When I initially introduced -pass-remarks, I thought it would be a
neat idea to make it additive. So, if one used it as:
$ llc -pass-remarks=inliner --pass-remarks=loop.*
the compiler would build the regular expression '(inliner)|(loop.*)'.
The more I think about it, the more I regret it. This is not how
other flags work. The standard semantics are right-to-left overrides.
This is how clang interprets -Rpass. And I think the two should be
compatible in this respect.