----------------------------------------------------
-- FileName : GCD.bs
-- Author   : Interra
-- BugID    : 142
-- CommandLine : bsc -verilog -g mkGCD GCD.bs
-- Status : Fixed for BSC 3.74
----------------------------------------------------

package GCD (GCD(..), mkGCD) where

-- import Int

interface GCD =
    start  :: Int 32 -> Int 32 -> Action
    result :: Int 32

mkGCD :: GCD -> Module GCD
mkGCD intrfce =
    module
        x :: Reg (Int 32)
        x <- mkRegU

        y :: Reg (Int 32)
        y <- mkReg 0

        rules
          "Swap":
            when x > y, y /= 0
              ==> action
                      x := y
                      y := x

          "Subtract":
            when x <= y, y /= 0
              ==> action
                      y := y - x

        interface
            start ix iy = action
                              x := ix
                              y := iy
                          when y == 0
            result = x when y == 0