The builtin’s current is signature is:
```
(Any.Type, Any.Type) -> Bool
```
This needs to be changed to this:
```
(any (~Copyable & ~Escapable).Type, any (~Copyable & ~Escapable).Type) -> Bool
```
This requires a bit of support work in AST synthesis.
rdar://145707064
Co-authored-by: Alejandro Alonso <alejandro_alonso@apple.com>
Distributed actors can be treated as actors by accessing the `asLocalActor`
property. When lowering `#isolation` in a distributed actor initializer,
use a separate builtin `flowSensitiveDistributedSelfIsolation` to
capture the conformance to `DistributedActor`, and have Definite
Initialization introduce the call to the `asLocalActor` getter when
needed.
We've been building up this exponential explosion of task-creation
builtins because it's not currently possible to overload builtins.
As long as all of the operands are scalar, though, it's pretty easy
to peephole optional injections in IRGen, which means we can at
least just use a single builtin in SIL and then break it apart in
IRGen to decide which options to set.
I also eliminated the metadata argument, which can easily be recreated
from the substitutions. I also added proper verification for the builtin,
which required (1) getting `@Sendable` right more consistently and (2)
updating a bunch of tests checking for things that are not actually
valid, like passing a function that returns an Int directly.
When building a generic signature for a builtin function, do not infer
Copyable and Escapable requirements. We should be explicit about what
invertible protocols are required of the generic parameters for a
builtin. This will require an audit of our existing Builtins to add the
requirements as-needed, which is a task I'm deferring for now.
And do a first pass of auditing existing uses of the parameter specifiers to
make sure that we look at the ValueOwnership mapping in most cases instead of
individual modifiers.
Right now this does not actually do anything beyond causing a move_value
instruction to be emitted. With time, I am going to use this to map T ->
@_moveOnly T in the fullness of time... but I am going to stage in that part in
a different commit once I add the MoveOnly type itself. I am trying to split up
that larger commit as much as possible to make it easy to review.
- Introduce an UnownedSerialExecutor type into the concurrency library.
- Create a SerialExecutor protocol which allows an executor type to
change how it executes jobs.
- Add an unownedExecutor requirement to the Actor protocol.
- Change the ABI for ExecutorRef so that it stores a SerialExecutor
witness table pointer in the implementation field. This effectively
makes ExecutorRef an `unowned(unsafe) SerialExecutor`, except that
default actors are represented without a witness table pointer (just
a bit-pattern).
- Synthesize the unownedExecutor method for default actors (i.e. actors
that don't provide an unownedExecutor property).
- Make synthesized unownedExecutor properties `final`, and give them
a semantics attribute specifying that they're for default actors.
- Split `Builtin.buildSerialExecutorRef` into a few more precise
builtins. We're not using the main-actor one yet, though.
Pitch thread:
https://forums.swift.org/t/support-custom-executors-in-swift-concurrency/44425
The immediate desire is to minimize the set of ABI dependencies
on the layout of an ExecutorRef. In addition to that, however,
I wanted to generally reduce the code size impact of an unsafe
continuation since it now requires accessing thread-local state,
and I wanted resumption to not have to create unnecessary type
metadata for the value type just to do the initialization.
Therefore, I've introduced a swift_continuation_init function
which handles the default initialization of a continuation
and returns a reference to the current task. I've also moved
the initialization of the normal continuation result into the
caller (out of the runtime), and I've moved the resumption-side
cmpxchg into the runtime (and prior to the task being enqueued).
