Subversion Repositories bluespec-h264

package mkSizedFIFO_fpga;

import FIFO::*;

import RWire::*;

import RegFile::*;

import IFPGA_FIFO::*;

module mkSizedFIFO_fpga (IFPGA_FIFO#(f_type, size))

  provisos(

            Bits#(f_type, f_type_length),

            Add#(TLog#(size), 0, lg_size),

            Add#(TLog#(size), 1, lg_size_plus),

            Add#(2, TLog#(size),lg_size_plus_plus),

            Add#(1, lg_size_plus, lg_size_plus_plus)

          );

  RegFile#(Bit#(TLog#(size)), f_type) data <- mkRegFile(0, fromInteger(valueof(TSub#(size,1))));

  Reg#(Bit#(lg_size_plus)) number_enqueued <- mkReg(0);

  Reg#(Bit#(TLog#(size))) base_ptr <- mkReg(0);

  RWire#(Bit#(0)) deque_pending <- mkRWire();

  RWire#(Bit#(0)) clear_pending <- mkRWire();

  RWire#(f_type) enque_pending <- mkRWire();

  // We'll have problems with non-saturating additions, so we ought to add some checks

  // Strongly Recommend power of 2 sizes to simpilfy logic.

  rule update;

    if(clear_pending.wget() matches tagged Valid .v)

      begin

        //clear is occuring, we drop a pending enqueue on the floor.

        number_enqueued <= 0;

        base_ptr <= 0;

      end

    else

      begin

       if(enque_pending.wget() matches tagged Valid .new_data)

         begin

           if(deque_pending.wget() matches tagged Valid .dp)

             begin

               // enque and deque occuring.. no change to net.

               base_ptr <= (zeroExtend(base_ptr) == fromInteger(valueof(size)-1))? 0:base_ptr + 1;

               Bit#(lg_size_plus_plus) offset = zeroExtend((zeroExtend(base_ptr) + number_enqueued));

               data.upd((offset >= fromInteger(valueof(size)))?

                           truncate(offset - truncate(fromInteger(valueof(size)))):

                          truncate(offset),

                       new_data);

             end

           else

             begin

               number_enqueued <= number_enqueued + 1;

               Bit#(lg_size_plus_plus) offset = zeroExtend((zeroExtend(base_ptr) + number_enqueued));

               data.upd((offset >= fromInteger(valueof(size)))?

                           truncate(offset - truncate(fromInteger(valueof(size)))):

                           truncate(offset),

                        new_data);

             end

         end

       else

         begin

           if(deque_pending.wget() matches tagged Valid .dp)

             begin

               //enque and deque occuring.. no change to net.

               base_ptr <= (zeroExtend(base_ptr) == truncate(fromInteger(valueof(size)-1)))? 0:base_ptr + 1;

               number_enqueued <= number_enqueued - 1;

             end

         end

      end

  endrule

  interface FIFO fifo;

    method Action enq (f_type value) if(number_enqueued < fromInteger(valueof(size)));

      enque_pending.wset(value);

    endmethod

    method Action deq()  if(number_enqueued > 0);

      deque_pending.wset(0);

    endmethod

    method f_type first() if(number_enqueued > 0);

      return data.sub(base_ptr);

    endmethod

    method Action clear();

      clear_pending.wset(0);

    endmethod

  endinterface

endmodule

endpackage