[Interpreter] Reduce temporary register usage in generated bytecode.

src/interpreter/bytecode-generator.h

Index: src/interpreter/bytecode-generator.h
diff --git a/src/interpreter/bytecode-generator.h b/src/interpreter/bytecode-generator.h
index 3ce65322cc4314c81798e37397b6531d70583451..1fa34ae7ea160287ba717aa478ebf7bfebc48558 100644
--- a/src/interpreter/bytecode-generator.h
+++ b/src/interpreter/bytecode-generator.h
@@ -30,6 +30,10 @@ class BytecodeGenerator : public AstVisitor {
  private:
   class ControlScope;
   class ControlScopeForIteration;
+  class ExpressionResultScope;
+  class AccumulatorResultScope;
+  class EffectResultScope;
+  class RegisterResultScope;
 
   DEFINE_AST_VISITOR_SUBCLASS_MEMBERS();
 
@@ -43,6 +47,17 @@ class BytecodeGenerator : public AstVisitor {
   void VisitTypeOf(UnaryOperation* expr);
   void VisitNot(UnaryOperation* expr);
 
+  // Visitors for obtaining expression result in the accumulator, in a
+  // register, or just getting the effect.
+  void VisitForAccumulatorValue(Expression* expression);
+  MUST_USE_RESULT Register VisitForRegisterValue(
+      Expression* expression, TemporaryRegisterScope* temporary_register_scope);
+  void VisitForEffect(Expression* node);
+
+  void SetResultRegister(Register reg);
+  Register GetResultRegister();
+  bool ResultRegisterIsEmpty() const;
+
   inline BytecodeArrayBuilder* builder() { return &builder_; }
   inline Scope* scope() const { return scope_; }
   inline void set_scope(Scope* scope) { scope_ = scope; }
@@ -51,6 +66,10 @@ class BytecodeGenerator : public AstVisitor {
   inline CompilationInfo* info() const { return info_; }
   inline void set_info(CompilationInfo* info) { info_ = info; }
   ZoneVector<Handle<Object>>* globals() { return &globals_; }
+  inline void set_result_scope(ExpressionResultScope* result_scope) {
+    result_scope_ = result_scope;
+  }
+  inline ExpressionResultScope* result_scope() const { return result_scope_; }
 
   LanguageMode language_mode() const;
   Strength language_mode_strength() const;
@@ -65,6 +84,8 @@ class BytecodeGenerator : public AstVisitor {
 
   // TODO(rmcilroy): Encapsulate this in an environment object.
   Register current_context_;
+  ExpressionResultScope* result_scope_;
+  Maybe<Register> result_register_;
 };
 
 }  // namespace interpreter