ship: Rotator

== Ports ===========================================================
in:   in
in:   inAmount

out:  out

  
== TeX ==============================================================

The Rotator performs bitwise rotations of words.  When a value is
present at both {\tt in} and {\tt inAmount}, both values are consumed,
the value {\tt in} is rotated {\it towards the least significant bit}
by {\tt inAmount} bits and emitted at {\tt out}.

The output is undefined if {\tt inAmount} is greater than or equal to
the number of bits in a word.


== Fleeterpreter ====================================================

public void service() {
  if (box_inAmount.dataReadyForShip() && box_in.dataReadyForShip() && box_out.readyForDataFromShip()) {
    long amount = box_inAmount.removeDataForShip();
    long data   = box_in.removeDataForShip();
    long mask = ~((-1L) << getInterpreter().getWordWidth());
    data = data & mask;
    long res = ((data >> amount) | (data << (getInterpreter().getWordWidth()-amount))) & mask;
    box_out.addDataFromShip(res, (res & (1L << (getInterpreter().getWordWidth()-1)))!=0);
  }
}


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

  reg [(`WORDWIDTH):0] out_d;
  assign out_d_ = out_d;

  reg full;
  initial full = 0;

  reg [5:0] shamt;
  initial shamt = 0;

  wire shamt_eq;
  assign shamt_eq = (shamt[5:0] == (inAmount_d[5:0]));

  always @(posedge clk) begin
    if (rst) begin
      `reset
      full <= 0;
    end else begin
      `cleanup
      if (`in_full && `inAmount_full && `out_empty) begin
        if (!full) begin
          out_d <= { 1'b0, in_d };
          shamt <= 0;
          full  <= 1;
        end else if (!shamt_eq) begin
          out_d <= { out_d[0], out_d[0], out_d[`WORDWIDTH-1:1] };
          shamt <= shamt+1;
        end else begin
          `drain_in
          `drain_inAmount
          `fill_out
          full <= 0;
        end
      end
    end
  end

== Test ==============================================================


// expected output
#expect 2
#expect 0
#expect -0x1000000000
#expect 1
#expect 44627559471
#expect 0


// ships required in order to run this code
#ship debug        : Debug
#ship rotator      : Rotator

debug.in: set ilc=*;  recv, deliver;

rotator.in:
   set word=1;
   deliver;
   set word=1;
   deliver;
   set word=21615257152;
   deliver;
rotator.inAmount:
   set word=36;
   deliver;
   set word=1;
   deliver;
   set word=17;
   deliver;
rotator.out:
   set olc=3;
   head;
   collect, send to debug.in;
   set flags a=c, b=b;
   [!a] set word=0;
   [a]  set word=1;
   send to debug.in;
   tail;



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