yosys/tests/arch/common/shifter.v

module top(out, clk, in);
    output [7:0] out;
    input signed clk, in;
    reg signed [7:0] out = 0;

    always @(posedge clk)
	begin
		out    <= out >> 1;
		out[7] <= in;
	end    
endmodule