[donaltroddyn]

I did think of similar approaches, but anything I could think of that helps you to quickly determine if a given string contains the password also helps an attacker if the passwords and salts are compromised.

In the suggested case, storing the length of the password alone massively reduces the search space, and storing the XOR (of the plaintext with the hash, I think you're suggesting?) negates the value of using a hashing algorithm suitable for passwords, since the point is that checking if a password matches a hash is an expensive operation.