[turbofan] Add support for elements kind transitions.

src/compiler/access-info.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_ACCESS_INFO_H_
 #define V8_COMPILER_ACCESS_INFO_H_
 
 #include <iosfwd>
 
 #include "src/field-index.h"
@@ skipping 10 matching lines @@
 
 
 namespace compiler {
 
 // Whether we are loading a property or storing to a property.
 enum class AccessMode { kLoad, kStore };
 
 std::ostream& operator<<(std::ostream&, AccessMode);
 
 
+// Mapping of transition source to transition target.
+typedef std::vector<std::pair<Handle<Map>, Handle<Map>>> MapTransitionList;
+
+
 // This class encapsulates all information required to access a certain element.
 class ElementAccessInfo final {
  public:
   ElementAccessInfo();
   ElementAccessInfo(Type* receiver_type, ElementsKind elements_kind,
-                    MaybeHandle<JSObject> holder)
-      : elements_kind_(elements_kind),
-        holder_(holder),
-        receiver_type_(receiver_type) {}
+                    MaybeHandle<JSObject> holder);
 
   MaybeHandle<JSObject> holder() const { return holder_; }
   ElementsKind elements_kind() const { return elements_kind_; }
   Type* receiver_type() const { return receiver_type_; }
+  MapTransitionList& transitions() { return transitions_; }
+  MapTransitionList const& transitions() const { return transitions_; }
 
  private:
   ElementsKind elements_kind_;
   MaybeHandle<JSObject> holder_;
   Type* receiver_type_;
+  MapTransitionList transitions_;
 };
 
 
 // This class encapsulates all information required to access a certain
 // object property, either on the object itself or on the prototype chain.
 class PropertyAccessInfo final {
  public:
   enum Kind { kInvalid, kNotFound, kDataConstant, kDataField };
 
   static PropertyAccessInfo NotFound(Type* receiver_type,
@@ skipping 78 matching lines @@
   Zone* const zone_;
 
   DISALLOW_COPY_AND_ASSIGN(AccessInfoFactory);
 };
 
 }  // namespace compiler
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_COMPILER_ACCESS_INFO_H_