[Concurrency] Add cancelAsyncTask() builtin. #34600
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…ion. This introduces a new builtin, `getCurrentAsyncTask()`, that produces a reference to the current task. This builtin can only be used within `async` functions, and IR generation merely grabs the task argument and packages it up. The type of this function is `() -> Builtin.NativeObject`, because we don't currently have a Swift-level representation of tasks, and can probably handle everything through builtins or runtime calls.
Rather than produce an "unowned" result from `getCurrentAsyncTask()`, take advantage of the fact that the task is effectively guaranteed in the scope. Do so be returning it as "unowned", and push an end_lifetime cleanup to end the lifetime. This eliminates unnecessary ref-count traffic as well as introducing another use of unowned. Approach is thanks to Michael Gottesman, bugs are mine.
Michael has ghostwritten all of this to address his own comments. Thank you!
Implement a new builtin, `cancelAsyncTask()`, to cancel the given asynchronous task. This lowers down to a call into the runtime operation `swift_task_cancel()`. Use this builtin to implement Task.Handle.cancel().
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Only the last commit is new; the rest is from #34595 |
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@swift-ci please smoke test |
ktoso
approved these changes
Nov 6, 2020
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Implement a new builtin,
cancelAsyncTask(), to cancel the givenasynchronous task. This lowers down to a call into the runtime
operation
swift_task_cancel().Use this builtin to implement Task.Handle.cancel().