[Interpreter] Collect type feedback for calls in the bytecode handler

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 bdc5370f5a30ac5779f65f6999c3470256a712cf..8ac0def9b653cc0047678c38900ac1609da6fc40 100644
--- a/src/interpreter/bytecode-generator.cc
+++ b/src/interpreter/bytecode-generator.cc
@@ -2522,8 +2522,16 @@ void BytecodeGenerator::VisitCall(Call* expr) {
   }
 
   builder()->SetExpressionPosition(expr);
-  builder()->Call(callee, receiver, 1 + args->length(),
-                  feedback_index(expr->CallFeedbackICSlot()),
+  int feedback_slot_index = feedback_index(expr->CallFeedbackICSlot());
+  if (expr->CallFeedbackICSlot().IsInvalid()) {
+    DCHECK(call_type == Call::POSSIBLY_EVAL_CALL);
+    // Valid type feedback slots can only be greater than kReservedIndexCount.
+    // We use 0 to indicate an invalid slot it. Statically assert that 0 cannot
+    // be a valid slot id.
+    STATIC_ASSERT(TypeFeedbackVector::kReservedIndexCount > 0);
+    feedback_slot_index = 0;

[mythria, 2016/07/12 09:01:34]

@mvstanton, this is where we pass 0 for invalid slot id. As discussed offline I
added a static assert. PTAL.

[rmcilroy, 2016/07/12 09:36:20]

I think feedback_slot_index will already be zero for an invalid slot. Could we
just do:

int feedback_slot_index = feedback_index(expr->CallFeedbackICSlot());

// Comment...
STATIC_ASSERT(TypeFeedbackVector::kReservedIndexCount > 0);
DCHECK(expr->CallFeedbackICSlot().Valid() || (
       (feedback_slot_index == 0 && call_type == Call::POSSIBLY_EVAL_CALL));

?

[mvstanton, 2016/07/12 13:25:22]

Sounds good.

[mythria, 2016/07/12 15:20:35]

As discussed offline, it will be 0 but it is dependent on kReservedIndexCount
being 1. Updated the code to if else to make it more readable. Done.

+  }
+  builder()->Call(callee, receiver, 1 + args->length(), feedback_slot_index,
                   expr->tail_call_mode());
   execution_result()->SetResultInAccumulator();
 }