Consequences of a polytime algorithm for a decision problem reducible to 3SAT

If there is a polynomial time algorithm for a decision problem $$A$$, which is m-reducible to 3SAT, and 3SAT is NP-complete, does this prove that P=NP?

The problem $$A = \emptyset$$ is polytime reducible to 3SAT (using a reduction running in constant time), and can be solved in polynomial time.