The back-deployed concurrency libraries and older Swift runtimes are
not compatible, so turn off runtime exclusivity checking when running on
older systems. Fixes rdar://84274148.
SwiftNativeNSObject is part of the core runtime on OS versions that
also have the concurrency library, so we need to include a copy of
it with the back-deployed concurrency library.
The exclusivity checking support for concurrency relies on having access
to the thread-local set of active memory accesses. Teach the
back-deployed concurrency library to use the same TLS context as the
runtime, which fortunately hasn't change. This fixes the
concurrency exclusivity-checking test in back-deployed configurations
that's tracked by rdar://83064974.
The goal here is not to eventually implement a concurrent thread
pool ourselves. We're just making it easier for integrators who
have their own pool and don't want to use Dispatch to build the
Swift concurrency runtime. Just hook the right functions and
you should be fine.
The necessary functions to hook are:
- swift_task_enqueueGlobal
- swift_task_enqueueGlobalAfterDelay
The following functions *would* be necessary to hook:
- swift_task_enqueueMainExecutor
- swift_task_asyncMainDrainQueue (only if you have an async main?)
However, this configuration does not currently properly support
the main executor, and so `@MainActor` should be avoided for now.
rdar://83513751
control swift extended frame information emission
On linux we default to disable the extended frame info (since the system
libraries don't support it).
On darwin the default is to automatically choose based on the deployment target.
The Concurrency library explicitly forces extended frame information and the
back deployment library explicitly disables it.
When back-deploying, create global-actor-qualified function types via a
separate entrypoint
(`swift_getFunctionTypeMetadataGlobalActorBackDeploy`) in the
compatibility library, which checks whether it is running with a
new-enough runtime to use `swift_getFunctionTypeMetadataGlobalActor`.
Failing that, it calls into a separate copy of the implementation that
exists only in the back-deployed concurrency library.
Fixes rdar://79153988.
The code that saves/restores the exclusivity checks for tasks was
newly introduced into the runtime. Clone that code into the back-
deployed version of the runtime.
When build-script is given `--back-deploy-concurrency`, also use that
to build other parts of Swift with the back-deployed versions:
* The compiler allows async and actors to be defined with the
back-deployed availability, e.g., the same as `-Xfrontend
-enable-experimental-back-deploy-concurrency`. (The latter will go
away soon)
* The standard library unit testing framework and distributed actors
library are build with the older OS versions.
* The tests use the older OS versions, with some adjustments to make
them agnostic to the back-deployment setting.
When enabling the build of the back-deployable concurrency library via
the build-script option `--back-deploy-concurrency`, also build the
compiler and (main) concurrency library to support older deployment targets.
Building the compiler for older deployment targets is effectively the
same as implicitly passing
`-Xfrontend -enable-experimental-back-deploy-concurrency`. That option
should probably go away.
Building the primary _Concurrency library for back-deployment means
setting the "SwiftStdlib 5.5" availability back to the earlier
deployment targets. This should have no effect on how the _Concurrency
library binary is built, but it does ensure that the right
availability annotations are in the _Concurrency module.
Introduce an additional build product to build-script to build
back-deployable concurrency libraries. These libraries would need to
be embedded in apps deployed prior to macOS 12/iOS 15 to support
concurrency.
The built-script option `--back-deploy-concurrency` can be provided to
build these back-deployment libraries. They are built in addition to
the normal concurrency libraries, as a separate product that installs
into `lib/swift-5.5/<platform>` within the toolchain. The macro
`SWIFT_CONCURRENCY_BACK_DEPLOYMENT` is set when building the
concurrency library, so that we can adapt the implementation to older
OS's.
