4 files changed, 18 insertions, 14 deletions
diff --git a/clang/lib/CodeGen/CodeGenModule.cpp b/clang/lib/CodeGen/CodeGenModule.cpp
index 17bca0a6f38..6c126718431 100644
--- a/clang/lib/CodeGen/CodeGenModule.cpp
+++ b/clang/lib/CodeGen/CodeGenModule.cpp
@@ -243,14 +243,14 @@ llvm::MDNode *CodeGenModule::getTBAAStructTagInfo(QualType BaseTy,
   return TBAA->getTBAAStructTagInfo(BaseTy, AccessN, O);
 }
 
-/// Decorate the instruction with a TBAA tag. For both scalar TBAA
-/// and struct-path aware TBAA, the tag has the same format:
-/// base type, access type and offset.
+/// Decorate the instruction with a TBAA tag. For scalar TBAA, the tag
+/// is the same as the type. For struct-path aware TBAA, the tag
+/// is different from the type: base type, access type and offset.
 /// When ConvertTypeToTag is true, we create a tag based on the scalar type.
 void CodeGenModule::DecorateInstruction(llvm::Instruction *Inst,
                                         llvm::MDNode *TBAAInfo,
                                         bool ConvertTypeToTag) {
-  if (ConvertTypeToTag && TBAA)
+  if (ConvertTypeToTag && TBAA && CodeGenOpts.StructPathTBAA)
     Inst->setMetadata(llvm::LLVMContext::MD_tbaa,
                       TBAA->getTBAAScalarTagInfo(TBAAInfo));
   else
diff --git a/clang/lib/CodeGen/CodeGenTBAA.cpp b/clang/lib/CodeGen/CodeGenTBAA.cpp
index a2c1d8a503e..f104c2f2f57 100644
--- a/clang/lib/CodeGen/CodeGenTBAA.cpp
+++ b/clang/lib/CodeGen/CodeGenTBAA.cpp
@@ -50,11 +50,16 @@ llvm::MDNode *CodeGenTBAA::getRoot() {
   return Root;
 }
 
-// For both scalar TBAA and struct-path aware TBAA, the scalar type has the
-// same format: name, parent node, and offset.
+// For struct-path aware TBAA, the scalar type has the same format as
+// the struct type: name, offset, pointer to another node in the type DAG.
+// For scalar TBAA, the scalar type is the same as the scalar tag:
+// name and a parent pointer.
 llvm::MDNode *CodeGenTBAA::createTBAAScalarType(StringRef Name,
                                                 llvm::MDNode *Parent) {
-  return MDHelper.createTBAAScalarTypeNode(Name, Parent);
+  if (CodeGenOpts.StructPathTBAA)
+    return MDHelper.createTBAAScalarTypeNode(Name, Parent);
+  else
+    return MDHelper.createTBAANode(Name, Parent);
 }
 
 llvm::MDNode *CodeGenTBAA::getChar() {
@@ -206,7 +211,8 @@ CodeGenTBAA::CollectFields(uint64_t BaseOffset,
   uint64_t Offset = BaseOffset;
   uint64_t Size = Context.getTypeSizeInChars(QTy).getQuantity();
   llvm::MDNode *TBAAInfo = MayAlias ? getChar() : getTBAAInfo(QTy);
-  llvm::MDNode *TBAATag = getTBAAScalarTagInfo(TBAAInfo);
+  llvm::MDNode *TBAATag = CodeGenOpts.StructPathTBAA ?
+                          getTBAAScalarTagInfo(TBAAInfo) : TBAAInfo;
   Fields.push_back(llvm::MDBuilder::TBAAStructField(Offset, Size, TBAATag));
   return true;
 }
@@ -287,12 +293,11 @@ CodeGenTBAA::getTBAAStructTypeInfo(QualType QTy) {
   return StructMetadataCache[Ty] = NULL;
 }
 
-/// Return a TBAA tag node for both scalar TBAA and struct-path aware TBAA.
 llvm::MDNode *
 CodeGenTBAA::getTBAAStructTagInfo(QualType BaseQTy, llvm::MDNode *AccessNode,
                                   uint64_t Offset) {
   if (!CodeGenOpts.StructPathTBAA)
-    return getTBAAScalarTagInfo(AccessNode);
+    return AccessNode;
 
   const Type *BTy = Context.getCanonicalType(BaseQTy).getTypePtr();
   TBAAPathTag PathTag = TBAAPathTag(BTy, AccessNode, Offset);
diff --git a/clang/lib/Driver/Tools.cpp b/clang/lib/Driver/Tools.cpp
index 93571ffcdff..dd48bc18e81 100644
--- a/clang/lib/Driver/Tools.cpp
+++ b/clang/lib/Driver/Tools.cpp
@@ -2183,9 +2183,8 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
                     options::OPT_fno_strict_aliasing,
                     getToolChain().IsStrictAliasingDefault()))
     CmdArgs.push_back("-relaxed-aliasing");
-  if (!Args.hasFlag(options::OPT_fstruct_path_tbaa,
-                    options::OPT_fno_struct_path_tbaa))
-    CmdArgs.push_back("-no-struct-path-tbaa");
+  if (Args.hasArg(options::OPT_fstruct_path_tbaa))
+    CmdArgs.push_back("-struct-path-tbaa");
   if (Args.hasFlag(options::OPT_fstrict_enums, options::OPT_fno_strict_enums,
                    false))
     CmdArgs.push_back("-fstrict-enums");
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 976ae41971f..58a6e25d5ca 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -344,7 +344,7 @@ static bool ParseCodeGenArgs(CodeGenOptions &Opts, ArgList &Args, InputKind IK,
   Opts.UseRegisterSizedBitfieldAccess = Args.hasArg(
     OPT_fuse_register_sized_bitfield_access);
   Opts.RelaxedAliasing = Args.hasArg(OPT_relaxed_aliasing);
-  Opts.StructPathTBAA = !Args.hasArg(OPT_no_struct_path_tbaa);
+  Opts.StructPathTBAA = Args.hasArg(OPT_struct_path_tbaa);
   Opts.DwarfDebugFlags = Args.getLastArgValue(OPT_dwarf_debug_flags);
   Opts.MergeAllConstants = !Args.hasArg(OPT_fno_merge_all_constants);
   Opts.NoCommon = Args.hasArg(OPT_fno_common);