Allocation type info advice consumed in bailout path leads to assert failure.

src/builtins.cc

Index: src/builtins.cc
diff --git a/src/builtins.cc b/src/builtins.cc
index 37ba1e5301a9e17a9e5f4f026e0ad902bb03fd9d..8a4ae71ff0a229daa97dfed558eb1da94716328f 100644
--- a/src/builtins.cc
+++ b/src/builtins.cc
@@ -209,15 +209,25 @@ RUNTIME_FUNCTION(MaybeObject*, ArrayConstructor_StubFailure) {
   Handle<Object> type_info = args.at<Object>(parameters_start + 1);
 
   bool holey = false;
-  if (caller_args->length() == 1 && (*caller_args)[0]->IsSmi()) {
-    int value = Smi::cast((*caller_args)[0])->value();
-    holey = (value > 0 && value < JSObject::kInitialMaxFastElementArray);
+  bool ignore_advice = false;

[danno, 2013/06/04 16:29:47]

ignore_type_feedback is probably more accurate.

[mvstanton, 2013/06/05 08:47:07]

Done.

+  if (caller_args->length() == 1) {
+    Object* argument_one = (*caller_args)[0];
+    if (argument_one->IsSmi()) {
+      int value = Smi::cast(argument_one)->value();
+      holey = (value > 0 && value < JSObject::kInitialMaxFastElementArray);

[danno, 2013/06/04 16:29:47]

Don't you mean >= 0? Or is the distinction important?

[mvstanton, 2013/06/05 08:47:07]

I think it's important because if someone calls new Array(0), they should get a
packed array instead of a holey one.

But your comment brought to light a bug in this new code. I would choose to
ignore type feedback if the value == 0, which is wrong. I've prepped a more
careful initialization of ignore_type_feedback.

+    }
+
+    // If we have a single argument, and we failed to set holey above,
+    // then we'll be forced down the dictionary path. In this case it's
+    // useless to consume allocation site info advice, even if we have it.
+    ignore_advice = !holey;
   }
 
   JSArray* array;
   MaybeObject* maybe_array;
   if (*type_info != isolate->heap()->undefined_value() &&
-      JSGlobalPropertyCell::cast(*type_info)->value()->IsSmi()) {
+      JSGlobalPropertyCell::cast(*type_info)->value()->IsSmi() &&
+      !ignore_advice) {
     JSGlobalPropertyCell* cell = JSGlobalPropertyCell::cast(*type_info);
     Smi* smi = Smi::cast(cell->value());
     ElementsKind to_kind = static_cast<ElementsKind>(smi->value());