read_verilog alu_sub.v
proc
hierarchy -auto-top

select -assert-mod-count 1 adder
select -assert-mod-count 1 wrapper
select -assert-mod-count 1 alu

sdc -keep_hierarchy alu_sub.sdc
flatten

select -assert-mod-count 0 adder
select -assert-mod-count 1 wrapper
select -assert-mod-count 1 alu