Index: include/clang/Driver/CC1Options.td
===================================================================
--- include/clang/Driver/CC1Options.td
+++ include/clang/Driver/CC1Options.td
@@ -224,6 +224,8 @@
   HelpText<"Use register sized accesses to bit-fields, when possible.">;
 def relaxed_aliasing : Flag<["-"], "relaxed-aliasing">,
   HelpText<"Turn off Type Based Alias Analysis">;
+def force_tbaa : Flag<["-"], "force-tbaa">,
+  HelpText<"Force Type Based Alias Analysis">;
 def no_struct_path_tbaa : Flag<["-"], "no-struct-path-tbaa">,
   HelpText<"Turn off struct-path aware Type Based Alias Analysis">;
 def masm_verbose : Flag<["-"], "masm-verbose">,
Index: include/clang/Driver/Options.td
===================================================================
--- include/clang/Driver/Options.td
+++ include/clang/Driver/Options.td
@@ -1391,6 +1391,8 @@
   HelpText<"Do not emit macro debug information">;
 def fstrict_aliasing : Flag<["-"], "fstrict-aliasing">, Group<f_Group>,
   Flags<[DriverOption, CoreOption]>;
+def fforce_tbaa : Flag<["-"], "fforce-tbaa">, Group<f_Group>,
+  Flags<[DriverOption, CoreOption]>;
 def fstrict_enums : Flag<["-"], "fstrict-enums">, Group<f_Group>, Flags<[CC1Option]>,
   HelpText<"Enable optimizations based on the strict definition of an enum's "
            "value range">;
Index: include/clang/Frontend/CodeGenOptions.def
===================================================================
--- include/clang/Frontend/CodeGenOptions.def
+++ include/clang/Frontend/CodeGenOptions.def
@@ -137,6 +137,7 @@
 
 CODEGENOPT(RelaxAll          , 1, 0) ///< Relax all machine code instructions.
 CODEGENOPT(RelaxedAliasing   , 1, 0) ///< Set when -fno-strict-aliasing is enabled.
+CODEGENOPT(ForceTBAA         , 1, 0) ///< Set if use of TBAA is forced.
 CODEGENOPT(StructPathTBAA    , 1, 0) ///< Whether or not to use struct-path TBAA.
 CODEGENOPT(SaveTempLabels    , 1, 0) ///< Save temporary labels.
 CODEGENOPT(SanitizeAddressUseAfterScope , 1, 0) ///< Enable use-after-scope detection
Index: lib/CodeGen/CodeGenModule.cpp
===================================================================
--- lib/CodeGen/CodeGenModule.cpp
+++ lib/CodeGen/CodeGenModule.cpp
@@ -129,10 +129,9 @@
   if (LangOpts.CUDA)
     createCUDARuntime();
 
-  // Enable TBAA unless it's suppressed. ThreadSanitizer needs TBAA even at O0.
-  if (LangOpts.Sanitize.has(SanitizerKind::Thread) ||
-      (!CodeGenOpts.RelaxedAliasing && CodeGenOpts.OptimizationLevel > 0))
-    TBAA.reset(new CodeGenTBAA(Context, VMContext, CodeGenOpts, getLangOpts(),
+  // Enable TBAA unless it's suppressed.
+  if (!CodeGenTBAA::isSuppressed(CodeGenOpts, LangOpts))
+    TBAA.reset(new CodeGenTBAA(Context, VMContext, CodeGenOpts, LangOpts,
                                getCXXABI().getMangleContext()));
 
   // If debug info or coverage generation is enabled, create the CGDebugInfo
Index: lib/CodeGen/CodeGenTBAA.h
===================================================================
--- lib/CodeGen/CodeGenTBAA.h
+++ lib/CodeGen/CodeGenTBAA.h
@@ -116,6 +116,16 @@
 
   /// Get the scalar tag MDNode for a given scalar type.
   llvm::MDNode *getTBAAScalarTagInfo(llvm::MDNode *AccessNode);
+
+  /// Return true if TBAA info shall not be emitted for regular types.
+  static bool isSuppressedForRegularTypes(const CodeGenOptions &CodeGenOpts);
+  bool isSuppressedForRegularTypes() const {
+    return isSuppressedForRegularTypes(CodeGenOpts);
+  }
+
+  /// Return true if TBAA info shall not be emitted.
+  static bool isSuppressed(const CodeGenOptions &CodeGenOpts,
+                           const LangOptions &LangOpts);
 };
 
 }  // end namespace CodeGen
Index: lib/CodeGen/CodeGenTBAA.cpp
===================================================================
--- lib/CodeGen/CodeGenTBAA.cpp
+++ lib/CodeGen/CodeGenTBAA.cpp
@@ -90,8 +90,7 @@
 
 llvm::MDNode *
 CodeGenTBAA::getTBAAInfo(QualType QTy) {
-  // At -O0 or relaxed aliasing, TBAA is not emitted for regular types.
-  if (CodeGenOpts.OptimizationLevel == 0 || CodeGenOpts.RelaxedAliasing)
+  if(isSuppressedForRegularTypes())
     return nullptr;
 
   // If the type has the may_alias attribute (even on a typedef), it is
@@ -327,3 +326,19 @@
   return ScalarTagMetadataCache[AccessNode] =
     MDHelper.createTBAAStructTagNode(AccessNode, AccessNode, 0);
 }
+
+bool
+CodeGenTBAA::isSuppressedForRegularTypes(const CodeGenOptions &CodeGenOpts) {
+  if (CodeGenOpts.ForceTBAA)
+    return false;
+  return CodeGenOpts.RelaxedAliasing || CodeGenOpts.OptimizationLevel == 0;
+}
+
+bool CodeGenTBAA::isSuppressed(const CodeGenOptions &CodeGenOpts,
+                               const LangOptions &LangOpts) {
+  // ThreadSanitizer needs TBAA info for virtual table accesses even at -O0;
+  // see r155430.
+  if (LangOpts.Sanitize.has(SanitizerKind::Thread))
+    return false;
+  return isSuppressedForRegularTypes(CodeGenOpts);
+}
Index: lib/Driver/ToolChains/Clang.cpp
===================================================================
--- lib/Driver/ToolChains/Clang.cpp
+++ lib/Driver/ToolChains/Clang.cpp
@@ -2379,6 +2379,8 @@
   // We turn strict aliasing off by default if we're in CL mode, since MSVC
   // doesn't do any TBAA.
   bool TBAAOnByDefault = !getToolChain().getDriver().IsCLMode();
+  if (Args.hasArg(options::OPT_fforce_tbaa))
+    CmdArgs.push_back("-force-tbaa");
   if (!Args.hasFlag(options::OPT_fstrict_aliasing, StrictAliasingAliasOption,
                     options::OPT_fno_strict_aliasing, TBAAOnByDefault))
     CmdArgs.push_back("-relaxed-aliasing");
Index: lib/Frontend/CompilerInvocation.cpp
===================================================================
--- lib/Frontend/CompilerInvocation.cpp
+++ lib/Frontend/CompilerInvocation.cpp
@@ -544,6 +544,7 @@
   Opts.UseRegisterSizedBitfieldAccess = Args.hasArg(
     OPT_fuse_register_sized_bitfield_access);
   Opts.RelaxedAliasing = Args.hasArg(OPT_relaxed_aliasing);
+  Opts.ForceTBAA = Args.hasArg(OPT_force_tbaa);
   Opts.StructPathTBAA = !Args.hasArg(OPT_no_struct_path_tbaa);
   Opts.DwarfDebugFlags = Args.getLastArgValue(OPT_dwarf_debug_flags);
   Opts.MergeAllConstants = !Args.hasArg(OPT_fno_merge_all_constants);
Index: test/CodeGen/tbaa-for-vptr.cpp
===================================================================
--- test/CodeGen/tbaa-for-vptr.cpp
+++ test/CodeGen/tbaa-for-vptr.cpp
@@ -1,9 +1,10 @@
 // RUN: %clang_cc1 -triple %itanium_abi_triple -emit-llvm -o - -fsanitize=thread %s | FileCheck %s
 // RUN: %clang_cc1 -triple %itanium_abi_triple -emit-llvm -o - -O1 %s | FileCheck %s
-// RUN: %clang_cc1 -triple %itanium_abi_triple -emit-llvm -o - -O1  -relaxed-aliasing -fsanitize=thread %s | FileCheck %s
+// RUN: %clang_cc1 -triple %itanium_abi_triple -emit-llvm -o - -O1 -relaxed-aliasing -fsanitize=thread %s | FileCheck %s
+// RUN: %clang_cc1 -triple %itanium_abi_triple -emit-llvm -o - -O1 -relaxed-aliasing -force-tbaa %s | FileCheck %s
 //
 // RUN: %clang_cc1 -triple %itanium_abi_triple -emit-llvm -o - %s | FileCheck %s --check-prefix=NOTBAA
-// RUN: %clang_cc1 -triple %itanium_abi_triple -emit-llvm -o - -O2  -relaxed-aliasing %s | FileCheck %s --check-prefix=NOTBAA
+// RUN: %clang_cc1 -triple %itanium_abi_triple -emit-llvm -o - -O2 -relaxed-aliasing %s | FileCheck %s --check-prefix=NOTBAA
 //
 // Check that we generate TBAA for vtable pointer loads and stores.
 // When -fsanitize=thread is used TBAA should be generated at all opt levels
Index: test/CodeGen/tbaa.cpp
===================================================================
--- test/CodeGen/tbaa.cpp
+++ test/CodeGen/tbaa.cpp
@@ -1,7 +1,9 @@
 // RUN: %clang_cc1 -triple x86_64-apple-darwin -O1 -no-struct-path-tbaa -disable-llvm-passes %s -emit-llvm -o - | FileCheck %s
 // RUN: %clang_cc1 -triple x86_64-apple-darwin -O1 -disable-llvm-passes %s -emit-llvm -o - | FileCheck %s -check-prefix=PATH
 // RUN: %clang_cc1 -triple x86_64-apple-darwin -O0 -disable-llvm-passes %s -emit-llvm -o - | FileCheck %s -check-prefix=NO-TBAA
+// RUN: %clang_cc1 -triple x86_64-apple-darwin -O0 -disable-llvm-passes -force-tbaa %s -emit-llvm -o - | FileCheck %s -check-prefix=PATH
 // RUN: %clang_cc1 -triple x86_64-apple-darwin -O1 -relaxed-aliasing -disable-llvm-passes %s -emit-llvm -o - | FileCheck %s -check-prefix=NO-TBAA
+// RUN: %clang_cc1 -triple x86_64-apple-darwin -O1 -relaxed-aliasing -disable-llvm-passes -force-tbaa %s -emit-llvm -o - | FileCheck %s -check-prefix=PATH
 // Test TBAA metadata generated by front-end.
 //
 // NO-TBAA-NOT: !tbaa
Index: test/Driver/force-tbaa.c
===================================================================
--- test/Driver/force-tbaa.c
+++ test/Driver/force-tbaa.c
@@ -0,0 +1,10 @@
+// RUN: %clang -fno-strict-aliasing -fforce-tbaa -### %s 2>&1 | FileCheck -check-prefix=CHECK-WITH-FORCE-TBAA %s
+// RUN: %clang -fno-strict-aliasing -### %s 2>&1 | FileCheck -check-prefix=CHECK-WITHOUT-FORCE-TBAA %s
+
+// CHECK-WITH-FORCE-TBAA: -cc1
+// CHECK-WITH-FORCE-TBAA: -force-tbaa
+// CHECK-WITH-FORCE-TBAA: -relaxed-aliasing
+
+// CHECK-WITHOUT-FORCE-TBAA: -cc1
+// CHECK-WITHOUT-FORCE-TBAA-NOT: -force-tbaa
+// CHECK-WITHOUT-FORCE-TBAA: -relaxed-aliasing