swift234

[simplify-cfg] Improve checked_cast_br jump-threading

If we have two checked_cast_br [exact] instructions which check the exact dynamic type of the same argument against different target types and the second checked_cast_br is reachable only via the success branch of the first one, then we know that the second cast will always fail, because the exact type was checked and matched by the first cast already and it was different from the type of the second checked_cast_br.

rdar://22690101

Swift SVN r31933