Refactor pthread and wasm worker init sequence (#24949)

Rather than running `createWasm` and then returning a promise based on
the `wasmModuleReceived` we now do something closer to the way it works
under `MINIMUL_RUNTIME`: We delay both `createWasm` and `run` calls
until the module is received via postMessage.

Author: sbc100

src/postamble.js

@@ -6,26 +6,38 @@
 
 // === Auto-generated postamble setup entry stuff ===
 
-#if MODULARIZE == 'instance'
 var wasmExports;
-#elif WASM_ASYNC_COMPILATION
+
+#if MODULARIZE != 'instance'
+
+#if WASM_WORKERS || PTHREADS
+if ({{{ ENVIRONMENT_IS_MAIN_THREAD() }}}) {
+// Call createWasm on startup if we are the main thread.
+// Worker threads call this once they receive the module via postMessage
+#endif
+
+#if WASM_ASYNC_COMPILATION
 
 #if MODULARIZE
 // In modularize mode the generated code is within a factory function so we
 // can use await here (since it's not top-level-await).
-var wasmExports = await createWasm();
+wasmExports = await createWasm();
 #else
-// With async instantation wasmExports is assigned asyncronously when the
-// the instance is received.
-var wasmExports;
+// With async instantation wasmExports is assigned asynchronously when the
+// instance is received.
 createWasm();
 #endif
 
 #else
-// With sync compilation wasmExports is directly returned from createWasm()
-var wasmExports = createWasm();
+wasmExports = createWasm();
+#endif
+
+#if WASM_WORKERS || PTHREADS
+}
 #endif
 
+#endif // MODULARIZE != 'instance'
+
 #if PROXY_TO_WORKER
 if (ENVIRONMENT_IS_WORKER) {
 #include "webGLWorker.js'
@@ -341,11 +353,6 @@ export default async function init(moduleArg = {}) {
   run();
 }
 
-#if (WASM_WORKERS || PTHREADS) && !WASM_ESM_INTEGRATION
-// When run as a worker thread run `init` immediately.
-if ({{{ ENVIRONMENT_IS_WORKER_THREAD() }}}) await init()
-#endif
-
 #if ENVIRONMENT_MAY_BE_NODE
 // When run as the main script under node we run `init` immediately.
 if (ENVIRONMENT_IS_NODE
@@ -367,10 +374,12 @@ if (ENVIRONMENT_IS_SHELL) {
 }
 #endif
 
-#else
+#else // MODULARIZE=instance
+
 preInit();
-run();
-#endif
+{{{ runIfMainThread('run();') }}}
+
+#endif // MODULARIZE=instance
 
 #if BUILD_AS_WORKER
 

src/preamble.js

@@ -959,14 +959,13 @@ function getWasmImports() {
 
 #if PTHREADS || WASM_WORKERS
   if ({{{ ENVIRONMENT_IS_WORKER_THREAD() }}}) {
-    return new Promise((resolve) => {
-      wasmModuleReceived = (module) => {
-        // Instantiate from the module posted from the main thread.
-        // We can just use sync instantiation in the worker.
-        var instance = new WebAssembly.Instance(module, getWasmImports());
-        resolve(receiveInstance(instance, module));
-      };
-    });
+    // Instantiate from the module that was recieved via postMessage from
+    // the main thread. We can just use sync instantiation in the worker.
+#if ASSERTIONS
+    assert(wasmModule, "wasmModule should have been received via postMessage");
+#endif
+    var instance = new WebAssembly.Instance(wasmModule, getWasmImports());
+    return receiveInstance(instance, wasmModule);
   }
 #endif
 

src/runtime_common.js

@@ -31,12 +31,7 @@ function growMemViews() {
 var readyPromiseResolve, readyPromiseReject;
 #endif
 
-#if PTHREADS || WASM_WORKERS
-#if !MINIMAL_RUNTIME
-var wasmModuleReceived;
-#endif
-
-#if ENVIRONMENT_MAY_BE_NODE && !WASM_ESM_INTEGRATION
+#if (PTHREADS || WASM_WORKERS) && (ENVIRONMENT_MAY_BE_NODE && !WASM_ESM_INTEGRATION)
 if (ENVIRONMENT_IS_NODE && {{{ ENVIRONMENT_IS_WORKER_THREAD() }}}) {
   // Create as web-worker-like an environment as we can.
   var parentPort = worker_threads['parentPort'];
@@ -46,8 +41,7 @@ if (ENVIRONMENT_IS_NODE && {{{ ENVIRONMENT_IS_WORKER_THREAD() }}}) {
     postMessage: (msg) => parentPort['postMessage'](msg),
   });
 }
-#endif // ENVIRONMENT_MAY_BE_NODE && !WASM_ESM_INTEGRATION
-#endif
+#endif // (PTHREADS || WASM_WORKERS) && (ENVIRONMENT_MAY_BE_NODE && !WASM_ESM_INTEGRATION)
 
 #if PTHREADS
 #include "runtime_pthread.js"

src/runtime_pthread.js

@@ -122,7 +122,13 @@ if (ENVIRONMENT_IS_PTHREAD) {
         Module['wasm'] = msgData.wasmModule;
         loadModule();
 #else
-        wasmModuleReceived(msgData.wasmModule);
+        wasmModule = msgData.wasmModule;
+#if MODULARIZE == 'instance'
+        init();
+#else
+        createWasm();
+        run();
+#endif
 #endif // MINIMAL_RUNTIME
 #endif
       } else if (cmd === 'run') {

src/wasm_worker.js

@@ -18,7 +18,13 @@ function startWasmWorker(props) {
   Module['wasm'] = props.wasm;
   loadModule()
 #else
-  wasmModuleReceived(props.wasm);
+  wasmModule = props.wasm;
+#if MODULARIZE == 'instance'
+  init();
+#else
+  createWasm();
+  run();
+#endif
 #endif
   // Drop now unneeded references to from the Module object in this Worker,
   // these are not needed anymore.

test/code_size/test_codesize_minimal_esm.json

@@ -1,10 +1,10 @@
 {
-  "a.out.js": 2513,
-  "a.out.js.gz": 1229,
+  "a.out.js": 2515,
+  "a.out.js.gz": 1230,
   "a.out.nodebug.wasm": 62,
   "a.out.nodebug.wasm.gz": 76,
-  "total": 2575,
-  "total_gz": 1305,
+  "total": 2577,
+  "total_gz": 1306,
   "sent": [],
   "imports": [],
   "exports": [

test/code_size/test_codesize_minimal_pthreads.json

@@ -1,10 +1,10 @@
 {
-  "a.out.js": 7529,
-  "a.out.js.gz": 3720,
+  "a.out.js": 7499,
+  "a.out.js.gz": 3719,
   "a.out.nodebug.wasm": 19588,
   "a.out.nodebug.wasm.gz": 9025,
-  "total": 27117,
-  "total_gz": 12745,
+  "total": 27087,
+  "total_gz": 12744,
   "sent": [
     "a (memory)",
     "b (emscripten_get_now)",

test/code_size/test_codesize_minimal_pthreads_memgrowth.json

@@ -1,9 +1,9 @@
 {
-  "a.out.js": 7956,
+  "a.out.js": 7922,
   "a.out.js.gz": 3920,
   "a.out.nodebug.wasm": 19589,
   "a.out.nodebug.wasm.gz": 9025,
-  "total": 27545,
+  "total": 27511,
   "total_gz": 12945,
   "sent": [
     "a (memory)",

test/code_size/test_unoptimized_code_size.json

@@ -1,16 +1,16 @@
 {
-  "hello_world.js": 54085,
-  "hello_world.js.gz": 17171,
+  "hello_world.js": 54086,
+  "hello_world.js.gz": 17172,
   "hello_world.wasm": 15143,
   "hello_world.wasm.gz": 7452,
-  "no_asserts.js": 26818,
-  "no_asserts.js.gz": 8989,
+  "no_asserts.js": 26819,
+  "no_asserts.js.gz": 8991,
   "no_asserts.wasm": 12227,
   "no_asserts.wasm.gz": 6008,
-  "strict.js": 52135,
-  "strict.js.gz": 16503,
+  "strict.js": 52136,
+  "strict.js.gz": 16504,
   "strict.wasm": 15143,
   "strict.wasm.gz": 7438,
-  "total": 175551,
-  "total_gz": 63561
+  "total": 175554,
+  "total_gz": 63565
 }

test/other/codesize/test_codesize_minimal_O0.expected.js

@@ -1309,9 +1309,10 @@ var _global_val = Module['_global_val'] = 65536;var wasmImports = {
 // include: postamble.js
 // === Auto-generated postamble setup entry stuff ===
 
+var wasmExports;
+
 // With async instantation wasmExports is assigned asyncronously when the
 // the instance is received.
-var wasmExports;
 createWasm();
 
 var calledRun;