Notation cexp := (canonic_exp beta fexp).

Theorem round_plus_ge_ulp_FLX : forall x y e, generic_format beta (FLX_exp prec) x -> generic_format beta (FLX_exp prec) y -> (bpow e <= Rabs x)%R -> round beta (FLX_exp prec) rnd (x+y) = 0%R \/ (bpow (e - prec) <= Rabs (round beta (FLX_exp prec) rnd (x+y)))%R.