mips_sys

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LIBRARY ieee;
USE ieee.std_logic_1164.all;
USE ieee.numeric_std.all;
USE work.mips_types.all;
ENTITY e_mips_shifter IS
    PORT (
        i_arith: IN  std_logic;
        i_left:  IN  std_logic;
        i_val:   IN  std_logic_vector(31 DOWNTO 0);
        i_num:   IN  std_logic_vector(31 DOWNTO 0);
        o_val:   OUT std_logic_vector(31 DOWNTO 0)
    );
END ENTITY e_mips_shifter;
ARCHITECTURE a_mips_shifter OF e_mips_shifter IS
    SIGNAL s_fill: std_logic;
    FUNCTION l_shift(b:    std_logic;
                     val:  std_logic_vector(31 DOWNTO 0);
                     n:    natural) RETURN std_logic_vector IS
        VARIABLE v_fill: std_logic_vector(31 DOWNTO 0);
    BEGIN
        v_fill := (OTHERS => '0');
        IF b = '1' THEN
            RETURN val(31 - n DOWNTO 0) & v_fill(n - 1 DOWNTO 0);
        ELSE
            RETURN val;
        END IF;
    END FUNCTION l_shift;
    FUNCTION r_shift(b:    std_logic;
                     val:  std_logic_vector(31 DOWNTO 0);
                     fill: std_logic;
                     n:    natural) RETURN std_logic_vector IS
        VARIABLE v_fill: std_logic_vector(31 DOWNTO 0);
    BEGIN
        v_fill := (OTHERS => fill);
        IF b = '1' THEN
            RETURN v_fill(n - 1 DOWNTO 0) & val(31 DOWNTO n);
        ELSE
            RETURN val;
        END IF;
    END FUNCTION r_shift;
BEGIN
    s_fill <= i_arith AND i_val(31);
    p_shift: PROCESS(i_left, i_val, i_num, s_fill)
 
 
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