X-Git-Url: http://plrg.eecs.uci.edu/git/?a=blobdiff_plain;f=include%2Fllvm%2FADT%2FSmallVector.h;h=10ae049ff91fc2d3c9c95a56c31aff5a8b04984f;hb=5dd76fa50a63c6460957d11d2542469f0a7d65d7;hp=ae258846e74c0c7e4d048663e1e0502679f7ea8b;hpb=b5677f933f918acd8b8525635510d22dfb26285e;p=oota-llvm.git

diff --git a/include/llvm/ADT/SmallVector.h b/include/llvm/ADT/SmallVector.h
index ae258846e74..10ae049ff91 100644
--- a/include/llvm/ADT/SmallVector.h
+++ b/include/llvm/ADT/SmallVector.h
@@ -2,8 +2,8 @@
 //
 //                     The LLVM Compiler Infrastructure
 //
-// This file was developed by Chris Lattner 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.
 //
 //===----------------------------------------------------------------------===//
 //
@@ -14,25 +14,51 @@
 #ifndef LLVM_ADT_SMALLVECTOR_H
 #define LLVM_ADT_SMALLVECTOR_H
 
+#include "llvm/Support/type_traits.h"
 #include <algorithm>
-#include <iterator>
+#include <cassert>
+#include <cstddef>
+#include <cstdlib>
+#include <cstring>
 #include <memory>
 
+#ifdef _MSC_VER
+namespace std {
+#if _MSC_VER <= 1310
+  // Work around flawed VC++ implementation of std::uninitialized_copy.  Define
+  // additional overloads so that elements with pointer types are recognized as
+  // scalars and not objects, causing bizarre type conversion errors.
+  template<class T1, class T2>
+  inline _Scalar_ptr_iterator_tag _Ptr_cat(T1 **, T2 **) {
+    _Scalar_ptr_iterator_tag _Cat;
+    return _Cat;
+  }
+
+  template<class T1, class T2>
+  inline _Scalar_ptr_iterator_tag _Ptr_cat(T1* const *, T2 **) {
+    _Scalar_ptr_iterator_tag _Cat;
+    return _Cat;
+  }
+#else
+// FIXME: It is not clear if the problem is fixed in VS 2005.  What is clear
+// is that the above hack won't work if it wasn't fixed.
+#endif
+}
+#endif
+
 namespace llvm {
 
-/// SmallVectorImpl - This class consists of common code factored out of the
-/// SmallVector class to reduce code duplication based on the SmallVector 'N'
-/// template parameter.
-template <typename T>
-class SmallVectorImpl {
-  T *Begin, *End, *Capacity;
-  
+/// SmallVectorBase - This is all the non-templated stuff common to all
+/// SmallVectors.
+class SmallVectorBase {
+protected:
+  void *BeginX, *EndX, *CapacityX;
+
   // Allocate raw space for N elements of type T.  If T has a ctor or dtor, we
   // don't want it to be automatically run, so we need to represent the space as
   // something else.  An array of char would work great, but might not be
-  // aligned sufficiently.  Instead, we either use GCC extensions, or some
-  // number of union instances for the space, which guarantee maximal alignment.
-protected:
+  // aligned sufficiently.  Instead we use some number of union instances for
+  // the space, which guarantee maximal alignment.
   union U {
     double D;
     long double LD;
@@ -40,181 +66,583 @@ protected:
     void *P;
   } FirstEl;
   // Space after 'FirstEl' is clobbered, do not add any instance vars after it.
-public:
-  // Default ctor - Initialize to empty.
-  SmallVectorImpl(unsigned N)
-    : Begin((T*)&FirstEl), End((T*)&FirstEl), Capacity((T*)&FirstEl+N) {
+
+protected:
+  SmallVectorBase(size_t Size)
+    : BeginX(&FirstEl), EndX(&FirstEl), CapacityX((char*)&FirstEl+Size) {}
+
+  /// isSmall - Return true if this is a smallvector which has not had dynamic
+  /// memory allocated for it.
+  bool isSmall() const {
+    return BeginX == static_cast<const void*>(&FirstEl);
   }
-  
-  ~SmallVectorImpl() {
-    // Destroy the constructed elements in the vector.
-    for (iterator I = Begin, E = End; I != E; ++I)
-      I->~T();
 
-    // If this wasn't grown from the inline copy, deallocate the old space.
-    if (!isSmall())
-      delete[] (char*)Begin;
+  /// size_in_bytes - This returns size()*sizeof(T).
+  size_t size_in_bytes() const {
+    return size_t((char*)EndX - (char*)BeginX);
   }
-  
+
+  /// capacity_in_bytes - This returns capacity()*sizeof(T).
+  size_t capacity_in_bytes() const {
+    return size_t((char*)CapacityX - (char*)BeginX);
+  }
+
+  /// grow_pod - This is an implementation of the grow() method which only works
+  /// on POD-like datatypes and is out of line to reduce code duplication.
+  void grow_pod(size_t MinSizeInBytes, size_t TSize);
+
+public:
+  bool empty() const { return BeginX == EndX; }
+};
+
+
+template <typename T>
+class SmallVectorTemplateCommon : public SmallVectorBase {
+protected:
+  void setEnd(T *P) { this->EndX = P; }
+public:
+  SmallVectorTemplateCommon(size_t Size) : SmallVectorBase(Size) {}
+
   typedef size_t size_type;
-  typedef T* iterator;
-  typedef const T* const_iterator;
-  typedef T& reference;
-  typedef const T& const_reference;
+  typedef ptrdiff_t difference_type;
+  typedef T value_type;
+  typedef T *iterator;
+  typedef const T *const_iterator;
 
-  bool empty() const { return Begin == End; }
-  size_type size() const { return End-Begin; }
-  
-  iterator begin() { return Begin; }
-  const_iterator begin() const { return Begin; }
+  typedef std::reverse_iterator<const_iterator> const_reverse_iterator;
+  typedef std::reverse_iterator<iterator> reverse_iterator;
+
+  typedef T &reference;
+  typedef const T &const_reference;
+  typedef T *pointer;
+  typedef const T *const_pointer;
+
+  // forward iterator creation methods.
+  iterator begin() { return (iterator)this->BeginX; }
+  const_iterator begin() const { return (const_iterator)this->BeginX; }
+  iterator end() { return (iterator)this->EndX; }
+  const_iterator end() const { return (const_iterator)this->EndX; }
+protected:
+  iterator capacity_ptr() { return (iterator)this->CapacityX; }
+  const_iterator capacity_ptr() const { return (const_iterator)this->CapacityX;}
+public:
+
+  // reverse iterator creation methods.
+  reverse_iterator rbegin()            { return reverse_iterator(end()); }
+  const_reverse_iterator rbegin() const{ return const_reverse_iterator(end()); }
+  reverse_iterator rend()              { return reverse_iterator(begin()); }
+  const_reverse_iterator rend() const { return const_reverse_iterator(begin());}
+
+  size_type size() const { return end()-begin(); }
+  size_type max_size() const { return size_type(-1) / sizeof(T); }
+
+  /// capacity - Return the total number of elements in the currently allocated
+  /// buffer.
+  size_t capacity() const { return capacity_ptr() - begin(); }
+
+  /// data - Return a pointer to the vector's buffer, even if empty().
+  pointer data() { return pointer(begin()); }
+  /// data - Return a pointer to the vector's buffer, even if empty().
+  const_pointer data() const { return const_pointer(begin()); }
 
-  iterator end() { return End; }
-  const_iterator end() const { return End; }
-  
   reference operator[](unsigned idx) {
-    return Begin[idx];
+    assert(begin() + idx < end());
+    return begin()[idx];
   }
   const_reference operator[](unsigned idx) const {
-    return Begin[idx];
+    assert(begin() + idx < end());
+    return begin()[idx];
   }
-  
+
+  reference front() {
+    return begin()[0];
+  }
+  const_reference front() const {
+    return begin()[0];
+  }
+
   reference back() {
     return end()[-1];
   }
   const_reference back() const {
     return end()[-1];
   }
+};
+
+/// SmallVectorTemplateBase<isPodLike = false> - This is where we put method
+/// implementations that are designed to work with non-POD-like T's.
+template <typename T, bool isPodLike>
+class SmallVectorTemplateBase : public SmallVectorTemplateCommon<T> {
+public:
+  SmallVectorTemplateBase(size_t Size) : SmallVectorTemplateCommon<T>(Size) {}
+
+  static void destroy_range(T *S, T *E) {
+    while (S != E) {
+      --E;
+      E->~T();
+    }
+  }
+
+  /// uninitialized_copy - Copy the range [I, E) onto the uninitialized memory
+  /// starting with "Dest", constructing elements into it as needed.
+  template<typename It1, typename It2>
+  static void uninitialized_copy(It1 I, It1 E, It2 Dest) {
+    std::uninitialized_copy(I, E, Dest);
+  }
+
+  /// grow - double the size of the allocated memory, guaranteeing space for at
+  /// least one more element or MinSize if specified.
+  void grow(size_t MinSize = 0);
+};
+
+// Define this out-of-line to dissuade the C++ compiler from inlining it.
+template <typename T, bool isPodLike>
+void SmallVectorTemplateBase<T, isPodLike>::grow(size_t MinSize) {
+  size_t CurCapacity = this->capacity();
+  size_t CurSize = this->size();
+  size_t NewCapacity = 2*CurCapacity + 1; // Always grow, even from zero.
+  if (NewCapacity < MinSize)
+    NewCapacity = MinSize;
+  T *NewElts = static_cast<T*>(malloc(NewCapacity*sizeof(T)));
+
+  // Copy the elements over.
+  this->uninitialized_copy(this->begin(), this->end(), NewElts);
+
+  // Destroy the original elements.
+  destroy_range(this->begin(), this->end());
+
+  // If this wasn't grown from the inline copy, deallocate the old space.
+  if (!this->isSmall())
+    free(this->begin());
+
+  this->setEnd(NewElts+CurSize);
+  this->BeginX = NewElts;
+  this->CapacityX = this->begin()+NewCapacity;
+}
+
+
+/// SmallVectorTemplateBase<isPodLike = true> - This is where we put method
+/// implementations that are designed to work with POD-like T's.
+template <typename T>
+class SmallVectorTemplateBase<T, true> : public SmallVectorTemplateCommon<T> {
+public:
+  SmallVectorTemplateBase(size_t Size) : SmallVectorTemplateCommon<T>(Size) {}
+
+  // No need to do a destroy loop for POD's.
+  static void destroy_range(T *, T *) {}
+
+  /// uninitialized_copy - Copy the range [I, E) onto the uninitialized memory
+  /// starting with "Dest", constructing elements into it as needed.
+  template<typename It1, typename It2>
+  static void uninitialized_copy(It1 I, It1 E, It2 Dest) {
+    // Arbitrary iterator types; just use the basic implementation.
+    std::uninitialized_copy(I, E, Dest);
+  }
+
+  /// uninitialized_copy - Copy the range [I, E) onto the uninitialized memory
+  /// starting with "Dest", constructing elements into it as needed.
+  template<typename T1, typename T2>
+  static void uninitialized_copy(T1 *I, T1 *E, T2 *Dest) {
+    // Use memcpy for PODs iterated by pointers (which includes SmallVector
+    // iterators): std::uninitialized_copy optimizes to memmove, but we can
+    // use memcpy here.
+    memcpy(Dest, I, (E-I)*sizeof(T));
+  }
+
+  /// grow - double the size of the allocated memory, guaranteeing space for at
+  /// least one more element or MinSize if specified.
+  void grow(size_t MinSize = 0) {
+    this->grow_pod(MinSize*sizeof(T), sizeof(T));
+  }
+};
+
+
+/// SmallVectorImpl - This class consists of common code factored out of the
+/// SmallVector class to reduce code duplication based on the SmallVector 'N'
+/// template parameter.
+template <typename T>
+class SmallVectorImpl : public SmallVectorTemplateBase<T, isPodLike<T>::value> {
+  typedef SmallVectorTemplateBase<T, isPodLike<T>::value > SuperClass;
   
-  void push_back(const_reference Elt) {
-    if (End < Capacity) {
-  Retry:
-      new (End) T(Elt);
-      ++End;
+  SmallVectorImpl(const SmallVectorImpl&); // DISABLED.
+public:
+  typedef typename SuperClass::iterator iterator;
+  typedef typename SuperClass::size_type size_type;
+
+  // Default ctor - Initialize to empty.
+  explicit SmallVectorImpl(unsigned N)
+    : SmallVectorTemplateBase<T, isPodLike<T>::value>(N*sizeof(T)) {
+  }
+
+  ~SmallVectorImpl() {
+    // Destroy the constructed elements in the vector.
+    this->destroy_range(this->begin(), this->end());
+
+    // If this wasn't grown from the inline copy, deallocate the old space.
+    if (!this->isSmall())
+      free(this->begin());
+  }
+
+
+  void clear() {
+    this->destroy_range(this->begin(), this->end());
+    this->EndX = this->BeginX;
+  }
+
+  void resize(unsigned N) {
+    if (N < this->size()) {
+      this->destroy_range(this->begin()+N, this->end());
+      this->setEnd(this->begin()+N);
+    } else if (N > this->size()) {
+      if (this->capacity() < N)
+        this->grow(N);
+      this->construct_range(this->end(), this->begin()+N, T());
+      this->setEnd(this->begin()+N);
+    }
+  }
+
+  void resize(unsigned N, const T &NV) {
+    if (N < this->size()) {
+      this->destroy_range(this->begin()+N, this->end());
+      this->setEnd(this->begin()+N);
+    } else if (N > this->size()) {
+      if (this->capacity() < N)
+        this->grow(N);
+      construct_range(this->end(), this->begin()+N, NV);
+      this->setEnd(this->begin()+N);
+    }
+  }
+
+  void reserve(unsigned N) {
+    if (this->capacity() < N)
+      this->grow(N);
+  }
+
+  void push_back(const T &Elt) {
+    if (this->EndX < this->CapacityX) {
+    Retry:
+      new (this->end()) T(Elt);
+      this->setEnd(this->end()+1);
       return;
     }
-    grow();
+    this->grow();
     goto Retry;
   }
-  
+
   void pop_back() {
-    --End;
-    End->~T();
+    this->setEnd(this->end()-1);
+    this->end()->~T();
   }
-  
-  void clear() {
-    while (End != Begin) {
-      End->~T();
-      --End;
-    }
+
+  T pop_back_val() {
+    T Result = this->back();
+    pop_back();
+    return Result;
   }
-  
+
+
+  void swap(SmallVectorImpl &RHS);
+
   /// append - Add the specified range to the end of the SmallVector.
   ///
   template<typename in_iter>
   void append(in_iter in_start, in_iter in_end) {
-    unsigned NumInputs = std::distance(in_start, in_end);
+    size_type NumInputs = std::distance(in_start, in_end);
     // Grow allocated space if needed.
-    if (End+NumInputs > Capacity)
-      grow(size()+NumInputs);
+    if (NumInputs > size_type(this->capacity_ptr()-this->end()))
+      this->grow(this->size()+NumInputs);
 
     // Copy the new elements over.
-    std::uninitialized_copy(in_start, in_end, End);
-    End += NumInputs;
+    // TODO: NEED To compile time dispatch on whether in_iter is a random access
+    // iterator to use the fast uninitialized_copy.
+    std::uninitialized_copy(in_start, in_end, this->end());
+    this->setEnd(this->end() + NumInputs);
   }
-  
+
+  /// append - Add the specified range to the end of the SmallVector.
+  ///
+  void append(size_type NumInputs, const T &Elt) {
+    // Grow allocated space if needed.
+    if (NumInputs > size_type(this->capacity_ptr()-this->end()))
+      this->grow(this->size()+NumInputs);
+
+    // Copy the new elements over.
+    std::uninitialized_fill_n(this->end(), NumInputs, Elt);
+    this->setEnd(this->end() + NumInputs);
+  }
+
   void assign(unsigned NumElts, const T &Elt) {
     clear();
-    if (Begin+NumElts > Capacity)
-      grow(NumElts);
-    End = Begin+NumElts;
-    for (; NumElts; --NumElts)
-      new (Begin+NumElts-1) T(Elt);
+    if (this->capacity() < NumElts)
+      this->grow(NumElts);
+    this->setEnd(this->begin()+NumElts);
+    construct_range(this->begin(), this->end(), Elt);
   }
-  
-  const SmallVectorImpl &operator=(const SmallVectorImpl &RHS);
-  
-private:
-  /// isSmall - Return true if this is a smallvector which has not had dynamic
-  /// memory allocated for it.
-  bool isSmall() const {
-    return (void*)Begin == (void*)&FirstEl;
+
+  iterator erase(iterator I) {
+    iterator N = I;
+    // Shift all elts down one.
+    std::copy(I+1, this->end(), I);
+    // Drop the last elt.
+    pop_back();
+    return(N);
   }
 
-  /// grow - double the size of the allocated memory, guaranteeing space for at
-  /// least one more element or MinSize if specified.
-  void grow(unsigned MinSize = 0);
+  iterator erase(iterator S, iterator E) {
+    iterator N = S;
+    // Shift all elts down.
+    iterator I = std::copy(E, this->end(), S);
+    // Drop the last elts.
+    this->destroy_range(I, this->end());
+    this->setEnd(I);
+    return(N);
+  }
+
+  iterator insert(iterator I, const T &Elt) {
+    if (I == this->end()) {  // Important special case for empty vector.
+      push_back(Elt);
+      return this->end()-1;
+    }
+
+    if (this->EndX < this->CapacityX) {
+    Retry:
+      new (this->end()) T(this->back());
+      this->setEnd(this->end()+1);
+      // Push everything else over.
+      std::copy_backward(I, this->end()-1, this->end());
+      *I = Elt;
+      return I;
+    }
+    size_t EltNo = I-this->begin();
+    this->grow();
+    I = this->begin()+EltNo;
+    goto Retry;
+  }
+
+  iterator insert(iterator I, size_type NumToInsert, const T &Elt) {
+    if (I == this->end()) {  // Important special case for empty vector.
+      append(NumToInsert, Elt);
+      return this->end()-1;
+    }
+
+    // Convert iterator to elt# to avoid invalidating iterator when we reserve()
+    size_t InsertElt = I - this->begin();
+
+    // Ensure there is enough space.
+    reserve(static_cast<unsigned>(this->size() + NumToInsert));
+
+    // Uninvalidate the iterator.
+    I = this->begin()+InsertElt;
+
+    // If there are more elements between the insertion point and the end of the
+    // range than there are being inserted, we can use a simple approach to
+    // insertion.  Since we already reserved space, we know that this won't
+    // reallocate the vector.
+    if (size_t(this->end()-I) >= NumToInsert) {
+      T *OldEnd = this->end();
+      append(this->end()-NumToInsert, this->end());
+
+      // Copy the existing elements that get replaced.
+      std::copy_backward(I, OldEnd-NumToInsert, OldEnd);
+
+      std::fill_n(I, NumToInsert, Elt);
+      return I;
+    }
+
+    // Otherwise, we're inserting more elements than exist already, and we're
+    // not inserting at the end.
+
+    // Copy over the elements that we're about to overwrite.
+    T *OldEnd = this->end();
+    this->setEnd(this->end() + NumToInsert);
+    size_t NumOverwritten = OldEnd-I;
+    this->uninitialized_copy(I, OldEnd, this->end()-NumOverwritten);
+
+    // Replace the overwritten part.
+    std::fill_n(I, NumOverwritten, Elt);
+
+    // Insert the non-overwritten middle part.
+    std::uninitialized_fill_n(OldEnd, NumToInsert-NumOverwritten, Elt);
+    return I;
+  }
+
+  template<typename ItTy>
+  iterator insert(iterator I, ItTy From, ItTy To) {
+    if (I == this->end()) {  // Important special case for empty vector.
+      append(From, To);
+      return this->end()-1;
+    }
+
+    size_t NumToInsert = std::distance(From, To);
+    // Convert iterator to elt# to avoid invalidating iterator when we reserve()
+    size_t InsertElt = I - this->begin();
+
+    // Ensure there is enough space.
+    reserve(static_cast<unsigned>(this->size() + NumToInsert));
+
+    // Uninvalidate the iterator.
+    I = this->begin()+InsertElt;
+
+    // If there are more elements between the insertion point and the end of the
+    // range than there are being inserted, we can use a simple approach to
+    // insertion.  Since we already reserved space, we know that this won't
+    // reallocate the vector.
+    if (size_t(this->end()-I) >= NumToInsert) {
+      T *OldEnd = this->end();
+      append(this->end()-NumToInsert, this->end());
+
+      // Copy the existing elements that get replaced.
+      std::copy_backward(I, OldEnd-NumToInsert, OldEnd);
+
+      std::copy(From, To, I);
+      return I;
+    }
+
+    // Otherwise, we're inserting more elements than exist already, and we're
+    // not inserting at the end.
+
+    // Copy over the elements that we're about to overwrite.
+    T *OldEnd = this->end();
+    this->setEnd(this->end() + NumToInsert);
+    size_t NumOverwritten = OldEnd-I;
+    this->uninitialized_copy(I, OldEnd, this->end()-NumOverwritten);
+
+    // Replace the overwritten part.
+    for (; NumOverwritten > 0; --NumOverwritten) {
+      *I = *From;
+      ++I; ++From;
+    }
+
+    // Insert the non-overwritten middle part.
+    this->uninitialized_copy(From, To, OldEnd);
+    return I;
+  }
+
+  const SmallVectorImpl
+  &operator=(const SmallVectorImpl &RHS);
+
+  bool operator==(const SmallVectorImpl &RHS) const {
+    if (this->size() != RHS.size()) return false;
+    return std::equal(this->begin(), this->end(), RHS.begin());
+  }
+  bool operator!=(const SmallVectorImpl &RHS) const {
+    return !(*this == RHS);
+  }
+
+  bool operator<(const SmallVectorImpl &RHS) const {
+    return std::lexicographical_compare(this->begin(), this->end(),
+                                        RHS.begin(), RHS.end());
+  }
+
+  /// set_size - Set the array size to \arg N, which the current array must have
+  /// enough capacity for.
+  ///
+  /// This does not construct or destroy any elements in the vector.
+  ///
+  /// Clients can use this in conjunction with capacity() to write past the end
+  /// of the buffer when they know that more elements are available, and only
+  /// update the size later. This avoids the cost of value initializing elements
+  /// which will only be overwritten.
+  void set_size(unsigned N) {
+    assert(N <= this->capacity());
+    this->setEnd(this->begin() + N);
+  }
+
+private:
+  static void construct_range(T *S, T *E, const T &Elt) {
+    for (; S != E; ++S)
+      new (S) T(Elt);
+  }
 };
 
-// Define this out-of-line to dissuade the C++ compiler from inlining it.
+
 template <typename T>
-void SmallVectorImpl<T>::grow(unsigned MinSize) {
-  unsigned CurCapacity = Capacity-Begin;
-  unsigned CurSize = size();
-  unsigned NewCapacity = 2*CurCapacity;
-  if (NewCapacity < MinSize)
-    NewCapacity = MinSize;
-  T *NewElts = reinterpret_cast<T*>(new char[NewCapacity*sizeof(T)]);
-  
-  // Copy the elements over.
-  std::uninitialized_copy(Begin, End, NewElts);
-  
-  // Destroy the original elements.
-  for (iterator I = Begin, E = End; I != E; ++I)
-    I->~T();
-  
-  // If this wasn't grown from the inline copy, deallocate the old space.
-  if (!isSmall())
-    delete[] (char*)Begin;
-  
-  Begin = NewElts;
-  End = NewElts+CurSize;
-  Capacity = Begin+NewCapacity;
+void SmallVectorImpl<T>::swap(SmallVectorImpl<T> &RHS) {
+  if (this == &RHS) return;
+
+  // We can only avoid copying elements if neither vector is small.
+  if (!this->isSmall() && !RHS.isSmall()) {
+    std::swap(this->BeginX, RHS.BeginX);
+    std::swap(this->EndX, RHS.EndX);
+    std::swap(this->CapacityX, RHS.CapacityX);
+    return;
+  }
+  if (RHS.size() > this->capacity())
+    this->grow(RHS.size());
+  if (this->size() > RHS.capacity())
+    RHS.grow(this->size());
+
+  // Swap the shared elements.
+  size_t NumShared = this->size();
+  if (NumShared > RHS.size()) NumShared = RHS.size();
+  for (unsigned i = 0; i != static_cast<unsigned>(NumShared); ++i)
+    std::swap((*this)[i], RHS[i]);
+
+  // Copy over the extra elts.
+  if (this->size() > RHS.size()) {
+    size_t EltDiff = this->size() - RHS.size();
+    this->uninitialized_copy(this->begin()+NumShared, this->end(), RHS.end());
+    RHS.setEnd(RHS.end()+EltDiff);
+    this->destroy_range(this->begin()+NumShared, this->end());
+    this->setEnd(this->begin()+NumShared);
+  } else if (RHS.size() > this->size()) {
+    size_t EltDiff = RHS.size() - this->size();
+    this->uninitialized_copy(RHS.begin()+NumShared, RHS.end(), this->end());
+    this->setEnd(this->end() + EltDiff);
+    this->destroy_range(RHS.begin()+NumShared, RHS.end());
+    RHS.setEnd(RHS.begin()+NumShared);
+  }
 }
-  
+
 template <typename T>
-const SmallVectorImpl<T> &
-SmallVectorImpl<T>::operator=(const SmallVectorImpl<T> &RHS) {
+const SmallVectorImpl<T> &SmallVectorImpl<T>::
+  operator=(const SmallVectorImpl<T> &RHS) {
   // Avoid self-assignment.
   if (this == &RHS) return *this;
-  
+
   // If we already have sufficient space, assign the common elements, then
   // destroy any excess.
-  unsigned RHSSize = RHS.size();
-  unsigned CurSize = size();
+  size_t RHSSize = RHS.size();
+  size_t CurSize = this->size();
   if (CurSize >= RHSSize) {
     // Assign common elements.
-    std::copy(RHS.Begin, RHS.Begin+RHSSize, Begin);
-    
+    iterator NewEnd;
+    if (RHSSize)
+      NewEnd = std::copy(RHS.begin(), RHS.begin()+RHSSize, this->begin());
+    else
+      NewEnd = this->begin();
+
     // Destroy excess elements.
-    for (unsigned i = RHSSize; i != CurSize; ++i)
-      Begin[i].~T();
-    
+    this->destroy_range(NewEnd, this->end());
+
     // Trim.
-    End = Begin + RHSSize;
+    this->setEnd(NewEnd);
     return *this;
   }
-  
+
   // If we have to grow to have enough elements, destroy the current elements.
   // This allows us to avoid copying them during the grow.
-  if (unsigned(Capacity-Begin) < RHSSize) {
+  if (this->capacity() < RHSSize) {
     // Destroy current elements.
-    for (iterator I = Begin, E = End; I != E; ++I)
-      I->~T();
-    End = Begin;
+    this->destroy_range(this->begin(), this->end());
+    this->setEnd(this->begin());
     CurSize = 0;
-    grow(RHSSize);
+    this->grow(RHSSize);
   } else if (CurSize) {
     // Otherwise, use assignment for the already-constructed elements.
-    std::copy(RHS.Begin, RHS.Begin+CurSize, Begin);
+    std::copy(RHS.begin(), RHS.begin()+CurSize, this->begin());
   }
-  
+
   // Copy construct the new elements in place.
-  std::uninitialized_copy(RHS.Begin+CurSize, RHS.End, Begin+CurSize);
-  
+  this->uninitialized_copy(RHS.begin()+CurSize, RHS.end(),
+                           this->begin()+CurSize);
+
   // Set end.
-  End = Begin+RHSSize;
+  this->setEnd(this->begin()+RHSSize);
+  return *this;
 }
-  
+
+
 /// SmallVector - This is a 'vector' (really, a variable-sized array), optimized
 /// for the case when the array is small.  It contains some number of elements
 /// in-place, which allows it to avoid heap allocation when the actual number of
@@ -228,21 +656,97 @@ class SmallVector : public SmallVectorImpl<T> {
   /// InlineElts - These are 'N-1' elements that are stored inline in the body
   /// of the vector.  The extra '1' element is stored in SmallVectorImpl.
   typedef typename SmallVectorImpl<T>::U U;
-  U InlineElts[(sizeof(T)*N+sizeof(U)-1)/sizeof(U) - 1];
-public:  
-  SmallVector() : SmallVectorImpl<T>(N) {
+  enum {
+    // MinUs - The number of U's require to cover N T's.
+    MinUs = (static_cast<unsigned int>(sizeof(T))*N +
+             static_cast<unsigned int>(sizeof(U)) - 1) /
+            static_cast<unsigned int>(sizeof(U)),
+
+    // NumInlineEltsElts - The number of elements actually in this array.  There
+    // is already one in the parent class, and we have to round up to avoid
+    // having a zero-element array.
+    NumInlineEltsElts = MinUs > 1 ? (MinUs - 1) : 1,
+
+    // NumTsAvailable - The number of T's we actually have space for, which may
+    // be more than N due to rounding.
+    NumTsAvailable = (NumInlineEltsElts+1)*static_cast<unsigned int>(sizeof(U))/
+                     static_cast<unsigned int>(sizeof(T))
+  };
+  U InlineElts[NumInlineEltsElts];
+public:
+  SmallVector() : SmallVectorImpl<T>(NumTsAvailable) {
   }
-  
+
+  explicit SmallVector(unsigned Size, const T &Value = T())
+    : SmallVectorImpl<T>(NumTsAvailable) {
+    this->reserve(Size);
+    while (Size--)
+      this->push_back(Value);
+  }
+
   template<typename ItTy>
-  SmallVector(ItTy S, ItTy E) : SmallVectorImpl<T>(N) {
-    append(S, E);
+  SmallVector(ItTy S, ItTy E) : SmallVectorImpl<T>(NumTsAvailable) {
+    this->append(S, E);
   }
-  
-  SmallVector(const SmallVector &RHS) : SmallVectorImpl<T>(N) {
-    operator=(RHS);
+
+  SmallVector(const SmallVector &RHS) : SmallVectorImpl<T>(NumTsAvailable) {
+    if (!RHS.empty())
+      SmallVectorImpl<T>::operator=(RHS);
+  }
+
+  const SmallVector &operator=(const SmallVector &RHS) {
+    SmallVectorImpl<T>::operator=(RHS);
+    return *this;
+  }
+
+};
+
+/// Specialize SmallVector at N=0.  This specialization guarantees
+/// that it can be instantiated at an incomplete T if none of its
+/// members are required.
+template <typename T>
+class SmallVector<T,0> : public SmallVectorImpl<T> {
+public:
+  SmallVector() : SmallVectorImpl<T>(0) {}
+
+  explicit SmallVector(unsigned Size, const T &Value = T())
+    : SmallVectorImpl<T>(0) {
+    this->reserve(Size);
+    while (Size--)
+      this->push_back(Value);
+  }
+
+  template<typename ItTy>
+  SmallVector(ItTy S, ItTy E) : SmallVectorImpl<T>(0) {
+    this->append(S, E);
+  }
+
+  SmallVector(const SmallVector &RHS) : SmallVectorImpl<T>(0) {
+    SmallVectorImpl<T>::operator=(RHS);
   }
+
+  SmallVector &operator=(const SmallVectorImpl<T> &RHS) {
+    return SmallVectorImpl<T>::operator=(RHS);
+  }
+
 };
 
 } // End llvm namespace
 
+namespace std {
+  /// Implement std::swap in terms of SmallVector swap.
+  template<typename T>
+  inline void
+  swap(llvm::SmallVectorImpl<T> &LHS, llvm::SmallVectorImpl<T> &RHS) {
+    LHS.swap(RHS);
+  }
+
+  /// Implement std::swap in terms of SmallVector swap.
+  template<typename T, unsigned N>
+  inline void
+  swap(llvm::SmallVector<T, N> &LHS, llvm::SmallVector<T, N> &RHS) {
+    LHS.swap(RHS);
+  }
+}
+
 #endif