[turbofan] Support fast access to the current global object.

src/compiler/js-global-object-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_GLOBAL_OBJECT_SPECIALIZATION_H_
-#define V8_COMPILER_JS_GLOBAL_OBJECT_SPECIALIZATION_H_
-
-#include "src/compiler/graph-reducer.h"
-
-namespace v8 {
-namespace internal {
-
-// Forward declarations.
-class CompilationDependencies;
-
-namespace compiler {
-
-// Forward declarations.
-class CommonOperatorBuilder;
-class JSGraph;
-class JSOperatorBuilder;
-class SimplifiedOperatorBuilder;
-class TypeCache;
-
-// Specializes a given JSGraph to a given global object, potentially constant
-// folding some {JSLoadGlobal} nodes or strength reducing some {JSStoreGlobal}
-// nodes.
-class JSGlobalObjectSpecialization final : public AdvancedReducer {
- public:
-  JSGlobalObjectSpecialization(Editor* editor, JSGraph* jsgraph,
-                               Handle<JSGlobalObject> global_object,
-                               CompilationDependencies* dependencies);
-
-  Reduction Reduce(Node* node) final;
-
- private:
-  Reduction ReduceJSLoadGlobal(Node* node);
-  Reduction ReduceJSStoreGlobal(Node* node);
-
-  struct ScriptContextTableLookupResult;
-  bool LookupInScriptContextTable(Handle<Name> name,
-                                  ScriptContextTableLookupResult* result);
-
-  Graph* graph() const;
-  JSGraph* jsgraph() const { return jsgraph_; }
-  Isolate* isolate() const;
-  CommonOperatorBuilder* common() const;
-  JSOperatorBuilder* javascript() const;
-  SimplifiedOperatorBuilder* simplified() const;
-  Handle<JSGlobalObject> global_object() const { return global_object_; }
-  CompilationDependencies* dependencies() const { return dependencies_; }
-
-  JSGraph* const jsgraph_;
-  Handle<JSGlobalObject> const global_object_;
-  CompilationDependencies* const dependencies_;
-  TypeCache const& type_cache_;
-
-  DISALLOW_COPY_AND_ASSIGN(JSGlobalObjectSpecialization);
-};
-
-}  // namespace compiler
-}  // namespace internal
-}  // namespace v8
-
-#endif  // V8_COMPILER_JS_GLOBAL_OBJECT_SPECIALIZATION_H_