LUT help!!!

I wrote this code.What i need to do is to insert 4 values at each clock which i store on a 2-dimensional array and i want to compute the sum of these values.

LIBRARY IEEE;

USE IEEE.STD_LOGIC_1164.ALL;

USE IEEE.STD_LOGIC_ARITH.ALL;

ENTITY test IS

PORT( x1 : IN INTEGER RANGE 0 TO 255;

clk,load : IN STD_LOGIC;

output1 : out INTEGER RANGE 0 TO 1020);

END test;

ARCHITECTURE behavioral OF test IS

TYPE windows IS ARRAY(0 TO 1,0 to 1) OF INTEGER RANGE 0 TO 255;

BEGIN

PROCESS(clk,x1)

VARIABLE window : windows;

VARIABLE sum : INTEGER RANGE 0 TO 1020;

BEGIN

IF(clk'EVENT AND clk='1') THEN

IF(load='1') THEN

FOR i IN 0 TO 1 LOOP

FOR j IN 0 TO 1 LOOP

window(i,j):=x1;

sum:=sum+window(i,j);

END LOOP;

END LOOP;

END IF;

END IF;

output1<=sum;

END PROCESS;

END behavioral;

The code has no problem while compiling but in the simulation the results are wrong!!!.Please help.I set in the simulation for the x1 to take 2 values per clock but the result shows that something is wrong.