problem for synthesis

hello i am doing a program that counts the ones in an input vector. It is asynchronous so i only have one input and one output (CounterDataIn, CounterDataOut).
If I do it it with wait statements it works but the wait is not suported in synthesis!!!
If I do it through a sensitivity list, it doesn't work!!!
How can I make it work without wait statements?

Here is the architecture:
begin
process (CounterDataIn)
variable count : integer := 0;
variable sum : integer := 0;
begin
if (count /= CounterDataIn'length) then
if (CounterDataIn(count) = '1') then
sum := sum + 1;
count := count + 1;
CounterDataOut <="1111";
elsif (CounterDataIn(count) = '0') then
count := count + 1;
CounterDataOut <="0000";
end if;
elsif (count = CounterDataIn'length) then
CounterDataOut <= std_logic_vector(to_unsigned(sum, CounterDataOut'length));
end if;
end process;

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