[Concurrency] repair cooperative global executor

stdlib/public/Concurrency/Executor.swift

@@ -93,6 +93,7 @@ func _checkExpectedExecutor(_filenameStart: Builtin.RawPointer,
     _filenameStart, _filenameLength, _filenameIsASCII, _line, _executor)
 }
 
+#if !SWIFT_STDLIB_SINGLE_THREADED_RUNTIME
 // This must take a DispatchQueueShim, not something like AnyObject,
 // or else SILGen will emit a retain/release in unoptimized builds,
 // which won't work because DispatchQueues aren't actually
@@ -119,3 +120,4 @@ internal final class DispatchQueueShim: UnsafeSendable, SerialExecutor {
     return UnownedSerialExecutor(ordinary: self)
   }
 }
+#endif

stdlib/public/Concurrency/GlobalExecutor.cpp

@@ -59,12 +59,15 @@
 #include "TaskPrivate.h"
 #include "Error.h"
 
+#if !SWIFT_CONCURRENCY_COOPERATIVE_GLOBAL_EXECUTOR
 #include <dispatch/dispatch.h>
 
 #if !defined(_WIN32)
 #include <dlfcn.h>
 #endif
 
+#endif
+
 using namespace swift;
 
 SWIFT_CC(swift)
@@ -180,7 +183,7 @@ void swift::donateThreadToGlobalExecutorUntil(bool (*condition)(void *),
   while (!condition(conditionContext)) {
     auto job = claimNextFromJobQueue();
     if (!job) return;
-    job->run(ExecutorRef::generic());
+    swift_job_run(job, ExecutorRef::generic());
   }
 }
 
@@ -405,21 +408,35 @@ void swift::swift_task_enqueueMainExecutor(Job *job) {
     swift_task_enqueueMainExecutorImpl(job);
 }
 
+#if !SWIFT_CONCURRENCY_COOPERATIVE_GLOBAL_EXECUTOR
 void swift::swift_task_enqueueOnDispatchQueue(Job *job,
                                               HeapObject *_queue) {
   JobPriority priority = job->getPriority();
   auto queue = reinterpret_cast<dispatch_queue_t>(_queue);
   dispatchEnqueue(queue, job, (dispatch_qos_class_t)priority, queue);
 }
+#endif
+
+#if SWIFT_CONCURRENCY_COOPERATIVE_GLOBAL_EXECUTOR
+static HeapObject _swift_mainExecutorIdentity;
+#endif
 
 ExecutorRef swift::swift_task_getMainExecutor() {
+#if SWIFT_CONCURRENCY_COOPERATIVE_GLOBAL_EXECUTOR
+  return ExecutorRef::forOrdinary(&_swift_mainExecutorIdentity, nullptr);
+#else
   return ExecutorRef::forOrdinary(
            reinterpret_cast<HeapObject*>(&_dispatch_main_q),
            _swift_task_getDispatchQueueSerialExecutorWitnessTable());
+#endif
 }
 
 bool ExecutorRef::isMainExecutor() const {
+#if SWIFT_CONCURRENCY_COOPERATIVE_GLOBAL_EXECUTOR
+  return Identity == &_swift_mainExecutorIdentity;
+#else
   return Identity == reinterpret_cast<HeapObject*>(&_dispatch_main_q);
+#endif
 }
 
 #define OVERRIDE_GLOBAL_EXECUTOR COMPATIBILITY_OVERRIDE

stdlib/public/Concurrency/Task.cpp

@@ -27,7 +27,9 @@
 #include "Debug.h"
 #include "Error.h"
 
+#if !SWIFT_CONCURRENCY_COOPERATIVE_GLOBAL_EXECUTOR
 #include <dispatch/dispatch.h>
+#endif
 
 #if !defined(_WIN32)
 #include <dlfcn.h>
@@ -242,12 +244,16 @@ static void destroyTask(SWIFT_CONTEXT HeapObject *obj) {
 }
 
 static ExecutorRef executorForEnqueuedJob(Job *job) {
+#if SWIFT_CONCURRENCY_COOPERATIVE_GLOBAL_EXECUTOR
+  return ExecutorRef::generic();
+#else
   void *jobQueue = job->SchedulerPrivate[Job::DispatchQueueIndex];
   if (jobQueue == DISPATCH_QUEUE_GLOBAL_EXECUTOR)
     return ExecutorRef::generic();
   else
     return ExecutorRef::forOrdinary(reinterpret_cast<HeapObject*>(jobQueue),
                     _swift_task_getDispatchQueueSerialExecutorWitnessTable());
+#endif
 }
 
 static void jobInvoke(void *obj, void *unused, uint32_t flags) {

stdlib/public/Concurrency/TaskGroup.cpp

@@ -34,7 +34,9 @@
 #include "queue" // TODO: remove and replace with usage of our mpsc queue
 #include <atomic>
 #include <assert.h>
+#if !SWIFT_CONCURRENCY_COOPERATIVE_GLOBAL_EXECUTOR
 #include <dispatch/dispatch.h>
+#endif
 
 #if !defined(_WIN32)
 #include <dlfcn.h>

stdlib/public/Concurrency/TaskPrivate.h

@@ -112,12 +112,14 @@ void _swift_tsan_release(void *addr);
 /// executors.
 #define DISPATCH_QUEUE_GLOBAL_EXECUTOR (void *)1
 
+#if !defined(SWIFT_STDLIB_SINGLE_THREADED_RUNTIME)
 inline SerialExecutorWitnessTable *
 _swift_task_getDispatchQueueSerialExecutorWitnessTable() {
   extern SerialExecutorWitnessTable wtable
     SWIFT_ASM_LABEL_WITH_PREFIX("$ss17DispatchQueueShimCScfsWP");
   return &wtable;
 }
+#endif
 
 // ==== ------------------------------------------------------------------------