The check for internalized strings relied on the fact that we had less

src/x64/macro-assembler-x64.h

Index: src/x64/macro-assembler-x64.h
diff --git a/src/x64/macro-assembler-x64.h b/src/x64/macro-assembler-x64.h
index 1b7e586c0a04995584171c30939e19d1aa195e0a..14228cc21cb6e3722d7f3d243c2b20a0116a226d 100644
--- a/src/x64/macro-assembler-x64.h
+++ b/src/x64/macro-assembler-x64.h
@@ -758,6 +758,12 @@ class MacroAssembler: public Assembler {
       Label* on_fail,
       Label::Distance near_jump = Label::kFar);
 
+  // Checks if the given register or operand is a unique name
+  void JumpIfNotUniqueName(Register reg, Label* not_unique_name,
+                           Label::Distance distance = Label::kFar);
+  void JumpIfNotUniqueName(Operand operand, Label* not_unique_name,
+                           Label::Distance distance = Label::kFar);
+
   // ---------------------------------------------------------------------------
   // Macro instructions.