[GENERAL] Missing feature - how to differentiate insert/update in plpgsqlfunction?

Hi,
I have a function, in PostgreSQL 9.6, which does:

INSERT INTO table () values (...)
ON CONFLICT DO UPDATE ...;

The thing is that the function should return information whether the row
was modified, or created - and currently it seems that this is not
available. Or am I missing something?

Best regards,

depesz