is there any mode for the ghci, which provides autocompletion like e.g. the bash?

GHCi on Unix provides autocomplete through the readline library (the same library used by bash) albeit only for filenames and directories. We don't compile with readline support on Windows (I'm not sure why). If you want completion of function names, type names, etc. then the answer is that we haven't implemented it, but it would be an interesting project. Cheers, Simon