[Interpreter] Optimize equality check with null/undefined with a check on the map.

src/compiler/typer.cc

 // Copyright 2014 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "src/compiler/typer.h"
 
 #include <iomanip>
 
 #include "src/base/flags.h"
 #include "src/bootstrapper.h"
@@ skipping 1028 matching lines @@
 }
 
 
 // JS unary operators.
 
 
 Type* Typer::Visitor::TypeJSTypeOf(Node* node) {
   return Type::InternalizedString();
 }
 
+Type* Typer::Visitor::TypeJSIsUndetectable(Node* node) {
+  return Type::Boolean();
+}
 
 // JS conversion operators.
 
 
 Type* Typer::Visitor::TypeJSToBoolean(Node* node) {
   return TypeUnaryOp(node, ToBoolean);
 }
 
 Type* Typer::Visitor::TypeJSToInteger(Node* node) {
   return TypeUnaryOp(node, ToInteger);
@@ skipping 776 matching lines @@
 Type* Typer::Visitor::TypeConstant(Handle<Object> value) {
   if (Type::IsInteger(*value)) {
     return Type::Range(value->Number(), value->Number(), zone());
   }
   return Type::NewConstant(value, zone());
 }
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8