[Haskell] how to use GHC's prof tools

Hi, I developed a program based on wxHaskell but it has serious performance problem. So I tried to compile the program using "-prof" in GHC. If I use "ghc --make -fglasgow-exts -package wx -prof Main.lhs", it always reports that it cannot find modules defined in wxHaskell like WXCore. However, if I compile it without the "-prof" option, it works well and can generate "a.out". Anyone can give any help? Thank you, Haitao