ship: Alu3

== Ports ===========================================================
data  in:   in1
data  in:   in2
data  in:   in3

data  out:  out1
data  out:  out2

== Constants ========================================================
== TeX ==============================================================

This ship performs addition of three inputs, producing two output
values in carry-save form.  To complete the addition, send the two
output values to an Alu2 with opcode ADD.  For summing a set of four
or more numbers, Alu3 followed by Alu2 is often faster than repeated
use of Alu2.

== Fleeterpreter ====================================================
public void service() {
  if (box_in1.dataReadyForShip() &&
      box_in2.dataReadyForShip() &&
      box_in3.dataReadyForShip() &&
      box_out1.readyForDataFromShip() &&
      box_out2.readyForDataFromShip()) {
      long v1     = box_in1.removeDataForShip();
      long v2     = box_in2.removeDataForShip();
      long v3     = box_in3.removeDataForShip();
      long o1     = ((v1 & v2) | (v2 & v3) | (v1 & v3)) << 1;
      long o2     = v1 ^ v2 ^ v3;
      box_out1.addDataFromShip(o1);
      box_out2.addDataFromShip(o2);
  }
}

== FleetSim ==============================================================

== FPGA ==============================================================

  reg                    have_a;
  reg [(`DATAWIDTH-1):0] a;
  reg                    have_b;
  reg [(`DATAWIDTH-1):0] b;
  reg                    have_c;
  reg [(`DATAWIDTH-1):0] c;
  reg                    have_out1;
  reg                    have_out2;

  always @(posedge clk) begin
    if (have_out1) begin
      `onwrite(out1_r, out1_a) have_out1 <= 0; end

    end else if (have_out2) begin
      `onwrite(out2_r, out2_a) have_out2 <= 0; end

    end else if (!have_out1 && !have_out2) begin
      if (!have_a) begin
        `onread(in1_r, in1_a) have_a <= 1; a <= in1_d; end
        end
      if (!have_b) begin
        `onread(in2_r, in2_a) have_b <= 1; b <= in2_d; end
        end
      if (!have_c) begin
        `onread(in3_r, in3_a) have_c <= 1; c <= in3_d; end
        end
  
      if (have_a && have_b && have_c) begin
        out1_d    <= { { ((a & b) | (b & c) | (a & c)) } , 1'b0 };
        out2_d    <= a ^ b ^ c;
        have_a    <= 0;
        have_b    <= 0;
        have_c    <= 0;
        have_out1 <= 1;
        have_out2 <= 1;
      end
    end
  end




== Contributors =========================================================
Adam Megacz <megacz@cs.berkeley.edu>