LIBRARY ieee;
USE ieee.std_logic_1164.all;
USE ieee.numeric_std.all;

PACKAGE mips_types IS

    -- operation
    TYPE t_op IS (
        op_none,
        op_alu, -- ALU operation
        op_j    -- jump or branch
    );

    -- link (store return address in register)
    TYPE t_link IS (
        link_none,
        link_link  -- link
    );

    -- compare mode
    TYPE t_cmp IS (
        cmp_none,
        cmp_eq,   -- equal
        cmp_gez,  -- greater or equal zero
        cmp_gtz,  -- greater than zero
        cmp_lez,  -- less or equal zero
        cmp_ltz,  -- less than zero
        cmp_ne    -- not equal
    );

    -- ALU operation
    TYPE t_alu IS (
        alu_none,
        alu_add,  -- addition
        alu_and,  -- bitwise AND
        alu_nor,  -- bitwise NOR
        alu_or,   -- bitwise OR
        alu_sub,  -- subtraction
        alu_sll,  -- shift left logically
        alu_sra,  -- shift right arithmetically
        alu_srl,  -- shift right logically
        alu_slt,  -- set on less than
        alu_sltu, -- set on less than unsigned
        alu_xor   -- bitwise XOR
    );

    -- immediate usage
    TYPE t_imm IS (
        imm_none,
        imm_a,    -- "a" immediate
        imm_16se, -- 16 bit immediate, sign-extension
        imm_16ze, -- 16 bit immediate, zero-extension
        imm_26    -- 26 bit immediate
    );

END PACKAGE;