let pebble_guard_neg ~loc pebble_set aux_var guard =
let v = Cil_const.make_logic_var aux_var.lv_name aux_var.lv_type in
let g = rename_pred aux_var v guard in
let g =
Logic_const.pimplies ~loc
(mk_sub ~loc pebble_set v, Logic_const.pnot ~loc g)
in
Logic_const.pforall ~loc ([v], g)