[Interpreter] Add support for for count operations.

src/interpreter/bytecode-generator.cc

Index: src/interpreter/bytecode-generator.cc
diff --git a/src/interpreter/bytecode-generator.cc b/src/interpreter/bytecode-generator.cc
index b051bd9bbb173e4070f6932d525e789f8ae96b97..2b80467bf91119a3bdfa83597b8a7c166ba47abc 100644
--- a/src/interpreter/bytecode-generator.cc
+++ b/src/interpreter/bytecode-generator.cc
@@ -1149,7 +1149,91 @@ void BytecodeGenerator::VisitUnaryOperation(UnaryOperation* expr) {
 
 
 void BytecodeGenerator::VisitCountOperation(CountOperation* expr) {
-  UNIMPLEMENTED();
+  DCHECK(expr->expression()->IsValidReferenceExpressionOrThis());
+
+  // Left-hand side can only be a property, a global or a variable slot.
+  Property* property = expr->expression()->AsProperty();
+  LhsKind assign_type = Property::GetAssignType(property);
+
+  // TODO(rmcilroy): Set is_postfix to false if visiting for effect.
+  bool is_postfix = expr->is_postfix();
+
+  // Evaluate LHS expression and get old value.
+  TemporaryRegisterScope temporary_register_scope(builder());
+  Register obj, key, old_value;
+  switch (assign_type) {
+    case VARIABLE: {
+      VariableProxy* proxy = expr->expression()->AsVariableProxy();
+      VisitVariableLoad(proxy->var(), proxy->VariableFeedbackSlot());
+      break;
+    }
+    case NAMED_PROPERTY: {
+      obj = temporary_register_scope.NewRegister();
+      key = temporary_register_scope.NewRegister();
+      FeedbackVectorSlot slot = property->PropertyFeedbackSlot();
+      Visit(property->obj());
+      builder()
+          ->StoreAccumulatorInRegister(obj)
+          .LoadLiteral(property->key()->AsLiteral()->AsPropertyName())
+          .StoreAccumulatorInRegister(key)
+          .LoadNamedProperty(obj, feedback_index(slot), language_mode());
+      break;
+    }
+    case KEYED_PROPERTY: {
+      obj = temporary_register_scope.NewRegister();
+      key = temporary_register_scope.NewRegister();
+      FeedbackVectorSlot slot = property->PropertyFeedbackSlot();
+      Visit(property->obj());
+      builder()->StoreAccumulatorInRegister(obj);
+      Visit(property->key());
+      builder()->StoreAccumulatorInRegister(key).LoadKeyedProperty(
+          obj, feedback_index(slot), language_mode());
+      break;
+    }
+    case NAMED_SUPER_PROPERTY:
+    case KEYED_SUPER_PROPERTY:
+      UNIMPLEMENTED();
+  }
+
+  // Convert old value into a number.
+  if (!is_strong(language_mode())) {
+    builder()->CastAccumulatorToNumber();
+  }
+
+  // Save result for postfix expressions.
+  if (is_postfix) {
+    old_value = temporary_register_scope.NewRegister();
+    builder()->StoreAccumulatorInRegister(old_value);
+  }
+
+  // Perform +1/-1 operation.
+  builder()->CountOperation(expr->binary_op(), language_mode_strength());
+
+  // Store the value.
+  FeedbackVectorSlot feedback_slot = expr->CountSlot();
+  switch (assign_type) {
+    case VARIABLE: {
+      Variable* variable = expr->expression()->AsVariableProxy()->var();
+      VisitVariableAssignment(variable, feedback_slot);
+      break;
+    }
+    case NAMED_PROPERTY: {
+      builder()->StoreNamedProperty(obj, key, feedback_index(feedback_slot),
+                                    language_mode());
+      break;
+    }
+    case KEYED_PROPERTY: {
+      builder()->StoreKeyedProperty(obj, key, feedback_index(feedback_slot),
+                                    language_mode());
+      break;
+    }
+    case NAMED_SUPER_PROPERTY:
+    case KEYED_SUPER_PROPERTY:
+      UNIMPLEMENTED();
+  }
+
+  // Restore old value for postfix expressions.
+  if (is_postfix) builder()->LoadAccumulatorWithRegister(old_value);
 }