3 files changed, 21 insertions, 2 deletions
diff --git a/clang/lib/AST/VTableBuilder.cpp b/clang/lib/AST/VTableBuilder.cpp
index a587f9b..cce0a50 100644
--- a/clang/lib/AST/VTableBuilder.cpp
+++ b/clang/lib/AST/VTableBuilder.cpp
@@ -665,7 +665,11 @@ CharUnits VCallAndVBaseOffsetBuilder::getCurrentOffsetOffset() const {
   // vtable address point. (We subtract 3 to account for the information just
   // above the address point, the RTTI info, the offset to top, and the
   // vcall offset itself).
-  int64_t OffsetIndex = -(int64_t)(3 + Components.size());
+  size_t NumComponentsAboveAddrPoint = 3;
+  if (Context.getLangOpts().OmitVTableRTTI)
+    NumComponentsAboveAddrPoint--;
+  int64_t OffsetIndex =
+      -(int64_t)(NumComponentsAboveAddrPoint + Components.size());
 
   // Under the relative ABI, the offset widths are 32-bit ints instead of
   // pointer widths.
@@ -1669,7 +1673,8 @@ void ItaniumVTableBuilder::LayoutPrimaryAndSecondaryVTables(
   Components.push_back(VTableComponent::MakeOffsetToTop(OffsetToTop));
 
   // Next, add the RTTI.
-  Components.push_back(VTableComponent::MakeRTTI(MostDerivedClass));
+  if (!Context.getLangOpts().OmitVTableRTTI)
+    Components.push_back(VTableComponent::MakeRTTI(MostDerivedClass));
 
   uint64_t AddressPoint = Components.size();
 
diff --git a/clang/lib/Driver/ToolChains/Clang.cpp b/clang/lib/Driver/ToolChains/Clang.cpp
index 531677e..40e6058 100644
--- a/clang/lib/Driver/ToolChains/Clang.cpp
+++ b/clang/lib/Driver/ToolChains/Clang.cpp
@@ -5526,6 +5526,9 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   Args.AddLastArg(CmdArgs, options::OPT_fexperimental_relative_cxx_abi_vtables,
                   options::OPT_fno_experimental_relative_cxx_abi_vtables);
 
+  Args.AddLastArg(CmdArgs, options::OPT_fexperimental_omit_vtable_rtti,
+                  options::OPT_fno_experimental_omit_vtable_rtti);
+
   // Handle segmented stacks.
   Args.addOptInFlag(CmdArgs, options::OPT_fsplit_stack,
                     options::OPT_fno_split_stack);
@@ -6007,6 +6010,9 @@ void Clang::ConstructJob(Compilation &C, const JobAction &JA,
   Args.AddLastArg(CmdArgs, options::OPT_fexperimental_relative_cxx_abi_vtables,
                   options::OPT_fno_experimental_relative_cxx_abi_vtables);
 
+  Args.AddLastArg(CmdArgs, options::OPT_fexperimental_omit_vtable_rtti,
+                  options::OPT_fno_experimental_omit_vtable_rtti);
+
   if (Arg *A = Args.getLastArg(options::OPT_ffuchsia_api_level_EQ))
     A->render(Args, CmdArgs);
 
diff --git a/clang/lib/Frontend/CompilerInvocation.cpp b/clang/lib/Frontend/CompilerInvocation.cpp
index 730db8e..2dd299b 100644
--- a/clang/lib/Frontend/CompilerInvocation.cpp
+++ b/clang/lib/Frontend/CompilerInvocation.cpp
@@ -4109,6 +4109,14 @@ bool CompilerInvocation::ParseLangArgs(LangOptions &Opts, ArgList &Args,
                    options::OPT_fno_experimental_relative_cxx_abi_vtables,
                    TargetCXXABI::usesRelativeVTables(T));
 
+  // RTTI is on by default.
+  bool HasRTTI = Args.hasFlag(options::OPT_frtti, options::OPT_fno_rtti, true);
+  Opts.OmitVTableRTTI =
+      Args.hasFlag(options::OPT_fexperimental_omit_vtable_rtti,
+                   options::OPT_fno_experimental_omit_vtable_rtti, false);
+  if (Opts.OmitVTableRTTI && HasRTTI)
+    Diags.Report(diag::err_drv_using_omit_rtti_component_without_no_rtti);
+
   for (const auto &A : Args.getAllArgValues(OPT_fmacro_prefix_map_EQ)) {
     auto Split = StringRef(A).split('=');
     Opts.MacroPrefixMap.insert(