intros. destruct q; destruct q'; try destruct f; destruct retv; simpl in *; try discriminate; try reflexivity.
Qed.
Definition RTL_core_sem : CoreSemantics genv RTL_core mem.
eapply @Build_CoreSemantics with (at_external:= RTL_at_external) (after_external:= RTL_after_external)(corestep:=RTL_corestep)(halted:= RTL_halted).
apply RTL_initial_core.
eapply corestep_not_external.
eapply corestep_not_halted.
eapply external_xor_halted.
eapply after_xor_at_external.
Defined.
(************************NOW SHOW THAT WE ALSO HAVE A COOPSEM******)

Lemma rtl_coop_forward : forall g c m c' m' (CS: RTL_corestep g c m c' m'),
mem_forward m m'.