[JSPI] Automatically add promising JSPI wrappers to thread entry points.

Use a WebAssembly.Promising wrapper on the thread entry points to allow
JSPI to be used from worker threads. The code that invokes the wrapper
also adds async/await to handle this async call to entry point.

Fixes #22354

Author: brendandahl

src/library_pthread.js

@@ -1043,7 +1043,7 @@ var LibraryPThread = {
     '$runtimeKeepaliveCounter',
 #endif
   ],
-  $invokeEntryPoint: (ptr, arg) => {
+  $invokeEntryPoint: {{{ asyncIf(ASYNCIFY == 2) }}} (ptr, arg) => {
 #if PTHREADS_DEBUG
     dbg(`invokeEntryPoint: ${ptrToString(ptr)}`);
 #endif
@@ -1079,7 +1079,11 @@ var LibraryPThread = {
     // *ThreadMain(void *arg) form, or try linking with the Emscripten linker
     // flag -sEMULATE_FUNCTION_POINTER_CASTS to add in emulation for this x86
     // ABI extension.
+#if ASYNCIFY == 2
+    var result = WebAssembly.promising({{{ makeDynCall('pp', 'ptr') }}})(arg);
+#else
     var result = {{{ makeDynCall('pp', 'ptr') }}}(arg);
+#endif
 #if STACK_OVERFLOW_CHECK
     checkStackCookie();
 #endif
@@ -1098,10 +1102,9 @@ var LibraryPThread = {
 #endif
     }
 #if ASYNCIFY == 2
-    Promise.resolve(result).then(finish);
-#else
-    finish(result);
+    result = await result;
 #endif
+    finish(result);
   },
 
 #if MAIN_MODULE

src/runtime_pthread.js

@@ -90,7 +90,7 @@ if (ENVIRONMENT_IS_PTHREAD) {
   // notified about them.
   self.onunhandledrejection = (e) => { throw e.reason || e; };
 
-  function handleMessage(e) {
+  {{{ asyncIf(ASYNCIFY == 2) }}} function handleMessage(e) {
     try {
       var msgData = e['data'];
       //dbg('msgData: ' + Object.keys(msgData));
@@ -201,7 +201,7 @@ if (ENVIRONMENT_IS_PTHREAD) {
         }
 
         try {
-          invokeEntryPoint(msgData.start_routine, msgData.arg);
+          {{{ awaitIf(ASYNCIFY == 2) }}} invokeEntryPoint(msgData.start_routine, msgData.arg);
         } catch(ex) {
           if (ex != 'unwind') {
             // The pthread "crashed".  Do not call `_emscripten_thread_exit` (which

test/core/test_pthread_join_and_asyncify.c

@@ -13,15 +13,17 @@ EM_ASYNC_JS(int, async_call, (), {
   return 42;
 });
 
-// TODO Remove EMSCRIPTEN_KEEPALIVE when support for async attributes is enabled.
-EMSCRIPTEN_KEEPALIVE void *run_thread(void *args) {
+void *run_thread(void *args) {
   int ret = async_call();
   assert(ret == 42);
   return NULL;
 }
 
 int main() {
   pthread_t id;
+  // Test that JSPI works on main thread.
+  emscripten_sleep(1);
+  // Also test that JSPI works on other threads.
   pthread_create(&id, NULL, run_thread, NULL);
   printf("joining thread!\n");
   pthread_join(id, NULL);

test/test_core.py

@@ -8300,7 +8300,7 @@ def test_pthread_join_and_asyncify(self):
     # TODO Test with ASYNCIFY=1 https://github.com/emscripten-core/emscripten/issues/17552
     self.require_jspi()
     self.do_runf('core/test_pthread_join_and_asyncify.c', 'joining thread!\njoined thread!',
-                 emcc_args=['-sJSPI_EXPORTS=run_thread',
+                 emcc_args=['-sJSPI',
                             '-sEXIT_RUNTIME=1',
                             '-pthread', '-sPROXY_TO_PTHREAD'])