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library ieee;

use ieee.std_logic_1164.all;

use ieee.std_logic_arith.all;

use ieee.std_logic_unsigned.all;

package mips_pkg is

-- FIXME this stuff belongs in the cache module where address decoding is made

-- (besides, they should be module generics, not package constants)

subtype t_addr_decode is std_logic_vector(31 downto 24);

constant ADDR_BOOT : t_addr_decode      := X"00";

constant ADDR_XRAM : t_addr_decode      := X"80";

constant ADDR_IO : t_addr_decode        := X"20";

subtype t_addr is std_logic_vector(31 downto 0);

subtype t_word is std_logic_vector(31 downto 0);

subtype t_dword is std_logic_vector(63 downto 0);

subtype t_regnum is std_logic_vector(4 downto 0);

type t_rbank is array(0 to 31) of t_word;

subtype t_pc is std_logic_vector(31 downto 2);

constant ZERO : t_word := (others => '0');

type t_alu_control is record

    logic_sel :         std_logic_vector(1 downto 0);

    shift_sel :         std_logic_vector(1 downto 0);

    shift_amount :      std_logic_vector(4 downto 0);

    neg_sel :           std_logic_vector(1 downto 0);

    use_arith :         std_logic;

    use_logic :         std_logic_vector(1 downto 0);

    cy_in :             std_logic;

    use_slt :           std_logic;

    arith_unsigned :    std_logic;

end record t_alu_control;

type t_alu_flags is record

    inp1_lt_zero :      std_logic;

    inp1_eq_zero :      std_logic;

    inp1_lt_inp2 :      std_logic;

    inp1_eq_inp2 :      std_logic;

end record t_alu_flags;

-- 32-cycle mul/div module control. Bits 4-3 & 1-0 of IR.

subtype t_mult_function is std_logic_vector(3 downto 0);

constant MULT_NOTHING       : t_mult_function := "0000";

constant MULT_READ_LO       : t_mult_function := "1010"; -- 18

constant MULT_READ_HI       : t_mult_function := "1000"; -- 16

constant MULT_WRITE_LO      : t_mult_function := "1011"; -- 19

constant MULT_WRITE_HI      : t_mult_function := "1001"; -- 17

constant MULT_MULT          : t_mult_function := "1101"; -- 25

constant MULT_SIGNED_MULT   : t_mult_function := "1100"; -- 24

constant MULT_DIVIDE        : t_mult_function := "1111"; -- 26

constant MULT_SIGNED_DIVIDE : t_mult_function := "1110"; -- 27

-- Computes ceil(log2(A)), e.g. address width of memory block

-- CAN BE USED IN SYNTHESIZABLE CODE as long as called with constant arguments

function log2(A : natural) return natural;

end package;

package body mips_pkg is

function log2(A : natural) return natural is

begin

    for I in 1 to 30 loop -- Works for up to 32 bit integers

        if(2**I > A) then

            return(I-1);

        end if;

    end loop;

    return(30);

end function log2;

end package body;