static <A> A vm_generalMap_getOrCreate(O key, F0<A> create) {
  ret vm_generalMap_getOrCreate(key, f0ToIF0(create));
}

static <A> A vm_generalMap_getOrCreate(O key, IF0<A> create) {
  Map generalMap = vm_generalMap();
  if (generalMap == null) null; // must be x30 init
  
  synchronized(generalMap) { // should switch to locks here
    A a = cast vm_generalMap_get(key);
    if (a == null)
      vm_generalMap_put(key, a = create?!);
    ret a;
  }
}