This design computes the greatest common divisor of two numbers. It is a
classic "High Level Synthesis" benchmark.

The algorithm is:

	while (x != y) {
		if (x < y) { 
			y = y - x;
		} else {
			x = x - y;
		}
	}

The external input LOAD is used to latch values into the X and Y
registers. The output DONE goes high for one clock cycle when the X
register, and thus the output bus GCD, contains the GCD of the two
numbers.

The file gcd.cmd is a ViewSim command file which will verify the correct
operation of the design. It loads X with the value 32, and Y with 12.
The GCD of these two numbers is 4. The steps executed by the command
file verify the contents of the X or Y register after each clock cycle.

