QQmlPropertyMap inserting new properties is O(N^2)

QQmlPropertyMap::insert(const QString &key, const QVariant &value) has O(N^2) complexity when inserting new properties. Feels like it should be linear or O(n log n) at least. This leads to UI freezes for a significant amount of time.

My numbers are (i7-2760 2400 MHz):
500 301 ms
1000 1206 ms
1500 2689 ms
2000 4759 ms
2500 7546 ms (UI is blocked for 7 secs here!)

Upd:
Found this one marked as done – https://bugreports.qt.io/browse/QTBUG-32720
Looks like it's a regression