[field type tracking] Use breadth first traversal instead of recursion when updating field types.

src/objects.cc

Index: src/objects.cc
diff --git a/src/objects.cc b/src/objects.cc
index db4e29ba484e80b7901b95cda24862e1349abb2c..8254ee7e9efcab696058f80d976d832c5bb27f9e 100644
--- a/src/objects.cc
+++ b/src/objects.cc
@@ -3281,25 +3281,40 @@ void Map::UpdateFieldType(int descriptor, Handle<Name> name,
                           Representation new_representation,
                           Handle<Object> new_wrapped_type) {
   DCHECK(new_wrapped_type->IsSmi() || new_wrapped_type->IsWeakCell());
+  // We store raw pointers in the queue, so no allocations are allowed.
   DisallowHeapAllocation no_allocation;
   PropertyDetails details = instance_descriptors()->GetDetails(descriptor);
   if (details.type() != DATA) return;
-  Object* transitions = raw_transitions();
-  int num_transitions = TransitionArray::NumberOfTransitions(transitions);
-  for (int i = 0; i < num_transitions; ++i) {
-    Map* target = TransitionArray::GetTarget(transitions, i);
-    target->UpdateFieldType(descriptor, name, new_representation,
-                            new_wrapped_type);
-  }
-  // It is allowed to change representation here only from None to something.
-  DCHECK(details.representation().Equals(new_representation) ||
-         details.representation().IsNone());
-
-  // Skip if already updated the shared descriptor.
-  if (instance_descriptors()->GetValue(descriptor) == *new_wrapped_type) return;
-  DataDescriptor d(name, instance_descriptors()->GetFieldIndex(descriptor),
-                   new_wrapped_type, details.attributes(), new_representation);
-  instance_descriptors()->Replace(descriptor, &d);
+
+  Zone zone(GetIsolate()->allocator());
+  ZoneQueue<Map*> backlog(&zone);
+  backlog.push(this);
+
+  while (!backlog.empty()) {
+    Map* current = backlog.front();
+    backlog.pop();
+
+    Object* transitions = current->raw_transitions();
+    int num_transitions = TransitionArray::NumberOfTransitions(transitions);
+    for (int i = 0; i < num_transitions; ++i) {
+      Map* target = TransitionArray::GetTarget(transitions, i);
+      backlog.push(target);
+    }
+    DescriptorArray* descriptors = current->instance_descriptors();
+    PropertyDetails details = descriptors->GetDetails(descriptor);
+
+    // It is allowed to change representation here only from None to something.
+    DCHECK(details.representation().Equals(new_representation) ||
+           details.representation().IsNone());
+
+    // Skip if already updated the shared descriptor.
+    if (descriptors->GetValue(descriptor) != *new_wrapped_type) {
+      DataDescriptor d(name, descriptors->GetFieldIndex(descriptor),
+                       new_wrapped_type, details.attributes(),
+                       new_representation);
+      descriptors->Replace(descriptor, &d);
+    }
+  }
 }
 
 bool FieldTypeIsCleared(Representation rep, FieldType* type) {