read_verilog << EOF
module mod_and_or (
    input a,
    input b,
    input c,
    input d,
    output reg y
);

always @(a,b,c,d) begin
    y <= (a&b)|(c&d);
end
endmodule
EOF
hierarchy -top mod_and_or
proc
opt
techmap -map ./bug3515.v
proc
extract -map ./bug3515.v -verbose
proc