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-- The Potato Processor - A simple processor for FPGAs

-- (c) Kristian Klomsten Skordal 2014 <kristian.skordal@wafflemail.net>

-- Report bugs and issues on <http://opencores.org/project,potato,bugtracker>

library ieee;

use ieee.std_logic_1164.all;

use ieee.numeric_std.all;

use work.pp_types.all;

--! @brief Multiplexer used to choose between ALU inputs.

entity pp_alu_mux is

        port(

                source : in alu_operand_source;

                register_value  : in std_logic_vector(31 downto 0);

                immediate_value : in std_logic_vector(31 downto 0);

                shamt_value     : in std_logic_vector( 4 downto 0);

                pc_value        : in std_logic_vector(31 downto 0);

                csr_value       : in std_logic_vector(31 downto 0);

                output : out std_logic_vector(31 downto 0)

        );

end entity pp_alu_mux;

architecture behaviour of pp_alu_mux is

begin

        mux: process(source, register_value, immediate_value, shamt_value, pc_value, csr_value)

        begin

                case source is

                        when ALU_SRC_REG =>

                                output <= register_value;

                        when ALU_SRC_IMM =>

                                output <= immediate_value;

                        when ALU_SRC_PC =>

                                output <= pc_value;

                        when ALU_SRC_PC_NEXT =>

                                output <= std_logic_vector(unsigned(pc_value) + 4);

                        when ALU_SRC_CSR =>

                                output <= csr_value;

                        when ALU_SRC_SHAMT =>

                                output <= (31 downto 5 => '0') & shamt_value;

                        when ALU_SRC_NULL =>

                                output <= (others => '0');

                end case;

        end process mux;

end architecture behaviour;