I am doing this since I discovered that we are not printing certain errors as
early as we used to (due to the refactoring I did here), which makes it harder
to see the errors that we are emitting while processing individual instructions
and before we run the actual dataflow.
A nice side-effect of this is that it will make it easy to dump the error in the
debugger rather than having to wait until the point in the code where the normal
logging takes place.
This makes it so that one does not need to deal with the differences in text in
between the task isolated case and the actor isolated case. This is done by
swallowing the entire part of this message in one method rather than having the
caller do the work.
The reason that I am changing this code is that getWithIsolationCrossing is a
bad API that was being used to infer actor isolation straight from an ApplyExpr
without adding an actor instance. This can cause us to reject programs
unnecessarily if we in other parts of the code correctly infer the SILValue
actor instance for the isolation.
Rather than allow for that, I am removing this code and I improved the rest of
the pattern matching here to ensure that we handled that with the normal actor
instance inferring code. This will prevent this type of mismerge from happening
by mistake. I fixed up the changes in the test cases.
The only usage of this left is for ApplyIsolationCrossings parsed straight from
SIL that we use only when testing. This is safe since if a test writer is using
the parsed SIL in this manner, they can make sure that mismerges do not happen.
Closures generally only inherit actor instance isolation if they directly
capture state from the actor instance. In this case, for some reason that is not
true, so we hit an assert that assumes that we will only see a global actor
isolated isolation.
Region Isolation should be able to handle code even if the closure isolation
invariant is violated by the frontend. So to do this, I am introducing a new
singleton actor instance to represent the isolation of a defer or closure
created in an actor instance isolated method. The reason why I am using a
singleton is that closures and defer are not methods so we do not actually know
which parameter is 'self' since it isn't in the abi. But we still need some
value to represent the captured values as belonging to. To square this circle, I
just did what we have done in a similar situation where we did not have a value:
(ActorAccessorInit). In that case, we just use a sentinel to represent the
instance (NOTE: This is represented just via a kind so ActorInstances that are
operator== equal will not &value equal since we are just using a kind).
We are already using this routine in other parts of TransferNonSendable to
ensure that we look through common insts that SILGen inserts that do not change
the actual underlying actor instance that we are using. In this case, I added
support for casts, optional formation, optional extraction, existential ref
initialization.
As an example of where this came up is the following test case where we fail to
look through an init_existential_ref.
```swift
public actor MyActor {
private var intDict: [Int: Int] = [:]
public func test() async {
await withTaskGroup(of: Void.self) { taskGroup in
for (_, _) in intDict {}
await taskGroup.waitForAll() // Isolation merge failure happens here
}
}
}
```
I also added the ability to at the SIL level actual test out this merge
condition using the analysis test runner. I used this to validate that this
functionality works as expected in a precise way.
rdar://130113744
Before we wouldn't print them in all situations and even more so a few of the
printing routines did not have it at all. This just adds a centralized
SILIsolationInfo::dumpOptions() method and then goes through all of the printing
helpers and changes them to use them as appropriate.
Given a function or a partial_apply with an isolated parameter, we do not know
immediately what the actual isolation is of the function or partial_apply since
we do not know which instance will be applied to the function or partial_apply.
In this commit, I introduce a new bit into SILIsolationInfo that tracks this
information upon construction and allows for it to merge with ownership that has
the appropriate type and a specific instance. Since the values that created the
two isolations, will be in the same region this should ensure that the value is
only ever in a flow sensitive manner in a region with only one actor instance
(since regions with isolations with differing actor instances are illegal).
Specifically:
1. We error now if one transfers an 'inout sending' parameter and does not
reinitialize it before the end of the function.
2. We error now if one merges an 'inout sending' parameter into an actor
isolated region and do not reinitialize it with a non-actor isolated value
before the end of the function.
rdar://126303739
From the perspective of the IR, we are changing SILIsolationInfo such that
inferring an actor instance means looking at equivalence classes of values where
we consider operands to look through instructions to be equivalent to their dest
value. The result is that cases where the IR maybe puts in a copy_value or the
like, we consider the copy_value to have the same isolation info as using the
actor directly. This prevents a class of crashes due to merge failings. Example:
```swift
actor MyActor {
init() async {
init(ns: NonSendableKlass) async {
self.k = NonSendableKlass()
self.helper(ns)
}
func helper(_ newK: NonSendableKlass) {}
}
```
Incidently, we already had a failing test case from this behavior rather than
the one that was the original genesis. Specifically:
1. If a function's SILIsolationInfo is the same as the isolation info of a
SILValue, we assume that no transfer actually occurs.
2. Since we were taking too static of a view of actor instances when comparing,
we would think that a SILIsolationInfo of a #isolation parameter to as an
argument would be different than the ambient's function isolation which is also
that same one. So we would emit a transfer non transferrable error if we pass in
any parameters of the ambient function into another isolated function. Example:
```swift
actor Test {
@TaskLocal static var local: Int?
func withTaskLocal(isolation: isolated (any Actor)? = #isolation,
_ body: (consuming NonSendableValue, isolated (any Actor)?) -> Void) async {
Self.$local.withValue(12) {
// We used to get these errors here since we thought that body's isolation
// was different than the body's isolation.
//
// warning: sending 'body' risks causing data races
// note: actor-isolated 'body' is captured by a actor-isolated closure...
body(NonSendableValue(), isolation)
}
}
}
```
rdar://129400019
When merging SILIsolationInfo for regions, we want to drop
nonisolated(unsafe). This is important since nonisolated(unsafe) should only
apply to the specific "value" that it belongs to, not the entire region.
This creates a problem since in a few places in the code base we initialize a
value (producing a disconnected value) and then initialize it by merging in an
actor isolation. This no longer work since we will then always have
nonisolated(unsafe) stripped, so no values would ever be considered to be
nonisolated(unsafe). After analyzing the use case, I realized that these were
just initialization patterns and in this commit, I added a specific
initialization operation called SILIsolationInfo::initializeTrackableValue and
eliminated those calls to SILIsolationInfo::mergeIsolationRegionInfo.
Since SILIsolationInfo no longer has any merge operation on it, I then
eliminated that code in this commit. This completes the behavior split that I
put into the type system in the last commit. Specifically, I defined a
composition type called SILDynamicMergedIsolationInfo. It represents a
SILIsolationInfo that has been merged... that is why I called it the
DynamicMergedIsolationInfo. It could probably use a better name = (.
This fixes one of the last weird test case that I wrote where we were not letting through valid
nonisolated(unsafe) code.
At the same time, I discovered an additional issue (which can be seen in the
TODOs in this commit), where we are being too conservative around a non-Sendable
class var field. I am going to fix that in the next commit.
rdar://128299305
Specifically, I introduced a new composition type called
SILDynamicMergedIsolationInfo that just contains a
SILIsolationInfo. Importantly, whenever one merges a SILIsolationInfo with
another SILIsolationInfo, one gets back a SILDynamicMergedIsolationInfo.
The reason why I am doing this is that we drop nonisolated(unsafe) when merging
so I want to ensure that parts of the code that use merging (where the dropping
occurs) and normal SILIsolationInfo where we do not want to merge is
distinguished.
The design change here is that instead of just initializing the regionInfo with
disconnected, we set it as .none and if we see .none, just return a newly
construct disconnected isolation region info when getIsolationRegionInfo() is
called.
This enables us to provide a setIsolationRegionInfo() helper for
RegionAnalysisValueMap::getTrackableValue that does not perform a merge. This is
important since for nonisolated(unsafe), we want to not have nonisolated(unsafe)
propagate through merging. So if we use merging to initialize the internal
regionInfo state of a SILIsolationInfo, we will never have a SILIsolationInfo
with that bit set since it will be lost in the merge. So we need some sort of
other assignment operator. Noting that we should only compute a value's
SILIsolationInfo once in RegionAnalysisValueMap before we cache it in the map,
it made sense to just represent it as an optional that way we can guarantee that
the regionInfo is only ever set exactly once by that routine.
