Adding custom ModulePass to llvm in cling

Hello!
I am currently playing with cling, the clang-based C++ interpreter.
I was wondering if it is possible to add a custom ModulePass to llvm with
cling - not via commandline or via libcling - I mean from within the driver
executable. Without patching clang of course.
I have not had any luck in finding the relevant interface in clang's doxygen,
nor has grepping clang's sources for anything along the lines of PassManager,
ModulePass, PassRegistry... yielded anything useful to me so I'm giving up.
So: is that somehow possible?

Thanks,

Thomas Gahr