Definition StoreEffect (tv:val)(vl : list memval) (b:Values.block) (z:Z):bool :=
  match tv with Vptr bb ofs => eq_block bb b &&
             zle (Ptrofs.unsigned ofs) z && zlt z (Ptrofs.unsigned ofs + Z.of_nat (length vl))
         | _ => false
  end.

Lemma StoreEffect_Storev: forall m chunk tv tv' m' (STORE : Mem.storev chunk m tv tv' = Some m'), Mem.unchanged_on (fun b ofs => StoreEffect tv (encode_val chunk tv') b ofs = false) m m'.