Merge pull request #41304 from apple/rokhinip/88700717-workaround

Workaround clang backend bug

Author: aschwaighofer

include/swift/Runtime/Config.h

@@ -202,6 +202,12 @@ extern uintptr_t __COMPATIBILITY_LIBRARIES_CANNOT_CHECK_THE_IS_SWIFT_BIT_DIRECTL
 #define SWIFT_ASYNC_CONTEXT
 #endif
 
+#if __has_attribute(optnone)
+#define SWIFT_OPTNONE __attribute__((optnone))
+#else
+#define SWIFT_OPTNONE
+#endif
+
 // SWIFT_CC(swiftasync) is the Swift async calling convention.
 // We assume that it supports mandatory tail call elimination.
 #if __has_feature(swiftasynccc) && __has_attribute(swiftasynccall)

stdlib/public/Concurrency/Actor.cpp

@@ -1564,10 +1564,13 @@ static void runOnAssumedThread(AsyncTask *task, ExecutorRef executor,
     asImpl(executor.getDefaultActor())->giveUpThread(runner);
 }
 
+// TODO (rokhinip): Workaround rdar://88700717. To be removed with
+// rdar://88711954
 SWIFT_CC(swiftasync)
 static void swift_task_switchImpl(SWIFT_ASYNC_CONTEXT AsyncContext *resumeContext,
                                   TaskContinuationFunction *resumeFunction,
-                                  ExecutorRef newExecutor) {
+                                  ExecutorRef newExecutor) SWIFT_OPTNONE {
+
   auto trackingInfo = ExecutorTrackingInfo::current();
   auto currentExecutor =
     (trackingInfo ? trackingInfo->getActiveExecutor()