read_verilog <<EOT
module top(inout io);
wire in;
wire t;
wire o;
IOBUF IOBUF(
.I(in),
.T(t),
.IO(io),
.O(o)
);
endmodule
EOT
synth_xilinx
cd top
select -assert-count 1 t:IOBUF
select -assert-none t:* t:IOBUF %d