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diff --git a/include/clang/AST/CXXInheritance.h b/include/clang/AST/CXXInheritance.h
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+//===------ CXXInheritance.h - C++ Inheritance ------------------*- C++ -*-===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is distributed under the University of Illinois Open Source
+// License. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+//
+// This file provides routines that help analyzing C++ inheritance hierarchies.
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef LLVM_CLANG_AST_CXXINHERITANCE_H
+#define LLVM_CLANG_AST_CXXINHERITANCE_H
+
+#include "clang/AST/DeclarationName.h"
+#include "clang/AST/DeclBase.h"
+#include "clang/AST/Type.h"
+#include "clang/AST/TypeOrdering.h"
+#include "llvm/ADT/SmallVector.h"
+#include <list>
+#include <map>
+#include <cassert>
+
+namespace clang {
+  
+class CXXBaseSpecifier;
+class CXXMethodDecl;
+class CXXRecordDecl;
+class NamedDecl;
+  
+/// \brief Represents an element in a path from a derived class to a
+/// base class. 
+/// 
+/// Each step in the path references the link from a
+/// derived class to one of its direct base classes, along with a
+/// base "number" that identifies which base subobject of the
+/// original derived class we are referencing.
+struct CXXBasePathElement {
+  /// \brief The base specifier that states the link from a derived
+  /// class to a base class, which will be followed by this base
+  /// path element.
+  const CXXBaseSpecifier *Base;
+  
+  /// \brief The record decl of the class that the base is a base of.
+  const CXXRecordDecl *Class;
+  
+  /// \brief Identifies which base class subobject (of type
+  /// \c Base->getType()) this base path element refers to. 
+  ///
+  /// This value is only valid if \c !Base->isVirtual(), because there
+  /// is no base numbering for the zero or one virtual bases of a
+  /// given type.
+  int SubobjectNumber;
+};
+
+/// \brief Represents a path from a specific derived class
+/// (which is not represented as part of the path) to a particular
+/// (direct or indirect) base class subobject.
+///
+/// Individual elements in the path are described by the \c CXXBasePathElement 
+/// structure, which captures both the link from a derived class to one of its
+/// direct bases and identification describing which base class
+/// subobject is being used.
+struct CXXBasePath : public llvm::SmallVector<CXXBasePathElement, 4> {
+  /// \brief The set of declarations found inside this base class
+  /// subobject.
+  DeclContext::lookup_result Decls;
+};
+
+/// BasePaths - Represents the set of paths from a derived class to
+/// one of its (direct or indirect) bases. For example, given the
+/// following class hierachy:
+///
+/// @code
+/// class A { };
+/// class B : public A { };
+/// class C : public A { };
+/// class D : public B, public C{ };
+/// @endcode
+///
+/// There are two potential BasePaths to represent paths from D to a
+/// base subobject of type A. One path is (D,0) -> (B,0) -> (A,0)
+/// and another is (D,0)->(C,0)->(A,1). These two paths actually
+/// refer to two different base class subobjects of the same type,
+/// so the BasePaths object refers to an ambiguous path. On the
+/// other hand, consider the following class hierarchy:
+///
+/// @code
+/// class A { };
+/// class B : public virtual A { };
+/// class C : public virtual A { };
+/// class D : public B, public C{ };
+/// @endcode
+///
+/// Here, there are two potential BasePaths again, (D, 0) -> (B, 0)
+/// -> (A,v) and (D, 0) -> (C, 0) -> (A, v), but since both of them
+/// refer to the same base class subobject of type A (the virtual
+/// one), there is no ambiguity.
+class CXXBasePaths {
+  /// \brief The type from which this search originated.
+  CXXRecordDecl *Origin;
+  
+  /// Paths - The actual set of paths that can be taken from the
+  /// derived class to the same base class.
+  std::list<CXXBasePath> Paths;
+  
+  /// ClassSubobjects - Records the class subobjects for each class
+  /// type that we've seen. The first element in the pair says
+  /// whether we found a path to a virtual base for that class type,
+  /// while the element contains the number of non-virtual base
+  /// class subobjects for that class type. The key of the map is
+  /// the cv-unqualified canonical type of the base class subobject.
+  std::map<QualType, std::pair<bool, unsigned>, QualTypeOrdering>
+    ClassSubobjects;
+  
+  /// FindAmbiguities - Whether Sema::IsDerivedFrom should try find
+  /// ambiguous paths while it is looking for a path from a derived
+  /// type to a base type.
+  bool FindAmbiguities;
+  
+  /// RecordPaths - Whether Sema::IsDerivedFrom should record paths
+  /// while it is determining whether there are paths from a derived
+  /// type to a base type.
+  bool RecordPaths;
+  
+  /// DetectVirtual - Whether Sema::IsDerivedFrom should abort the search
+  /// if it finds a path that goes across a virtual base. The virtual class
+  /// is also recorded.
+  bool DetectVirtual;
+  
+  /// ScratchPath - A BasePath that is used by Sema::IsDerivedFrom
+  /// to help build the set of paths.
+  CXXBasePath ScratchPath;
+  
+  /// DetectedVirtual - The base class that is virtual.
+  const RecordType *DetectedVirtual;
+  
+  /// \brief Array of the declarations that have been found. This
+  /// array is constructed only if needed, e.g., to iterate over the
+  /// results within LookupResult.
+  NamedDecl **DeclsFound;
+  unsigned NumDeclsFound;
+  
+  friend class CXXRecordDecl;
+  
+  void ComputeDeclsFound();
+  
+public:
+  typedef std::list<CXXBasePath>::const_iterator paths_iterator;
+  typedef NamedDecl **decl_iterator;
+  
+  /// BasePaths - Construct a new BasePaths structure to record the
+  /// paths for a derived-to-base search.
+  explicit CXXBasePaths(bool FindAmbiguities = true,
+                        bool RecordPaths = true,
+                        bool DetectVirtual = true)
+    : FindAmbiguities(FindAmbiguities), RecordPaths(RecordPaths),
+      DetectVirtual(DetectVirtual), DetectedVirtual(0), DeclsFound(0),
+      NumDeclsFound(0) { }
+  
+  ~CXXBasePaths() { delete [] DeclsFound; }
+  
+  paths_iterator begin() const { return Paths.begin(); }
+  paths_iterator end()   const { return Paths.end(); }
+  
+  CXXBasePath&       front()       { return Paths.front(); }
+  const CXXBasePath& front() const { return Paths.front(); }
+  
+  decl_iterator found_decls_begin();
+  decl_iterator found_decls_end();
+  
+  /// \brief Determine whether the path from the most-derived type to the
+  /// given base type is ambiguous (i.e., it refers to multiple subobjects of
+  /// the same base type).
+  bool isAmbiguous(QualType BaseType);
+  
+  /// \brief Whether we are finding multiple paths to detect ambiguities.
+  bool isFindingAmbiguities() const { return FindAmbiguities; }
+  
+  /// \brief Whether we are recording paths.
+  bool isRecordingPaths() const { return RecordPaths; }
+  
+  /// \brief Specify whether we should be recording paths or not.
+  void setRecordingPaths(bool RP) { RecordPaths = RP; }
+  
+  /// \brief Whether we are detecting virtual bases.
+  bool isDetectingVirtual() const { return DetectVirtual; }
+  
+  /// \brief The virtual base discovered on the path (if we are merely
+  /// detecting virtuals).
+  const RecordType* getDetectedVirtual() const {
+    return DetectedVirtual;
+  }
+  
+  /// \brief Retrieve the type from which this base-paths search
+  /// began
+  CXXRecordDecl *getOrigin() const { return Origin; }
+  void setOrigin(CXXRecordDecl *Rec) { Origin = Rec; }
+  
+  /// \brief Clear the base-paths results.
+  void clear();
+  
+  /// \brief Swap this data structure's contents with another CXXBasePaths 
+  /// object.
+  void swap(CXXBasePaths &Other);
+};
+  
+} // end namespace clang
+
+#endif