Allow merging of monomorphic accesses to tracked fields.

src/hydrogen.h

 // Copyright 2012 the V8 project authors. All rights reserved.
 // Redistribution and use in source and binary forms, with or without
 // modification, are permitted provided that the following conditions are
 // met:
 //
 //     * Redistributions of source code must retain the above copyright
 //       notice, this list of conditions and the following disclaimer.
 //     * Redistributions in binary form must reproduce the above
 //       copyright notice, this list of conditions and the following
 //       disclaimer in the documentation and/or other materials provided
@@ skipping 2398 matching lines @@
     }
 
     bool has_holder() { return !holder_.is_null(); }
     bool IsLoad() const { return access_type_ == LOAD; }
 
     LookupResult* lookup() { return &lookup_; }
     Handle<JSObject> holder() { return holder_; }
     Handle<JSFunction> accessor() { return accessor_; }
     Handle<Object> constant() { return constant_; }
     Handle<Map> transition() { return handle(lookup_.GetTransitionTarget()); }
-    Handle<Map> field_map() { return field_map_; }
+    SmallMapList* field_maps() { return &field_maps_; }
     HObjectAccess access() { return access_; }
 
    private:
     Type* ToType(Handle<Map> map) { return builder_->ToType(map); }
+    Zone* zone() { return builder_->zone(); }
     Isolate* isolate() { return lookup_.isolate(); }
     CompilationInfo* top_info() { return builder_->top_info(); }
     CompilationInfo* current_info() { return builder_->current_info(); }
 
     bool LoadResult(Handle<Map> map);
-    void LoadFieldMap(Handle<Map> map);
+    void LoadFieldMaps(Handle<Map> map);
     bool LookupDescriptor();
     bool LookupInPrototypes();
     bool IsCompatible(PropertyAccessInfo* other);
 
     void GeneralizeRepresentation(Representation r) {
       access_ = access_.WithRepresentation(
           access_.representation().generalize(r));
     }
 
     LookupResult lookup_;
     HOptimizedGraphBuilder* builder_;
     PropertyAccessType access_type_;
     Type* type_;
     Handle<String> name_;
     Handle<JSObject> holder_;
     Handle<JSFunction> accessor_;
     Handle<JSObject> api_holder_;
     Handle<Object> constant_;
-    Handle<Map> field_map_;
+    SmallMapList field_maps_;
     HObjectAccess access_;
   };
 
   HInstruction* BuildMonomorphicAccess(PropertyAccessInfo* info,
                                        HValue* object,
                                        HValue* checked_object,
                                        HValue* value,
                                        BailoutId ast_id,
                                        BailoutId return_id,
                                        bool can_inline_accessor = true);
@@ skipping 345 matching lines @@
   }
 
  private:
   HGraphBuilder* builder_;
 };
 
 
 } }  // namespace v8::internal
 
 #endif  // V8_HYDROGEN_H_