Index: include/clang/Driver/SanitizerArgs.h
===================================================================
--- include/clang/Driver/SanitizerArgs.h
+++ include/clang/Driver/SanitizerArgs.h
@@ -78,6 +78,7 @@
 
   bool requiresPIE() const;
   bool needsUnwindTables() const;
+  bool needsLTO() const;
   bool linkCXXRuntimes() const { return LinkCXXRuntimes; }
   bool hasCrossDsoCfi() const { return CfiCrossDso; }
   void addArgs(const ToolChain &TC, const llvm::opt::ArgList &Args,
Index: lib/Driver/SanitizerArgs.cpp
===================================================================
--- lib/Driver/SanitizerArgs.cpp
+++ lib/Driver/SanitizerArgs.cpp
@@ -207,6 +207,10 @@
   return Sanitizers.Mask & NeedsUnwindTables;
 }
 
+bool SanitizerArgs::needsLTO() const {
+  return Sanitizers.Mask & NeedsLTO;
+}
+
 SanitizerArgs::SanitizerArgs(const ToolChain &TC,
                              const llvm::opt::ArgList &Args) {
   SanitizerMask AllRemove = 0;  // During the loop below, the accumulated set of
Index: lib/Driver/ToolChains/Clang.cpp
===================================================================
--- lib/Driver/ToolChains/Clang.cpp
+++ lib/Driver/ToolChains/Clang.cpp
@@ -3364,21 +3364,6 @@
     // the use-list order, since serialization to bitcode is part of the flow.
     if (JA.getType() == types::TY_LLVM_BC)
       CmdArgs.push_back("-emit-llvm-uselists");
-
-    // Device-side jobs do not support LTO.
-    bool isDeviceOffloadAction = !(JA.isDeviceOffloading(Action::OFK_None) ||
-                                   JA.isDeviceOffloading(Action::OFK_Host));
-
-    if (D.isUsingLTO() && !isDeviceOffloadAction) {
-      Args.AddLastArg(CmdArgs, options::OPT_flto, options::OPT_flto_EQ);
-
-      // The Darwin and PS4 linkers currently use the legacy LTO API, which
-      // does not support LTO unit features (CFI, whole program vtable opt)
-      // under ThinLTO.
-      if (!(RawTriple.isOSDarwin() || RawTriple.isPS4()) ||
-          D.getLTOMode() == LTOK_Full)
-        CmdArgs.push_back("-flto-unit");
-    }
   }
 
   if (const Arg *A = Args.getLastArg(options::OPT_fthinlto_index_EQ)) {
@@ -4980,6 +4965,25 @@
     CmdArgs.push_back("-fwhole-program-vtables");
   }
 
+  // Device-side jobs do not support LTO.
+  bool isDeviceOffloadAction = !(JA.isDeviceOffloading(Action::OFK_None) ||
+                                 JA.isDeviceOffloading(Action::OFK_Host));
+
+  if (D.isUsingLTO() &&
+      (isa<CompileJobAction>(JA) || isa<BackendJobAction>(JA)) &&
+      !isDeviceOffloadAction) {
+    Args.AddLastArg(CmdArgs, options::OPT_flto, options::OPT_flto_EQ);
+
+    // Enable LTO unit if need for CFI or whole program vtable optimization.
+    // The Darwin and PS4 linkers currently use the legacy LTO API, which
+    // does not support LTO unit features (CFI, whole program vtable opt)
+    // under ThinLTO.
+    bool SupportsLTOUnit = !(RawTriple.isOSDarwin() || RawTriple.isPS4()) ||
+                           D.getLTOMode() == LTOK_Full;
+    if ((WholeProgramVTables || Sanitize.needsLTO()) && SupportsLTOUnit)
+      CmdArgs.push_back("-flto-unit");
+  }
+
   if (Arg *A = Args.getLastArg(options::OPT_fexperimental_isel,
                                options::OPT_fno_experimental_isel)) {
     CmdArgs.push_back("-mllvm");
Index: test/Driver/lto-unit.c
===================================================================
--- test/Driver/lto-unit.c
+++ test/Driver/lto-unit.c
@@ -1,9 +1,9 @@
-// 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
-// RUN: %clang -target x86_64-scei-ps4 -### %s -flto=full 2>&1 | FileCheck --check-prefix=UNIT %s
-// RUN: %clang -target x86_64-scei-ps4 -### %s -flto=thin 2>&1 | FileCheck --check-prefix=NOUNIT %s
+// RUN: %clang -target x86_64-unknown-linux -### %s -flto=full -fwhole-program-vtables 2>&1 | FileCheck --check-prefix=UNIT %s
+// RUN: %clang -target x86_64-unknown-linux -### %s -flto=thin -fwhole-program-vtables 2>&1 | FileCheck --check-prefix=UNIT %s
+// RUN: %clang -target x86_64-apple-darwin13.3.0 -### %s -flto=full -fwhole-program-vtables 2>&1 | FileCheck --check-prefix=UNIT %s
+// RUN: %clang -target x86_64-apple-darwin13.3.0 -### %s -flto=thin -fwhole-program-vtables 2>&1 | FileCheck --check-prefix=NOUNIT %s
+// RUN: %clang -target x86_64-scei-ps4 -### %s -flto=full -fwhole-program-vtables 2>&1 | FileCheck --check-prefix=UNIT %s
+// RUN: %clang -target x86_64-scei-ps4 -### %s -flto=thin -fwhole-program-vtables 2>&1 | FileCheck --check-prefix=NOUNIT %s
 
 // UNIT: "-flto-unit"
 // NOUNIT-NOT: "-flto-unit"