[dart2wasm] Only include deferred/dynamic loading code in mjs if needed

This removes 1.6 KB from the default mjs file in case neither deferred
loading nor dynamic loading is used.

=> Fixes size regression introduced by dynamic modules support ([0])

[0] https://dart-review.googlesource.com/c/sdk/+/397721

Change-Id: Id5bba9883117038b1fb4139b16f17a91478c7ded
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/414000
Reviewed-by: Ömer Ağacan <[email protected]>
Reviewed-by: Nate Biggs <[email protected]>
Commit-Queue: Martin Kustermann <[email protected]>

Author: mkustermann

pkg/dart2wasm/lib/compile.dart

@@ -331,6 +331,9 @@ Future<CompilationResult> compileToModule(
       translator.functions.translatedProcedures,
       translator.internalizedStringsForJSRuntime,
       translator.options.requireJsStringBuiltin,
+      translator.options.enableDeferredLoading ||
+          translator.options.enableMultiModuleStressTestMode ||
+          translator.dynamicModuleSupportEnabled,
       mode);
 
   final supportJs = _generateSupportJs(options.translatorOptions);

pkg/dart2wasm/lib/constant_evaluator.dart

@@ -18,10 +18,12 @@ class ConstantEvaluator extends kernel.ConstantEvaluator
   final bool _checkBounds;
   final bool _minify;
   final bool _hasDynamicModuleSupport;
+  final bool _deferredLoadingEnabled;
 
   final Procedure _dartInternalCheckBoundsGetter;
   final Procedure _dartInternalMinifyGetter;
   final Procedure _dartInternalHasDynamicModuleSupportGetter;
+  final Procedure _dartInternalDeferredLoadingEnabled;
 
   ConstantEvaluator(
       WasmCompilerOptions options,
@@ -33,13 +35,18 @@ class ConstantEvaluator extends kernel.ConstantEvaluator
       : _checkBounds = !options.translatorOptions.omitBoundsChecks,
         _minify = options.translatorOptions.minify,
         _hasDynamicModuleSupport = options.dynamicModuleMainUri != null,
+        _deferredLoadingEnabled =
+            options.translatorOptions.enableDeferredLoading ||
+                options.translatorOptions.enableMultiModuleStressTestMode,
         _dartInternalCheckBoundsGetter = libraryIndex.getTopLevelProcedure(
             "dart:_internal", "get:checkBounds"),
         _dartInternalMinifyGetter =
             libraryIndex.getTopLevelProcedure("dart:_internal", "get:minify"),
         _dartInternalHasDynamicModuleSupportGetter =
             libraryIndex.getTopLevelProcedure(
                 "dart:_internal", "get:hasDynamicModuleSupport"),
+        _dartInternalDeferredLoadingEnabled = libraryIndex.getTopLevelProcedure(
+            "dart:_internal", "get:deferredLoadingEnabled"),
         super(
           target.dartLibrarySupport,
           target.constantsBackend,
@@ -64,6 +71,9 @@ class ConstantEvaluator extends kernel.ConstantEvaluator
     if (target == _dartInternalHasDynamicModuleSupportGetter) {
       return canonicalize(BoolConstant(_hasDynamicModuleSupport));
     }
+    if (target == _dartInternalDeferredLoadingEnabled) {
+      return canonicalize(BoolConstant(_deferredLoadingEnabled));
+    }
 
     return super.visitStaticGet(node);
   }
@@ -76,5 +86,6 @@ class ConstantEvaluator extends kernel.ConstantEvaluator
   bool shouldEvaluateMember(Member node) =>
       node == _dartInternalCheckBoundsGetter ||
       node == _dartInternalMinifyGetter ||
-      node == _dartInternalHasDynamicModuleSupportGetter;
+      node == _dartInternalHasDynamicModuleSupportGetter ||
+      node == _dartInternalDeferredLoadingEnabled;
 }

pkg/dart2wasm/lib/js/runtime_blob.dart

@@ -111,53 +111,12 @@ class CompiledApp {
 
     <<JS_STRING_POLYFILL_METHODS>>
 
-    const loadModuleFromBytes = async (bytes) => {
-        const module = await WebAssembly.compile(bytes, this.builtins);
-        return await WebAssembly.instantiate(module, {
-          ...baseImports,
-          ...additionalImports,
-          "wasm:js-string": jsStringPolyfill,
-          "module0": dartInstance.exports,
-        });
-    }
-
-    const loadModule = async (loader, loaderArgument) => {
-        const source = await Promise.resolve(loader(loaderArgument));
-        const module = await ((source instanceof Response)
-            ? WebAssembly.compileStreaming(source, this.builtins)
-            : WebAssembly.compile(source, this.builtins));
-        return await WebAssembly.instantiate(module, {
-          ...baseImports,
-          ...additionalImports,
-          <<JS_POLYFILL_IMPORT>>
-          "module0": dartInstance.exports,
-        });
-    }
-
-    const deferredLibraryHelper = {
-      "loadModule": async (moduleName) => {
-        if (!loadDeferredWasm) {
-          throw "No implementation of loadDeferredWasm provided.";
-        }
-        return await loadModule(loadDeferredWasm, moduleName);
-      },
-      "loadDynamicModuleFromUri": async (uri) => {
-        if (!loadDynamicModule) {
-          throw "No implementation of loadDynamicModule provided.";
-        }
-        const loadedModule = await loadModule(loadDynamicModule, uri);
-        return loadedModule.exports.$invokeEntryPoint;
-      },
-      "loadDynamicModuleFromBytes": async (bytes) => {
-        const loadedModule = await loadModuleFromBytes(loadDynamicModule, uri);
-        return loadedModule.exports.$invokeEntryPoint;
-      },
-    };
+    <<DEFERRED_LIBRARY_HELPER_METHODS>>
 
     dartInstance = await WebAssembly.instantiate(this.module, {
       ...baseImports,
       ...additionalImports,
-      "deferredLibraryHelper": deferredLibraryHelper,
+      <<MODULE_LOADING_IMPORT>>
       <<JS_POLYFILL_IMPORT>>
     });
 
@@ -223,6 +182,51 @@ const jsStringPolyfill = {
     };
 ''';
 
+final moduleLoadingHelperTemplate = Template(r'''
+const loadModuleFromBytes = async (bytes) => {
+        const module = await WebAssembly.compile(bytes, this.builtins);
+        return await WebAssembly.instantiate(module, {
+          ...baseImports,
+          ...additionalImports,
+          <<JS_POLYFILL_IMPORT>>
+          "module0": dartInstance.exports,
+        });
+    }
+
+    const loadModule = async (loader, loaderArgument) => {
+        const source = await Promise.resolve(loader(loaderArgument));
+        const module = await ((source instanceof Response)
+            ? WebAssembly.compileStreaming(source, this.builtins)
+            : WebAssembly.compile(source, this.builtins));
+        return await WebAssembly.instantiate(module, {
+          ...baseImports,
+          ...additionalImports,
+          <<JS_POLYFILL_IMPORT>>
+          "module0": dartInstance.exports,
+        });
+    }
+
+    const moduleLoadingHelper = {
+      "loadModule": async (moduleName) => {
+        if (!loadDeferredWasm) {
+          throw "No implementation of loadDeferredWasm provided.";
+        }
+        return await loadModule(loadDeferredWasm, moduleName);
+      },
+      "loadDynamicModuleFromUri": async (uri) => {
+        if (!loadDynamicModule) {
+          throw "No implementation of loadDynamicModule provided.";
+        }
+        const loadedModule = await loadModule(loadDynamicModule, uri);
+        return loadedModule.exports.$invokeEntryPoint;
+      },
+      "loadDynamicModuleFromBytes": async (bytes) => {
+        const loadedModule = await loadModuleFromBytes(loadDynamicModule, uri);
+        return loadedModule.exports.$invokeEntryPoint;
+      },
+    };
+''');
+
 class Template {
   static final _templateVariableRegExp = RegExp(r'<<(?<varname>[A-Z_]+)>>');
   final List<_TemplatePart> _parts = [];

pkg/dart2wasm/lib/js/runtime_generator.dart

@@ -58,6 +58,7 @@ class RuntimeFinalizer {
       Iterable<Procedure> translatedProcedures,
       List<String> constantStrings,
       bool requireJsBuiltin,
+      bool supportsAdditionalModuleLoading,
       wasm_target.Mode mode) {
     String escape(String s) => json.encode(s);
 
@@ -104,13 +105,30 @@ class RuntimeFinalizer {
 ''';
     }
 
+    final jsStringBuiltinPolyfillImportVars = {
+      'JS_POLYFILL_IMPORT':
+          requireJsBuiltin ? '' : '"wasm:js-string": jsStringPolyfill,',
+    };
+    final moduleLoadingImportVars = {
+      'MODULE_LOADING_IMPORT': supportsAdditionalModuleLoading
+          ? '"moduleLoadingHelper": moduleLoadingHelper,'
+          : '',
+    };
+
+    final moduleLoadingHelperMethods = supportsAdditionalModuleLoading
+        ? moduleLoadingHelperTemplate.instantiate({
+            ...jsStringBuiltinPolyfillImportVars,
+          })
+        : '';
+
     return jsRuntimeBlobTemplate.instantiate({
+      ...jsStringBuiltinPolyfillImportVars,
+      ...moduleLoadingImportVars,
       'BUILTINS_MAP_BODY': builtins.join(', '),
       'JS_METHODS': jsMethods.toString(),
       'IMPORTED_JS_STRINGS_IN_MJS': internalizedStrings,
       'JS_STRING_POLYFILL_METHODS': requireJsBuiltin ? '' : jsPolyFillMethods,
-      'JS_POLYFILL_IMPORT':
-          requireJsBuiltin ? '' : '"wasm:js-string": jsStringPolyfill,'
+      'DEFERRED_LIBRARY_HELPER_METHODS': moduleLoadingHelperMethods,
     });
   }
 }

sdk/lib/_internal/wasm/lib/deferred.dart

@@ -10,7 +10,7 @@ final Map<String, Set<String>> _loadedLibraries = {};
 
 external Map<String, Map<String, List<String>>> get _importMapping;
 
-@pragma("wasm:import", "deferredLibraryHelper.loadModule")
+@pragma("wasm:import", "moduleLoadingHelper.loadModule")
 external WasmExternRef _loadModule(WasmExternRef moduleName);
 
 class DeferredNotLoadedError extends Error implements NoSuchMethodError {
@@ -49,6 +49,10 @@ Future<void> loadLibrary(String enclosingLibrary, String importPrefix) {
     return Future.value();
   }
 
+  if (!deferredLoadingEnabled) {
+    throw DeferredLoadException('Compiler did not enable deferred loading.');
+  }
+
   // Start loading modules
   final List<Future> loadFutures = [];
   for (final moduleName in moduleNames) {

sdk/lib/_internal/wasm/lib/dynamic_module.dart

@@ -4,10 +4,10 @@
 
 part of "internal_patch.dart";
 
-@pragma("wasm:import", "deferredLibraryHelper.loadDynamicModuleFromUri")
+@pragma("wasm:import", "moduleLoadingHelper.loadDynamicModuleFromUri")
 external WasmExternRef _loadModuleFromUri(WasmExternRef moduleUri);
 
-@pragma("wasm:import", "deferredLibraryHelper.loadDynamicModuleFromBytes")
+@pragma("wasm:import", "moduleLoadingHelper.loadDynamicModuleFromBytes")
 external WasmExternRef _loadModuleFromBytes(WasmExternRef moduleUri);
 
 @patch

sdk/lib/_internal/wasm/lib/internal_patch.dart

@@ -194,7 +194,7 @@ String jsonEncode(String object) => jsStringToDartString(
 /// Bounds checks are disabled with `--omit-bounds-checks`, which is implied by
 /// `-O4`.
 ///
-/// Reads of this variable is evaluated before the TFA by the constant
+/// Reads of this variable are evaluated before the TFA by the constant
 /// evaluator, and its value depends on `--omit-bounds-checks`.
 external bool get checkBounds;
 
@@ -203,7 +203,7 @@ external bool get checkBounds;
 /// If minification is on we do not retain specific error message details (e.g.
 /// omit the index in index errors).
 ///
-/// Reads of this variable is evaluated before the TFA by the constant
+/// Reads of this variable are evaluated before the TFA by the constant
 /// evaluator, and its value depends on `--minify`.
 external bool get minify;
 
@@ -212,10 +212,19 @@ external bool get minify;
 /// Enables shortcuts in some runtime logic if it is known that no support is
 /// needed for dynamic modules.
 ///
-/// Reads of this variable is evaluated before the TFA by the constant
+/// Reads of this variable are evaluated before the TFA by the constant
 /// evaluator, and its value depends on `--dynamic-module-main`.
 external bool get hasDynamicModuleSupport;
 
+/// Whether deferred loading is enabled.
+///
+/// If true, then there may be deferred modules that can be loaded at runtime.
+///
+/// Reads of this variable are evaluated before the TFA by the constant
+/// evaluator, and its value depends on `--enable-deferred-loading` and
+/// `--enable-multi-module-stress-test-mode`.
+external bool get deferredLoadingEnabled;
+
 /// Compiler intrinsic to push an element to a Wasm array in a class field or
 /// variable.
 ///