[turbofan] Optimize certain chains of Branch into a Switch.

src/compiler/control-flow-optimizer.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_CONTROL_FLOW_OPTIMIZER_H_
+#define V8_COMPILER_CONTROL_FLOW_OPTIMIZER_H_
+
+#include "src/compiler/node-marker.h"
+#include "src/zone-containers.h"
+
+namespace v8 {
+namespace internal {
+namespace compiler {
+
+// Forward declarations.
+class CommonOperatorBuilder;
+class Graph;
+class JSGraph;
+class MachineOperatorBuilder;
+class Node;
+
+
+class ControlFlowOptimizer FINAL {
+ public:
+  ControlFlowOptimizer(JSGraph* jsgraph, Zone* zone);
+
+  void Optimize();
+
+ private:
+  void Enqueue(Node* node);
+  void VisitNode(Node* node);
+  void VisitBranch(Node* node);
+
+  CommonOperatorBuilder* common() const;
+  Graph* graph() const;
+  JSGraph* jsgraph() const { return jsgraph_; }
+  MachineOperatorBuilder* machine() const;
+  Zone* zone() const { return zone_; }
+
+  JSGraph* const jsgraph_;
+  ZoneQueue<Node*> queue_;
+  NodeMarker<bool> queued_;
+  Zone* const zone_;
+
+  DISALLOW_COPY_AND_ASSIGN(ControlFlowOptimizer);
+};
+
+}  // namespace compiler
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_COMPILER_CONTROL_FLOW_OPTIMIZER_H_