The bloom filter is used to estimate, inside the GPU, whether the reverse of a RIPEMD160 hash is inside a set of SHA256 hashes. Public keys of addresses are hashes with SHA256 followed by RIPEMD160 to get the bulk of the address (there is another part of it called the checksum that's computed differently but I don't think checksums are validated in the code). I think these things have more to do with the puzzle transaction.

I'm impressed I was able to understand what the source code is doing without ever running the program. I am a C/C++ developer, so it may have something to do with that.