Passing Twine by value

Twine.h says twines should only be accepted as const references in arguments, but there are a bunch of functions that take Twine by value (e.g. you’ll find lots of them in CGObjCMac.cpp in clang). Is this just a potential performance issue, or are there potential correctness issues from passing a twine by value as well?

I don’t believe there’s any correctness issue with passing Twine by value.

Not sure it’d even be a performance problem - the sizeof(Twine) looks like it’d be small enough (like StringRef - though a bit bigger, StringRef should be two words, Twine would be three) not to worry too much either way.