Index: cfe/trunk/include/clang/Driver/CC1Options.td
===================================================================
--- cfe/trunk/include/clang/Driver/CC1Options.td
+++ cfe/trunk/include/clang/Driver/CC1Options.td
@@ -307,6 +307,9 @@
 def flto_visibility_public_std:
     Flag<["-"], "flto-visibility-public-std">,
     HelpText<"Use public LTO visibility for classes in std and stdext namespaces">;
+def flto_unit: Flag<["-"], "flto-unit">,
+    HelpText<"Emit IR to support LTO unit features (CFI, whole program vtable opt)">;
+def fno_lto_unit: Flag<["-"], "fno-lto-unit">;
 
 //===----------------------------------------------------------------------===//
 // Dependency Output Options
Index: cfe/trunk/include/clang/Frontend/CodeGenOptions.def
===================================================================
--- cfe/trunk/include/clang/Frontend/CodeGenOptions.def
+++ cfe/trunk/include/clang/Frontend/CodeGenOptions.def
@@ -89,6 +89,8 @@
                                      ///< compile step.
 CODEGENOPT(EmitSummaryIndex, 1, 0)   ///< Set when -flto=thin is enabled on the
                                      ///< compile step.
+CODEGENOPT(LTOUnit, 1, 0) ///< Emit IR to support LTO unit features (CFI, whole
+                          ///< program vtable opt).
 CODEGENOPT(IncrementalLinkerCompatible, 1, 0) ///< Emit an object file which can
                                               ///< be used with an incremental
                                               ///< linker.
Index: cfe/trunk/lib/CodeGen/CGVTables.cpp
===================================================================
--- cfe/trunk/lib/CodeGen/CGVTables.cpp
+++ cfe/trunk/lib/CodeGen/CGVTables.cpp
@@ -942,7 +942,7 @@
 
 void CodeGenModule::EmitVTableTypeMetadata(llvm::GlobalVariable *VTable,
                                            const VTableLayout &VTLayout) {
-  if (!getCodeGenOpts().PrepareForLTO)
+  if (!getCodeGenOpts().LTOUnit)
     return;
 
   CharUnits PointerWidth =
Index: cfe/trunk/lib/CodeGen/MicrosoftCXXABI.cpp
===================================================================
--- cfe/trunk/lib/CodeGen/MicrosoftCXXABI.cpp
+++ cfe/trunk/lib/CodeGen/MicrosoftCXXABI.cpp
@@ -1554,7 +1554,7 @@
 void MicrosoftCXXABI::emitVTableTypeMetadata(const VPtrInfo &Info,
                                              const CXXRecordDecl *RD,
                                              llvm::GlobalVariable *VTable) {
-  if (!CGM.getCodeGenOpts().PrepareForLTO)
+  if (!CGM.getCodeGenOpts().LTOUnit)
     return;
 
   // The location of the first virtual function pointer in the virtual table,
Index: cfe/trunk/lib/Driver/Tools.cpp
===================================================================
--- cfe/trunk/lib/Driver/Tools.cpp
+++ cfe/trunk/lib/Driver/Tools.cpp
@@ -4238,8 +4238,16 @@
     if (JA.getType() == types::TY_LLVM_BC)
       CmdArgs.push_back("-emit-llvm-uselists");
 
-    if (D.isUsingLTO())
+    if (D.isUsingLTO()) {
       Args.AddLastArg(CmdArgs, options::OPT_flto, options::OPT_flto_EQ);
+
+      // The Darwin linker currently uses the legacy LTO API, which does not
+      // support LTO unit features (CFI, whole program vtable opt) under
+      // ThinLTO.
+      if (!getToolChain().getTriple().isOSDarwin() ||
+          D.getLTOMode() == LTOK_Full)
+        CmdArgs.push_back("-flto-unit");
+    }
   }
 
   if (const Arg *A = Args.getLastArg(options::OPT_fthinlto_index_EQ)) {
Index: cfe/trunk/lib/Frontend/CompilerInvocation.cpp
===================================================================
--- cfe/trunk/lib/Frontend/CompilerInvocation.cpp
+++ cfe/trunk/lib/Frontend/CompilerInvocation.cpp
@@ -631,6 +631,7 @@
   Opts.PrepareForLTO = Args.hasArg(OPT_flto, OPT_flto_EQ);
   const Arg *A = Args.getLastArg(OPT_flto, OPT_flto_EQ);
   Opts.EmitSummaryIndex = A && A->containsValue("thin");
+  Opts.LTOUnit = Args.hasFlag(OPT_flto_unit, OPT_fno_lto_unit, false);
   if (Arg *A = Args.getLastArg(OPT_fthinlto_index_EQ)) {
     if (IK != IK_LLVM_IR)
       Diags.Report(diag::err_drv_argument_only_allowed_with)
Index: cfe/trunk/test/CodeGenCXX/cfi-ms-rtti.cpp
===================================================================
--- cfe/trunk/test/CodeGenCXX/cfi-ms-rtti.cpp
+++ cfe/trunk/test/CodeGenCXX/cfi-ms-rtti.cpp
@@ -1,5 +1,5 @@
-// RUN: %clang_cc1 -flto -emit-llvm -o - -triple=x86_64-pc-win32 %s -fsanitize=cfi-vcall | FileCheck --check-prefix=RTTI %s
-// RUN: %clang_cc1 -flto -emit-llvm -o - -triple=x86_64-pc-win32 %s -fsanitize=cfi-vcall -fno-rtti-data | FileCheck --check-prefix=NO-RTTI %s
+// RUN: %clang_cc1 -flto -flto-unit -emit-llvm -o - -triple=x86_64-pc-win32 %s -fsanitize=cfi-vcall | FileCheck --check-prefix=RTTI %s
+// RUN: %clang_cc1 -flto -flto-unit -emit-llvm -o - -triple=x86_64-pc-win32 %s -fsanitize=cfi-vcall -fno-rtti-data | FileCheck --check-prefix=NO-RTTI %s
 
 struct A {
   A();
Index: cfe/trunk/test/CodeGenCXX/no-lto-unit.cpp
===================================================================
--- cfe/trunk/test/CodeGenCXX/no-lto-unit.cpp
+++ cfe/trunk/test/CodeGenCXX/no-lto-unit.cpp
@@ -0,0 +1,13 @@
+// RUN: %clang_cc1 -flto=thin -triple x86_64-unknown-linux -fvisibility hidden -emit-llvm-bc -o %t %s
+// RUN: llvm-dis -o - %t | FileCheck %s
+// RUN: %clang_cc1 -flto=thin -flto-unit -fno-lto-unit -triple x86_64-unknown-linux -fvisibility hidden -emit-llvm-bc -o %t %s
+// RUN: llvm-dis -o - %t | FileCheck %s
+
+// CHECK-NOT: !type
+class A {
+  virtual void f() {}
+};
+
+A *f() {
+  return new A;
+}
Index: cfe/trunk/test/CodeGenCXX/type-metadata.cpp
===================================================================
--- cfe/trunk/test/CodeGenCXX/type-metadata.cpp
+++ cfe/trunk/test/CodeGenCXX/type-metadata.cpp
@@ -1,16 +1,16 @@
 // Tests for the cfi-vcall feature:
-// RUN: %clang_cc1 -flto -triple x86_64-unknown-linux -fvisibility hidden -fsanitize=cfi-vcall -fsanitize-trap=cfi-vcall -emit-llvm -o - %s | FileCheck --check-prefix=CFI --check-prefix=CFI-NVT --check-prefix=ITANIUM --check-prefix=TT-ITANIUM --check-prefix=NDIAG %s
-// RUN: %clang_cc1 -flto -triple x86_64-unknown-linux -fvisibility hidden -fsanitize=cfi-vcall -emit-llvm -o - %s | FileCheck --check-prefix=CFI --check-prefix=CFI-NVT --check-prefix=ITANIUM --check-prefix=TT-ITANIUM --check-prefix=ITANIUM-DIAG --check-prefix=DIAG --check-prefix=DIAG-ABORT %s
-// RUN: %clang_cc1 -flto -triple x86_64-unknown-linux -fvisibility hidden -fsanitize=cfi-vcall -fsanitize-recover=cfi-vcall -emit-llvm -o - %s | FileCheck --check-prefix=CFI --check-prefix=CFI-NVT --check-prefix=ITANIUM --check-prefix=TT-ITANIUM --check-prefix=ITANIUM-DIAG --check-prefix=DIAG --check-prefix=DIAG-RECOVER %s
-// RUN: %clang_cc1 -flto -triple x86_64-pc-windows-msvc -fsanitize=cfi-vcall -fsanitize-trap=cfi-vcall -emit-llvm -o - %s | FileCheck --check-prefix=CFI --check-prefix=CFI-NVT --check-prefix=MS --check-prefix=TT-MS --check-prefix=NDIAG %s
+// RUN: %clang_cc1 -flto -flto-unit -triple x86_64-unknown-linux -fvisibility hidden -fsanitize=cfi-vcall -fsanitize-trap=cfi-vcall -emit-llvm -o - %s | FileCheck --check-prefix=CFI --check-prefix=CFI-NVT --check-prefix=ITANIUM --check-prefix=TT-ITANIUM --check-prefix=NDIAG %s
+// RUN: %clang_cc1 -flto -flto-unit -triple x86_64-unknown-linux -fvisibility hidden -fsanitize=cfi-vcall -emit-llvm -o - %s | FileCheck --check-prefix=CFI --check-prefix=CFI-NVT --check-prefix=ITANIUM --check-prefix=TT-ITANIUM --check-prefix=ITANIUM-DIAG --check-prefix=DIAG --check-prefix=DIAG-ABORT %s
+// RUN: %clang_cc1 -flto -flto-unit -triple x86_64-unknown-linux -fvisibility hidden -fsanitize=cfi-vcall -fsanitize-recover=cfi-vcall -emit-llvm -o - %s | FileCheck --check-prefix=CFI --check-prefix=CFI-NVT --check-prefix=ITANIUM --check-prefix=TT-ITANIUM --check-prefix=ITANIUM-DIAG --check-prefix=DIAG --check-prefix=DIAG-RECOVER %s
+// RUN: %clang_cc1 -flto -flto-unit -triple x86_64-pc-windows-msvc -fsanitize=cfi-vcall -fsanitize-trap=cfi-vcall -emit-llvm -o - %s | FileCheck --check-prefix=CFI --check-prefix=CFI-NVT --check-prefix=MS --check-prefix=TT-MS --check-prefix=NDIAG %s
 
 // Tests for the whole-program-vtables feature:
-// RUN: %clang_cc1 -flto -triple x86_64-unknown-linux -fvisibility hidden -fwhole-program-vtables -emit-llvm -o - %s | FileCheck --check-prefix=VTABLE-OPT --check-prefix=ITANIUM --check-prefix=TT-ITANIUM %s
-// RUN: %clang_cc1 -flto -triple x86_64-pc-windows-msvc -fwhole-program-vtables -emit-llvm -o - %s | FileCheck --check-prefix=VTABLE-OPT --check-prefix=MS --check-prefix=TT-MS %s
+// RUN: %clang_cc1 -flto -flto-unit -triple x86_64-unknown-linux -fvisibility hidden -fwhole-program-vtables -emit-llvm -o - %s | FileCheck --check-prefix=VTABLE-OPT --check-prefix=ITANIUM --check-prefix=TT-ITANIUM %s
+// RUN: %clang_cc1 -flto -flto-unit -triple x86_64-pc-windows-msvc -fwhole-program-vtables -emit-llvm -o - %s | FileCheck --check-prefix=VTABLE-OPT --check-prefix=MS --check-prefix=TT-MS %s
 
 // Tests for cfi + whole-program-vtables:
-// RUN: %clang_cc1 -flto -triple x86_64-unknown-linux -fvisibility hidden -fsanitize=cfi-vcall -fsanitize-trap=cfi-vcall -fwhole-program-vtables -emit-llvm -o - %s | FileCheck --check-prefix=CFI --check-prefix=CFI-VT --check-prefix=ITANIUM --check-prefix=TC-ITANIUM %s
-// RUN: %clang_cc1 -flto -triple x86_64-pc-windows-msvc -fsanitize=cfi-vcall -fsanitize-trap=cfi-vcall -fwhole-program-vtables -emit-llvm -o - %s | FileCheck --check-prefix=CFI --check-prefix=CFI-VT --check-prefix=MS --check-prefix=TC-MS %s
+// RUN: %clang_cc1 -flto -flto-unit -triple x86_64-unknown-linux -fvisibility hidden -fsanitize=cfi-vcall -fsanitize-trap=cfi-vcall -fwhole-program-vtables -emit-llvm -o - %s | FileCheck --check-prefix=CFI --check-prefix=CFI-VT --check-prefix=ITANIUM --check-prefix=TC-ITANIUM %s
+// RUN: %clang_cc1 -flto -flto-unit -triple x86_64-pc-windows-msvc -fsanitize=cfi-vcall -fsanitize-trap=cfi-vcall -fwhole-program-vtables -emit-llvm -o - %s | FileCheck --check-prefix=CFI --check-prefix=CFI-VT --check-prefix=MS --check-prefix=TC-MS %s
 
 // ITANIUM: @_ZTV1A = {{[^!]*}}, !type [[A16:![0-9]+]]
 // ITANIUM-DIAG-SAME: !type [[ALL16:![0-9]+]]
Index: cfe/trunk/test/Driver/lto-unit.c
===================================================================
--- cfe/trunk/test/Driver/lto-unit.c
+++ cfe/trunk/test/Driver/lto-unit.c
@@ -0,0 +1,7 @@
+// RUN: %clang -target x86_64-unknown-linux -### %s -flto=full 2>&1 | FileCheck --check-prefix=UNIT %s
+// RUN: %clang -target x86_64-unknown-linux -### %s -flto=thin 2>&1 | FileCheck --check-prefix=UNIT %s
+// RUN: %clang -target x86_64-apple-darwin13.3.0 -### %s -flto=full 2>&1 | FileCheck --check-prefix=UNIT %s
+// RUN: %clang -target x86_64-apple-darwin13.3.0 -### %s -flto=thin 2>&1 | FileCheck --check-prefix=NOUNIT %s
+
+// UNIT: "-flto-unit"
+// NOUNIT-NOT: "-flto-unit"