RDF is designed to be target agnostic. Therefore it would be useful to have it available for other targets, such as X86.
LGTM other than the question about the functionality change.
Thanks for this patch! Qq, is this some functionality change? Why does the refactor require this update?
The original RDF implementation didn't need to handle Windows targets. The TLI::getExceptionSelectionRegister() method has an assertion testing that it is not called for Windows EH personality functions. There is no exception selector register on Windows.