[mips] Removal of microMIPS64R6

microMIPS64R6 is removed from backend, and therefore frontend
will show an error when target is microMIPS64R6.

This is Clang part of patch.

Differential Revision: https://reviews.llvm.org/D35624

llvm-svn: 320351
diff --git a/clang/lib/Basic/Targets/Mips.cpp b/clang/lib/Basic/Targets/Mips.cpp
index 3eb39b3..5563505 100644
--- a/clang/lib/Basic/Targets/Mips.cpp
+++ b/clang/lib/Basic/Targets/Mips.cpp
@@ -206,6 +206,13 @@
 }
 
 bool MipsTargetInfo::validateTarget(DiagnosticsEngine &Diags) const {
+  // microMIPS64R6 backend is removed
+  if ((getTriple().getArch() == llvm::Triple::mips64 ||
+       getTriple().getArch() == llvm::Triple::mips64el) &&
+       IsMicromips && (ABI == "n32" || ABI == "n64")) {
+    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") {