Index: lib/Driver/Tools.cpp
===================================================================
--- lib/Driver/Tools.cpp
+++ lib/Driver/Tools.cpp
@@ -939,7 +939,8 @@
 
 /// getAArch64TargetCPU - Get the (LLVM) name of the AArch64 cpu we are
 /// targeting.
-static std::string getAArch64TargetCPU(const ArgList &Args) {
+static std::string getAArch64TargetCPU(const ArgList &Args,
+                                       bool *IsNative) {
   Arg *A;
   std::string CPU;
   // If we have -mtune or -mcpu, use that.
@@ -950,7 +951,11 @@
     CPU = Mcpu.split("+").first.lower();
   }
 
-  // Handle CPU name is 'native'.
+  // Set IsNative if it's not null.
+  if (IsNative)
+    *IsNative = CPU == "native";
+
+  // Handle CPU name is 'native'. 
   if (CPU == "native")
     return llvm::sys::getHostCPUName();
   else if (CPU.size())
@@ -964,6 +969,10 @@
   return "generic";
 }
 
+static std::string getAArch64TargetCPU(const ArgList &Args) {
+  return getAArch64TargetCPU(Args, nullptr);
+}
+
 void Clang::AddAArch64TargetArgs(const ArgList &Args,
                                  ArgStringList &CmdArgs) const {
   std::string TripleStr = getToolChain().ComputeEffectiveClangTriple(Args);
@@ -2055,17 +2064,20 @@
                                      const llvm::Triple &Triple,
                                      const ArgList &Args,
                                      std::vector<const char *> &Features) {
-  Arg *A;
-  bool success = true;
+  Arg *A = nullptr;
+  bool success = true, IsNative;
+  std::string CPU;
+
   // Enable NEON by default.
   Features.push_back("+neon");
   if ((A = Args.getLastArg(options::OPT_march_EQ)))
     success = getAArch64ArchFeaturesFromMarch(D, A->getValue(), Args, Features);
   else if ((A = Args.getLastArg(options::OPT_mcpu_EQ)))
     success = getAArch64ArchFeaturesFromMcpu(D, A->getValue(), Args, Features);
-  else if (Args.hasArg(options::OPT_arch))
-    success = getAArch64ArchFeaturesFromMcpu(D, getAArch64TargetCPU(Args), Args,
-                                             Features);
+  else if (Args.hasArg(options::OPT_arch)) {
+    CPU = getAArch64TargetCPU(Args, &IsNative);
+    success = getAArch64ArchFeaturesFromMcpu(D, CPU, Args, Features);
+  }
 
   if (success && (A = Args.getLastArg(options::OPT_mtune_EQ)))
     success =
@@ -2073,12 +2085,14 @@
   else if (success && (A = Args.getLastArg(options::OPT_mcpu_EQ)))
     success =
         getAArch64MicroArchFeaturesFromMcpu(D, A->getValue(), Args, Features);
-  else if (Args.hasArg(options::OPT_arch))
-    success = getAArch64MicroArchFeaturesFromMcpu(D, getAArch64TargetCPU(Args),
-                                                  Args, Features);
+  else if (Args.hasArg(options::OPT_arch)) {
+    CPU = getAArch64TargetCPU(Args, &IsNative);
+    success = getAArch64MicroArchFeaturesFromMcpu(D, CPU, Args, Features);
+  }
 
   if (!success)
-    D.Diag(diag::err_drv_clang_unsupported) << A->getAsString(Args);
+    D.Diag(diag::err_drv_clang_unsupported)
+      << (A ? A->getAsString(Args) : (IsNative ? "native" : CPU));
 
   if (Args.getLastArg(options::OPT_mgeneral_regs_only)) {
     Features.push_back("-fp-armv8");