[mips] Mark microMIPS64 as being unsupported.

There are no provided instruction definitions for this architecture.

Reviewers: smaksimovic, atanasyan, abeserminji

Differential Revision: https://reviews.llvm.org/D48320

llvm-svn: 335057
diff --git a/llvm/lib/Target/Mips/MipsSubtarget.cpp b/llvm/lib/Target/Mips/MipsSubtarget.cpp
index f71031c..e5ba4fa 100644
--- a/llvm/lib/Target/Mips/MipsSubtarget.cpp
+++ b/llvm/lib/Target/Mips/MipsSubtarget.cpp
@@ -116,6 +116,8 @@
   if (hasMips64r6() && InMicroMipsMode)
     report_fatal_error("microMIPS64R6 is not supported", false);
 
+  if (!isABI_O32() && InMicroMipsMode)
+    report_fatal_error("microMIPS64 is not supported.", false);
 
   if (UseIndirectJumpsHazard) {
     if (InMicroMipsMode)