[SILGen] Don't emit executor references when '_checkExpectedExecutor' is unavailable

Avoid emitting an unused executor reference for dynamic actor
isolation checking.

Author: xedin

lib/SILGen/SILGenBridging.cpp

@@ -1619,9 +1619,7 @@ void SILGenFunction::emitNativeToForeignThunk(SILDeclRef thunk) {
       // executor, since the task will end after we invoke the completion handler.
       emitPrologGlobalActorHop(loc, isolation->getGlobalActor());
     } else {
-      auto executor =
-        emitLoadGlobalActorExecutor(isolation->getGlobalActor());
-      emitPreconditionCheckExpectedExecutor(loc, executor);
+      emitPreconditionCheckExpectedExecutor(loc, *isolation, std::nullopt);
     }
   }
 

lib/SILGen/SILGenConcurrency.cpp

@@ -590,11 +590,10 @@ void SILGenFunction::emitHopToActorValue(SILLocation loc, ManagedValue actor) {
                         executor, /*mandatory*/ true);
 }
 
-void SILGenFunction::emitPreconditionCheckExpectedExecutor(
-    SILLocation loc, SILValue executorOrActor) {
+static bool isCheckExpectedExecutorIntrinsicAvailable(SILGenModule &SGM) {
   auto checkExecutor = SGM.getCheckExpectedExecutor();
   if (!checkExecutor)
-    return;
+    return false;
 
   // Forego a check if instrinsic is unavailable, this could happen
   // in main-actor context.
@@ -603,10 +602,28 @@ void SILGenFunction::emitPreconditionCheckExpectedExecutor(
     auto deploymentAvailability = AvailabilityContext::forDeploymentTarget(C);
     auto declAvailability =
         AvailabilityInference::availableRange(checkExecutor, C);
-    if (!deploymentAvailability.isContainedIn(declAvailability))
-      return;
+    return deploymentAvailability.isContainedIn(declAvailability);
   }
 
+  return true;
+}
+
+void SILGenFunction::emitPreconditionCheckExpectedExecutor(
+    SILLocation loc, ActorIsolation isolation,
+    std::optional<ManagedValue> actorSelf) {
+  if (!isCheckExpectedExecutorIntrinsicAvailable(SGM))
+    return;
+
+  auto executor = emitExecutor(loc, isolation, actorSelf);
+  assert(executor);
+  emitPreconditionCheckExpectedExecutor(loc, *executor);
+}
+
+void SILGenFunction::emitPreconditionCheckExpectedExecutor(
+    SILLocation loc, SILValue executorOrActor) {
+  if (!isCheckExpectedExecutorIntrinsicAvailable(SGM))
+    return;
+
   // We don't want the debugger to step into these.
   loc.markAutoGenerated();
 
@@ -617,7 +634,7 @@ void SILGenFunction::emitPreconditionCheckExpectedExecutor(
   auto args = emitSourceLocationArgs(loc.getSourceLoc(), loc);
 
   emitApplyOfLibraryIntrinsic(
-      loc, checkExecutor, SubstitutionMap(),
+      loc, SGM.getCheckExpectedExecutor(), SubstitutionMap(),
       {args.filenameStartPointer, args.filenameLength, args.filenameIsAscii,
        args.line, ManagedValue::forObjectRValueWithoutOwnership(executor)},
       SGFContext());

lib/SILGen/SILGenFunction.h

@@ -1165,6 +1165,13 @@ class LLVM_LIBRARY_VISIBILITY SILGenFunction
                                        ActorIsolation isolation,
                                        std::optional<ManagedValue> maybeSelf);
 
+  /// Emit a precondition check to ensure that the function is executing in
+  /// the expected isolation context.
+  void
+  emitPreconditionCheckExpectedExecutor(SILLocation loc,
+                                        ActorIsolation isolation,
+                                        std::optional<ManagedValue> actorSelf);
+
   /// Emit a precondition check to ensure that the function is executing in
   /// the expected isolation context.
   void emitPreconditionCheckExpectedExecutor(

lib/SILGen/SILGenPoly.cpp

@@ -7021,8 +7021,7 @@ void SILGenFunction::emitProtocolWitness(
 
     if (!F.isAsync()) {
       assert(isPreconcurrency);
-      auto executor = emitExecutor(loc, *enterIsolation, actorSelf);
-      emitPreconditionCheckExpectedExecutor(loc, *executor);
+      emitPreconditionCheckExpectedExecutor(loc, *enterIsolation, actorSelf);
     } else {
       emitHopToTargetActor(loc, enterIsolation, actorSelf);
     }
@@ -7247,12 +7246,10 @@ ManagedValue SILGenFunction::emitActorIsolationErasureThunk(
 
     buildThunkBody(
         thunkSGF, loc, AbstractionPattern(isolatedType), isolatedType,
-        AbstractionPattern(nonIsolatedType), nonIsolatedType,
-        expectedType, dynamicSelfType,
-        [&loc, &globalActor](SILGenFunction &thunkSGF) {
-          auto expectedExecutor =
-              thunkSGF.emitLoadGlobalActorExecutor(globalActor);
-          thunkSGF.emitPreconditionCheckExpectedExecutor(loc, expectedExecutor);
+        AbstractionPattern(nonIsolatedType), nonIsolatedType, expectedType,
+        dynamicSelfType, [&loc, &globalActor](SILGenFunction &thunkSGF) {
+          thunkSGF.emitPreconditionCheckExpectedExecutor(
+              loc, ActorIsolation::forGlobalActor(globalActor), std::nullopt);
         });
 
     SGM.emitLazyConformancesForFunction(thunk);

test/Concurrency/dynamic_checks_for_func_refs_in_preconcurrency_apis_objc.swift

@@ -1,4 +1,4 @@
-// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -enable-experimental-feature DynamicActorIsolation -emit-silgen -verify %s | %FileCheck %s
+// RUN: %target-swift-frontend(mock-sdk: %clang-importer-sdk) -target arm64-apple-macosx10.15 -enable-experimental-feature DynamicActorIsolation -emit-silgen -verify %s | %FileCheck %s
 // REQUIRES: objc_interop
 // REQUIRES: asserts
 

test/SILGen/preconcurrency_conformances_backdeploy.swift

@@ -16,4 +16,5 @@ struct IsolatedType<T> : @preconcurrency P {
 }
 
 // CHECK-LABEL: sil private [transparent] [thunk] [ossa] @$s38preconcurrency_conformances_backdeploy12IsolatedTypeVyxGAA1PA2aEP2fn1TQzSgyFTW
+// CHECK-NOT: function_ref @$sScM6sharedScMvgZ
 // CHECK-NOT: function_ref @$ss22_checkExpectedExecutor14_filenameStart01_D6Length01_D7IsASCII5_line9_executoryBp_BwBi1_BwBetF