Hey,
In one case.(not that I’m recommending it at all, just saying 
) we pass them via environment variable and invoke parsing explicitly. One could also follow the precedent of Xclang mllvm approach (as your edit also points too).
I’d be cautious about exposing the flags directly except for testing/development: the pass command line options are intended for a different user than flang is, with different stability expectations. You’d probably not want users to set some of the things that mlir-opt can do, nor would you want them to rely on it. So exposing something higher level/more stable and then constructing the passes as desired would probably work out better - additional cost that looks like duplication in some cases, but should be more sustainable.
– Jacques