yosys/tests/csa_tree/csa_tree_idempotent.ys

read_verilog add_chain_8.v
hierarchy -auto-top
proc; opt_clean

csa_tree
stat
select -assert-count 6 t:$fa
select -assert-count 1 t:$add

csa_tree
stat

select -assert-count 6 t:$fa
select -assert-count 1 t:$add
select -assert-none t:$sub