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 StoreEffectD: forall vaddr v b ofs (STE: StoreEffect vaddr v b ofs = true), exists i, vaddr = Vptr b i /\ (Ptrofs.unsigned i) <= ofs < (Ptrofs.unsigned i + Z.of_nat (length v)).