[SE-0313] Hop to the exector if an async function with an isolated parameter

Author: DougGregor

lib/SILGen/SILGenProlog.cpp

@@ -502,6 +502,24 @@ void SILGenFunction::emitProlog(CaptureInfo captureInfo,
     switch (actorIsolation.getKind()) {
     case ActorIsolation::Unspecified:
     case ActorIsolation::Independent:
+      // If this is an async function that has an isolated parameter, hop
+      // to it.
+      if (F.isAsync()) {
+        for (auto param : *funcDecl->getParameters()) {
+          if (param->isIsolated()) {
+            auto loc = RegularLocation::getAutoGeneratedLocation(F.getLocation());
+            Type actorType = param->getType();
+            RValue actorInstanceRV = emitRValueForDecl(
+                loc, param, actorType, AccessSemantics::Ordinary);
+            ManagedValue actorInstance =
+                std::move(actorInstanceRV).getScalarValue();
+            ExpectedExecutor = emitLoadActorExecutor(loc, actorInstance);
+            break;
+          }
+        }
+      }
+      break;
+
     case ActorIsolation::GlobalActorUnsafe:
       break;
 

test/SILGen/hop_to_executor.swift

@@ -381,3 +381,11 @@ func testImplicitAsyncIsolatedParam(
   // CHECK-NEXT: hop_to_executor [[CURRENT]] : $Optional<Builtin.Executor>
   await otherActor.otherIsolated(i, actor, d)
 }
+
+// CHECK-LABEL: sil hidden [ossa] @$s4test22asyncWithIsolatedParam1i5actor1dySi_AA7MyActorCYiSdtYaF : $@convention(thin) @async (Int, @guaranteed MyActor, Double) -> ()
+func asyncWithIsolatedParam(i: Int, actor: isolated MyActor, d: Double) async {
+  // CHECK: [[ACTOR:%.*]] = copy_value %1 : $MyActor
+  // CHECK-NEXT: [[BORROWED:%.*]] = begin_borrow [[ACTOR]] : $MyActor
+  // CHECK-NEXT: hop_to_executor [[BORROWED]] : $MyActor
+  // CHECK-NEXT: end_borrow [[BORROWED]] : $MyActor
+}