[Interpreter] Introduce IncStub and DecStub.

src/interpreter/bytecode-generator.cc

 // 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.
 
 #include "src/interpreter/bytecode-generator.h"
 
 #include "src/ast/scopes.h"
 #include "src/compiler.h"
 #include "src/interpreter/bytecode-register-allocator.h"
 #include "src/interpreter/control-flow-builders.h"
@@ skipping 2778 matching lines @@
       SuperPropertyReference* super_property =
           property->obj()->AsSuperPropertyReference();
       VisitForRegisterValue(super_property->this_var(), object);
       VisitForRegisterValue(super_property->home_object(), home_object);
       VisitForRegisterValue(property->key(), key);
       BuildKeyedSuperPropertyLoad(object, home_object, key);
       break;
     }
   }
 
-  // Convert old value into a number.
-  builder()->CastAccumulatorToNumber();
-
   // Save result for postfix expressions.
   if (is_postfix) {
     old_value = register_allocator()->outer()->NewRegister();
-    builder()->StoreAccumulatorInRegister(old_value);
+
+    // Convert old value into a number before saving it.
+    builder()->CastAccumulatorToNumber().StoreAccumulatorInRegister(old_value);
   }
 
   // Perform +1/-1 operation.
   builder()->CountOperation(expr->binary_op());
 
   // Store the value.
   builder()->SetExpressionPosition(expr);
   FeedbackVectorSlot feedback_slot = expr->CountSlot();
   switch (assign_type) {
     case VARIABLE: {
@@ skipping 396 matching lines @@
 }
 
 
 int BytecodeGenerator::feedback_index(FeedbackVectorSlot slot) const {
   return info()->shared_info()->feedback_vector()->GetIndex(slot);
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8