darwin: add threading support and use it by default

compileopts/target.go

@@ -385,7 +385,7 @@ func defaultTarget(options *Options) (*TargetSpec, error) {
 			platformVersion = "11.0.0" // first macosx platform with arm64 support
 		}
 		llvmvendor = "apple"
-		spec.Scheduler = "tasks"
+		spec.Scheduler = "threads"
 		spec.Linker = "ld.lld"
 		spec.Libc = "darwin-libSystem"
 		// Use macosx* instead of darwin, otherwise darwin/arm64 will refer to
@@ -399,6 +399,7 @@ func defaultTarget(options *Options) (*TargetSpec, error) {
 		)
 		spec.ExtraFiles = append(spec.ExtraFiles,
 			"src/internal/futex/futex_darwin.c",
+			"src/internal/task/task_threads.c",
 			"src/runtime/os_darwin.c",
 			"src/runtime/runtime_unix.c",
 			"src/runtime/signal.c")

src/internal/task/darwin.go

@@ -0,0 +1,11 @@
+//go:build darwin
+
+package task
+
+import "unsafe"
+
+// MacOS uses a pointer so unsafe.Pointer should be fine:
+//
+//	typedef struct _opaque_pthread_t *__darwin_pthread_t;
+//	typedef __darwin_pthread_t pthread_t;
+type threadID unsafe.Pointer

src/internal/task/task_threads.c

@@ -2,16 +2,28 @@
 
 #define _GNU_SOURCE
 #include <pthread.h>
-#include <semaphore.h>
 #include <signal.h>
 #include <stdint.h>
 #include <stdio.h>
 #include <unistd.h>
 
-// BDWGC also uses SIGRTMIN+6 on Linux, which seems like a reasonable choice.
 #ifdef __linux__
+#include <semaphore.h>
+
+// BDWGC also uses SIGRTMIN+6 on Linux, which seems like a reasonable choice.
 #define taskPauseSignal (SIGRTMIN + 6)
-#endif
+
+#elif __APPLE__
+#include <dispatch/dispatch.h>
+// SIGIO is for interrupt-driven I/O.
+// I don't think anybody should be using this nowadays, so I think we can
+// repurpose it as a signal for GC.
+// BDWGC uses a special way to pause/resume other threads on MacOS, which may be
+// better but needs more work. Using signal keeps the code similar between Linux
+// and MacOS.
+#define taskPauseSignal SIGIO
+
+#endif // __linux__, __APPLE__
 
 // Pointer to the current task.Task structure.
 // Ideally the entire task.Task structure would be a thread-local variable but
@@ -23,7 +35,11 @@ struct state_pass {
     void      *args;
     void      *task;
     uintptr_t *stackTop;
+    #if __APPLE__
+    dispatch_semaphore_t startlock;
+    #else
     sem_t     startlock;
+    #endif
 };
 
 // Handle the GC pause in Go.
@@ -68,7 +84,11 @@ static void* start_wrapper(void *arg) {
 
     // Notify the caller that the thread has successfully started and
     // initialized.
+    #if __APPLE__
+    dispatch_semaphore_signal(state->startlock);
+    #else
     sem_post(&state->startlock);
+    #endif
 
     // Run the goroutine function.
     start(args);
@@ -92,11 +112,19 @@ int tinygo_task_start(uintptr_t fn, void *args, void *task, pthread_t *thread, u
         .task      = task,
         .stackTop  = stackTop,
     };
+    #if __APPLE__
+    state.startlock = dispatch_semaphore_create(0);
+    #else
     sem_init(&state.startlock, 0, 0);
+    #endif
     int result = pthread_create(thread, NULL, &start_wrapper, &state);
 
     // Wait until the thread has been created and read all state_pass variables.
+    #if __APPLE__
+    dispatch_semaphore_wait(state.startlock, DISPATCH_TIME_FOREVER);
+    #else
     sem_wait(&state.startlock);
+    #endif
 
     return result;
 }