[tenaf0]

Well, code size is another interesting aspect here. A JIT compiler can effectively create any number of versions for a hot method, based on even very aggressive assumptions (an easy one would be that a given object is non-null, or that the interface only has a single instance loaded). The checks for these are cheap (e.g. it could be encoded as trapping an invalid page address in case of NPEs), and invalidation’s cost is amortized.

Contrast this with the problem of specialization in AOT languages, which can easily result in bloated binaries (PGO does help here quite a lot, that much is true). For example, generics might output a completely new function for every type it gets instantiated with - if the function is not that hot, it actually makes sense to rather try to handle more cases with the same code.