[interpreter] Introduce fused bytecodes for common sequences.

src/interpreter/bytecode-peephole-optimizer.h

Index: src/interpreter/bytecode-peephole-optimizer.h
diff --git a/src/interpreter/bytecode-peephole-optimizer.h b/src/interpreter/bytecode-peephole-optimizer.h
index 19813958cd8ff56d83bb33f7e3d2943b08aa4243..2cf96a7b49d072758e301ab31e1ef8574d03084f 100644
--- a/src/interpreter/bytecode-peephole-optimizer.h
+++ b/src/interpreter/bytecode-peephole-optimizer.h
@@ -29,10 +29,17 @@ class BytecodePeepholeOptimizer final : public BytecodePipelineStage,
  private:
   BytecodeNode* Optimize(BytecodeNode* current);
 
-  void UpdateCurrentBytecode(BytecodeNode* const current);
+  bool SimpleSubstitution(BytecodeNode* const current);
   bool CanElideCurrent(const BytecodeNode* const current) const;
   bool CanElideLast(const BytecodeNode* const current) const;
 
+  // Simple substitution methods.
+  void ChangeLoadStarToLdrLdar(Bytecode new_bytecode,
+                               BytecodeNode* const current);
+  bool RemoveToBooleanFromJump(BytecodeNode* const current);
+  bool RemoveToBooleanFromLogicalNot(BytecodeNode* const current);
+  bool ChangeLoadToLdr(BytecodeNode* const current);
+
   void InvalidateLast();
   bool LastIsValid() const;
   void SetLast(const BytecodeNode* const node);