--- /dev/null
+module \$_DFF_P_ (D, C, Q);
+
+ input D, C;
+ output Q;
+
+ FDRE fpga_dff (
+ .D(D), .Q(Q), .C(C),
+ .CE(1'b1), .R(1'b0)
+ );
+
+endmodule
+
+module \$lut (I, O);
+
+ parameter WIDTH = 0;
+ parameter LUT = 0;
+
+ input [WIDTH-1:0] I;
+ output O;
+
+ generate
+ if (WIDTH == 1) begin:lut1
+ LUT1 #(.INIT(LUT)) fpga_lut (.O(O),
+ .I0(I[0]));
+ end else
+ if (WIDTH == 2) begin:lut2
+ LUT2 #(.INIT(LUT)) fpga_lut (.O(O),
+ .I0(I[0]), .I1(I[1]));
+ end else
+ if (WIDTH == 3) begin:lut3
+ LUT3 #(.INIT(LUT)) fpga_lut (.O(O),
+ .I0(I[0]), .I1(I[1]), .I2(I[2]));
+ end else
+ if (WIDTH == 4) begin:lut4
+ LUT4 #(.INIT(LUT)) fpga_lut (.O(O),
+ .I0(I[0]), .I1(I[1]), .I2(I[2]),
+ .I3(I[3]));
+ end else
+ if (WIDTH == 5) begin:lut5
+ LUT5 #(.INIT(LUT)) fpga_lut (.O(O),
+ .I0(I[0]), .I1(I[1]), .I2(I[2]),
+ .I3(I[3]), .I4(I[4]));
+ end else
+ if (WIDTH == 6) begin:lut6
+ LUT6 #(.INIT(LUT)) fpga_lut (.O(O),
+ .I0(I[0]), .I1(I[1]), .I2(I[2]),
+ .I3(I[3]), .I4(I[4]), .I5(I[5]));
+ end else begin:error
+ wire TECHMAP_FAIL;
+ end
+ endgenerate
+
+endmodule
--- /dev/null
+module counter (clk, rst, en, count);
+
+ input clk, rst, en;
+ output reg [3:0] count;
+
+ always @(posedge clk)
+ if (rst)
+ count <= 4'd0;
+ else if (en)
+ count <= count + 4'd1;
+
+endmodule
--- /dev/null
+`timescale 1 ns / 1 ps
+
+module testbench;
+
+reg clk, en, rst;
+wire [3:0] count;
+
+counter uut_counter(
+ .clk(clk),
+ .count(count),
+ .en(en),
+ .rst(rst)
+);
+
+initial begin
+ clk <= 0;
+ forever begin
+ #50;
+ clk <= ~clk;
+ end
+end
+
+initial begin
+ @(posedge clk);
+ forever begin
+ @(posedge clk);
+ $display("%d", count);
+ end
+end
+
+initial begin
+ rst <= 1; en <= 0; @(posedge clk);
+ rst <= 1; en <= 0; @(posedge clk);
+ rst <= 0; en <= 0; @(posedge clk);
+ rst <= 0; en <= 1; @(posedge clk);
+ rst <= 0; en <= 1; @(posedge clk);
+ rst <= 0; en <= 1; @(posedge clk);
+ rst <= 0; en <= 0; @(posedge clk);
+ rst <= 0; en <= 1; @(posedge clk);
+ rst <= 0; en <= 1; @(posedge clk);
+ rst <= 0; en <= 1; @(posedge clk);
+ rst <= 1; en <= 1; @(posedge clk);
+ rst <= 0; en <= 0; @(posedge clk);
+ rst <= 0; en <= 1; @(posedge clk);
+ rst <= 0; en <= 1; @(posedge clk);
+ rst <= 0; en <= 0; @(posedge clk);
+ rst <= 0; en <= 1; @(posedge clk);
+ rst <= 0; en <= 1; @(posedge clk);
+ rst <= 0; en <= 0; @(posedge clk);
+ rst <= 1; en <= 0; @(posedge clk);
+ rst <= 0; en <= 1; @(posedge clk);
+ rst <= 0; en <= 0; @(posedge clk);
+ rst <= 0; en <= 1; @(posedge clk);
+ rst <= 0; en <= 1; @(posedge clk);
+ rst <= 0; en <= 0; @(posedge clk);
+ rst <= 0; en <= 1; @(posedge clk);
+ rst <= 0; en <= 0; @(posedge clk);
+ $finish;
+end
+
+endmodule
--- /dev/null
+#!/bin/bash
+
+set -ex
+
+XILINX_DIR=/opt/Xilinx/14.5/ISE_DS/ISE/
+
+../../yosys - <<- EOT
+ # read design
+ read_verilog counter.v
+
+ # high-level synthesis
+ hierarchy -check -top counter
+ proc; opt; fsm; opt; techmap; opt
+
+ # mapping logic to LUTs using Berkeley ABC
+ abc -lut 6; opt
+
+ # map internal cells to FPGA cells
+ techmap -map cells.v; opt
+
+ # write netlist
+ write_verilog -noattr testbench_synth.v
+EOT
+
+iverilog -o testbench_gold counter_tb.v counter.v
+iverilog -o testbench_gate counter_tb.v testbench_synth.v \
+ $XILINX_DIR/verilog/src/{glbl,unisims/{FDRE,LUT1,LUT2,LUT3,LUT4,LUT5,LUT6}}.v
+
+./testbench_gold > testbench_gold.txt
+./testbench_gate > testbench_gate.txt
+
+if diff -u testbench_gold.txt testbench_gate.txt; then
+ set +x; echo; echo; banner " PASS "
+else
+ exit 1
+fi
+
+if [ "$*" = "-clean" ]; then
+ rm -f testbench_{synth.v,{gold,gate}{,.txt}}
+fi
+