if e1 = e2 then ac_stacks st m1 m2 else false
| B.GRef (_, u1), None, B.GRef (_, u2), None ->
if U.eq u1 u2 && assert_iterations m1 m2 then ac_stacks st m1 m2 else false
| B.GRef ({E.n_apix = e1}, u1), Some v1,
if e1 = e2 then ac_stacks st m1 m2 else false
| B.GRef (_, u1), None, B.GRef (_, u2), None ->
if U.eq u1 u2 && assert_iterations m1 m2 then ac_stacks st m1 m2 else false
| B.GRef ({E.n_apix = e1}, u1), Some v1,