Index: cfe/trunk/lib/Driver/Tools.cpp
===================================================================
--- cfe/trunk/lib/Driver/Tools.cpp
+++ cfe/trunk/lib/Driver/Tools.cpp
@@ -1140,9 +1140,9 @@
 // ARM tools end.
 
 /// getAArch64TargetCPU - Get the (LLVM) name of the AArch64 cpu we are
-/// targeting.
-static std::string getAArch64TargetCPU(const ArgList &Args) {
-  Arg *A;
+/// targeting. Set \p A to the Arg corresponding to the -mcpu or -mtune
+/// arguments if they are provided, or to nullptr otherwise.
+static std::string getAArch64TargetCPU(const ArgList &Args, Arg *&A) {
   std::string CPU;
   // If we have -mtune or -mcpu, use that.
   if ((A = Args.getLastArg(options::OPT_mtune_EQ))) {
@@ -1919,13 +1919,15 @@
 
 static std::string getCPUName(const ArgList &Args, const llvm::Triple &T,
                               bool FromAs = false) {
+  Arg *A;
+
   switch (T.getArch()) {
   default:
     return "";
 
   case llvm::Triple::aarch64:
   case llvm::Triple::aarch64_be:
-    return getAArch64TargetCPU(Args);
+    return getAArch64TargetCPU(Args, A);
 
   case llvm::Triple::arm:
   case llvm::Triple::armeb:
@@ -2443,8 +2445,8 @@
   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);
+    success = getAArch64ArchFeaturesFromMcpu(D, getAArch64TargetCPU(Args, A),
+                                             Args, Features);
 
   if (success && (A = Args.getLastArg(options::OPT_mtune_EQ)))
     success =
@@ -2452,9 +2454,9 @@
   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 (success && Args.hasArg(options::OPT_arch))
+    success = getAArch64MicroArchFeaturesFromMcpu(
+        D, getAArch64TargetCPU(Args, A), Args, Features);
 
   if (!success)
     D.Diag(diag::err_drv_clang_unsupported) << A->getAsString(Args);
Index: cfe/trunk/test/Driver/arm-cortex-cpus.c
===================================================================
--- cfe/trunk/test/Driver/arm-cortex-cpus.c
+++ cfe/trunk/test/Driver/arm-cortex-cpus.c
@@ -303,7 +303,10 @@
 
 // ================== Check that a bogus CPU gives an error
 // RUN: %clang -target arm -mcpu=bogus -### -c %s 2>&1 | FileCheck -check-prefix=CHECK-BOGUS-CPU %s
+// RUN: %clang -target armv8-apple-darwin -arch arm64 -mcpu=bogus -### -c %s 2>&1 | FileCheck -check-prefix=CHECK-BOGUS-CPU %s
 // CHECK-BOGUS-CPU: error: {{.*}} does not support '-mcpu=bogus'
+// RUN: %clang -target armv8-apple-darwin -arch arm64 -mtune=bogus -### -c %s 2>&1 | FileCheck -check-prefix=CHECK-BOGUS-TUNE %s
+// CHECK-BOGUS-TUNE: error: {{.*}} does not support '-mtune=bogus'
 
 // ================== Check default Architecture on each ARM11 CPU
 // RUN: %clang -target arm-linux-gnueabi -mcpu=arm1136j-s -### -c %s 2>&1 | FileCheck -check-prefix=CHECK-CPUV6 %s