MIPS64: Support short and long branches

Change-Id: I618c960bd211048166d9fde78d4106bd3ca42b3a
diff --git a/compiler/utils/assembler_test.h b/compiler/utils/assembler_test.h
index f1233ca..9457da1 100644
--- a/compiler/utils/assembler_test.h
+++ b/compiler/utils/assembler_test.h
@@ -840,12 +840,17 @@
     return str;
   }
 
+  // Override this to pad the code with NOPs to a certain size if needed.
+  virtual void Pad(std::vector<uint8_t>& data ATTRIBUTE_UNUSED) {
+  }
+
   void DriverWrapper(std::string assembly_text, std::string test_name) {
     assembler_->FinalizeCode();
     size_t cs = assembler_->CodeSize();
     std::unique_ptr<std::vector<uint8_t>> data(new std::vector<uint8_t>(cs));
     MemoryRegion code(&(*data)[0], data->size());
     assembler_->FinalizeInstructions(code);
+    Pad(*data);
     test_helper_->Driver(*data, assembly_text, test_name);
   }