let int_op = function
| PlusA -> F.e_iop Formula.Iadd
| MinusA -> F.e_iop Formula.Isub
| Mult -> F.e_iop Formula.Imul
| Div -> F.e_iop Formula.Idiv
| Mod -> F.e_iop Formula.Imod
| BAnd -> F.e_band
| BXor -> F.e_bxor
| BOr -> F.e_bor
| Shiftlt -> F.e_lshift
| Shiftrt -> F.e_rshift
| _ -> WpLog.fatal "[int_op] non integer operator"