swift234

[sil-simplify-cfg] Implementation of a dominator-based jump-threading for checked_cast_br [exact]

it is very beneficial for code that:
 - references the same object multiple times (e.g. x.f1() + x.f2())
 - and for method invocation chaining (e.g. x.f3().f4().f5())

rdar://18914224

Swift SVN r23515