SmallSize) {
+    assert(SmallSize && (SmallSize & (SmallSize-1)) == 0 &&
+           "Initial size must be a power of two!");
+    CurArray = &SmallArray[0];
+    CurArraySize = SmallSize;
+    // The end pointer, always valid, is set to a valid element to help the
+    // iterator.
+    CurArray[SmallSize] = 0;
+    clear();
+  }
+  ~SmallPtrSetImpl();
+
+public:
+  bool empty() const { return size() == 0; }
+  unsigned size() const { return NumElements; }
+
+  void clear() {
+    // If the capacity of the array is huge, and the # elements used is small,
+    // shrink the array.
+    if (!isSmall() && NumElements*4 < CurArraySize && CurArraySize > 32)
+      return shrink_and_clear();
+
+    // Fill the array with empty markers.
+    memset(CurArray, -1, CurArraySize*sizeof(void*));
+    NumElements = 0;
+    NumTombstones = 0;
+  }
+
+protected:
+  static void *getTombstoneMarker() { return reinterpret_cast<void*>(-2); }
+  static void *getEmptyMarker() {
+    // Note that -1 is chosen to make clear() efficiently implementable with
+    // memset and because it's not a valid pointer value.
+    return reinterpret_cast<void*>(-1);
+  }
+
+  /// insert_imp - This returns true if the pointer was new to the set, false if
+  /// it was already in the set.  This is hidden from the client so that the
+  /// derived class can check that the right type of pointer is passed in.
+  bool insert_imp(const void * Ptr);
+
+  /// erase_imp - If the set contains the specified pointer, remove it and
+  /// return true, otherwise return false.  This is hidden from the client so
+  /// that the derived class can check that the right type of pointer is passed
+  /// in.
+  bool erase_imp(const void * Ptr);
+
+  bool count_imp(const void * Ptr) const {
+    if (isSmall()) {
+      // Linear search for the item.
+      for (const void *const *APtr = SmallArray,
+                      *const *E = SmallArray+NumElements; APtr != E; ++APtr)
+        if (*APtr == Ptr)
+          return true;
+      return false;
+    }
+
+    // Big set case.
+    return *FindBucketFor(Ptr) == Ptr;
+  }
+
+private:
+  bool isSmall() const { return CurArray == &SmallArray[0]; }
+
+  unsigned Hash(const void *Ptr) const {
+    return static_cast<unsigned>(((uintptr_t)Ptr >> 4) & (CurArraySize-1));
+  }
+  const void * const *FindBucketFor(const void *Ptr) const;
+  void shrink_and_clear();
+
+  /// Grow - Allocate a larger backing store for the buckets and move it over.
+  void Grow();
+
+  void operator=(const SmallPtrSetImpl &RHS);  // DO NOT IMPLEMENT.
+protected:
+  void CopyFrom(const SmallPtrSetImpl &RHS);
+};
+
+/// SmallPtrSetIteratorImpl - This is the common base class shared between all
+/// instances of SmallPtrSetIterator.
+class SmallPtrSetIteratorImpl {
+protected:
+  const void *const *Bucket;
+public:
+  explicit SmallPtrSetIteratorImpl(const void *const *BP) : Bucket(BP) {
+    AdvanceIfNotValid();
+  }
+
+  bool operator==(const SmallPtrSetIteratorImpl &RHS) const {
+    return Bucket == RHS.Bucket;
+  }
+  bool operator!=(const SmallPtrSetIteratorImpl &RHS) const {
+    return Bucket != RHS.Bucket;
+  }
+
+protected:
+  /// AdvanceIfNotValid - If the current bucket isn't valid, advance to a bucket
+  /// that is.   This is guaranteed to stop because the end() bucket is marked
+  /// valid.
+  void AdvanceIfNotValid() {
+    while (*Bucket == SmallPtrSetImpl::getEmptyMarker() ||
+           *Bucket == SmallPtrSetImpl::getTombstoneMarker())
+      ++Bucket;
+  }
+};
+
+/// SmallPtrSetIterator - This implements a const_iterator for SmallPtrSet.
+template<typename PtrTy>
+class SmallPtrSetIterator : public SmallPtrSetIteratorImpl {
+  typedef PointerLikeTypeTraits<PtrTy> PtrTraits;
+public:
+  explicit SmallPtrSetIterator(const void *const *BP)
+    : SmallPtrSetIteratorImpl(BP) {}
+
+  // Most methods provided by baseclass.
+
+  const PtrTy operator*() const {
+    return PtrTraits::getFromVoidPointer(const_cast<void*>(*Bucket));
+  }
+
+  inline SmallPtrSetIterator& operator++() {          // Preincrement
+    ++Bucket;
+    AdvanceIfNotValid();
+    return *this;
+  }
+
+  SmallPtrSetIterator operator++(int) {        // Postincrement
+    SmallPtrSetIterator tmp = *this; ++*this; return tmp;
+  }
+};
+
+/// NextPowerOfTwo - This is a helper template that rounds N up to the next
+/// power of two.
+template<unsigned N>
+struct NextPowerOfTwo;
+
+/// NextPowerOfTwoH - If N is not a power of two, increase it.  This is a helper
+/// template used to implement NextPowerOfTwo.
+template<unsigned N, bool isPowerTwo>
+struct NextPowerOfTwoH {
+  enum { Val = N };
+};
+template<unsigned N>
+struct NextPowerOfTwoH<N, false> {
+  enum {
+    // We could just use NextVal = N+1, but this converges faster.  N|(N-1) sets
+    // the right-most zero bits to one all at once, e.g. 0b0011000 -> 0b0011111.
+    Val = NextPowerOfTwo<(N|(N-1)) + 1>::Val
+  };
+};
+
+template<unsigned N>
+struct NextPowerOfTwo {
+  enum { Val = NextPowerOfTwoH<N, (N&(N-1)) == 0>::Val };
+};
+  
+
+/// SmallPtrSet - This class implements a set which is optimizer for holding
+/// SmallSize or less elements.  This internally rounds up SmallSize to the next
+/// power of two if it is not already a power of two.  See the comments above
+/// SmallPtrSetImpl for details of the algorithm.
+template<class PtrType, unsigned SmallSize>
+class SmallPtrSet : public SmallPtrSetImpl {
+  // Make sure that SmallSize is a power of two, round up if not.
+  enum { SmallSizePowTwo = NextPowerOfTwo<SmallSize>::Val };
+  void *SmallArray[SmallSizePowTwo];
+  typedef PointerLikeTypeTraits<PtrType> PtrTraits;
+public:
+  SmallPtrSet() : SmallPtrSetImpl(NextPowerOfTwo<SmallSizePowTwo>::Val) {}
+  SmallPtrSet(const SmallPtrSet &that) : SmallPtrSetImpl(that) {}
+
+  template<typename It>
+  SmallPtrSet(It I, It E)
+    : SmallPtrSetImpl(NextPowerOfTwo<SmallSizePowTwo>::Val) {
+    insert(I, E);
+  }
+
+  /// insert - This returns true if the pointer was new to the set, false if it
+  /// was already in the set.
+  bool insert(PtrType Ptr) {
+    return insert_imp(PtrTraits::getAsVoidPointer(Ptr));
+  }
+
+  /// erase - If the set contains the specified pointer, remove it and return
+  /// true, otherwise return false.
+  bool erase(PtrType Ptr) {
+    return erase_imp(PtrTraits::getAsVoidPointer(Ptr));
+  }
+
+  /// count - Return true if the specified pointer is in the set.
+  bool count(PtrType Ptr) const {
+    return count_imp(PtrTraits::getAsVoidPointer(Ptr));
+  }
+
+  template <typename IterT>
+  void insert(IterT I, IterT E) {
+    for (; I != E; ++I)
+      insert(*I);
+  }
+
+  typedef SmallPtrSetIterator<PtrType> iterator;
+  typedef SmallPtrSetIterator<PtrType> const_iterator;
+  inline iterator begin() const {
+    return iterator(CurArray);
+  }
+  inline iterator end() const {
+    return iterator(CurArray+CurArraySize);
+  }
+
+  // Allow assignment from any smallptrset with the same element type even if it
+  // doesn't have the same smallsize.
+  const SmallPtrSet<PtrType, SmallSize>&
+  operator=(const SmallPtrSet<PtrType, SmallSize> &RHS) {
+    CopyFrom(RHS);
+    return *this;
+  }
+
+};
+
+}
+
+#endif