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

src/x64/macro-assembler-x64.cc

Index: src/x64/macro-assembler-x64.cc
diff --git a/src/x64/macro-assembler-x64.cc b/src/x64/macro-assembler-x64.cc
index 55759856a54a6581c859bdfc0294d723dbf70343..a4d64b9fd5ad936f756a6246aee18024071ea67d 100644
--- a/src/x64/macro-assembler-x64.cc
+++ b/src/x64/macro-assembler-x64.cc
@@ -2308,6 +2308,32 @@ void MacroAssembler::JumpIfBothInstanceTypesAreNotSequentialAscii(
 }
 
 
+template<class T>
+static void JumpIfNotUniqueNameHelper(MacroAssembler* masm,
+                                      T operand_or_register,
+                                      Label* not_unique_name,
+                                      Label::Distance distance) {
+  STATIC_ASSERT(((SYMBOL_TYPE - 1) & kIsInternalizedMask) == kInternalizedTag);
+  masm->cmpb(operand_or_register, Immediate(kInternalizedTag));
+  masm->j(less, not_unique_name, distance);
+  masm->cmpb(operand_or_register, Immediate(SYMBOL_TYPE));
+  masm->j(greater, not_unique_name, distance);
+}
+
+
+void MacroAssembler::JumpIfNotUniqueName(Operand operand,
+                                         Label* not_unique_name,
+                                         Label::Distance distance) {
+  JumpIfNotUniqueNameHelper<Operand>(this, operand, not_unique_name, distance);
+}
+
+
+void MacroAssembler::JumpIfNotUniqueName(Register reg,
+                                         Label* not_unique_name,
+                                         Label::Distance distance) {
+  JumpIfNotUniqueNameHelper<Register>(this, reg, not_unique_name, distance);
+}
+
 
 void MacroAssembler::Move(Register dst, Register src) {
   if (!dst.is(src)) {