read_verilog shifter.v
hierarchy -top top
proc
flatten
equiv_opt -assert -map +/xilinx/cells_sim.v synth_xilinx # equivalency check
design -load postopt # load the post-opt design (otherwise equiv_opt loads the pre-opt design)
cd top # Constrain all select calls below inside the top module

select -assert-count 1 t:BUFG
select -assert-count 8 t:FDRE
select -assert-none t:BUFG t:FDRE %% t:* %D