[turbofan] Collect and use type feedback on ToNumber.

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 417873f47665cb2add328976e2ac7cc7fb23cc24..8093514343ae9ed5e63e4eb88c68dfc165a00db5 100644
--- a/src/interpreter/bytecode-generator.cc
+++ b/src/interpreter/bytecode-generator.cc
@@ -2976,17 +2976,17 @@ void BytecodeGenerator::VisitCountOperation(CountOperation* expr) {
   }
 
   // Save result for postfix expressions.
+  FeedbackSlot count_slot = expr->CountBinaryOpFeedbackSlot();

[rmcilroy, 2017/04/06 11:21:31]

Hmm, we are now recording this type feedback twice. I guess this is fine for
now, but it suggests we should rework this since the only place we use either
the ToNumber or Count bytecodes is for count operations. Maybe we can think
about having a single bytecode for CountPostfix (need to think about how we
deopt though) ? WDYT?

[Benedikt Meurer, 2017/04/06 11:30:00]

I'd be in favor of that long-/middle-term. I'll put a TODO here.

   if (is_postfix) {
     // Convert old value into a number before saving it.
     old_value = register_allocator()->NewRegister();
     builder()
-        ->ConvertAccumulatorToNumber(old_value)
+        ->ConvertAccumulatorToNumber(old_value, feedback_index(count_slot))
         .LoadAccumulatorWithRegister(old_value);
   }
 
   // Perform +1/-1 operation.
-  FeedbackSlot slot = expr->CountBinaryOpFeedbackSlot();
-  builder()->CountOperation(expr->binary_op(), feedback_index(slot));
+  builder()->CountOperation(expr->binary_op(), feedback_index(count_slot));
 
   // Store the value.
   builder()->SetExpressionPosition(expr);