[WIP] JSForInLowering and JSForInHasOwnProperty.

src/compiler/js-for-in-lowering.h

+// Copyright 2017 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_FOR_IN_LOWERING_H_
+#define V8_COMPILER_JS_FOR_IN_LOWERING_H_
+
+#include "src/compiler/graph-reducer.h"
+
+namespace v8 {
+namespace internal {
+namespace compiler {
+
+// Forward declarations.
+class CommonOperatorBuilder;
+class Graph;
+class JSGraph;
+class SimplifiedOperatorBuilder;
+
+// Lowers for-in operators to simplified operators.
+class JSForInLowering final : public NON_EXPORTED_BASE(AdvancedReducer) {
+ public:
+  JSForInLowering(Editor* editor, JSGraph* jsgraph)
+      : AdvancedReducer(editor), jsgraph_(jsgraph) {}
+  ~JSForInLowering() final {}
+
+  Reduction Reduce(Node* node) final;
+
+ private:
+  Reduction ReduceJSForInHasOwnProperty(Node* node);
+  Reduction ReduceJSForInLoadProperty(Node* node);
+  Reduction ReduceJSForInNext(Node* node);
+  Reduction ReduceJSForInPrepare(Node* node);
+
+  CommonOperatorBuilder* common() const;
+  Graph* graph() const;
+  Isolate* isolate() const;
+  JSGraph* jsgraph() const { return jsgraph_; }
+  SimplifiedOperatorBuilder* simplified() const;
+
+  JSGraph* const jsgraph_;
+};
+
+}  // namespace compiler
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_COMPILER_JS_FOR_IN_LOWERING_H_