Allow the createWasm function to use async/await where possible

The advantage if using `await` in the cases where we can is that it avoids the generation or wrapper function for each export. So instead of ``` var wasmExport = createWasm(); // returns empty object ... var malloc = ((..) => (malloc = wasmExports['malloc'])() ``` We can just generate: ``` var wasmExport = createWasm(); // returns empty object ... var malloc = wasmExports['malloc']; ``` This only currently works in MODULARIZE mode where the code is running inside a factory function. Otherwise it would end up using top-level-await. One wrinkle here is that this is not currently supported when closure is enabled because we run closure only on the contents of the factory function so closure ends up seeing this as a top level await when its not.
emscripten-core · Dec 18, 2024 · a7bb4fa · a7bb4fa
1 parent 669e01a
commit a7bb4fa
Show file tree

Hide file tree

Showing 87 changed files with 131 additions and 113 deletions.
diff --git a/ChangeLog.md b/ChangeLog.md
@@ -25,6 +25,11 @@ See docs/process.md for more on how version tagging works.
   This paves the way for marking the function as `async` which does not allow
   `new` to be used.  This usage of `new` here was never documented and is
   considered and antipattern. (#23210)
+- The factory function exposed in `-sMODULARIZE` mode is now marked as `async`,
+  which allows us to use `await` within it.  One side effect of this is that
+  it is no longer possible to use this function with the `new` keyword.  Prior
+  to this change it was technically possible to do `var m = new Module()`, but
+  this will not result in `Module is not a constructor`. (#23157)
 - `PATH.basename()` no longer calls `PATH.normalize()`, so that
   `PATH.basename("a/.")` returns `"."` instead of `"a"` and
   `PATH.basename("a/b/..")` returns `".."` instead of `"a"`. This is in line with

diff --git a/src/preamble.js b/src/preamble.js
@@ -1036,11 +1036,11 @@ function getWasmImports() {
     trueModule = null;
 #endif
 #if SHARED_MEMORY || RELOCATABLE
-    receiveInstance(result['instance'], result['module']);
+    return receiveInstance(result['instance'], result['module']);
 #else
     // TODO: Due to Closure regression https://github.com/google/closure-compiler/issues/3193, the above line no longer optimizes out down to the following line.
     // When the regression is fixed, can restore the above PTHREADS-enabled path.
-    receiveInstance(result['instance']);
+    return receiveInstance(result['instance']);
 #endif
   }
 #endif // WASM_ASYNC_COMPILATION
@@ -1076,8 +1076,7 @@ function getWasmImports() {
         // 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());
-        receiveInstance(instance, module);
-        resolve();
+        resolve(receiveInstance(instance, module));
       };
     });
   }
@@ -1095,16 +1094,16 @@ function getWasmImports() {
   try {
 #endif
     var result = await instantiateAsync(wasmBinary, wasmBinaryFile, info);
-    receiveInstantiationResult(result);
+    var exports = receiveInstantiationResult(result);
 #if LOAD_SOURCE_MAP
     receiveSourceMapJSON(await getSourceMapAsync());
 #endif
-    return result;
+    return exports;
 #if MODULARIZE
   } catch (e) {
     // If instantiation fails, reject the module ready promise.
     readyPromiseReject(e);
-    return;
+    return Promise.reject(e);
   }
 #endif
 #else // WASM_ASYNC_COMPILATION

diff --git a/test/code_size/hello_webgl2_wasm.json b/test/code_size/hello_webgl2_wasm.json
@@ -1,10 +1,10 @@
 {
   "a.html": 454,
   "a.html.gz": 328,
-  "a.js": 4532,
-  "a.js.gz": 2315,
+  "a.js": 4538,
+  "a.js.gz": 2320,
   "a.wasm": 10402,
   "a.wasm.gz": 6703,
-  "total": 15388,
-  "total_gz": 9346
+  "total": 15394,
+  "total_gz": 9351
 }
diff --git a/test/code_size/hello_webgl2_wasm2js.json b/test/code_size/hello_webgl2_wasm2js.json
@@ -1,8 +1,8 @@
 {
   "a.html": 346,
   "a.html.gz": 262,
-  "a.js": 22200,
-  "a.js.gz": 11583,
-  "total": 22546,
-  "total_gz": 11845
+  "a.js": 22206,
+  "a.js.gz": 11589,
+  "total": 22552,
+  "total_gz": 11851
 }
diff --git a/test/code_size/hello_webgl_wasm.json b/test/code_size/hello_webgl_wasm.json
@@ -1,10 +1,10 @@
 {
   "a.html": 454,
   "a.html.gz": 328,
-  "a.js": 4070,
-  "a.js.gz": 2158,
+  "a.js": 4076,
+  "a.js.gz": 2163,
   "a.wasm": 10402,
   "a.wasm.gz": 6703,
-  "total": 14926,
-  "total_gz": 9189
+  "total": 14932,
+  "total_gz": 9194
 }
diff --git a/test/code_size/hello_webgl_wasm2js.json b/test/code_size/hello_webgl_wasm2js.json
@@ -1,8 +1,8 @@
 {
   "a.html": 346,
   "a.html.gz": 262,
-  "a.js": 21726,
-  "a.js.gz": 11413,
-  "total": 22072,
-  "total_gz": 11675
+  "a.js": 21732,
+  "a.js.gz": 11419,
+  "total": 22078,
+  "total_gz": 11681
 }
diff --git a/test/other/codesize/test_codesize_cxx_ctors1.gzsize b/test/other/codesize/test_codesize_cxx_ctors1.gzsize
@@ -1 +1 @@
-8482
+8479
diff --git a/test/other/codesize/test_codesize_cxx_ctors1.jssize b/test/other/codesize/test_codesize_cxx_ctors1.jssize
@@ -1 +1 @@
-20818
+20814
diff --git a/test/other/codesize/test_codesize_cxx_ctors2.gzsize b/test/other/codesize/test_codesize_cxx_ctors2.gzsize
@@ -1 +1 @@
-8466
+8464
diff --git a/test/other/codesize/test_codesize_cxx_ctors2.jssize b/test/other/codesize/test_codesize_cxx_ctors2.jssize
@@ -1 +1 @@
-20786
+20782
diff --git a/test/other/codesize/test_codesize_cxx_except.gzsize b/test/other/codesize/test_codesize_cxx_except.gzsize
@@ -1 +1 @@
-9516
+9515
diff --git a/test/other/codesize/test_codesize_cxx_except.jssize b/test/other/codesize/test_codesize_cxx_except.jssize
@@ -1 +1 @@
-24663
+24659
diff --git a/test/other/codesize/test_codesize_cxx_except_wasm.gzsize b/test/other/codesize/test_codesize_cxx_except_wasm.gzsize
@@ -1 +1 @@
-8443
+8442
diff --git a/test/other/codesize/test_codesize_cxx_except_wasm.jssize b/test/other/codesize/test_codesize_cxx_except_wasm.jssize
@@ -1 +1 @@
-20711
+20707
diff --git a/test/other/codesize/test_codesize_cxx_except_wasm_exnref.gzsize b/test/other/codesize/test_codesize_cxx_except_wasm_exnref.gzsize
@@ -1 +1 @@
-8443
+8442
diff --git a/test/other/codesize/test_codesize_cxx_except_wasm_exnref.jssize b/test/other/codesize/test_codesize_cxx_except_wasm_exnref.jssize
@@ -1 +1 @@
-20711
+20707
diff --git a/test/other/codesize/test_codesize_cxx_lto.jssize b/test/other/codesize/test_codesize_cxx_lto.jssize
@@ -1 +1 @@
-20402
+20398
diff --git a/test/other/codesize/test_codesize_cxx_mangle.gzsize b/test/other/codesize/test_codesize_cxx_mangle.gzsize
@@ -1 +1 @@
-9523
+9520
diff --git a/test/other/codesize/test_codesize_cxx_mangle.jssize b/test/other/codesize/test_codesize_cxx_mangle.jssize
@@ -1 +1 @@
-24663
+24659
diff --git a/test/other/codesize/test_codesize_cxx_noexcept.gzsize b/test/other/codesize/test_codesize_cxx_noexcept.gzsize
@@ -1 +1 @@
-8482
+8479
diff --git a/test/other/codesize/test_codesize_cxx_noexcept.jssize b/test/other/codesize/test_codesize_cxx_noexcept.jssize
@@ -1 +1 @@
-20818
+20814
diff --git a/test/other/codesize/test_codesize_cxx_wasmfs.gzsize b/test/other/codesize/test_codesize_cxx_wasmfs.gzsize
@@ -1 +1 @@
-3769
+3767
diff --git a/test/other/codesize/test_codesize_cxx_wasmfs.jssize b/test/other/codesize/test_codesize_cxx_wasmfs.jssize
@@ -1 +1 @@
-8493
+8489
diff --git a/test/other/codesize/test_codesize_files_js_fs.gzsize b/test/other/codesize/test_codesize_files_js_fs.gzsize
@@ -1 +1 @@
-7621
+7619
diff --git a/test/other/codesize/test_codesize_files_js_fs.jssize b/test/other/codesize/test_codesize_files_js_fs.jssize
@@ -1 +1 @@
-18731
+18727
diff --git a/test/other/codesize/test_codesize_files_wasmfs.gzsize b/test/other/codesize/test_codesize_files_wasmfs.gzsize
@@ -1 +1 @@
-2866
+2864
diff --git a/test/other/codesize/test_codesize_files_wasmfs.jssize b/test/other/codesize/test_codesize_files_wasmfs.jssize
@@ -1 +1 @@
-6140
+6136
diff --git a/test/other/codesize/test_codesize_hello_O0.gzsize b/test/other/codesize/test_codesize_hello_O0.gzsize
@@ -1 +1 @@
-8003
+8001
diff --git a/test/other/codesize/test_codesize_hello_O0.jssize b/test/other/codesize/test_codesize_hello_O0.jssize
@@ -1 +1 @@
-21535
+21526
diff --git a/test/other/codesize/test_codesize_hello_O1.gzsize b/test/other/codesize/test_codesize_hello_O1.gzsize
@@ -1 +1 @@
-2713
+2710
diff --git a/test/other/codesize/test_codesize_hello_O1.jssize b/test/other/codesize/test_codesize_hello_O1.jssize
@@ -1 +1 @@
-6921
+6909
diff --git a/test/other/codesize/test_codesize_hello_O2.gzsize b/test/other/codesize/test_codesize_hello_O2.gzsize
@@ -1 +1 @@
-2369
+2367
diff --git a/test/other/codesize/test_codesize_hello_O2.jssize b/test/other/codesize/test_codesize_hello_O2.jssize
@@ -1 +1 @@
-4844
+4840
diff --git a/test/other/codesize/test_codesize_hello_O3.gzsize b/test/other/codesize/test_codesize_hello_O3.gzsize
@@ -1 +1 @@
-2283
+2281
diff --git a/test/other/codesize/test_codesize_hello_O3.jssize b/test/other/codesize/test_codesize_hello_O3.jssize
@@ -1 +1 @@
-4695
+4691
diff --git a/test/other/codesize/test_codesize_hello_Os.gzsize b/test/other/codesize/test_codesize_hello_Os.gzsize
@@ -1 +1 @@
-2283
+2281
diff --git a/test/other/codesize/test_codesize_hello_Os.jssize b/test/other/codesize/test_codesize_hello_Os.jssize
@@ -1 +1 @@
-4695
+4691
diff --git a/test/other/codesize/test_codesize_hello_Oz.gzsize b/test/other/codesize/test_codesize_hello_Oz.gzsize
@@ -1 +1 @@
-2265
+2264
diff --git a/test/other/codesize/test_codesize_hello_Oz.jssize b/test/other/codesize/test_codesize_hello_Oz.jssize
@@ -1 +1 @@
-4662
+4658
diff --git a/test/other/codesize/test_codesize_hello_dylink.gzsize b/test/other/codesize/test_codesize_hello_dylink.gzsize
@@ -1 +1 @@
-6150
+6155
diff --git a/test/other/codesize/test_codesize_hello_dylink.jssize b/test/other/codesize/test_codesize_hello_dylink.jssize
@@ -1 +1 @@
-13609
+13626
diff --git a/test/other/codesize/test_codesize_hello_export_nothing.gzsize b/test/other/codesize/test_codesize_hello_export_nothing.gzsize
@@ -1 +1 @@
-1667
+1664
diff --git a/test/other/codesize/test_codesize_hello_export_nothing.jssize b/test/other/codesize/test_codesize_hello_export_nothing.jssize
@@ -1 +1 @@
-3575
+3571
diff --git a/test/other/codesize/test_codesize_hello_wasmfs.gzsize b/test/other/codesize/test_codesize_hello_wasmfs.gzsize
@@ -1 +1 @@
-2283
+2281
diff --git a/test/other/codesize/test_codesize_hello_wasmfs.jssize b/test/other/codesize/test_codesize_hello_wasmfs.jssize
@@ -1 +1 @@
-4695
+4691
diff --git a/test/other/codesize/test_codesize_libcxxabi_message_O3.gzsize b/test/other/codesize/test_codesize_libcxxabi_message_O3.gzsize
@@ -1 +1 @@
-1862
+1859
diff --git a/test/other/codesize/test_codesize_libcxxabi_message_O3.jssize b/test/other/codesize/test_codesize_libcxxabi_message_O3.jssize
@@ -1 +1 @@
-3938
+3934
diff --git a/test/other/codesize/test_codesize_libcxxabi_message_O3_standalone.gzsize b/test/other/codesize/test_codesize_libcxxabi_message_O3_standalone.gzsize
@@ -1 +1 @@
-1899
+1897
diff --git a/test/other/codesize/test_codesize_libcxxabi_message_O3_standalone.jssize b/test/other/codesize/test_codesize_libcxxabi_message_O3_standalone.jssize
@@ -1 +1 @@
-3986
+3982
diff --git a/test/other/codesize/test_codesize_mem_O3.jssize b/test/other/codesize/test_codesize_mem_O3.jssize
@@ -1 +1 @@
-4830
+4826
diff --git a/test/other/codesize/test_codesize_mem_O3_grow.gzsize b/test/other/codesize/test_codesize_mem_O3_grow.gzsize
@@ -1 +1 @@
-2461
+2459
diff --git a/test/other/codesize/test_codesize_mem_O3_grow.jssize b/test/other/codesize/test_codesize_mem_O3_grow.jssize
@@ -1 +1 @@
-5115
+5110
diff --git a/test/other/codesize/test_codesize_mem_O3_grow_standalone.gzsize b/test/other/codesize/test_codesize_mem_O3_grow_standalone.gzsize
@@ -1 +1 @@
-2164
+2161
diff --git a/test/other/codesize/test_codesize_mem_O3_grow_standalone.jssize b/test/other/codesize/test_codesize_mem_O3_grow_standalone.jssize
@@ -1 +1 @@
-4523
+4519
diff --git a/test/other/codesize/test_codesize_mem_O3_standalone.gzsize b/test/other/codesize/test_codesize_mem_O3_standalone.gzsize
@@ -1 +1 @@
-2128
+2125
diff --git a/test/other/codesize/test_codesize_mem_O3_standalone.jssize b/test/other/codesize/test_codesize_mem_O3_standalone.jssize
@@ -1 +1 @@
-4455
+4451
diff --git a/test/other/codesize/test_codesize_mem_O3_standalone_lib.gzsize b/test/other/codesize/test_codesize_mem_O3_standalone_lib.gzsize
@@ -1 +1 @@
-1885
+1883
diff --git a/test/other/codesize/test_codesize_mem_O3_standalone_lib.jssize b/test/other/codesize/test_codesize_mem_O3_standalone_lib.jssize
@@ -1 +1 @@
-3985
+3981
diff --git a/test/other/codesize/test_codesize_mem_O3_standalone_narg.gzsize b/test/other/codesize/test_codesize_mem_O3_standalone_narg.gzsize
@@ -1 +1 @@
-1899
+1897
diff --git a/test/other/codesize/test_codesize_mem_O3_standalone_narg.jssize b/test/other/codesize/test_codesize_mem_O3_standalone_narg.jssize
@@ -1 +1 @@
-3986
+3982
diff --git a/test/other/codesize/test_codesize_mem_O3_standalone_narg_flto.gzsize b/test/other/codesize/test_codesize_mem_O3_standalone_narg_flto.gzsize
@@ -1 +1 @@
-1899
+1897
diff --git a/test/other/codesize/test_codesize_mem_O3_standalone_narg_flto.jssize b/test/other/codesize/test_codesize_mem_O3_standalone_narg_flto.jssize
@@ -1 +1 @@
-3986
+3982
diff --git a/test/other/codesize/test_codesize_minimal_64.gzsize b/test/other/codesize/test_codesize_minimal_64.gzsize
@@ -1 +1 @@
-1439
+1441
diff --git a/test/other/codesize/test_codesize_minimal_64.jssize b/test/other/codesize/test_codesize_minimal_64.jssize
@@ -1 +1 @@
-3064
+3058
diff --git a/test/other/codesize/test_codesize_minimal_O1.gzsize b/test/other/codesize/test_codesize_minimal_O1.gzsize
@@ -1 +1 @@
-1520
+1524
diff --git a/test/other/codesize/test_codesize_minimal_O1.jssize b/test/other/codesize/test_codesize_minimal_O1.jssize
@@ -1 +1 @@
-3664
+3653
diff --git a/test/other/codesize/test_codesize_minimal_O2.jssize b/test/other/codesize/test_codesize_minimal_O2.jssize
@@ -1 +1 @@
-2769
+2763
diff --git a/test/other/codesize/test_codesize_minimal_O3.gzsize b/test/other/codesize/test_codesize_minimal_O3.gzsize
@@ -1 +1 @@
-1336
+1338
diff --git a/test/other/codesize/test_codesize_minimal_O3.jssize b/test/other/codesize/test_codesize_minimal_O3.jssize
@@ -1 +1 @@
-2719
+2713
diff --git a/test/other/codesize/test_codesize_minimal_Os.gzsize b/test/other/codesize/test_codesize_minimal_Os.gzsize
@@ -1 +1 @@
-1336
+1338
diff --git a/test/other/codesize/test_codesize_minimal_Os.jssize b/test/other/codesize/test_codesize_minimal_Os.jssize
@@ -1 +1 @@
-2719
+2713
diff --git a/test/other/codesize/test_codesize_minimal_Oz-ctors.gzsize b/test/other/codesize/test_codesize_minimal_Oz-ctors.gzsize
@@ -1 +1 @@
-1327
+1328
diff --git a/test/other/codesize/test_codesize_minimal_Oz-ctors.jssize b/test/other/codesize/test_codesize_minimal_Oz-ctors.jssize
@@ -1 +1 @@
-2704
+2698
diff --git a/test/other/codesize/test_codesize_minimal_Oz.gzsize b/test/other/codesize/test_codesize_minimal_Oz.gzsize
@@ -1 +1 @@
-1336
+1338
diff --git a/test/other/codesize/test_codesize_minimal_Oz.jssize b/test/other/codesize/test_codesize_minimal_Oz.jssize
@@ -1 +1 @@
-2719
+2713
diff --git a/test/other/codesize/test_codesize_minimal_esm.gzsize b/test/other/codesize/test_codesize_minimal_esm.gzsize
@@ -1 +1 @@
-1487
+1500
diff --git a/test/other/codesize/test_codesize_minimal_esm.jssize b/test/other/codesize/test_codesize_minimal_esm.jssize
@@ -1 +1 @@
-3095
+3114
diff --git a/test/other/codesize/test_codesize_minimal_pthreads.gzsize b/test/other/codesize/test_codesize_minimal_pthreads.gzsize
@@ -1 +1 @@
-4118
+4125
diff --git a/test/other/codesize/test_codesize_minimal_pthreads.jssize b/test/other/codesize/test_codesize_minimal_pthreads.jssize
@@ -1 +1 @@
-8556
+8572
diff --git a/test/other/codesize/test_codesize_minimal_wasmfs.gzsize b/test/other/codesize/test_codesize_minimal_wasmfs.gzsize
@@ -1 +1 @@
-1336
+1338
diff --git a/test/other/codesize/test_codesize_minimal_wasmfs.jssize b/test/other/codesize/test_codesize_minimal_wasmfs.jssize
@@ -1 +1 @@
-2719
+2713
diff --git a/test/other/test_unoptimized_code_size.js.size b/test/other/test_unoptimized_code_size.js.size
@@ -1 +1 @@
-53709
+53731
diff --git a/test/other/test_unoptimized_code_size_no_asserts.js.size b/test/other/test_unoptimized_code_size_no_asserts.js.size
@@ -1 +1 @@
-29018
+29040
diff --git a/test/other/test_unoptimized_code_size_strict.js.size b/test/other/test_unoptimized_code_size_strict.js.size
@@ -1 +1 @@
-52531
+52553
diff --git a/test/test_unicode_js_library.out b/test/test_unicode_js_library.out
@@ -1,2 +1,2 @@
-Unicode postjs: àČšñéáúÍųåêâăščếệüçλληνικάбългарскиPусскийСрпскиУкраїнська한국어中文普通话(中国大陆)普通话(香港)中文(台灣)粵語(香港)日本語हिन्दीภาษาไทย
 Unicode snowman ☃ says hello! àČšñéáúÍųåêâăščếệüçλληνικάбългарскиPусскийСрпскиУкраїнська한국어中文普通话(中国大陆)普通话(香港)中文(台灣)粵語(香港)日本語हिन्दीภาษาไทย
+Unicode postjs: àČšñéáúÍųåêâăščếệüçλληνικάбългарскиPусскийСрпскиУкраїнська한국어中文普通话(中国大陆)普通话(香港)中文(台灣)粵語(香港)日本語हिन्दीภาษาไทย
diff --git a/tools/emscripten.py b/tools/emscripten.py
@@ -893,6 +893,16 @@ def create_sending(metadata, library_symbols):
   return '{\n  ' + ',\n  '.join(elems) + '\n}'
 
 
+def can_use_await():
+  # In MODULARIZE mode we can use `await` since the factory function itself
+  # is marked as `async` and the generated code all lives inside that factory
+  # function.
+  # However, because closure does see this (it runs only on the inner code),
+  # it sees this as a top-level-await, which it does not yet support.
+  # FIXME(https://github.com/emscripten-core/emscripten/issues/23158)
+  return settings.MODULARIZE and not settings.USE_CLOSURE_COMPILER
+
+
 def make_export_wrappers(function_exports):
   assert not settings.MINIMAL_RUNTIME
 
@@ -932,7 +942,7 @@ def install_wrapper(sym):
       # With assertions enabled we create a wrapper that are calls get routed through, for
       # the lifetime of the program.
       wrapper += f"createExportWrapper('{name}', {nargs});"
-    elif settings.WASM_ASYNC_COMPILATION or settings.PTHREADS:
+    elif (settings.WASM_ASYNC_COMPILATION and not can_use_await()) or settings.PTHREADS:
       # With WASM_ASYNC_COMPILATION wrapper will replace the global var and Module var on
       # first use.
       args = [f'a{i}' for i in range(nargs)]
@@ -998,7 +1008,11 @@ def create_module(receiving, metadata, global_exports, library_symbols):
 
   if not settings.MINIMAL_RUNTIME:
     if settings.WASM_ASYNC_COMPILATION:
-      module.append("var wasmExports;\ncreateWasm();\n")
+      if can_use_await():
+        # In modullize mode the generated code is within a factory function.
+        module.append("var wasmExports = await createWasm();\n")
+      else:
+        module.append("var wasmExports;\ncreateWasm();\n")
     else:
       module.append("var wasmExports = createWasm();\n")