Ltac hint_msg_aux R1 A :=
lazymatch A with
| data_at => idtac
| field_at => idtac
| data_at_ => idtac
| field_at_ => idtac
| memory_block => idtac
| @exp _ _ _ _  => idtac "
Or, perhaps you need to do [Intros x] to introduce the EXistential" R1 "in your SEP clause."
| _ _ => idtac
| _ => idtac "
Or, perhaps the definition [" A "] needs to be unfolded so that your SEP conjuct" R1 "can be used effectively."
end.
Ltac hint_msg_aux2 R p2 :=
match R with
| nil => idtac
| ?R1 :: ?R' =>
lazymatch R1 with
| ?A _ _ _ _ _ _ _ _ _ _ p2 => hint_msg_aux R1 A
| ?A _ _ _ _ _ _ _ _ _ p2 => hint_msg_aux R1 A
| ?A _ _ _ _ _ _ _ _ p2 => hint_msg_aux R1 A
| ?A _ _ _ _ _ _ _ p2 => hint_msg_aux R1 A
| ?A _ _ _ _ _ _ p2 => hint_msg_aux R1 A
| ?A _ _ _ _ _ p2 => hint_msg_aux R1 A
| ?A _ _ _ _ p2 => hint_msg_aux R1 A
| ?A _ _ _ p2 => hint_msg_aux R1 A
| ?A _ _ p2 => hint_msg_aux R1 A
| ?A _ p2 => hint_msg_aux R1 A
| ?A p2 => hint_msg_aux R1 A
| context [p2] => hint_msg_aux R1 R1
| _ => idtac
end;
hint_msg_aux2 R' p2
end.
Ltac hint_msg LOCAL2PTREE Delta e :=
match goal with |- semax _ (|> PROPx _ (LOCALx _ (SEPx ?R))) _ _ =>
eapply (hint_msg_lemma Delta e);
[ exact LOCAL2PTREE
| reflexivity
| solve_msubst_eval_lvalue
| solve_msubst_eval_LR
| solve_msubst_efield_denote
| econstructor
| solve_field_address_gen
| ];
match goal with
| |- ?eq1 /\ ?eq2 /\ False =>
match eq1 with ?p1 = field_address _ _ ?p =>
try match p1 with offset_val _ ?p2 => hint_msg_aux2 R p2 end;
first [ constr_eq eq1 eq2;
fail 1000 "
It is not obvious how to move forward here.  One way:
Find a SEP clause of the form [data_at _ _ _ " p"] (or field_at, data_at_, field_at_),
then use assert_PROP to prove an equality of the form" eq1 ", then try [forward] again."
| fail 1000 "
It is not obvious how to move forward here.  One way:
Find a SEP clause of the form [data_at _ _ _ " p"] (or field_at, data_at_, field_at_),
then use assert_PROP to prove an equality of the form" eq1
"or if this does not hold, prove an equality of the form" eq2 ", then try [forward] again."
]
end
end
end.
Section SEMAX_PTREE.
Context {cs: compspecs}.

Lemma semax_PTree_set:
forall {Espec: OracleKind},
forall Delta id P Q R T1 T2 GV (e2: expr) t v,
local2ptree Q = (T1, T2, nil, GV) ->
typeof_temp Delta id = Some t ->
is_neutral_cast (implicit_deref (typeof e2)) t = true ->
msubst_eval_expr Delta T1 T2 GV e2 = Some v ->
ENTAIL Delta, PROPx P (LOCALx Q (SEPx R)) |--
(tc_expr Delta e2) ->
semax Delta (|>PROPx P (LOCALx Q (SEPx R)))
(Sset id e2)
(normal_ret_assert
(PROPx P
(LOCALx (temp id v :: remove_localdef_temp id Q)
(SEPx R)))).