[turbofan] Remove unnecessary prototype checks for element access.

src/compiler/js-native-context-specialization.h

 // Copyright 2015 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.
 
 #ifndef V8_COMPILER_JS_NATIVE_CONTEXT_SPECIALIZATION_H_
 #define V8_COMPILER_JS_NATIVE_CONTEXT_SPECIALIZATION_H_
 
 #include "src/base/flags.h"
 #include "src/compiler/graph-reducer.h"
 #include "src/deoptimize-reason.h"
@@ skipping 109 matching lines @@
 
   // Construct an appropriate heap object check.
   Node* BuildCheckTaggedPointer(Node* receiver, Node* effect, Node* control);
 
   // Adds stability dependencies on all prototypes of every class in
   // {receiver_type} up to (and including) the {holder}.
   void AssumePrototypesStable(std::vector<Handle<Map>> const& receiver_maps,
                               Handle<Context> native_context,
                               Handle<JSObject> holder);
 
+  // Checks if we can turn the hole into undefined when loading an element
+  // from an object with one of the {receiver_maps}; sets up appropriate
+  // code dependencies and might use the array protector cell.
+  bool CanTreatHoleAsUndefined(std::vector<Handle<Map>> const& receiver_maps,
+                               Handle<Context> native_context);
+
   // Extract receiver maps from {nexus} and filter based on {receiver} if
   // possible.
   bool ExtractReceiverMaps(Node* receiver, Node* effect,
                            FeedbackNexus const& nexus,
                            MapHandleList* receiver_maps);
 
   // Try to infer a map for the given {receiver} at the current {effect}.
   // If a map is returned then you can be sure that the {receiver} definitely
   // has the returned map at this point in the program (identified by {effect}).
   MaybeHandle<Map> InferReceiverMap(Node* receiver, Node* effect);
@@ skipping 27 matching lines @@
   DISALLOW_COPY_AND_ASSIGN(JSNativeContextSpecialization);
 };
 
 DEFINE_OPERATORS_FOR_FLAGS(JSNativeContextSpecialization::Flags)
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_JS_NATIVE_CONTEXT_SPECIALIZATION_H_