rewrite Zabs_Zopp; auto with float.
rewrite <- Zopp_mult_distr_r; rewrite Zabs_Zopp; auto with float.
Qed.

Theorem FsubnormFabs : forall p : float, Fsubnormal p -> Fsubnormal (Fabs p).
intros p; case p; intros a e H; split; auto with float.