[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..338aeb406d48e70ab7ea554191947ba38157e28b 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 CanElideCurrent(const BytecodeNode* const current) const;
+  bool SimpleSubstitution(BytecodeNode* const current);
+  bool CanElideCurrent(const BytecodeNode* const current);
   bool CanElideLast(const BytecodeNode* const current) const;
 
+  // Simple substitution methods.
+  void RewriteLastLoadAndStar(Bytecode new_bytecode,
+                              BytecodeNode* const current);
+  bool RemoveToBooleanFromJump(BytecodeNode* const current);
+  bool ChangeLdaToLdr(BytecodeNode* const current);
+  bool ChangeLdarMovToLdarStar(BytecodeNode* const current);
+
   void InvalidateLast();
   bool LastIsValid() const;
   void SetLast(const BytecodeNode* const node);