Initial support for struct-path aware TBAA.

Added TBAABaseType and TBAAOffset in LValue. These two fields are initialized to
the actual type and 0, and are updated in EmitLValueForField.
Path-aware TBAA tags are enabled for EmitLoadOfScalar and EmitStoreOfScalar.
Added command line option -struct-path-tbaa.


git-svn-id: https://llvm.org/svn/llvm-project/cfe/trunk@178797 91177308-0d34-0410-b5e6-96231b3b80d8
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