swift

35679508 - IRGen: Reenable caching opaque type metadata accessors.

IRGen: Reenable caching opaque type metadata accessors. Dynamic replacement can only really get away with replacing opaque return types if a function's opaque type has never been instantiated in the first place. Meanwhile, repeatedly instantiating the metadata is too slow for many clients to tolerate. Fixes rdar://problem/53213600.