How to automatically combine Multipe Haskell modules in one

Suppose I have several Haskell modules and I want to run them in an environment that requires the entire program to be injected as a single module (e.g. static analyzers, programming websites, etc.). It can also be interesting for performance to see if GHC improves when it sees all the application code at once.

Without considering corner cases, such as differences in the set of language pragmas or orphaned instances, it seems plausible that there is a way to combine these modules into one (and I could do it manually).

But is there a better, automatic way?