Only swap undefined for the global object if necessary in the prologue

src/hydrogen.h

 // Copyright 2012 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_HYDROGEN_H_
 #define V8_HYDROGEN_H_
 
 #include "src/v8.h"
 
 #include "src/accessors.h"
@@ skipping 392 matching lines @@
     return use_optimistic_licm_;
   }
 
   void set_use_optimistic_licm(bool value) {
     use_optimistic_licm_ = value;
   }
 
   void MarkRecursive() { is_recursive_ = true; }
   bool is_recursive() const { return is_recursive_; }
 
-  void MarkThisHasUses() { this_has_uses_ = true; }
-  bool this_has_uses() const { return this_has_uses_; }
-
   void MarkDependsOnEmptyArrayProtoElements() {
     // Add map dependency if not already added.
     if (depends_on_empty_array_proto_elements_) return;
     info()->dependencies()->AssumePropertyCell(
         isolate()->factory()->array_protector());
     depends_on_empty_array_proto_elements_ = true;
   }
 
   bool depends_on_empty_array_proto_elements() {
     return depends_on_empty_array_proto_elements_;
@@ skipping 60 matching lines @@
   SetOncePointer<HConstant> constant_null_;
   SetOncePointer<HConstant> constant_invalid_context_;
   SetOncePointer<HArgumentsObject> arguments_object_;
 
   HOsrBuilder* osr_;
 
   CompilationInfo* info_;
   Zone* zone_;
 
   bool is_recursive_;
-  bool this_has_uses_;
   bool use_optimistic_licm_;
   bool depends_on_empty_array_proto_elements_;
   int type_change_checksum_;
   int maximum_environment_size_;
   int no_side_effects_scope_count_;
   bool disallow_adding_new_values_;
 
   DISALLOW_COPY_AND_ASSIGN(HGraph);
 };
 
@@ skipping 2546 matching lines @@
   }
 
  private:
   HGraphBuilder* builder_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_H_