Mike Ash bd62fdb2db [Concurrency] Make Job/AsyncTask minimally compatible with dispatch object layout ...

Create a TargetDispatchClassMetadata for Swift metadata that also has a dispatch-compatible vtable. Dispatch leaves room for ObjC class metadata so the two regions don't overlap. (The vtable currently consists of a single dummy entry; this will be filled out later.)

Rearrange the Job and AsyncTask hierarchy so that AsyncTask inherits only from Job, which in turn inherits from HeapObject. This gives all Job instances a dispatch-compatible isa field. It also gives them a refcount word, which is wasted on instances that aren't AsyncTask instances. Maybe we can find some use for that space in the future.

rdar://75227953

2021-03-10 10:04:30 -05:00

23 KiB

Raw Blame History

View Raw