how to build 4 serial inverters

[Altera_Forum]

I want to build 4 serial inverters but at last when programming the FPGA quartus automatically fixes it as if no inverters exists.how can I do some thing to ignore this auto fixing?

[Altera_Forum]

--- Quote Start ---  I want to build 4 serial inverters but at last when programming the FPGA quartus automatically fixes it as if no inverters exists.how can I do some thing to ignore this auto fixing?  --- Quote End ---    altera has provided various attributes useful in controlling fitter. for comb. nodes(wires) try this attribute:  signal invert : std_logic;   attribute keep: boolean;  attribute keep of invert: signal is true;  apply to all relevant wires in your chain.

[Altera_Forum]

Thank you for the code but I don't know how to apply it to my nodes in quartus.would you please help about that?

[Altera_Forum]

--- Quote Start ---  Thank you for the code but I don't know how to apply it to my nodes in quartus.would you please help about that?  --- Quote End ---    You don't apply attribute to quartus. You add it to your vhdl code. I have already done it for you. Juat change name of "invert" to your signal name(s). insert where you declared that signal