[Concurrency] repair cooperative global executor (#39092)

`SWIFT_STDLIB_SINGLE_THREADED_RUNTIME` mode has been broken for a long time.

This patch guards some includes and use of libdispatch headers so that platforms
that doesn't support libdispatch can build cooperative executor runtime.
And fixed missing implementations for cooperative mode.

Author: kateinoigakukun

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
 
 // ==== ------------------------------------------------------------------------