read_verilog <<EOT

module uut(
    input  [3:0] a, b,
    output [3:0] y, z
);
    assign y = a + b;
    assign z = b + a;
endmodule

EOT

copy uut after
opt_merge after
clean

show -format dot -prefix opt_merge_full -notitle -color cornflowerblue uut
