[Interpreter] Enable assignments in expressions.

src/interpreter/bytecode-generator.h

 // Copyright 2015 the V8 project authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef V8_INTERPRETER_BYTECODE_GENERATOR_H_
 #define V8_INTERPRETER_BYTECODE_GENERATOR_H_
 
 #include "src/ast.h"
 #include "src/interpreter/bytecode-array-builder.h"
 #include "src/interpreter/bytecodes.h"
 
 namespace v8 {
 namespace internal {
 namespace interpreter {
 
-class BytecodeGenerator : public AstVisitor {
+class BytecodeGenerator final : public AstVisitor {
  public:
   BytecodeGenerator(Isolate* isolate, Zone* zone);
-  virtual ~BytecodeGenerator();
 
   Handle<BytecodeArray> MakeBytecode(CompilationInfo* info);
 
 #define DECLARE_VISIT(type) void Visit##type(type* node) override;
   AST_NODE_LIST(DECLARE_VISIT)
 #undef DECLARE_VISIT
 
   // Visiting function for declarations list is overridden.
   void VisitDeclarations(ZoneList<Declaration*>* declarations) override;
 
  private:
   class ContextScope;
   class ControlScope;
   class ControlScopeForIteration;
   class ControlScopeForSwitch;
   class ExpressionResultScope;
   class EffectResultScope;
   class AccumulatorResultScope;
   class RegisterResultScope;
+  class AssignmentHazardScope;
+
+  // Helper class that aliases locals and parameters when assignment
+  // hazards occur in binary expressions. For y = x + (x = 1) has an
+  // assignment hazard because the lhs evaluates to the register
+  // holding x and the rhs (x = 1) potentially updates x. When this
+  // hazard is detected, the rhs uses a temporary to hold the newer
+  // value of x while preserving the lhs for the binary expresion
+  // evaluation. The newer value is spilled to x at the end of the
+  // binary expression evaluation.
+  class AssignmentHazardHelper final {
+   public:
+    explicit AssignmentHazardHelper(BytecodeGenerator* generator);
+    void EnterScope();
+    void LeaveScope();

[rmcilroy, 2015/11/12 12:49:15]

nit - move Enter / Leave to private and make AssignmentHazardScope a friend
class?

[oth, 2015/11/13 12:43:30]

Done.

+    MUST_USE_RESULT Register GetRegisterForLoad(Register reg);
+    MUST_USE_RESULT Register GetRegisterForStore(Register reg);
+
+   private:
+    void RestoreAliasedLocalsAndParameters();
+
+    BytecodeGenerator* generator_;
+    ZoneMap<int, int> alias_mappings_;
+    ZoneSet<int> aliased_locals_and_parameters_;
+    ExpressionResultScope* execution_result_;
+    int scope_depth_;
+
+    DISALLOW_COPY_AND_ASSIGN(AssignmentHazardHelper);
+  };
 
   void MakeBytecodeBody();
   Register NextContextRegister() const;
 
   DEFINE_AST_VISITOR_SUBCLASS_MEMBERS();
 
   // Dispatched from VisitBinaryOperation.
   void VisitArithmeticExpression(BinaryOperation* binop);
   void VisitCommaExpression(BinaryOperation* binop);
   void VisitLogicalOrExpression(BinaryOperation* binop);
   void VisitLogicalAndExpression(BinaryOperation* binop);
 
   // Dispatched from VisitUnaryOperation.
   void VisitVoid(UnaryOperation* expr);
   void VisitTypeOf(UnaryOperation* expr);
   void VisitNot(UnaryOperation* expr);
   void VisitDelete(UnaryOperation* expr);
 
+  // Used by flow control routines to evaluate loop condition.
+  void VisitCondition(Expression* expr);
+
   // Helper visitors which perform common operations.
   Register VisitArguments(ZoneList<Expression*>* arguments);
 
   void VisitPropertyLoad(Register obj, Property* expr);
   void VisitPropertyLoadForAccumulator(Register obj, Property* expr);
 
   void VisitVariableLoad(Variable* variable, FeedbackVectorSlot slot,
                          TypeofMode typeof_mode = NOT_INSIDE_TYPEOF);
   void VisitVariableLoadForAccumulatorValue(
       Variable* variable, FeedbackVectorSlot slot,
@@ skipping 10 matching lines @@
   void VisitBuildLocalActivationContext();
   void VisitNewLocalBlockContext(Scope* scope);
   void VisitFunctionClosureForContext();
   void VisitSetHomeObject(Register value, Register home_object,
                           ObjectLiteralProperty* property, int slot_number = 0);
   void VisitObjectLiteralAccessor(Register home_object,
                                   ObjectLiteralProperty* property,
                                   Register value_out);
   void VisitForInAssignment(Expression* expr, FeedbackVectorSlot slot);
 
-
   // 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);
 
-  // Methods marking the start and end of binary expressions.
-  void PrepareForBinaryExpression();
-  void CompleteBinaryExpression();
-
   // Methods for tracking and remapping register.
   void RecordStoreToRegister(Register reg);
   Register LoadFromAliasedRegister(Register reg);
 
   inline BytecodeArrayBuilder* builder() { return &builder_; }
 
   inline Isolate* isolate() const { return isolate_; }
   inline Zone* zone() const { return zone_; }
 
   inline Scope* scope() const { return scope_; }
   inline void set_scope(Scope* scope) { scope_ = scope; }
   inline CompilationInfo* info() const { return info_; }
   inline void set_info(CompilationInfo* info) { info_ = info; }
 
   inline ControlScope* execution_control() const { return execution_control_; }
   inline void set_execution_control(ControlScope* scope) {
     execution_control_ = scope;
   }
   inline ContextScope* execution_context() const { return execution_context_; }
   inline void set_execution_context(ContextScope* context) {
     execution_context_ = context;
   }
   inline void set_execution_result(ExpressionResultScope* execution_result) {
     execution_result_ = execution_result;
   }
   ExpressionResultScope* execution_result() const { return execution_result_; }
+  inline AssignmentHazardHelper* assignment_hazard_helper() {
+    return &assignment_hazard_helper_;
+  }
 
   ZoneVector<Handle<Object>>* globals() { return &globals_; }
   inline LanguageMode language_mode() const;
   Strength language_mode_strength() const;
   int feedback_index(FeedbackVectorSlot slot) const;
 
   Isolate* isolate_;
   Zone* zone_;
   BytecodeArrayBuilder builder_;
   CompilationInfo* info_;
   Scope* scope_;
   ZoneVector<Handle<Object>> globals_;
   ControlScope* execution_control_;
   ContextScope* execution_context_;
   ExpressionResultScope* execution_result_;
-
-  int binary_expression_depth_;
-  ZoneSet<int> binary_expression_hazard_set_;
+  AssignmentHazardHelper assignment_hazard_helper_;
 };
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8
 
 #endif  // V8_INTERPRETER_BYTECODE_GENERATOR_H_