diff --git a/lib/CodeGen/CGExpr.cpp b/lib/CodeGen/CGExpr.cpp
index 9bfaacb..2f5186d 100644
--- a/lib/CodeGen/CGExpr.cpp
+++ b/lib/CodeGen/CGExpr.cpp
@@ -1044,7 +1044,8 @@
 llvm::Value *CodeGenFunction::EmitLoadOfScalar(LValue lvalue) {
   return EmitLoadOfScalar(lvalue.getAddress(), lvalue.isVolatile(),
                           lvalue.getAlignment().getQuantity(),
-                          lvalue.getType(), lvalue.getTBAAInfo());
+                          lvalue.getType(), lvalue.getTBAAInfo(),
+                          lvalue.getTBAABaseType(), lvalue.getTBAAOffset());
 }
 
 static bool hasBooleanRepresentation(QualType Ty) {
@@ -1106,7 +1107,9 @@
 
 llvm::Value *CodeGenFunction::EmitLoadOfScalar(llvm::Value *Addr, bool Volatile,
                                               unsigned Alignment, QualType Ty,
-                                              llvm::MDNode *TBAAInfo) {
+                                              llvm::MDNode *TBAAInfo,
+                                              QualType TBAABaseType,
+                                              uint64_t TBAAOffset) {
   // For better performance, handle vector loads differently.
   if (Ty->isVectorType()) {
     llvm::Value *V;
@@ -1158,8 +1161,11 @@
     Load->setVolatile(true);
   if (Alignment)
     Load->setAlignment(Alignment);
-  if (TBAAInfo)
-    CGM.DecorateInstruction(Load, TBAAInfo);
+  if (TBAAInfo) {
+    llvm::MDNode *TBAAPath = CGM.getTBAAStructTagInfo(TBAABaseType, TBAAInfo,
+                                                      TBAAOffset);
+    CGM.DecorateInstruction(Load, TBAAPath);
+  }
 
   if ((SanOpts->Bool && hasBooleanRepresentation(Ty)) ||
       (SanOpts->Enum && Ty->getAs<EnumType>())) {
@@ -1217,7 +1223,8 @@
                                         bool Volatile, unsigned Alignment,
                                         QualType Ty,
                                         llvm::MDNode *TBAAInfo,
-                                        bool isInit) {
+                                        bool isInit, QualType TBAABaseType,
+                                        uint64_t TBAAOffset) {
   
   // Handle vectors differently to get better performance.
   if (Ty->isVectorType()) {
@@ -1268,15 +1275,19 @@
   llvm::StoreInst *Store = Builder.CreateStore(Value, Addr, Volatile);
   if (Alignment)
     Store->setAlignment(Alignment);
-  if (TBAAInfo)
-    CGM.DecorateInstruction(Store, TBAAInfo);
+  if (TBAAInfo) {
+    llvm::MDNode *TBAAPath = CGM.getTBAAStructTagInfo(TBAABaseType, TBAAInfo,
+                                                      TBAAOffset);
+    CGM.DecorateInstruction(Store, TBAAPath);
+  }
 }
 
 void CodeGenFunction::EmitStoreOfScalar(llvm::Value *value, LValue lvalue,
                                         bool isInit) {
   EmitStoreOfScalar(value, lvalue.getAddress(), lvalue.isVolatile(),
                     lvalue.getAlignment().getQuantity(), lvalue.getType(),
-                    lvalue.getTBAAInfo(), isInit);
+                    lvalue.getTBAAInfo(), isInit, lvalue.getTBAABaseType(),
+                    lvalue.getTBAAOffset());
 }
 
 /// EmitLoadOfLValue - Given an expression that represents a value lvalue, this
@@ -2494,9 +2505,12 @@
 
   llvm::Value *addr = base.getAddress();
   unsigned cvr = base.getVRQualifiers();
+  bool TBAAPath = CGM.getCodeGenOpts().StructPathTBAA;
   if (rec->isUnion()) {
     // For unions, there is no pointer adjustment.
     assert(!type->isReferenceType() && "union has reference member");
+    // TODO: handle path-aware TBAA for union.
+    TBAAPath = false;
   } else {
     // For structs, we GEP to the field that the record layout suggests.
     unsigned idx = CGM.getTypes().getCGRecordLayout(rec).getLLVMFieldNo(field);
@@ -2508,6 +2522,8 @@
       if (cvr & Qualifiers::Volatile) load->setVolatile(true);
       load->setAlignment(alignment.getQuantity());
 
+      // Loading the reference will disable path-aware TBAA.
+      TBAAPath = false;
       if (CGM.shouldUseTBAA()) {
         llvm::MDNode *tbaa;
         if (mayAlias)
@@ -2541,6 +2557,16 @@
 
   LValue LV = MakeAddrLValue(addr, type, alignment);
   LV.getQuals().addCVRQualifiers(cvr);
+  if (TBAAPath) {
+    const ASTRecordLayout &Layout =
+        getContext().getASTRecordLayout(field->getParent());
+    // Set the base type to be the base type of the base LValue and
+    // update offset to be relative to the base type.
+    LV.setTBAABaseType(base.getTBAABaseType());
+    LV.setTBAAOffset(base.getTBAAOffset() +
+                     Layout.getFieldOffset(field->getFieldIndex()) /
+                                           getContext().getCharWidth());
+  }
 
   // __weak attribute on a field is ignored.
   if (LV.getQuals().getObjCGCAttr() == Qualifiers::Weak)
diff --git a/lib/CodeGen/CGValue.h b/lib/CodeGen/CGValue.h
index 0657fdc..b625b86 100644
--- a/lib/CodeGen/CGValue.h
+++ b/lib/CodeGen/CGValue.h
@@ -157,6 +157,11 @@
 
   Expr *BaseIvarExp;
 
+  /// Used by struct-path-aware TBAA.
+  QualType TBAABaseType;
+  /// Offset relative to the base type.
+  uint64_t TBAAOffset;
+
   /// TBAAInfo - TBAA information to attach to dereferences of this LValue.
   llvm::MDNode *TBAAInfo;
 
@@ -175,6 +180,10 @@
     this->ImpreciseLifetime = false;
     this->ThreadLocalRef = false;
     this->BaseIvarExp = 0;
+
+    // Initialize fields for TBAA.
+    this->TBAABaseType = Type;
+    this->TBAAOffset = 0;
     this->TBAAInfo = TBAAInfo;
   }
 
@@ -232,6 +241,12 @@
   Expr *getBaseIvarExp() const { return BaseIvarExp; }
   void setBaseIvarExp(Expr *V) { BaseIvarExp = V; }
 
+  QualType getTBAABaseType() const { return TBAABaseType; }
+  void setTBAABaseType(QualType T) { TBAABaseType = T; }
+
+  uint64_t getTBAAOffset() const { return TBAAOffset; }
+  void setTBAAOffset(uint64_t O) { TBAAOffset = O; }
+
   llvm::MDNode *getTBAAInfo() const { return TBAAInfo; }
   void setTBAAInfo(llvm::MDNode *N) { TBAAInfo = N; }
 
diff --git a/lib/CodeGen/CodeGenFunction.h b/lib/CodeGen/CodeGenFunction.h
index f76022f..645d5ff 100644
--- a/lib/CodeGen/CodeGenFunction.h
+++ b/lib/CodeGen/CodeGenFunction.h
@@ -2211,7 +2211,9 @@
   /// the LLVM value representation.
   llvm::Value *EmitLoadOfScalar(llvm::Value *Addr, bool Volatile,
                                 unsigned Alignment, QualType Ty,
-                                llvm::MDNode *TBAAInfo = 0);
+                                llvm::MDNode *TBAAInfo = 0,
+                                QualType TBAABaseTy = QualType(),
+                                uint64_t TBAAOffset = 0);
 
   /// EmitLoadOfScalar - Load a scalar value from an address, taking
   /// care to appropriately convert from the memory representation to
@@ -2224,7 +2226,9 @@
   /// the LLVM value representation.
   void EmitStoreOfScalar(llvm::Value *Value, llvm::Value *Addr,
                          bool Volatile, unsigned Alignment, QualType Ty,
-                         llvm::MDNode *TBAAInfo = 0, bool isInit=false);
+                         llvm::MDNode *TBAAInfo = 0, bool isInit = false,
+                         QualType TBAABaseTy = QualType(),
+                         uint64_t TBAAOffset = 0);
 
   /// EmitStoreOfScalar - Store a scalar value to an address, taking
   /// care to appropriately convert from the memory representation to
diff --git a/lib/CodeGen/CodeGenModule.cpp b/lib/CodeGen/CodeGenModule.cpp
index 6d85a88..c518a55 100644
--- a/lib/CodeGen/CodeGenModule.cpp
+++ b/lib/CodeGen/CodeGenModule.cpp
@@ -227,6 +227,20 @@
   return TBAA->getTBAAStructInfo(QTy);
 }
 
+llvm::MDNode *CodeGenModule::getTBAAStructTypeInfo(QualType QTy) {
+  if (!TBAA)
+    return 0;
+  return TBAA->getTBAAStructTypeInfo(QTy);
+}
+
+llvm::MDNode *CodeGenModule::getTBAAStructTagInfo(QualType BaseTy,
+                                                  llvm::MDNode *AccessN,
+                                                  uint64_t O) {
+  if (!TBAA)
+    return 0;
+  return TBAA->getTBAAStructTagInfo(BaseTy, AccessN, O);
+}
+
 void CodeGenModule::DecorateInstruction(llvm::Instruction *Inst,
                                         llvm::MDNode *TBAAInfo) {
   Inst->setMetadata(llvm::LLVMContext::MD_tbaa, TBAAInfo);
diff --git a/lib/CodeGen/CodeGenModule.h b/lib/CodeGen/CodeGenModule.h
index fcd4830..5b2153e 100644
--- a/lib/CodeGen/CodeGenModule.h
+++ b/lib/CodeGen/CodeGenModule.h
@@ -501,6 +501,11 @@
   llvm::MDNode *getTBAAInfo(QualType QTy);
   llvm::MDNode *getTBAAInfoForVTablePtr();
   llvm::MDNode *getTBAAStructInfo(QualType QTy);
+  /// Return the MDNode in the type DAG for the given struct type.
+  llvm::MDNode *getTBAAStructTypeInfo(QualType QTy);
+  /// Return the path-aware tag for given base type, access node and offset.
+  llvm::MDNode *getTBAAStructTagInfo(QualType BaseTy, llvm::MDNode *AccessN,
+                                     uint64_t O);
 
   bool isTypeConstant(QualType QTy, bool ExcludeCtorDtor);
 
diff --git a/lib/CodeGen/CodeGenTBAA.cpp b/lib/CodeGen/CodeGenTBAA.cpp
index cfa141e..7e4d34a 100644
--- a/lib/CodeGen/CodeGenTBAA.cpp
+++ b/lib/CodeGen/CodeGenTBAA.cpp
@@ -21,6 +21,7 @@
 #include "clang/AST/Mangle.h"
 #include "clang/AST/RecordLayout.h"
 #include "clang/Frontend/CodeGenOptions.h"
+#include "llvm/ADT/SmallSet.h"
 #include "llvm/IR/Constants.h"
 #include "llvm/IR/LLVMContext.h"
 #include "llvm/IR/Metadata.h"
@@ -225,3 +226,87 @@
   // For now, handle any other kind of type conservatively.
   return StructMetadataCache[Ty] = NULL;
 }
+
+/// Check if the given type can be handled by path-aware TBAA.
+static bool isTBAAPathStruct(QualType QTy) {
+  if (const RecordType *TTy = QTy->getAs<RecordType>()) {
+    const RecordDecl *RD = TTy->getDecl()->getDefinition();
+    // RD can be struct, union, class, interface or enum.
+    // For now, we only handle struct.
+    if (RD->isStruct() && !RD->hasFlexibleArrayMember())
+      return true;
+  }
+  return false;
+}
+
+llvm::MDNode *
+CodeGenTBAA::getTBAAStructTypeInfo(QualType QTy) {
+  const Type *Ty = Context.getCanonicalType(QTy).getTypePtr();
+  assert(isTBAAPathStruct(QTy));
+
+  if (llvm::MDNode *N = StructTypeMetadataCache[Ty])
+    return N;
+
+  if (const RecordType *TTy = QTy->getAs<RecordType>()) {
+    const RecordDecl *RD = TTy->getDecl()->getDefinition();
+
+    const ASTRecordLayout &Layout = Context.getASTRecordLayout(RD);
+    SmallVector <std::pair<uint64_t, llvm::MDNode*>, 4> Fields;
+    // To reduce the size of MDNode for a given struct type, we only output
+    // once for all the fields with the same scalar types.
+    // Offsets for scalar fields in the type DAG are not used.
+    llvm::SmallSet <llvm::MDNode*, 4> ScalarFieldTypes;
+    unsigned idx = 0;
+    for (RecordDecl::field_iterator i = RD->field_begin(),
+         e = RD->field_end(); i != e; ++i, ++idx) {
+      QualType FieldQTy = i->getType();
+      llvm::MDNode *FieldNode;
+      if (isTBAAPathStruct(FieldQTy))
+        FieldNode = getTBAAStructTypeInfo(FieldQTy);
+      else {
+        FieldNode = getTBAAInfo(FieldQTy);
+        // Ignore this field if the type already exists.
+        if (ScalarFieldTypes.count(FieldNode))
+          continue;
+        ScalarFieldTypes.insert(FieldNode);
+       }
+      if (!FieldNode)
+        return StructTypeMetadataCache[Ty] = NULL;
+      Fields.push_back(std::make_pair(
+          Layout.getFieldOffset(idx) / Context.getCharWidth(), FieldNode));
+    }
+
+    // TODO: This is using the RTTI name. Is there a better way to get
+    // a unique string for a type?
+    SmallString<256> OutName;
+    llvm::raw_svector_ostream Out(OutName);
+    MContext.mangleCXXRTTIName(QualType(Ty, 0), Out);
+    Out.flush();
+    // Create the struct type node with a vector of pairs (offset, type).
+    return StructTypeMetadataCache[Ty] =
+      MDHelper.createTBAAStructTypeNode(OutName, Fields);
+  }
+
+  return StructMetadataCache[Ty] = NULL;
+}
+
+llvm::MDNode *
+CodeGenTBAA::getTBAAStructTagInfo(QualType BaseQTy, llvm::MDNode *AccessNode,
+                                  uint64_t Offset) {
+  if (!CodeGenOpts.StructPathTBAA)
+    return AccessNode;
+
+  const Type *BTy = Context.getCanonicalType(BaseQTy).getTypePtr();
+  TBAAPathTag PathTag = TBAAPathTag(BTy, AccessNode, Offset);
+  if (llvm::MDNode *N = StructTagMetadataCache[PathTag])
+    return N;
+
+  llvm::MDNode *BNode = 0;
+  if (isTBAAPathStruct(BaseQTy))
+    BNode  = getTBAAStructTypeInfo(BaseQTy);
+  if (!BNode)
+    return StructTagMetadataCache[PathTag] = AccessNode;
+
+  return StructTagMetadataCache[PathTag] =
+    MDHelper.createTBAAStructTagNode(BNode, AccessNode, Offset);
+}
diff --git a/lib/CodeGen/CodeGenTBAA.h b/lib/CodeGen/CodeGenTBAA.h
index 4c6e045..9ddc3aa 100644
--- a/lib/CodeGen/CodeGenTBAA.h
+++ b/lib/CodeGen/CodeGenTBAA.h
@@ -35,6 +35,14 @@
 namespace CodeGen {
   class CGRecordLayout;
 
+  struct TBAAPathTag {
+    TBAAPathTag(const Type *B, const llvm::MDNode *A, uint64_t O)
+      : BaseT(B), AccessN(A), Offset(O) {}
+    const Type *BaseT;
+    const llvm::MDNode *AccessN;
+    uint64_t Offset;
+  };
+
 /// CodeGenTBAA - This class organizes the cross-module state that is used
 /// while lowering AST types to LLVM types.
 class CodeGenTBAA {
@@ -46,8 +54,13 @@
   // MDHelper - Helper for creating metadata.
   llvm::MDBuilder MDHelper;
 
-  /// MetadataCache - This maps clang::Types to llvm::MDNodes describing them.
+  /// MetadataCache - This maps clang::Types to scalar llvm::MDNodes describing
+  /// them.
   llvm::DenseMap<const Type *, llvm::MDNode *> MetadataCache;
+  /// This maps clang::Types to a struct node in the type DAG.
+  llvm::DenseMap<const Type *, llvm::MDNode *> StructTypeMetadataCache;
+  /// This maps TBAAPathTags to a tag node.
+  llvm::DenseMap<TBAAPathTag, llvm::MDNode *> StructTagMetadataCache;
 
   /// StructMetadataCache - This maps clang::Types to llvm::MDNodes describing
   /// them for struct assignments.
@@ -89,9 +102,49 @@
   /// getTBAAStructInfo - Get the TBAAStruct MDNode to be used for a memcpy of
   /// the given type.
   llvm::MDNode *getTBAAStructInfo(QualType QTy);
+
+  /// Get the MDNode in the type DAG for given struct type QType.
+  llvm::MDNode *getTBAAStructTypeInfo(QualType QType);
+  /// Get the tag MDNode for a given base type, the actual sclar access MDNode
+  /// and offset into the base type.
+  llvm::MDNode *getTBAAStructTagInfo(QualType BaseQType,
+                                     llvm::MDNode *AccessNode, uint64_t Offset);
 };
 
 }  // end namespace CodeGen
 }  // end namespace clang
 
+namespace llvm {
+
+template<> struct DenseMapInfo<clang::CodeGen::TBAAPathTag> {
+  static clang::CodeGen::TBAAPathTag getEmptyKey() {
+    return clang::CodeGen::TBAAPathTag(
+      DenseMapInfo<const clang::Type *>::getEmptyKey(),
+      DenseMapInfo<const MDNode *>::getEmptyKey(),
+      DenseMapInfo<uint64_t>::getEmptyKey());
+  }
+
+  static clang::CodeGen::TBAAPathTag getTombstoneKey() {
+    return clang::CodeGen::TBAAPathTag(
+      DenseMapInfo<const clang::Type *>::getTombstoneKey(),
+      DenseMapInfo<const MDNode *>::getTombstoneKey(),
+      DenseMapInfo<uint64_t>::getTombstoneKey());
+  }
+
+  static unsigned getHashValue(const clang::CodeGen::TBAAPathTag &Val) {
+    return DenseMapInfo<const clang::Type *>::getHashValue(Val.BaseT) ^
+           DenseMapInfo<const MDNode *>::getHashValue(Val.AccessN) ^
+           DenseMapInfo<uint64_t>::getHashValue(Val.Offset);
+  }
+
+  static bool isEqual(const clang::CodeGen::TBAAPathTag &LHS,
+                      const clang::CodeGen::TBAAPathTag &RHS) {
+    return LHS.BaseT == RHS.BaseT &&
+           LHS.AccessN == RHS.AccessN &&
+           LHS.Offset == RHS.Offset;
+  }
+};
+
+}  // end namespace llvm
+
 #endif