sdc-plugin/tests/period_check/period_check.v

module top((* CLOCK_SIGNAL = "yes", WAVEFORM = "0 5" *) input clk,
        input clk2,
	input [1:0] in,
	output [5:0] out );

reg [1:0] cnt = 0;
wire clk_int_1, clk_int_2;
IBUF ibuf_proxy(.I(clk), .O(ibuf_proxy_out));
IBUF ibuf_inst(.I(ibuf_proxy_out), .O(ibuf_out));
assign clk_int_1 = ibuf_out;
assign clk_int_2 = clk_int_1;

always @(posedge clk_int_2) begin
	cnt <= cnt + 1;
end

middle middle_inst_1(.clk(ibuf_out), .out(out[2]));
middle middle_inst_2(.clk(clk_int_1), .out(out[3]));
middle middle_inst_3(.clk(clk_int_2), .out(out[4]));
middle middle_inst_4(.clk(clk2), .out(out[5]));

assign out[1:0] = {cnt[0], in[0]};
endmodule

module middle(input clk,
	output out);

reg [1:0] cnt = 0;
wire clk_int;
assign clk_int = clk;
always @(posedge clk_int) begin
	cnt <= cnt + 1;
end

assign out = cnt[0];
endmodule