Definition force_valid_pointers m v1 v2 :=
match v1, v2 with
| Vptr b1 ofs1, Vptr b2 ofs2 =>
(Mem.valid_pointer m b1 (Ptrofs.unsigned ofs1) &&
Mem.valid_pointer m b2 (Ptrofs.unsigned ofs2))%bool
| _, _ => false
end.
Definition blocks_match op v1 v2 :=
match op with Cop.Olt | Cop.Ogt | Cop.Ole | Cop.Oge =>
match v1, v2 with
Vptr b _, Vptr b2 _ => b=b2
| _, _ => False
end
| _ => True
end.

Lemma mapsto_valid_pointer : forall b o sh t jm,
nonidentity sh ->
(mapsto_ sh (t) (Vptr b o) * TT)%pred (m_phi jm) ->
Mem.valid_pointer (m_dry jm) b (Ptrofs.unsigned o) = true.