[turbofan]: Add a context relaxation Reducer

src/compiler/context-relaxation.h

+// Copyright 2014 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_CONTEXT_RELAXATION_H_
+#define V8_COMPILER_CONTEXT_RELAXATION_H_
+
+#include "src/code-factory.h"
+#include "src/compiler/graph-reducer.h"
+
+namespace v8 {
+namespace internal {
+namespace compiler {
+
+// Ensures that operations that only need to access the native context use the
+// outer-most context rather than the specific context given by the AST graph
+// builder. The makes it possible to use they operations with context

[Michael Starzinger, 2015/07/02 10:29:26]

nit: s/The/This/ and s/they/these/

+// specialization (e.g. for generating stubs) without embedding forcing inner

[Michael Starzinger, 2015/07/02 10:29:26]

nit: s/embedding//

+// contexts to be embedded in generated code thus causing leaks.
+class ContextRelaxation final : public Reducer {
+ public:
+  explicit ContextRelaxation(Node* start, Node* relaxed_context)

[Michael Starzinger, 2015/07/02 10:29:26]

nit: Doesn't need to be marked "explicit".

+      : start_(start),
+        relaxed_context_(relaxed_context),
+        context_is_wired_(false) {}
+  ~ContextRelaxation() final{};
+
+  Reduction Reduce(Node* node) final;
+
+ private:
+  Node* start_;
+  Node* relaxed_context_;
+  bool context_is_wired_;
+};
+
+}  // namespace compiler
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_COMPILER_CONTEXT_RELAXATION_H_