Using negation and swapping, all of these operators boil down to just two (addition and equality): + - < > ?= <= != == << >> .
Subtractor: use an adder but instead pass in a one as the leading borrow-bar and complement each bit from the second operand.
A subtractor will generate a borrow output. If a < b then a-b will need a borrow, hence the raw subtractor implements less-than.
Greater than or equal is just the complement of less than.
For the other two inequalities: just swap the operands.
Equality test: one could use a subtractor and check the output is zero, but it's simpler to use a dijunction of XORs (i.e. we don't need to consider carry operations).