Porting across r-code versions sometimes requires recompiling. The r-code version always changes between major releases. It might or might not change between minor point releases depending on the added functionality.
If you port to:
A lower or higher major release, you must recompile.
A higher point release within a major release, you might or might not need to recompile, depending on the new functionality in the point release.
A lower point release within a major release, you might or might not need to recompile. However, it is highly recommended that you recompile.
A lower or higher major release, you must recompile.