Another way would be to use one register for "zero" vs. "non-zero", and another for negative (basically 2 bit sign-magnitude representation). C_sgn = A_sgn

Another way would be to use one register for "zero" vs. "non-zero", and another for negative (basically 2 bit sign-magnitude representation). C_sgn = A_sgn ^ B_sgn C_mag = A_mag & B_mag The result can then be converted into bitmasks for positive and negative: C_plus = C_mag & ~C_sgn C_minus = C_mag & C_sgn This solution should be more efficient if there is an "AND NOT" instruction, or when multiplying more than two factors.