(18 . 8)(18 . 8)
------------------------------------------------------------------------------

with Words;    use Words;
with W_Shifts; use W_Shifts;
with FZ_Basic; use FZ_Basic;
with FZ_Pred;  use FZ_Pred;
with FZ_Arith; use FZ_Arith;
with FZ_Shift; use FZ_Shift;

(32 . 15)(32 . 14)
                             XY_Lo : out FZ;
                             XY_Hi : out FZ) is
      
      L : constant Indices := X'Length;
      
      -- Register holding running product
      XY : FZ(1 .. X'Length + Y'Length);
      
      -- X-Slide
      XS : FZ(1 .. X'Length + Y'Length);
      
      -- Y-Slide
      YS : FZ(Y'Range) := Y;
      
   begin
      -- Product register begins empty
      FZ_Clear(XY);
(49 . 18)(48 . 33)
      XS(1            .. X'Length) := X;
      XS(X'Length + 1 .. XS'Last)  := (others => 0);
      
      -- For each bit of Y:
      for i in 1 .. FZ_Bitness(Y) loop
         
         -- If lowest bit of Y-Slide is 1, X-Slide is added into XY
         FZ_Add_Gated(X    => XY, Y => XS, Sum => XY,
                      Gate => FZ_OddP(YS));
         
         -- X-Slide := X-Slide * 2
         FZ_ShiftLeft(XS, XS, 1);
      -- For each word of Y:
      for i in Y'Range loop
         
         -- Y-Slide := Y-Slide / 2
         FZ_ShiftRight(YS, YS, 1);
         declare
            -- Current word of Y
            W : Word  := Y(i);
            
            -- Current cut of XY and XS. Stay ahead by a word to handle carry.
            Cut : constant Indices := L + i;
            XYc : FZ renames XY(1 .. Cut);
            XSc : FZ renames XS(1 .. Cut);
            
         begin
            for b in 1 .. Bitness loop
               
               -- If current Y bit is 1, X-Slide Cut is added into XY Cut
               FZ_Add_Gated(X    => XYc, Y => XSc, Sum => XYc,
                            Gate => W and 1);
               
               -- Crank the next bit of Y into the bottom position of W
               W := Shift_Right(W, 1);
               
               -- X-Slide := X-Slide * 2
               FZ_ShiftLeft(XSc, XSc, 1);
               
            end loop;
         end;
         
      end loop;