simulation error occuring

the program i have given below applies a multiplication block using a paakage ..i m having problem when i generate a waveform for given inputs its not multiplying it the error is probably due to res:= res_lcl(vector length ) can any one debug this.

the project is modelling of fir filter using general equation of fir

addition package

library ieee;

use ieee.std_logic_1164.all;

package add_std is

function "+" (A,B : in std_logic_vector)

return std_logic_vector;

end add_std;

package body add_std is

function "+" (A,B : in std_logic_vector)

return std_logic_vector is

variable C: std_logic_vector(A'length - 1 downto 0);

variable D: std_logic_vector(A'length downto 0);

begin

D(0):= '0';

C:= (A xor B) xor D(A'length - 1 downto 0);

D(A'length downto 1):= (A and B) or (A and D(A'length - 1 downto 0)) or (D(A'length - 1 downto 0) and B);

return C;

end "+";

end add_std;

multiplication block

library ieee;

use ieee.std_logic_1164.all;

use work.add_std.all;

entity mult is

port(br, qr : in std_logic_vector(3 downto 0);

res : out std_logic_vector(6 downto 0));

end mult;

architecture beh of mult is

begin

process(br,qr)

variable br_bar : std_logic_vector(3 downto 0);

variable res_lcl : std_logic_vector(8 downto 0);

begin

br_bar := not br;

res_lcl := "0000" & qr & '0';

for i in 0 to 3

loop

case res_lcl(1 downto 0) is

when "00" =>

res_lcl(7 downto 0):= res_lcl(8 downto 1);

when "01" =>

res_lcl(8 downto 5):= res_lcl(8 downto 5) + br;

res_lcl(7 downto 0):= res_lcl(8 downto 1);

when "10" =>

res_lcl(8 downto 5):= res_lcl(8 downto 5) + br_bar + "0001";

res_lcl(7 downto 0):= res_lcl(8 downto 1);

when "11" =>

res_lcl(7 downto 0):= res_lcl(8 downto 1);

when others =>

res_lcl:= res_lcl;

end case;

end loop;

res<= res_lcl(7 downto 1);

end process;

end beh;