[Interpreter] Ensure ValueOf is only called once for post-increment operations.

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/compile-time-value.h"
 #include "src/ast/scopes.h"
 #include "src/code-stubs.h"
 #include "src/compilation-info.h"
@@ skipping 2732 matching lines @@
       VisitForRegisterValue(property->key(), load_super_args[2]);
       builder()->CallRuntime(Runtime::kLoadKeyedFromSuper, load_super_args);
       break;
     }
   }
 
   // Save result for postfix expressions.
   if (is_postfix) {
     // Convert old value into a number before saving it.
     old_value = register_allocator()->NewRegister();
-    builder()->ConvertAccumulatorToNumber(old_value);
+    builder()
+        ->ConvertAccumulatorToNumber(old_value)
+        .LoadAccumulatorWithRegister(old_value);

[Jarin, 2016/11/08 14:39:28]

Does not this mean that the feedback for the binop will be a bit bogus?

   }
 
   // Perform +1/-1 operation.
   FeedbackVectorSlot slot = expr->CountBinaryOpFeedbackSlot();
   builder()->CountOperation(expr->binary_op(), feedback_index(slot));
 
   // Store the value.
   builder()->SetExpressionPosition(expr);
   FeedbackVectorSlot feedback_slot = expr->CountSlot();
   switch (assign_type) {
@@ skipping 452 matching lines @@
 }
 
 Runtime::FunctionId BytecodeGenerator::StoreKeyedToSuperRuntimeId() {
   return is_strict(language_mode()) ? Runtime::kStoreKeyedToSuper_Strict
                                     : Runtime::kStoreKeyedToSuper_Sloppy;
 }
 
 }  // namespace interpreter
 }  // namespace internal
 }  // namespace v8