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[SILOptimizer] Prevent devirtualization of call to distributed witness requirements
This is a narrow fix, we are going to work on fixing this properly and allowing both devirtualization and specialization for distributed requirement witnesses. Anything that uses an ad-hoc serialization requirement scheme cannot be devirtualized because that would result in loss of ad-hoc conformance in new substitution map. Resolves: #79318 Resolves: rdar://146101172 (cherry picked from commit 0415b40)
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‎lib/SILOptimizer/Utils/Devirtualize.cpp

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@@ -810,6 +810,24 @@ bool swift::canDevirtualizeClassMethod(FullApplySite applySite, ClassDecl *cd,
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return false;
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}
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// A narrow fix for https://github.com/swiftlang/swift/issues/79318
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// to make sure that uses of distributed requirement witnesses are
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// not devirtualized because that results in a loss of the ad-hoc
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// requirement infomation in the re-created substitution map.
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//
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// We have a similar check in `canSpecializeFunction` which presents
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// specialization for exactly the same reason.
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//
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// TODO: A better way to fix this would be to record the ad-hoc conformance
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// requirement in `RequirementEnvironment` and adjust IRGen to handle it.
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if (f->hasLocation()) {
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if (auto *funcDecl =
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dyn_cast_or_null<FuncDecl>(f->getLocation().getAsDeclContext())) {
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if (funcDecl->isDistributedWitnessWithAdHocSerializationRequirement())
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return false;
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}
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}
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return true;
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}
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‎test/Distributed/distributed_actor_adhoc_requirements_optimized_build.swift

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// RUN: %empty-directory(%t)
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// RUN: %target-swift-frontend -emit-ir -swift-version 6 -O -I %t %s
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// RUN: %target-swift-frontend -emit-sil -swift-version 6 -O -I %t %s | %FileCheck %s
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// REQUIRES: concurrency
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// REQUIRES: distributed
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import Distributed
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// NOTE: None of the ad-hoc protocol requirement implementations
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public protocol Transferable: Sendable {}
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// NOT final on purpose
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public class TheSpecificResultHandlerWhichIsANonFinalClass: DistributedTargetInvocationResultHandler {
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public typealias SerializationRequirement = Transferable
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public func onReturn<Success>(value: Success) async throws where Success: Transferable {
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}
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public func onReturnVoid() async throws {
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fatalError()
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}
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public func onThrow<Err>(error: Err) async throws where Err : Error {
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fatalError()
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}
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}
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// NOT final on purpose
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public class FakeInvocationDecoder: DistributedTargetInvocationDecoder {
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public typealias SerializationRequirement = Transferable
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public func decodeGenericSubstitutions() throws -> [Any.Type] {
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[]
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}
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public func decodeNextArgument<Argument: SerializationRequirement>() throws -> Argument {
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fatalError()
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}
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public func decodeErrorType() throws -> Any.Type? {
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nil
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}
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public func decodeReturnType() throws -> Any.Type? {
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nil
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}
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}
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// NOT final on purpose
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public class FakeInvocationEncoder : DistributedTargetInvocationEncoder {
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public typealias SerializationRequirement = Transferable
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public func recordArgument<Value: SerializationRequirement>(
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_ argument: RemoteCallArgument<Value>) throws {
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}
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public func recordGenericSubstitution<T>(_ type: T.Type) throws {
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}
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public func recordErrorType<E: Error>(_ type: E.Type) throws {
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}
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public func recordReturnType<R: SerializationRequirement>(_ type: R.Type) throws {
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}
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public func doneRecording() throws {
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}
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}
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// NOT final on purpose
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public class NotFinalActorSystemForAdHocRequirementTest: DistributedActorSystem, @unchecked Sendable {
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public typealias ActorID = String
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public typealias InvocationEncoder = FakeInvocationEncoder
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public typealias InvocationDecoder = FakeInvocationDecoder
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public typealias SerializationRequirement = Transferable
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public typealias ResultHandler = TheSpecificResultHandlerWhichIsANonFinalClass
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public init() {}
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public func resolve<Act>(id: ActorID, as actorType: Act.Type)
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throws -> Act? where Act: DistributedActor {
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fatalError()
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}
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public func assignID<Act>(_ actorType: Act.Type) -> ActorID
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where Act: DistributedActor {
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fatalError()
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}
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public func actorReady<Act>(_ actor: Act) where Act: DistributedActor, Act.ID == ActorID {
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fatalError()
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}
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public func resignID(_ id: ActorID) {
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fatalError()
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}
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public func makeInvocationEncoder() -> InvocationEncoder {
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fatalError()
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}
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public func remoteCall<Act, Err, Res>(
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on actor: Act,
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target: RemoteCallTarget,
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invocation: inout InvocationEncoder,
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throwing errorType: Err.Type,
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returning returnType: Res.Type
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) async throws -> Res
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where Act: DistributedActor,
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Act.ID == ActorID,
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Err: Error,
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Res: SerializationRequirement {
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fatalError()
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}
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public func remoteCallVoid<Act, Err>(
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on actor: Act,
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target: RemoteCallTarget,
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invocation: inout InvocationEncoder,
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throwing errorType: Err.Type
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) async throws
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where Act: DistributedActor,
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Act.ID == ActorID,
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Err: Error {
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fatalError()
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}
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}
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// FIXME: This call should be devirtualized but it cannot be done at the moment due to issues with ad-hoc serialization requirement.
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// CHECK-LABEL: sil shared [transparent] [thunk] @$s52distributed_actor_adhoc_requirements_optimized_build42NotFinalActorSystemForAdHocRequirementTestC11Distributed0piJ0AadEP10remoteCall2on6target10invocation8throwing9returningqd_1_qd___AD06RemoteR6TargetV17InvocationEncoderQzzqd_0_mqd_1_mtYaKAD0pI0Rd__s5ErrorRd_0_2IDQyd__0I2IDRtzr1_lFTW
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// CHECK: bb0(%0 : $*τ_0_2, %1 : $τ_0_0, %2 : $*RemoteCallTarget, %3 : $*FakeInvocationEncoder, %4 : $@thick τ_0_1.Type, %5 : $@thick τ_0_2.Type, %6 : $*NotFinalActorSystemForAdHocRequirementTest):
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// CHECK-NEXT: [[DIST_IMPL:%.*]] = load %6
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// CHECK-NEXT: [[REMOTE_CALL_WITNESS:%.*]] = class_method [[DIST_IMPL]] : $NotFinalActorSystemForAdHocRequirementTest, #NotFinalActorSystemForAdHocRequirementTest.remoteCall
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// CHECK-NEXT: try_apply [[REMOTE_CALL_WITNESS]]<τ_0_0, τ_0_1, τ_0_2>(%0, %1, %2, %3, %4, %5, [[DIST_IMPL]])

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