[interpreter] Introduce bytecode generation pipeline.

src/interpreter/bytecode-peephole-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_INTERPRETER_BYTECODE_PEEPHOLE_OPTIMIZER_H_
+#define V8_INTERPRETER_BYTECODE_PEEPHOLE_OPTIMIZER_H_
+
+#include "src/interpreter/bytecode-pipeline.h"
+
+namespace v8 {
+namespace internal {
+namespace interpreter {
+
+class ConstantArrayBuilder;
+
+class BytecodePeepholeOptimizer : public BytecodePipelineStage,

[rmcilroy, 2016/05/12 12:15:13]

nit - add class comment

[oth, 2016/05/12 14:59:53]

Done.

+                                  public ZoneObject {
+ public:
+  BytecodePeepholeOptimizer(ConstantArrayBuilder* constant_array_builder,
+                            BytecodePipelineStage* next_stage);
+
+  size_t FlushForOffset() override;
+  void FlushBasicBlock() override;
+  void Write(BytecodeNode* node) override;
+
+ private:
+  void UpdateCurrentBytecode(BytecodeNode* const current);
+  bool CanElideCurrent(const BytecodeNode* const current) const;
+  bool CanElideLast(const BytecodeNode* const current) const;
+  BytecodeNode* Optimize(BytecodeNode* current);

[rmcilroy, 2016/05/12 12:15:13]

nit - move Optimize up top and put a newline between it and the other helpers.

[oth, 2016/05/12 14:59:52]

Done.

+
+  void InvalidateLast();
+  bool LastIsValid() const;
+  void SetLast(const BytecodeNode* const node);
+
+  bool LastBytecodePutsNameInAccumulator() const;
+
+  Handle<Object> GetConstantForIndexOperand(const BytecodeNode* const node,
+                                            int index) const;
+
+  ConstantArrayBuilder* constant_array_builder_;
+  BytecodePipelineStage* next_stage_;
+  BytecodeNode last_;
+  bool last_is_valid_;
+  bool last_is_discardable_;
+
+  DISALLOW_COPY_AND_ASSIGN(BytecodePeepholeOptimizer);
+};
+
+}  // namespace interpreter
+}  // namespace internal
+}  // namespace v8
+
+#endif  // V8_INTERPRETER_BYTECODE_PEEPHOLE_OPTIMIZER_H_