[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 e79ff787e9246ba278bddfa09a3e48daf21a7fc2..e9c558245002899345fbe31220081c15226e8754 100644
--- a/src/interpreter/bytecode-generator.h
+++ b/src/interpreter/bytecode-generator.h
@@ -31,14 +31,18 @@ class BytecodeGenerator : public AstVisitor {
   class ContextScope;
   class ControlScope;
   class ControlScopeForIteration;
+  class ExpressionResultScope;
+  class TopLevelResultScope;
+  class AccumulatorResultScope;
+  class EffectResultScope;
+  class RegisterResultScope;
 
   void MakeBytecodeBody();
   Register NextContextRegister() const;
 
   DEFINE_AST_VISITOR_SUBCLASS_MEMBERS();
 
-  Register VisitArguments(ZoneList<Expression*>* arguments,
-                          TemporaryRegisterScope* caller_scope);
+  Register VisitArguments(ZoneList<Expression*>* arguments);
   void VisitArithmeticExpression(BinaryOperation* binop);
   void VisitCommaExpression(BinaryOperation* binop);
   void VisitLogicalOrExpression(BinaryOperation* binop);
@@ -61,6 +65,18 @@ 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);
+  void VisitForEffect(Expression* node);
+
+  // Binary expression state machine and load-store tracking.
+  void PrepareForBinaryExpression();
+  Register LoadForBinaryExpression(Register reg);
+  void StoreForBinaryExpression(Register reg);
+  void CompleteBinaryExpression();
+
   inline BytecodeArrayBuilder* builder() { return &builder_; }
 
   inline Isolate* isolate() const { return isolate_; }
@@ -80,6 +96,12 @@ class BytecodeGenerator : public AstVisitor {
     execution_context_ = context;
   }
 
+  void set_result_scope(ExpressionResultScope* result_scope);
+  ExpressionResultScope* result_scope() const;
+  ExpressionResultScope* parent_result_scope() const;
+  TopLevelResultScope* top_level_result_scope() const;
+  void set_top_level_result_scope(TopLevelResultScope* result_scope);
+
   ZoneVector<Handle<Object>>* globals() { return &globals_; }
   inline LanguageMode language_mode() const;
   Strength language_mode_strength() const;
@@ -93,6 +115,11 @@ class BytecodeGenerator : public AstVisitor {
   ZoneVector<Handle<Object>> globals_;
   ControlScope* execution_control_;
   ContextScope* execution_context_;
+  ExpressionResultScope* result_scope_;
+  TopLevelResultScope* top_level_result_scope_;

[rmcilroy, 2015/10/19 12:56:23]

This doesn't seem to be used? Can we remove it for now (or make use of it
instead of having PrepareForBinaryExpression / CompleteBinaryExpression? 

As an aside for when it is later needed, personally I would prefer the top level
result scope not to be separate from the result_scope chain (i.e., it is just
stored at the top of the result_scope_ chain, and possibly has a 'short cut'
method in ExpressionResultScope which points to the top-level so we don't need
to walk the whole chain to get it.

[oth, 2015/10/20 15:28:53]

Removed for now. Having a central reference saves (chain_length - 1) words of
stack.

+
+  int binary_expression_depth_;
+  ZoneSet<int> binary_expression_hazard_set_;
 };
 
 }  // namespace interpreter