Testing f2:
16'hFFFF << 4'b000 = 16'b11111111
16'hFFFF << 4'b001 = 16'b11111110
16'hFFFF << 4'b010 = 16'b11111100
16'hFFFF << 4'b011 = 16'b11111000
16'hFFFF << 4'b100 = 16'b11110000
16'hFFFF << 4'b101 = 16'b11100000
16'hFFFF << 4'b110 = 16'b11000000
16'hFFFF << 4'b111 = 16'b10000000
Done