Index: Basic/Targets.cpp
===================================================================
--- Basic/Targets.cpp
+++ Basic/Targets.cpp
@@ -8534,6 +8534,13 @@
   }
 
   bool validateTarget(DiagnosticsEngine &Diags) const override {
+    if ((getTriple().getArch() == llvm::Triple::mips64 ||
+         getTriple().getArch() == llvm::Triple::mips64el) &&
+         IsMicromips && CPU == "mips64r6") {
+      Diags.Report(diag::err_target_unsupported_cpu_for_micromips) << CPU;
+      return false;
+    }
+
     // FIXME: It's valid to use O32 on a 64-bit CPU but the backend can't handle
     //        this yet. It's better to fail here than on the backend assertion.
     if (processorSupportsGPR64() && ABI == "o32") {
Index: clang/Basic/DiagnosticCommonKinds.td
===================================================================
--- clang/Basic/DiagnosticCommonKinds.td
+++ clang/Basic/DiagnosticCommonKinds.td
@@ -185,6 +185,7 @@
 def err_target_unknown_triple : Error<
   "unknown target triple '%0', please use -triple or -arch">;
 def err_target_unknown_cpu : Error<"unknown target CPU '%0'">;
+def err_target_unsupported_cpu_for_micromips : Error<"micromips is not supported for target CPU '%0'">;
 def err_target_unknown_abi : Error<"unknown target ABI '%0'">;
 def err_target_unsupported_abi : Error<"ABI '%0' is not supported on CPU '%1'">;
 def err_target_unsupported_abi_for_triple : Error<