[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 4f2cd1895d88f212ee49abc58b4efb37ea4c1e8e..82c593fbc4e28acae3d4a03a37e07e3a782d5bb1 100644
--- a/src/interpreter/bytecode-peephole-optimizer.h
+++ b/src/interpreter/bytecode-peephole-optimizer.h
@@ -29,12 +29,20 @@ class BytecodePeepholeOptimizer final : public BytecodePipelineStage,
  private:
   BytecodeNode* Optimize(BytecodeNode* current);
 
-  void UpdateLastAndCurrentBytecodes(BytecodeNode* const current);
+  void TryToRemoveLastExpressionPosition(const BytecodeNode* const current);
+  bool UpdateLastAndCurrentBytecodes(BytecodeNode* const current);
   bool CanElideCurrent(const BytecodeNode* const current) const;
   bool CanElideLast(const BytecodeNode* const current) const;
   bool CanElideLastBasedOnSourcePosition(
       const BytecodeNode* const current) const;
 
+  // Simple substitution methods.
+  void ChangeLoadStarToLdrLdar(Bytecode new_bytecode,

[rmcilroy, 2016/05/24 10:53:56]

This is a helper function for ChangeLoadToLdr, not a function called by
SimpleSubstitution directly, and I think the name is a bit confusingly similar
to ChangeLoadtoLdr as well. How about making this a static (annoymous name
space) helper which you pass last_ to explicitly and calling it
TransformLdaToLdr.

[oth, 2016/05/24 13:37:12]

Done modulo the name of the internal function keeps the Star and Ldar components
to convey the pairwise transformation happening here.

+                               BytecodeNode* const current);
+  bool RemoveToBooleanFromJump(BytecodeNode* const current);
+  bool RemoveToBooleanFromLogicalNot(BytecodeNode* const current);
+  bool ChangeLoadToLdr(BytecodeNode* const current);

[rmcilroy, 2016/05/24 10:53:56]

nit - ChangeLdaToLdr ?

[oth, 2016/05/24 13:37:12]

Done.

+
   void InvalidateLast();
   bool LastIsValid() const;
   void SetLast(const BytecodeNode* const node);