JIT: Set the IP and check for invalidation in `POP_TOP` only if `Py_Dealloc` is called.

The optimizer removes many POP_TOPs, but quite a few remain.

The code for POP_TOP looks like this:

    inst(POP_TOP, (value --)) {
        PyStackRef_XCLOSE(value);
    }

which is fine for the interprete but in the JIT, as POP_TOP is marked as escaping, we need to set the IP before and check for invalidation afterwards.

What we could do, is have a version of POP_TOP that sets the IP and checks for invalidation only if Py_Dealloc is called, so we don't need to add SET_IP and CHECK_VALIDITY.

The new form of POP_TOP would look like this:

    op(_POP_TOP_SET_IP_CHECK_INVALID, (value --)) {
        if (do_decref_and_refcnt_is_zero(value)) {
            SET_IP()
            Py_Dealloc()
            CHECK_VALID();
        }
   }

_POP_TOP_SET_IP_CHECK_INVALID should be inserted in the same pass that we insert _SET_IP and _CHECK_VALIDITY as we know whether we need to insert those uops, and leave POP_TOP alone in those cases.

Overall, this should speed things up as it doesn't increase the overall code size, but it does execute less code in many cases.

Inspecciona la implementación JIT de POP_TOP y el paso que inserta _SET_IP y _CHECK_VALIDITY. Rastrea do_decref_and_refcnt_is_zero y las rutas existentes SET_IP, Py_Dealloc y CHECK_VALID; el trabajo estará terminado cuando la forma especializada se inserte solo donde sea necesaria, mientras POP_TOP permanezca sin cambios en el resto y se preserve el comportamiento de invalidación.