Mark null and undefined as undetectable, and use it to handle abstract equality comparison in the g…

src/mips/macro-assembler-mips.h

Index: src/mips/macro-assembler-mips.h
diff --git a/src/mips/macro-assembler-mips.h b/src/mips/macro-assembler-mips.h
index b4c832813b2e374df16713acd502b705731c88b8..f0aa2c7f5f965d66ac68d5c41f2f85bcc437fb3e 100644
--- a/src/mips/macro-assembler-mips.h
+++ b/src/mips/macro-assembler-mips.h
@@ -1065,6 +1065,11 @@ class MacroAssembler: public Assembler {
                      Register map,
                      Register type_reg);
 
+  void GetInstanceType(Register object_map, Register object_instance_type) {
+    lbu(object_instance_type,
+        FieldMemOperand(object_map, Map::kInstanceTypeOffset));
+  }
+
   // Check if a map for a JSObject indicates that the object has fast elements.
   // Jump to the specified label if it does not.
   void CheckFastElements(Register map,