From fdeb9dc5757ca9bf88c319f003a355e7d4acf5ad Mon Sep 17 00:00:00 2001
From: Nate Biggs <natebiggs@google.com>
Date: Mon, 1 Dec 2025 21:50:29 -0800
Subject: [PATCH] [dart2wasm] Introduce an opt phase to dart2wasm.

To help facilitate this we move all IO into a separate helper
library/class. This makes it easier to have symmetric read/write
functions and to do IO within compile.dart where necessary.

Adding the new `opt` phase allows us to remove the duplicated code
between dartdev and compile_benchmark simplifying those two files a lot.
It will also allow us to more easily invoke wasm-opt within our internal
build pipeline.

For compile_benchmark we still run the opt phase independently (but
through dart2wasm) to keep the benchmark data as consistent as possible.

Change-Id: Iaa855dbc3a05abfedbc3eea4af32e3ba27e84600
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/464640
Commit-Queue: Nate Biggs <natebiggs@google.com>
Reviewed-by: Martin Kustermann <kustermann@google.com>
---
 .../benchmark/self_compile_benchmark.dart     |  57 +++-
 pkg/dart2wasm/lib/compile.dart                | 261 +++++++++++-------
 pkg/dart2wasm/lib/compiler_options.dart       |  36 ++-
 pkg/dart2wasm/lib/dart2wasm.dart              |  16 +-
 .../lib/dynamic_module_kernel_metadata.dart   |  27 +-
 pkg/dart2wasm/lib/generate_wasm.dart          |  55 +---
 pkg/dart2wasm/lib/io_util.dart                | 184 ++++++++++++
 pkg/dart2wasm/lib/modules.dart                |  16 +-
 pkg/dart2wasm/lib/option.dart                 |  12 +-
 pkg/dart2wasm/lib/translator.dart             |  35 ++-
 pkg/dart2wasm/test/phases/phases_test.dart    |  96 +++++--
 pkg/dart2wasm/test/util.dart                  |   3 +
 pkg/dart2wasm/tool/compile_benchmark          | 106 +------
 pkg/dartdev/lib/src/commands/compile.dart     | 244 ++--------------
 14 files changed, 606 insertions(+), 542 deletions(-)
 create mode 100644 pkg/dart2wasm/lib/io_util.dart

diff --git a/pkg/dart2wasm/benchmark/self_compile_benchmark.dart b/pkg/dart2wasm/benchmark/self_compile_benchmark.dart
index 7b37b69fb8b..c56ef60bc18 100644
--- a/pkg/dart2wasm/benchmark/self_compile_benchmark.dart
+++ b/pkg/dart2wasm/benchmark/self_compile_benchmark.dart
@@ -2,41 +2,70 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
+import 'dart:typed_data';
+
 import 'package:_fe_analyzer_shared/src/util/colors.dart' as colors;
 import 'package:dart2wasm/compile.dart';
 import 'package:dart2wasm/compiler_options.dart';
+import 'package:dart2wasm/io_util.dart';
 
 import 'filesystem_io.dart' if (dart.library.js_interop) 'filesystem_js.dart';
 
+class _BenchmarkIOManager extends CompilerPhaseInputOutputManager {
+  final WasmCompilerFileSystem benchmarkFileSystem;
+  Uint8List? moduleBytes;
+
+  _BenchmarkIOManager(this.benchmarkFileSystem, WasmCompilerOptions options)
+      : super(benchmarkFileSystem, options);
+
+  @override
+  Future<void> writeWasmModule(Uint8List wasmModule, String moduleName) async {
+    moduleBytes = wasmModule;
+  }
+
+  @override
+  Future<void> writeWasmSourceMap(String sourceMap, String moduleName) async {}
+
+  @override
+  Future<void> writeJsRuntime(String jsRuntime) async {}
+
+  @override
+  Future<void> writeSupportJs(String supportJs) async {}
+
+  void flushWasmModules(String wasmFile) {
+    benchmarkFileSystem.writeBytesSync(wasmFile, moduleBytes!);
+  }
+}
+
 Future main(List<String> args) async {
   final sw = Stopwatch()..start();
   final fileSystem = WasmCompilerFileSystem();
-  final result = await compileBenchmark(
-      fileSystem, 'pkg/dart2wasm/benchmark/self_compile_benchmark.dart');
+  final mainFile = 'pkg/dart2wasm/benchmark/self_compile_benchmark.dart';
+  final main = Uri.file('${fileSystem.sdkRoot}/$mainFile');
+
+  final options = WasmCompilerOptions(mainUri: main, outputFile: 'out.wasm');
+  final ioManager = _BenchmarkIOManager(fileSystem, options);
+
+  options.librariesSpecPath =
+      Uri.file('${fileSystem.sdkRoot}/sdk/lib/libraries.json');
+
+  await compileBenchmark(options, ioManager);
   print('Dart2WasmSelfCompile(RunTimeRaw): ${sw.elapsed.inMilliseconds} ms.');
 
   if (args.isNotEmpty) {
-    final module = result.wasmModules.values.single;
     final wasmFile = args.single;
-    fileSystem.writeBytesSync(wasmFile, module.moduleBytes);
+    ioManager.flushWasmModules(wasmFile);
   }
 }
 
-Future<CodegenResult> compileBenchmark(
-    WasmCompilerFileSystem fileSystem, String mainFile) async {
+Future<CodegenResult> compileBenchmark(WasmCompilerOptions options,
+    CompilerPhaseInputOutputManager ioManager) async {
   // Avoid CFE self-detecting whether `stdout`/`stderr` is terminal and supports
   // colors (as we don't have `dart:io` available when we run dart2wasm in a
   // wasm runtime).
   colors.enableColors = false;
 
-  final main = Uri.file('${fileSystem.sdkRoot}/$mainFile');
-
-  final options = WasmCompilerOptions(mainUri: main, outputFile: 'out.wasm');
-  options.librariesSpecPath =
-      Uri.file('${fileSystem.sdkRoot}/sdk/lib/libraries.json');
-
-  final result = await compile(
-      options, fileSystem, (mod) => Uri.parse('$mod.maps'), (diag) {
+  final result = await compile(options, ioManager, (diag) {
     print('Diagnostics: ${diag.severity} ${diag.plainTextFormatted}');
   });
   if (result is! CompilationSuccess) {
diff --git a/pkg/dart2wasm/lib/compile.dart b/pkg/dart2wasm/lib/compile.dart
index c9ec7426bc8..a76fa34ad18 100644
--- a/pkg/dart2wasm/lib/compile.dart
+++ b/pkg/dart2wasm/lib/compile.dart
@@ -2,11 +2,6 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'dart:io' show File;
-import 'dart:typed_data';
-
-import 'package:build_integration/file_system/multi_root.dart'
-    show MultiRootFileSystem, MultiRootFileSystemEntity;
 import 'package:front_end/src/api_prototype/dynamic_module_validator.dart'
     show DynamicInterfaceYamlFile;
 import 'package:front_end/src/api_prototype/file_system.dart' show FileSystem;
@@ -18,14 +13,9 @@ import 'package:front_end/src/api_unstable/vm.dart'
         kernelForProgram,
         CfeSeverity;
 import 'package:kernel/ast.dart';
-import 'package:kernel/binary/ast_from_binary.dart'
-    show BinaryBuilderWithMetadata;
 import 'package:kernel/class_hierarchy.dart';
 import 'package:kernel/core_types.dart';
-import 'package:kernel/kernel.dart'
-    show writeComponentToText, loadComponentFromBytes;
 import 'package:kernel/library_index.dart';
-import 'package:kernel/text/ast_to_text.dart';
 import 'package:kernel/type_environment.dart';
 import 'package:kernel/verifier.dart';
 import 'package:vm/kernel_front_end.dart' show writeDepfile;
@@ -46,6 +36,7 @@ import 'deferred_loading.dart';
 import 'dry_run.dart';
 import 'dynamic_module_kernel_metadata.dart';
 import 'dynamic_modules.dart';
+import 'io_util.dart';
 import 'js/method_collector.dart' show JSMethods;
 import 'js/runtime_generator.dart' as js;
 import 'modules.dart';
@@ -93,11 +84,17 @@ class TfaResult extends CompilationSuccess {
 }
 
 class CodegenResult extends CompilationSuccess {
-  final Map<String, ({Uint8List moduleBytes, String? sourceMap})> wasmModules;
-  final String jsRuntime;
-  final String supportJs;
+  final String mainWasmFile;
+  final int numModules;
 
-  CodegenResult(this.wasmModules, this.jsRuntime, this.supportJs);
+  CodegenResult(this.mainWasmFile, this.numModules);
+}
+
+class OptResult extends CompilationSuccess {
+  final String mainWasmFile;
+  final int numModules;
+
+  OptResult(this.mainWasmFile, this.numModules);
 }
 
 abstract class CompilationError extends CompilationResult {}
@@ -148,6 +145,43 @@ const List<String> _librariesToIndex = [
   "dart:typed_data",
 ];
 
+const List<String> _binaryenFlags = [
+  '--enable-gc',
+  '--enable-reference-types',
+  '--enable-multivalue',
+  '--enable-exception-handling',
+  '--enable-nontrapping-float-to-int',
+  '--enable-sign-ext',
+  '--enable-bulk-memory',
+  '--enable-threads',
+  '--no-inline=*<noInline>*',
+  '--closed-world',
+  '--traps-never-happen',
+  '--type-unfinalizing',
+  '-Os',
+  '--type-ssa',
+  '--gufa',
+  '-Os',
+  '--type-merging',
+  '-Os',
+  '--type-finalizing',
+  '--minimize-rec-groups',
+];
+
+const List<String> _binaryenFlagsMultiModule = [
+  '--enable-gc',
+  '--enable-reference-types',
+  '--enable-multivalue',
+  '--enable-exception-handling',
+  '--enable-nontrapping-float-to-int',
+  '--enable-sign-ext',
+  '--enable-bulk-memory',
+  '--enable-threads',
+  '--no-inline=*<noInline>*',
+  '--traps-never-happen',
+  '-Os',
+];
+
 /// Compile a Dart file into a Wasm module.
 ///
 /// Returns `null` if an error occurred during compilation. The
@@ -161,8 +195,7 @@ const List<String> _librariesToIndex = [
 /// mappings.
 Future<CompilationResult> compile(
     compiler.WasmCompilerOptions options,
-    FileSystem fileSystem,
-    Uri Function(String moduleName)? sourceMapUrlGenerator,
+    CompilerPhaseInputOutputManager ioManager,
     void Function(CfeDiagnosticMessage) handleDiagnosticMessage) async {
   final wasm.Mode mode;
   if (options.translatorOptions.jsCompatibility) {
@@ -177,15 +210,9 @@ Future<CompilationResult> compile(
       removeAsserts: !options.translatorOptions.enableAsserts,
       mode: mode);
 
-  if (options.multiRootScheme != null) {
-    fileSystem = MultiRootFileSystem(
-        options.multiRootScheme!,
-        options.multiRoots.isEmpty ? [Uri.base] : options.multiRoots,
-        fileSystem);
-  }
-
   CfeResult? cfeResult;
   TfaResult? tfaResult;
+  CodegenResult? codegenResult;
   CompilationResult? lastResult;
 
   for (final phase in options.phases) {
@@ -194,7 +221,8 @@ Future<CompilationResult> compile(
         lastResult = await _runCfePhase(
           options,
           target,
-          fileSystem,
+          ioManager.fileSystem,
+          ioManager,
           handleDiagnosticMessage,
         );
         if (lastResult is! CfeResult) return lastResult;
@@ -202,31 +230,40 @@ Future<CompilationResult> compile(
 
       case compiler.CompilerPhase.tfa:
         lastResult = await _runTfaPhase(
-          cfeResult ?? await _loadCfeResult(options, fileSystem),
+          cfeResult ?? await _loadCfeResult(options, ioManager),
           options,
           target,
-          fileSystem,
+          ioManager,
         );
         if (lastResult is! TfaResult) return lastResult;
         tfaResult = lastResult;
 
       case compiler.CompilerPhase.codegen:
         lastResult = await _runCodegenPhase(
-            tfaResult ?? await _loadTfaResult(options, target, fileSystem),
+            tfaResult ?? await _loadTfaResult(options, target, ioManager),
             options,
-            fileSystem,
-            sourceMapUrlGenerator);
+            ioManager);
+
+        if (lastResult is! CodegenResult) return lastResult;
+        codegenResult = lastResult;
+
+      case compiler.CompilerPhase.opt:
+        lastResult = await _runOptPhase(
+            codegenResult ?? await _loadCodegenResult(options, ioManager),
+            options,
+            ioManager);
+
+        if (lastResult is! OptResult) return lastResult;
     }
   }
 
   return lastResult!;
 }
 
-Future<CfeResult> _loadCfeResult(
-    compiler.WasmCompilerOptions options, FileSystem fileSystem) async {
-  final component = loadComponentFromBytes(
-      await File.fromUri((await _resolveUri(fileSystem, options.mainUri))!)
-          .readAsBytes());
+Future<CfeResult> _loadCfeResult(compiler.WasmCompilerOptions options,
+    CompilerPhaseInputOutputManager ioManager) async {
+  final component = Component();
+  await ioManager.readComponent(options.mainUri, component);
   final coreTypes = CoreTypes(component);
   return CfeResult(component, coreTypes);
 }
@@ -235,6 +272,7 @@ Future<CompilationResult> _runCfePhase(
     compiler.WasmCompilerOptions options,
     WasmTarget target,
     FileSystem fileSystem,
+    CompilerPhaseInputOutputManager ioManager,
     void Function(CfeDiagnosticMessage) handleDiagnosticMessage) async {
   var hadCompileTimeError = false;
   void diagnosticMessageHandler(CfeDiagnosticMessage message) {
@@ -276,10 +314,7 @@ Future<CompilationResult> _runCfePhase(
   if (isDynamicMainModule) {
     final dynamicInterfaceUri = options.dynamicInterfaceUri;
     if (dynamicInterfaceUri != null) {
-      final resolvedDynamicInterfaceUri =
-          await _resolveUri(fileSystem, dynamicInterfaceUri);
-      final contents =
-          File.fromUri(resolvedDynamicInterfaceUri!).readAsStringSync();
+      final contents = await ioManager.readString(dynamicInterfaceUri);
       final dynamicInterfaceYamlFile = DynamicInterfaceYamlFile(contents);
       additionalSources = dynamicInterfaceYamlFile
           .getUserLibraryUris(dynamicInterfaceUri)
@@ -288,7 +323,7 @@ Future<CompilationResult> _runCfePhase(
   }
 
   final dynamicMainModuleUri =
-      await _resolveUri(fileSystem, options.dynamicMainModuleUri);
+      await ioManager.resolveUri(options.dynamicMainModuleUri);
   final isDynamicSubmodule =
       options.dynamicModuleType == DynamicModuleType.submodule;
   if (isDynamicSubmodule) {
@@ -324,35 +359,43 @@ Future<CompilationResult> _runCfePhase(
   final component = compilerResult!.component!;
 
   if (options.dumpKernelAfterCfe != null) {
-    writeComponentToText(component,
-        path: options.dumpKernelAfterCfe!, showMetadata: true);
+    ioManager.writeComponentAsText(component, options.dumpKernelAfterCfe!);
+  }
+
+  if (options.emitCfe) {
+    await ioManager.writeComponent(component, options.outputFile);
   }
 
   return CfeResult(component, compilerResult.coreTypes!);
 }
 
 Future<TfaResult> _loadTfaResult(compiler.WasmCompilerOptions options,
-    WasmTarget target, FileSystem fileSystem) async {
+    WasmTarget target, CompilerPhaseInputOutputManager ioManager) async {
   final component = createEmptyComponent();
   final recordClassesRepository = _RecordClassesRepository();
   final interopMethodsRepository = _InteropMethodsRepository();
   component.addMetadataRepository(recordClassesRepository);
   component.addMetadataRepository(interopMethodsRepository);
 
-  BinaryBuilderWithMetadata(
-          await File.fromUri((await _resolveUri(fileSystem, options.mainUri))!)
-              .readAsBytes())
-      .readComponent(component);
+  await ioManager.readComponent(options.mainUri, component);
+
   final coreTypes = CoreTypes(component);
   final libraryIndex = LibraryIndex(component, _librariesToIndex);
   final classHierarchy = ClassHierarchy(component, coreTypes);
   final dynamicMainModuleUri =
-      await _resolveUri(fileSystem, options.dynamicMainModuleUri);
+      await ioManager.resolveUri(options.dynamicMainModuleUri);
   final dynamicInterfaceUri =
-      await _resolveUri(fileSystem, options.dynamicInterfaceUri);
+      await ioManager.resolveUri(options.dynamicInterfaceUri);
 
-  final moduleStrategy = _createModuleStrategy(options, component, coreTypes,
-      target, classHierarchy, dynamicMainModuleUri, dynamicInterfaceUri);
+  final moduleStrategy = await _createModuleStrategy(
+      options,
+      ioManager,
+      component,
+      coreTypes,
+      target,
+      classHierarchy,
+      dynamicMainModuleUri,
+      dynamicInterfaceUri);
 
   final recordClasses = <RecordShape, Class>{};
   recordClassesRepository.mapping.forEach((cls, shape) {
@@ -368,7 +411,7 @@ Future<TfaResult> _loadTfaResult(compiler.WasmCompilerOptions options,
 
   if (isDynamicSubmodule) {
     mainModuleMetadata =
-        await deserializeMainModuleMetadata(component, options);
+        await deserializeMainModuleMetadata(component, ioManager);
     mainModuleMetadata.verifyDynamicSubmoduleOptions(options);
   } else if (isDynamicMainModule) {
     MainModuleMetadata.verifyMainModuleOptions(options);
@@ -382,7 +425,7 @@ Future<CompilationResult> _runTfaPhase(
     CfeResult cfeResult,
     compiler.WasmCompilerOptions options,
     WasmTarget target,
-    FileSystem fileSystem) async {
+    CompilerPhaseInputOutputManager ioManager) async {
   var CfeResult(:component, :coreTypes) = cfeResult;
 
   ClosedWorldClassHierarchy classHierarchy =
@@ -400,9 +443,9 @@ Future<CompilationResult> _runTfaPhase(
       classHierarchy);
 
   final dynamicMainModuleUri =
-      await _resolveUri(fileSystem, options.dynamicMainModuleUri);
+      await ioManager.resolveUri(options.dynamicMainModuleUri);
   final dynamicInterfaceUri =
-      await _resolveUri(fileSystem, options.dynamicInterfaceUri);
+      await ioManager.resolveUri(options.dynamicInterfaceUri);
   final isDynamicMainModule =
       options.dynamicModuleType == DynamicModuleType.main;
   final isDynamicSubmodule =
@@ -435,12 +478,18 @@ Future<CompilationResult> _runTfaPhase(
   target.recordClasses = recordClasses;
 
   if (options.dumpKernelBeforeTfa != null) {
-    writeComponentToText(component,
-        path: options.dumpKernelBeforeTfa!, showMetadata: true);
+    ioManager.writeComponentAsText(component, options.dumpKernelBeforeTfa!);
   }
 
-  final moduleStrategy = _createModuleStrategy(options, component, coreTypes,
-      target, classHierarchy, dynamicMainModuleUri, dynamicInterfaceUri);
+  final moduleStrategy = await _createModuleStrategy(
+      options,
+      ioManager,
+      component,
+      coreTypes,
+      target,
+      classHierarchy,
+      dynamicMainModuleUri,
+      dynamicInterfaceUri);
 
   // Ensure we annotate AST nodes as entry points prior to other transformations
   // looking at pragmas (such as mixin_deduplication and TFA).
@@ -469,11 +518,12 @@ Future<CompilationResult> _runTfaPhase(
 
   if (isDynamicSubmodule) {
     mainModuleMetadata =
-        await deserializeMainModuleMetadata(component, options);
+        await deserializeMainModuleMetadata(component, ioManager);
     mainModuleMetadata.verifyDynamicSubmoduleOptions(options);
   } else if (isDynamicMainModule) {
     MainModuleMetadata.verifyMainModuleOptions(options);
-    await serializeMainModuleComponent(component, dynamicMainModuleUri!,
+    await serializeMainModuleComponent(
+        ioManager, component, dynamicMainModuleUri!,
         optimized: false);
   }
 
@@ -498,7 +548,7 @@ Future<CompilationResult> _runTfaPhase(
     libraryIndex = LibraryIndex(component, _librariesToIndex);
   }
 
-  if (options.phases.last == compiler.CompilerPhase.tfa) {
+  if (options.emitTfa) {
     // Store metadata needed for codegen so that it can be serialized.
     final recordClassesRepo = _RecordClassesRepository();
     recordClasses.forEach((shape, cls) {
@@ -520,19 +570,27 @@ Future<CompilationResult> _runTfaPhase(
   }());
 
   if (options.dumpKernelAfterTfa != null) {
-    writeComponentToText(component,
-        path: options.dumpKernelAfterTfa!, showMetadata: true);
+    ioManager.writeComponentAsText(component, options.dumpKernelAfterTfa!);
+  }
+
+  if (options.emitTfa) {
+    await ioManager.writeComponent(component, options.outputFile);
   }
 
   return TfaResult(component, coreTypes, libraryIndex, moduleStrategy,
       mainModuleMetadata, jsInteropMethods, recordClasses);
 }
 
+Future<CodegenResult> _loadCodegenResult(compiler.WasmCompilerOptions options,
+    CompilerPhaseInputOutputManager ioManager) async {
+  return CodegenResult(options.mainUri.toFilePath(),
+      await ioManager.getModuleCount(options.mainUri));
+}
+
 Future<CompilationResult> _runCodegenPhase(
     TfaResult tfaSuccess,
     compiler.WasmCompilerOptions options,
-    FileSystem fileSystem,
-    Uri Function(String moduleName)? sourceMapUrlGenerator) async {
+    CompilerPhaseInputOutputManager ioManager) async {
   final TfaResult(
     :component,
     :coreTypes,
@@ -558,29 +616,32 @@ Future<CompilationResult> _runCodegenPhase(
 
   String? depFile = options.depFile;
   if (depFile != null) {
-    writeDepfile(
-        fileSystem, component.uriToSource.keys, options.outputFile, depFile);
+    writeDepfile(ioManager.fileSystem, component.uriToSource.keys,
+        options.outputFile, depFile);
   }
 
   final generateSourceMaps = options.translatorOptions.generateSourceMaps;
-  final modules = translator.translate(sourceMapUrlGenerator);
-  final wasmModules = <String, ({Uint8List moduleBytes, String? sourceMap})>{};
+  final modules = translator.translate(ioManager.sourceMapUrlGenerator);
+  final writeFutures = <Future<void>>[];
   modules.forEach((moduleOutput, module) {
     if (moduleOutput.skipEmit) return;
     final serializer = Serializer();
     module.serialize(serializer);
-    final wasmModuleSerialized = serializer.data;
+    writeFutures.add(
+        ioManager.writeWasmModule(serializer.data, moduleOutput.moduleName));
 
-    final sourceMap =
-        generateSourceMaps ? serializer.sourceMapSerializer.serialize() : null;
-    wasmModules[moduleOutput.moduleName] =
-        (moduleBytes: wasmModuleSerialized, sourceMap: sourceMap);
+    if (generateSourceMaps) {
+      final sourceMap = serializer.sourceMapSerializer.serialize();
+      writeFutures.add(
+          ioManager.writeWasmSourceMap(sourceMap, moduleOutput.moduleName));
+    }
   });
+  await Future.wait(writeFutures);
 
   final jsRuntimeFinalizer = js.RuntimeFinalizer(jsInteropMethods);
 
   final dynamicMainModuleUri =
-      await _resolveUri(fileSystem, options.dynamicMainModuleUri);
+      await ioManager.resolveUri(options.dynamicMainModuleUri);
   final isDynamicMainModule =
       options.dynamicModuleType == DynamicModuleType.main;
   final isDynamicSubmodule =
@@ -602,8 +663,9 @@ Future<CompilationResult> _runCodegenPhase(
 
   final supportJs = _generateSupportJs(options.translatorOptions);
   if (isDynamicMainModule) {
-    await serializeMainModuleMetadata(component, translator, options);
-    await serializeMainModuleComponent(component, dynamicMainModuleUri!,
+    await serializeMainModuleMetadata(component, translator, ioManager);
+    await serializeMainModuleComponent(
+        ioManager, component, dynamicMainModuleUri!,
         optimized: true);
   }
 
@@ -612,17 +674,39 @@ Future<CompilationResult> _runCodegenPhase(
     await writeLoadIdsFile(component, coreTypes, options, loadingMap);
   }
 
-  return CodegenResult(wasmModules, jsRuntime, supportJs);
+  await ioManager.writeJsRuntime(jsRuntime);
+  await ioManager.writeSupportJs(supportJs);
+
+  return CodegenResult(options.outputFile, modules.length);
 }
 
-ModuleStrategy _createModuleStrategy(
+Future<CompilationResult> _runOptPhase(
+    CodegenResult codegenResult,
     compiler.WasmCompilerOptions options,
+    CompilerPhaseInputOutputManager ioManager) async {
+  final futures = <Future<void>>[];
+  final numModules = codegenResult.numModules;
+  for (int i = 0; i < numModules; i++) {
+    futures.add(ioManager.runWasmOpt(
+        codegenResult.mainWasmFile,
+        i,
+        options.useMultiModuleOpt
+            ? _binaryenFlagsMultiModule
+            : _binaryenFlags));
+  }
+  await Future.wait(futures);
+  return OptResult(options.outputFile, numModules);
+}
+
+Future<ModuleStrategy> _createModuleStrategy(
+    compiler.WasmCompilerOptions options,
+    CompilerPhaseInputOutputManager ioManager,
     Component component,
     CoreTypes coreTypes,
     WasmTarget target,
     ClassHierarchy classHierarchy,
     Uri? dynamicMainModuleUri,
-    Uri? dynamicInterfaceUri) {
+    Uri? dynamicInterfaceUri) async {
   final isDynamicMainModule =
       options.dynamicModuleType == DynamicModuleType.main;
   final isDynamicSubmodule =
@@ -637,7 +721,7 @@ ModuleStrategy _createModuleStrategy(
         component,
         coreTypes,
         options,
-        File.fromUri(dynamicInterfaceUri!).readAsStringSync(),
+        await ioManager.readString(dynamicInterfaceUri!),
         options.dynamicInterfaceUri!);
   } else if (isDynamicSubmodule) {
     return DynamicSubmoduleStrategy(
@@ -677,15 +761,6 @@ void _patchMainTearOffs(CoreTypes coreTypes, Component component) {
   if (mainHasType(mainArg0Type)) return patchToReturnMainTearOff(mainTearOff0);
 }
 
-Future<Uri?> _resolveUri(FileSystem fileSystem, Uri? uri) async {
-  if (uri == null) return null;
-  var fileSystemEntity = fileSystem.entityForUri(uri);
-  if (fileSystemEntity is MultiRootFileSystemEntity) {
-    fileSystemEntity = await fileSystemEntity.delegate;
-  }
-  return fileSystemEntity.uri;
-}
-
 class _RecordClassesRepository extends MetadataRepository<RecordShape> {
   static const String _tag = 'dart2wasm.recordClasses';
   @override
@@ -780,9 +855,3 @@ String _generateSupportJs(TranslatorOptions options) {
   ];
   return '(${requiredFeatures.join('&&')})';
 }
-
-String writeComponentToString(Component component) {
-  final buffer = StringBuffer();
-  Printer(buffer).writeComponentFile(component);
-  return '$buffer';
-}
diff --git a/pkg/dart2wasm/lib/compiler_options.dart b/pkg/dart2wasm/lib/compiler_options.dart
index dcb81c77529..bd03cd66805 100644
--- a/pkg/dart2wasm/lib/compiler_options.dart
+++ b/pkg/dart2wasm/lib/compiler_options.dart
@@ -20,7 +20,8 @@ import 'translator.dart';
 enum CompilerPhase {
   cfe,
   tfa,
-  codegen;
+  codegen,
+  opt;
 
   static CompilerPhase parse(String name) {
     for (final phase in values) {
@@ -31,6 +32,7 @@ enum CompilerPhase {
 }
 
 class WasmCompilerOptions {
+  static const int mainModuleId = 0;
   final TranslatorOptions translatorOptions = TranslatorOptions();
 
   Uri? platformPath;
@@ -54,6 +56,9 @@ class WasmCompilerOptions {
   String? dumpKernelBeforeTfa;
   String? dumpKernelAfterTfa;
   bool dryRun = false;
+  Uri? wasmOptPath;
+  bool saveUnopt = false;
+  bool stripWasm = true;
   List<CompilerPhase> phases = const [
     CompilerPhase.cfe,
     CompilerPhase.tfa,
@@ -67,6 +72,21 @@ class WasmCompilerOptions {
 
   bool get enableDynamicModules => dynamicModuleType != null;
 
+  bool get useMultiModuleOpt =>
+      translatorOptions.enableDeferredLoading ||
+      translatorOptions.enableMultiModuleStressTestMode ||
+      enableDynamicModules;
+
+  String moduleNameForId(String filePath, int id, {bool emitAsMain = false}) =>
+      emitAsMain || id == mainModuleId
+          ? path.basename(filePath)
+          : path.basename(path.setExtension(filePath, '_module$id.wasm'));
+
+  bool get emitCfe => phases.last == CompilerPhase.cfe;
+  bool get emitTfa => phases.last == CompilerPhase.tfa;
+  bool get emitCodegen => phases.last == CompilerPhase.tfa;
+  bool get readCodegen => phases.first == CompilerPhase.codegen;
+
   void validate() {
     if (translatorOptions.importSharedMemory &&
         translatorOptions.sharedMemoryMaxPages == null) {
@@ -125,6 +145,10 @@ class WasmCompilerOptions {
         if (inputExtension != '.dill') {
           throw ArgumentError('Input to codegen phase must be a .dill file.');
         }
+      case CompilerPhase.opt:
+        if (inputExtension != '.wasm') {
+          throw ArgumentError('Input to opt phase must be a .wasm file.');
+        }
     }
 
     // Ensure correct output file type
@@ -143,6 +167,16 @@ class WasmCompilerOptions {
           throw ArgumentError(
               'Output from codegen phase must be a .wasm file.');
         }
+      case CompilerPhase.opt:
+        if (outputExtension != '.wasm') {
+          throw ArgumentError('Output from opt phase must be a .wasm file.');
+        }
+    }
+
+    if (phases.contains(CompilerPhase.opt) &&
+        translatorOptions.optimizationLevel == 0) {
+      throw ArgumentError(
+          'Cannot specify "opt" phase with optimization level 0');
     }
   }
 }
diff --git a/pkg/dart2wasm/lib/dart2wasm.dart b/pkg/dart2wasm/lib/dart2wasm.dart
index ce1ee02cff5..56875d89dbc 100644
--- a/pkg/dart2wasm/lib/dart2wasm.dart
+++ b/pkg/dart2wasm/lib/dart2wasm.dart
@@ -19,13 +19,14 @@ final WasmCompilerOptions _d = WasmCompilerOptions.defaultOptions();
 
 final List<Option> options = [
   Flag("help", (o, _) {}, abbr: "h", negatable: false, defaultsTo: false),
+  IntOption("optimization-level",
+      (o, value) => o.translatorOptions.optimizationLevel = value,
+      abbr: "O"),
   Flag("import-shared-memory",
       (o, value) => o.translatorOptions.importSharedMemory = value,
       defaultsTo: _d.translatorOptions.importSharedMemory),
-  Flag("inlining", (o, value) => o.translatorOptions.inlining = value,
-      defaultsTo: _d.translatorOptions.inlining),
-  Flag("minify", (o, value) => o.translatorOptions.minify = value,
-      defaultsTo: _d.translatorOptions.minify),
+  Flag("inlining", (o, value) => o.translatorOptions.inliningOverride = value),
+  Flag("minify", (o, value) => o.translatorOptions.minifyOverride = value),
   Flag("dry-run", (o, value) => o.dryRun = value, defaultsTo: _d.dryRun),
   StringMultiOption(
       "phases",
@@ -49,10 +50,10 @@ final List<Option> options = [
       (o, value) => o.translatorOptions.omitExplicitTypeChecks = value,
       defaultsTo: _d.translatorOptions.omitExplicitTypeChecks),
   Flag("omit-implicit-checks",
-      (o, value) => o.translatorOptions.omitImplicitTypeChecks = value,
+      (o, value) => o.translatorOptions.omitImplicitTypeChecksOverride = value,
       defaultsTo: _d.translatorOptions.omitImplicitTypeChecks),
   Flag("omit-bounds-checks", (o, value) {
-    o.translatorOptions.omitBoundsChecks = value;
+    o.translatorOptions.omitBoundsChecksOverride = value;
   }, defaultsTo: _d.translatorOptions.omitBoundsChecks),
   Flag("verbose", (o, value) => o.translatorOptions.verbose = value,
       defaultsTo: _d.translatorOptions.verbose),
@@ -141,6 +142,9 @@ final List<Option> options = [
   Flag("validate-dynamic-modules",
       (o, value) => o.validateDynamicModules = value,
       defaultsTo: true, negatable: true),
+  UriOption("wasm-opt", (o, value) => o.wasmOptPath = value),
+  Flag("save-unopt", (o, value) => o.saveUnopt = value),
+  Flag("strip-wasm", (o, value) => o.stripWasm = value, negatable: true),
 ];
 
 Map<fe.ExperimentalFlag, bool> processFeExperimentalFlags(
diff --git a/pkg/dart2wasm/lib/dynamic_module_kernel_metadata.dart b/pkg/dart2wasm/lib/dynamic_module_kernel_metadata.dart
index e92ce58f86d..81e2c07dc70 100644
--- a/pkg/dart2wasm/lib/dynamic_module_kernel_metadata.dart
+++ b/pkg/dart2wasm/lib/dynamic_module_kernel_metadata.dart
@@ -9,15 +9,14 @@ import 'package:kernel/ast.dart';
 import 'package:kernel/binary/ast_from_binary.dart'
     show BinaryBuilderWithMetadata;
 import 'package:kernel/core_types.dart';
-import 'package:kernel/kernel.dart'
-    show writeComponentToBinary, writeComponentToBytes;
+import 'package:kernel/kernel.dart' show writeComponentToBytes;
 import 'package:kernel/library_index.dart';
-import 'package:path/path.dart' as path;
 
 import 'class_info.dart';
 import 'compiler_options.dart';
 import 'dispatch_table.dart';
 import 'dynamic_modules.dart';
+import 'io_util.dart';
 import 'js/method_collector.dart' show JSMethods;
 import 'serialization.dart';
 import 'translator.dart';
@@ -460,11 +459,13 @@ String _makeOptDillPath(String path) =>
     '${path.substring(0, path.length - '.dill'.length)}.opt.dill';
 
 Future<void> serializeMainModuleComponent(
-    Component component, Uri dynamicModuleMainUri,
+    CompilerPhaseInputOutputManager ioManager,
+    Component component,
+    Uri dynamicModuleMainUri,
     {required bool optimized}) async {
   // TODO(natebiggs): Serialize as a summary and filter to only necessary
   // libraries.
-  await writeComponentToBinary(
+  await ioManager.writeComponent(
       component,
       optimized
           ? _makeOptDillPath(dynamicModuleMainUri.path)
@@ -505,21 +506,15 @@ Future<(Component, JSMethods)> generateDynamicSubmoduleComponent(
 }
 
 Future<MainModuleMetadata> deserializeMainModuleMetadata(
-    Component component, WasmCompilerOptions options) async {
-  final filename = options.dynamicModuleMetadataFile ??
-      Uri.parse(path.setExtension(
-          options.dynamicMainModuleUri!.toFilePath(), '.dyndata'));
-  final dynamicModuleMetadataBytes = await File.fromUri(filename).readAsBytes();
-  final source = DataDeserializer(dynamicModuleMetadataBytes, component);
+    Component component, CompilerPhaseInputOutputManager ioManager) async {
+  final source = DataDeserializer(
+      await ioManager.readMainDynModuleMetadataBytes(), component);
   return MainModuleMetadata.deserialize(source);
 }
 
 Future<void> serializeMainModuleMetadata(Component component,
-    Translator translator, WasmCompilerOptions options) async {
-  final filename = options.dynamicModuleMetadataFile ??
-      Uri.parse(path.setExtension(
-          options.dynamicMainModuleUri!.toFilePath(), '.dyndata'));
+    Translator translator, CompilerPhaseInputOutputManager ioManager) async {
   final serializer = DataSerializer(component);
   translator.dynamicModuleInfo!.metadata.serialize(serializer, translator);
-  await File.fromUri(filename).writeAsBytes(serializer.takeBytes());
+  await ioManager.writeMainDynModuleMetadataBytes(serializer.takeBytes());
 }
diff --git a/pkg/dart2wasm/lib/generate_wasm.dart b/pkg/dart2wasm/lib/generate_wasm.dart
index eecea4532a9..d08ceef2917 100644
--- a/pkg/dart2wasm/lib/generate_wasm.dart
+++ b/pkg/dart2wasm/lib/generate_wasm.dart
@@ -2,16 +2,13 @@
 // for details. All rights reserved. Use of this source code is governed by a
 // BSD-style license that can be found in the LICENSE file.
 
-import 'dart:io';
-
 import 'package:front_end/src/api_prototype/standard_file_system.dart'
     show StandardFileSystem;
 import 'package:front_end/src/api_unstable/vm.dart' show printDiagnosticMessage;
-import 'package:kernel/kernel.dart';
-import 'package:path/path.dart' as path;
 
 import 'compile.dart';
 import 'compiler_options.dart';
+import 'io_util.dart';
 
 export 'package:dart2wasm/compiler_options.dart';
 
@@ -61,25 +58,9 @@ Future<int> generateWasm(WasmCompilerOptions options,
         '  - watch points = [${translatorOptions.watchPoints.map((p) => p.toString()).join(',')}]');
   }
 
-  String moduleNameToWasmOutputFile(String moduleName) {
-    return path.join(path.dirname(options.outputFile), moduleName);
-  }
-
-  String moduleNameToSourceMapFile(String moduleName) {
-    return '${moduleNameToWasmOutputFile(moduleName)}.map';
-  }
-
-  Uri moduleNameToRelativeSourceMapUri(String moduleName) {
-    return Uri.file(path.basename(moduleNameToSourceMapFile(moduleName)));
-  }
-
-  final relativeSourceMapUrlMapper = translatorOptions.generateSourceMaps
-      ? moduleNameToRelativeSourceMapUri
-      : null;
-
+  final fileSystem = StandardFileSystem.instance;
   CompilationResult result = await compile(
-      options, StandardFileSystem.instance, relativeSourceMapUrlMapper,
-      (message) {
+      options, CompilerPhaseInputOutputManager(fileSystem, options), (message) {
     if (!options.dryRun) printDiagnosticMessage(message, errorPrinter);
   });
 
@@ -109,35 +90,5 @@ Future<int> generateWasm(WasmCompilerOptions options,
     return 255;
   }
 
-  switch (result) {
-    case CfeResult(:final component):
-      await File(options.outputFile)
-          .writeAsBytes(writeComponentToBytes(component));
-    case TfaResult(:final component):
-      await File(options.outputFile)
-          .writeAsBytes(writeComponentToBytes(component));
-    case CodegenResult(:final wasmModules, :final jsRuntime, :final supportJs):
-      final writeFutures = <Future>[];
-      wasmModules.forEach((moduleName, moduleInfo) {
-        final (:moduleBytes, :sourceMap) = moduleInfo;
-        final File outFile = File(moduleNameToWasmOutputFile(moduleName));
-        outFile.parent.createSync(recursive: true);
-        writeFutures.add(outFile.writeAsBytes(moduleBytes));
-
-        if (sourceMap != null) {
-          writeFutures.add(File(moduleNameToSourceMapFile(moduleName))
-              .writeAsString(sourceMap));
-        }
-      });
-      await Future.wait(writeFutures);
-
-      final jsFile = path.setExtension(options.outputFile, '.mjs');
-      await File(jsFile).writeAsString(jsRuntime);
-
-      final supportJsFile =
-          path.setExtension(options.outputFile, '.support.js');
-      await File(supportJsFile).writeAsString(supportJs);
-  }
-
   return 0;
 }
diff --git a/pkg/dart2wasm/lib/io_util.dart b/pkg/dart2wasm/lib/io_util.dart
new file mode 100644
index 00000000000..7711314376a
--- /dev/null
+++ b/pkg/dart2wasm/lib/io_util.dart
@@ -0,0 +1,184 @@
+// Copyright (c) 2025, the Dart project authors.  Please see the AUTHORS file
+// for details. All rights reserved. Use of this source code is governed by a
+// BSD-style license that can be found in the LICENSE file.
+
+import 'dart:io' show File, Directory, Process, ProcessResult;
+import 'dart:typed_data';
+
+import 'package:build_integration/file_system/multi_root.dart'
+    show MultiRootFileSystemEntity, MultiRootFileSystem;
+import 'package:front_end/src/api_prototype/file_system.dart' show FileSystem;
+import 'package:kernel/ast.dart' show Component;
+import 'package:kernel/binary/ast_from_binary.dart'
+    show BinaryBuilderWithMetadata;
+import 'package:kernel/kernel.dart'
+    show writeComponentToBinary, writeComponentToText;
+import 'package:path/path.dart' as path;
+
+import 'compiler_options.dart';
+
+class CompilerPhaseInputOutputManager {
+  final FileSystem fileSystem;
+  final WasmCompilerOptions options;
+
+  CompilerPhaseInputOutputManager(FileSystem fileSystem, this.options)
+      : fileSystem = options.multiRootScheme != null
+            ? MultiRootFileSystem(
+                options.multiRootScheme!,
+                options.multiRoots.isEmpty ? [Uri.base] : options.multiRoots,
+                fileSystem)
+            : fileSystem;
+
+  String _moduleNameToWasmFile(String prefix, String moduleName) {
+    return path.join(path.dirname(prefix), moduleName);
+  }
+
+  String _moduleNameToSourceMapFile(String prefix, String moduleName) {
+    return '${_moduleNameToWasmFile(prefix, moduleName)}.map';
+  }
+
+  Uri _moduleNameToRelativeSourceMapUri(String moduleName) {
+    return Uri.file(path
+        .basename(_moduleNameToSourceMapFile(options.outputFile, moduleName)));
+  }
+
+  Uri Function(String)? get sourceMapUrlGenerator =>
+      options.translatorOptions.generateSourceMaps
+          ? _moduleNameToRelativeSourceMapUri
+          : null;
+
+  Future<String> readString(Uri uri) async {
+    return await File.fromUri((await resolveUri(uri))!).readAsString();
+  }
+
+  Future<List<int>> readBytes(Uri uri) async {
+    return await File.fromUri((await resolveUri(uri))!).readAsBytes();
+  }
+
+  Future<void> readComponent(Uri componentUri, Component component) async {
+    BinaryBuilderWithMetadata(
+            await File.fromUri((await resolveUri(componentUri))!).readAsBytes())
+        .readComponent(component);
+  }
+
+  Future<void> writeComponent(Component component, String path,
+      {bool includeSource = true}) {
+    return writeComponentToBinary(component, path,
+        includeSource: includeSource);
+  }
+
+  void writeComponentAsText(Component component, String path) {
+    writeComponentToText(component, path: path, showMetadata: true);
+  }
+
+  Future<void> writeWasmModule(Uint8List wasmModule, String moduleName) {
+    final wasmFileName = _moduleNameToWasmFile(options.outputFile, moduleName);
+    final Directory dir = Directory(path.dirname(wasmFileName));
+    // Do this synchronously to make sure it happens before subsequent async
+    // operations.
+    if (!dir.existsSync()) {
+      dir.createSync(recursive: true);
+    }
+
+    return File(wasmFileName).writeAsBytes(wasmModule);
+  }
+
+  Future<void> writeWasmSourceMap(String sourceMap, String moduleName) {
+    return File(_moduleNameToSourceMapFile(options.outputFile, moduleName))
+        .writeAsString(sourceMap);
+  }
+
+  Future<void> writeJsRuntime(String jsRuntime) {
+    return File(path.setExtension(options.outputFile, '.mjs'))
+        .writeAsString(jsRuntime);
+  }
+
+  Future<void> writeSupportJs(String supportJs) {
+    return File(path.setExtension(options.outputFile, '.support.js'))
+        .writeAsString(supportJs);
+  }
+
+  Future<void> runWasmOpt(
+      String mainWasmModule, int moduleId, List<String> flags) async {
+    final inputModuleName = options.moduleNameForId(mainWasmModule, moduleId);
+
+    final outputModuleName =
+        options.moduleNameForId(options.outputFile, moduleId);
+    final wasmOutName =
+        _moduleNameToWasmFile(options.outputFile, outputModuleName);
+    final wasmInName = _moduleNameToWasmFile(mainWasmModule, inputModuleName);
+    final args = [
+      ...flags,
+      wasmInName,
+      '-o',
+      wasmOutName,
+      if (options.translatorOptions.generateSourceMaps) ...[
+        '-ism',
+        _moduleNameToSourceMapFile(mainWasmModule, inputModuleName),
+        '-osm',
+        _moduleNameToSourceMapFile(options.outputFile, outputModuleName),
+      ],
+      if (!options.stripWasm) '-g',
+    ];
+    if (options.saveUnopt) {
+      await File(wasmInName)
+          .copy(path.setExtension(wasmOutName, '.unopt.wasm'));
+    }
+    final wasmOptPath = options.wasmOptPath?.toFilePath() ?? 'wasm-opt';
+    final result = await _runProcess(wasmOptPath, args);
+    if (result.exitCode != 0) {
+      throw Exception('wasm-opt failed with exit code ${result.exitCode}:'
+          '\n${result.stdout}\n${result.stderr}');
+    }
+  }
+
+  Future<ProcessResult> _runProcess(
+      String executable, List<String> args) async {
+    return await Process.run(executable, args);
+  }
+
+  Future<int> getModuleCount(Uri mainWasmFile) async {
+    final mainPath = (await resolveUri(mainWasmFile))!.toFilePath();
+    final files = (await Directory(path.dirname(mainPath)).list().toList());
+    final prefix = path.basenameWithoutExtension(mainPath);
+    bool isMultiModule = false;
+    int maxModuleId = 0;
+    for (final file in files) {
+      if (file is! File) continue;
+      final fileBase = path.basename(file.path);
+      if (!fileBase.startsWith(prefix)) continue;
+      if (path.extension(fileBase) != '.wasm') continue;
+      final fileSuffix =
+          path.setExtension(fileBase, '').substring(prefix.length);
+      if (!fileSuffix.startsWith('_module')) continue;
+      isMultiModule = true;
+      final moduleId = int.tryParse(fileSuffix.substring('_module'.length));
+      if (moduleId == null) continue;
+      maxModuleId = moduleId > maxModuleId ? moduleId : maxModuleId;
+    }
+    return isMultiModule ? maxModuleId + 1 : 1;
+  }
+
+  Future<Uint8List> readMainDynModuleMetadataBytes() async {
+    final filename = options.dynamicModuleMetadataFile ??
+        Uri.parse(path.setExtension(
+            options.dynamicMainModuleUri!.toFilePath(), '.dyndata'));
+    return await File.fromUri(filename).readAsBytes();
+  }
+
+  Future<void> writeMainDynModuleMetadataBytes(Uint8List bytes) async {
+    final filename = options.dynamicModuleMetadataFile ??
+        Uri.parse(path.setExtension(
+            options.dynamicMainModuleUri!.toFilePath(), '.dyndata'));
+    await File.fromUri(filename).writeAsBytes(bytes);
+  }
+
+  Future<Uri?> resolveUri(Uri? uri) async {
+    if (uri == null) return null;
+    var fileSystemEntity = fileSystem.entityForUri(uri);
+    if (fileSystemEntity is MultiRootFileSystemEntity) {
+      fileSystemEntity = await fileSystemEntity.delegate;
+    }
+    return fileSystemEntity.uri;
+  }
+}
diff --git a/pkg/dart2wasm/lib/modules.dart b/pkg/dart2wasm/lib/modules.dart
index 083ca6864d5..5ee80a914cd 100644
--- a/pkg/dart2wasm/lib/modules.dart
+++ b/pkg/dart2wasm/lib/modules.dart
@@ -4,14 +4,11 @@
 
 import 'package:kernel/ast.dart';
 import 'package:kernel/core_types.dart';
-import 'package:path/path.dart' as path;
 
 import 'compiler_options.dart';
 import 'target.dart';
 import 'util.dart';
 
-const _mainModuleId = 0;
-
 Library? _enclosingLibraryForReference(Reference reference) {
   TreeNode? current = reference.node;
   // References generated for constants will not have a node attached.
@@ -24,7 +21,7 @@ Library? _enclosingLibraryForReference(Reference reference) {
 }
 
 class ModuleMetadataBuilder {
-  int _counter = _mainModuleId;
+  int _counter = WasmCompilerOptions.mainModuleId;
   final WasmCompilerOptions options;
 
   ModuleMetadataBuilder(this.options);
@@ -34,14 +31,9 @@ class ModuleMetadataBuilder {
     final id = _counter++;
     final moduleImportName =
         options.translatorOptions.minify ? intToMinString(id) : 'module$id';
-    return ModuleMetadata._(
-        moduleImportName,
-        emitAsMain || id == _mainModuleId
-            ? path.basename(options.outputFile)
-            : path.basename(
-                path.setExtension(options.outputFile, '_module$id.wasm')),
-        skipEmit: skipEmit,
-        isMain: id == _mainModuleId);
+    return ModuleMetadata._(moduleImportName,
+        options.moduleNameForId(options.outputFile, id, emitAsMain: emitAsMain),
+        skipEmit: skipEmit, isMain: id == WasmCompilerOptions.mainModuleId);
   }
 }
 
diff --git a/pkg/dart2wasm/lib/option.dart b/pkg/dart2wasm/lib/option.dart
index 89ddb5b4d75..cd9a288d814 100644
--- a/pkg/dart2wasm/lib/option.dart
+++ b/pkg/dart2wasm/lib/option.dart
@@ -44,17 +44,21 @@ class ValueOption<T> extends Option<T> {
       void Function(WasmCompilerOptions o, T v) applyToOptions,
       T Function(dynamic v) converter,
       {String? defaultsTo,
+      String? abbr,
       bool hide = false})
-      : super(name, (a) => a.addOption(name, defaultsTo: defaultsTo),
-            applyToOptions, converter);
+      : super(
+            name,
+            (a) => a.addOption(name, defaultsTo: defaultsTo, abbr: abbr),
+            applyToOptions,
+            converter);
 }
 
 class IntOption extends ValueOption<int> {
   IntOption(
       String name, void Function(WasmCompilerOptions o, int v) applyToOptions,
-      {String? defaultsTo})
+      {String? defaultsTo, String? abbr})
       : super(name, applyToOptions, (v) => int.parse(v),
-            defaultsTo: defaultsTo);
+            defaultsTo: defaultsTo, abbr: abbr);
 }
 
 class StringOption extends ValueOption<String> {
diff --git a/pkg/dart2wasm/lib/translator.dart b/pkg/dart2wasm/lib/translator.dart
index 780ba2a8b30..6ce0069cd2e 100644
--- a/pkg/dart2wasm/lib/translator.dart
+++ b/pkg/dart2wasm/lib/translator.dart
@@ -44,15 +44,16 @@ import 'util.dart' as util;
 class TranslatorOptions {
   bool enableAsserts = false;
   bool importSharedMemory = false;
-  bool inlining = true;
+  int optimizationLevel = 1;
+  bool? inliningOverride;
   bool jsCompatibility = false;
-  bool omitImplicitTypeChecks = false;
+  bool? omitImplicitTypeChecksOverride;
   bool omitExplicitTypeChecks = false;
-  bool omitBoundsChecks = false;
+  bool? omitBoundsChecksOverride;
   bool polymorphicSpecialization = false;
   bool printKernel = false;
   bool printWasm = false;
-  bool minify = false;
+  bool? minifyOverride;
   bool verifyTypeChecks = false;
   bool verbose = false;
   bool enableExperimentalFfi = false;
@@ -67,18 +68,26 @@ class TranslatorOptions {
   bool requireJsStringBuiltin = false;
   List<int> watchPoints = [];
 
+  bool get inlining => inliningOverride ?? optimizationLevel >= 1;
+  bool get minify => minifyOverride ?? optimizationLevel >= 2;
+  bool get omitImplicitTypeChecks =>
+      omitImplicitTypeChecksOverride ?? optimizationLevel >= 3;
+  bool get omitBoundsChecks =>
+      omitBoundsChecksOverride ?? optimizationLevel >= 4;
+
   void serialize(DataSerializer sink) {
     sink.writeBool(enableAsserts);
     sink.writeBool(importSharedMemory);
-    sink.writeBool(inlining);
+    sink.writeInt(optimizationLevel);
+    sink.writeNullable(inliningOverride, sink.writeBool);
     sink.writeBool(jsCompatibility);
-    sink.writeBool(omitImplicitTypeChecks);
+    sink.writeNullable(omitImplicitTypeChecksOverride, sink.writeBool);
     sink.writeBool(omitExplicitTypeChecks);
-    sink.writeBool(omitBoundsChecks);
+    sink.writeNullable(omitBoundsChecksOverride, sink.writeBool);
     sink.writeBool(polymorphicSpecialization);
     sink.writeBool(printKernel);
     sink.writeBool(printWasm);
-    sink.writeBool(minify);
+    sink.writeNullable(minifyOverride, sink.writeBool);
     sink.writeBool(verifyTypeChecks);
     sink.writeBool(verbose);
     sink.writeBool(enableExperimentalFfi);
@@ -97,15 +106,17 @@ class TranslatorOptions {
     final TranslatorOptions options = TranslatorOptions();
     options.enableAsserts = source.readBool();
     options.importSharedMemory = source.readBool();
-    options.inlining = source.readBool();
+    options.optimizationLevel = source.readInt();
+    options.inliningOverride = source.readNullable(source.readBool);
     options.jsCompatibility = source.readBool();
-    options.omitImplicitTypeChecks = source.readBool();
+    options.omitImplicitTypeChecksOverride =
+        source.readNullable(source.readBool);
     options.omitExplicitTypeChecks = source.readBool();
-    options.omitBoundsChecks = source.readBool();
+    options.omitBoundsChecksOverride = source.readNullable(source.readBool);
     options.polymorphicSpecialization = source.readBool();
     options.printKernel = source.readBool();
     options.printWasm = source.readBool();
-    options.minify = source.readBool();
+    options.minifyOverride = source.readNullable(source.readBool);
     options.verifyTypeChecks = source.readBool();
     options.verbose = source.readBool();
     options.enableExperimentalFfi = source.readBool();
diff --git a/pkg/dart2wasm/test/phases/phases_test.dart b/pkg/dart2wasm/test/phases/phases_test.dart
index 9ccb2973baf..324d2d7ae79 100644
--- a/pkg/dart2wasm/test/phases/phases_test.dart
+++ b/pkg/dart2wasm/test/phases/phases_test.dart
@@ -13,6 +13,7 @@ final String mainDart = '${path.dirname(Platform.script.path)}/data/main.dart';
 final String cfeDillName = 'main.cfe.dill';
 final String tfaDillName = 'main.tfa.dill';
 final String wasmOutName = 'main.wasm';
+final String wasmOptOutName = 'main.opt.wasm';
 
 Future<void> main() async {
   await testSuccessCases();
@@ -21,11 +22,10 @@ Future<void> main() async {
 
 Future<void> testSuccessCases() async {
   await withTempDir((tmpDirPath) async {
-    final tmpDir = File(tmpDirPath);
-
-    final cfeDill = File.fromUri(tmpDir.uri.resolve(cfeDillName));
-    final tfaDill = File.fromUri(tmpDir.uri.resolve(tfaDillName));
-    final wasmOut = File.fromUri(tmpDir.uri.resolve(wasmOutName));
+    final cfeDill = File(path.join(tmpDirPath, cfeDillName));
+    final tfaDill = File(path.join(tmpDirPath, tfaDillName));
+    final wasmOut = File(path.join(tmpDirPath, wasmOutName));
+    final wasmOptOut = File(path.join(tmpDirPath, wasmOptOutName));
 
     // Run CFE and expect output
     await run([
@@ -62,13 +62,24 @@ Future<void> testSuccessCases() async {
     ]);
     Expect.isTrue(await wasmOut.exists());
     Expect.isTrue((await wasmOut.stat()).size > 0);
+
+    // Run opt and expect output
+    await run([
+      dartAotExecutable,
+      dart2wasmSnapshot,
+      '--platform=$platformDill',
+      '--phases=opt',
+      '--wasm-opt=$wasmOptExecutable',
+      wasmOut.path,
+      wasmOptOut.path,
+    ]);
+    Expect.isTrue(await wasmOptOut.exists());
+    Expect.isTrue((await wasmOptOut.stat()).size > 0);
   });
 
   await withTempDir((tmpDirPath) async {
-    final tmpDir = File(tmpDirPath);
-
-    final tfaDill = File.fromUri(tmpDir.uri.resolve(tfaDillName));
-    final wasmOut = File.fromUri(tmpDir.uri.resolve(wasmOutName));
+    final tfaDill = File(path.join(tmpDirPath, tfaDillName));
+    final wasmOut = File(path.join(tmpDirPath, wasmOutName));
 
     // Run CFE & TFA and expect output
     await run([
@@ -96,10 +107,8 @@ Future<void> testSuccessCases() async {
   });
 
   await withTempDir((tmpDirPath) async {
-    final tmpDir = File(tmpDirPath);
-
-    final cfeDill = File.fromUri(tmpDir.uri.resolve(tfaDillName));
-    final wasmOut = File.fromUri(tmpDir.uri.resolve(wasmOutName));
+    final cfeDill = File(path.join(tmpDirPath, cfeDillName));
+    final wasmOut = File(path.join(tmpDirPath, wasmOutName));
 
     // Run CFE and expect output
     await run([
@@ -127,9 +136,7 @@ Future<void> testSuccessCases() async {
   });
 
   await withTempDir((tmpDirPath) async {
-    final tmpDir = File(tmpDirPath);
-
-    final wasmOut = File.fromUri(tmpDir.uri.resolve(wasmOutName));
+    final wasmOut = File(path.join(tmpDirPath, wasmOutName));
 
     // Run CFE & TFA & codegen and expect output
     await run([
@@ -143,15 +150,31 @@ Future<void> testSuccessCases() async {
     Expect.isTrue(await wasmOut.exists());
     Expect.isTrue((await wasmOut.stat()).size > 0);
   });
+
+  await withTempDir((tmpDirPath) async {
+    final wasmOptOut = File(path.join(tmpDirPath, wasmOptOutName));
+
+    // Run CFE & TFA & codegen & opt and expect output
+    await run([
+      dartAotExecutable,
+      dart2wasmSnapshot,
+      '--platform=$platformDill',
+      '--phases=cfe,tfa,codegen,opt',
+      '--wasm-opt=$wasmOptExecutable',
+      mainDart,
+      wasmOptOut.path,
+    ]);
+    Expect.isTrue(await wasmOptOut.exists());
+    Expect.isTrue((await wasmOptOut.stat()).size > 0);
+  });
 }
 
 Future<void> testFailureCases() async {
   await withTempDir((tmpDirPath) async {
-    final tmpDir = File(tmpDirPath);
-
-    final cfeDill = File.fromUri(tmpDir.uri.resolve(cfeDillName));
-    final tfaDill = File.fromUri(tmpDir.uri.resolve(tfaDillName));
-    final wasmOut = File.fromUri(tmpDir.uri.resolve(wasmOutName));
+    final cfeDill = File(path.join(tmpDirPath, cfeDillName));
+    final tfaDill = File(path.join(tmpDirPath, tfaDillName));
+    final wasmOut = File(path.join(tmpDirPath, wasmOutName));
+    final wasmOptOut = File(path.join(tmpDirPath, wasmOptOutName));
 
     // CFE checks
     await expectFailedRun([
@@ -177,7 +200,6 @@ Future<void> testFailureCases() async {
       dartAotExecutable,
       dart2wasmSnapshot,
       '--platform=$platformDill',
-      '--platform=$platformDill',
       '--phases=tfa',
       mainDart,
       tfaDill.path
@@ -197,7 +219,6 @@ Future<void> testFailureCases() async {
       dartAotExecutable,
       dart2wasmSnapshot,
       '--platform=$platformDill',
-      '--platform=$platformDill',
       '--phases=codegen',
       mainDart,
       wasmOut.path
@@ -212,6 +233,25 @@ Future<void> testFailureCases() async {
       cfeDill.path
     ], 'Output from codegen phase must be a .wasm file');
 
+    // Opt checks
+    await expectFailedRun([
+      dartAotExecutable,
+      dart2wasmSnapshot,
+      '--platform=$platformDill',
+      '--phases=opt',
+      mainDart,
+      wasmOptOut.path
+    ], 'Input to opt phase must be a .wasm file');
+
+    await expectFailedRun([
+      dartAotExecutable,
+      dart2wasmSnapshot,
+      '--platform=$platformDill',
+      '--phases=opt',
+      wasmOut.path,
+      cfeDill.path
+    ], 'Output from opt phase must be a .wasm file');
+
     // Other checks
     await expectFailedRun([
       dartAotExecutable,
@@ -230,6 +270,16 @@ Future<void> testFailureCases() async {
       mainDart,
       cfeDill.path
     ], 'Invalid compiler phase name');
+
+    await expectFailedRun([
+      dartAotExecutable,
+      dart2wasmSnapshot,
+      '--platform=$platformDill',
+      '--phases=opt',
+      '-O0',
+      wasmOut.path,
+      wasmOptOut.path
+    ], 'Cannot specify "opt" phase with optimization level 0');
   });
 }
 
diff --git a/pkg/dart2wasm/test/util.dart b/pkg/dart2wasm/test/util.dart
index 3952b7c195f..55adc43837c 100644
--- a/pkg/dart2wasm/test/util.dart
+++ b/pkg/dart2wasm/test/util.dart
@@ -10,6 +10,9 @@ final dartAotExecutable = Uri.parse(Platform.resolvedExecutable)
 final dart2wasmSnapshot = Uri.parse(Platform.resolvedExecutable)
     .resolve('snapshots/dart2wasm_product.snapshot')
     .toFilePath();
+final wasmOptExecutable = Uri.parse(Platform.resolvedExecutable)
+    .resolve('utils/wasm-opt')
+    .toFilePath();
 final platformDill = Uri.parse(Platform.resolvedExecutable)
     .resolve('../lib/_internal/dart2wasm_platform.dill')
     .toFilePath();
diff --git a/pkg/dart2wasm/tool/compile_benchmark b/pkg/dart2wasm/tool/compile_benchmark
index 7cf7ed8d488..c1e900eeae8 100755
--- a/pkg/dart2wasm/tool/compile_benchmark
+++ b/pkg/dart2wasm/tool/compile_benchmark
@@ -58,17 +58,8 @@ LIBRARIES_JSON_ARG="--libraries-spec=$SDK_DIR/sdk/lib/libraries.json"
 function find_flags {
   echo -en "$(sed -n "/$1 =/,/end of $1/ p" $SDK_DIR/pkg/dartdev/lib/src/commands/compile.dart  | sed  '1d' | sed '$d' | tr '\n' ' ' | sed 's#\s\+# #g' | sed 's#^\s\+##' | sed 's#\s\+$##')"
 }
-# Use same flags as `dart compile exe`
-BINARYEN_FLAGS=($(find_flags 'binaryenFlags'))
-BINARYEN_FLAGS_DEFERRED_LOADING=($(find_flags 'binaryenFlagsDeferredLoading'))
-OPT_FLAGS_L0=($(find_flags 'optimizationLevel0Flags'))
-OPT_FLAGS_L1=($(find_flags 'optimizationLevel1Flags'))
-OPT_FLAGS_L2=($(find_flags 'optimizationLevel2Flags'))
-OPT_FLAGS_L3=($(find_flags 'optimizationLevel3Flags'))
-OPT_FLAGS_L4=($(find_flags 'optimizationLevel4Flags'))
 
 RUN_BINARYEN=1
-MULTI_MODULE=0
 RUN_SRC=0
 GENERATE_SOURCE_MAP=1
 COMPILE_BENCHMARK_BASE_NAME=""
@@ -79,7 +70,6 @@ SNAPSHOT_NAME="dart2wasm"
 # flags.
 VM_ARGS=()
 DART2WASM_ARGS=("--require-js-string-builtin")
-ADDITIONAL_BINARYEN_FLAGS=()
 DART_FILE=""
 OUTPUT_FILE=""
 while [ $# -gt 0 ]; do
@@ -100,11 +90,6 @@ while [ $# -gt 0 ]; do
       shift
       ;;
 
-    -g | --no-strip-wasm)
-      ADDITIONAL_BINARYEN_FLAGS+=("-g")
-      shift
-      ;;
-
     --compiler-asserts)
       SNAPSHOT_NAME="dart2wasm_asserts"
       VM_ARGS+=("--enable-asserts")
@@ -112,52 +97,16 @@ while [ $# -gt 0 ]; do
       ;;
 
     -O0 | --optimization-level=0)
-      DART2WASM_ARGS+=(${OPT_FLAGS_L0[@]})
+      DART2WASM_ARGS+=("-O0")
       RUN_BINARYEN=0
       shift
       ;;
 
-    -O1 | --optimization-level=1)
-      DART2WASM_ARGS+=(${OPT_FLAGS_L1[@]})
-      RUN_BINARYEN=1
-      shift
-      ;;
-
-    -O2 | --optimization-level=2)
-      DART2WASM_ARGS+=(${OPT_FLAGS_L2[@]})
-      RUN_BINARYEN=1
-      shift
-      ;;
-
-    -O3 | --optimization-level=3)
-      DART2WASM_ARGS+=(${OPT_FLAGS_L3[@]})
-      RUN_BINARYEN=1
-      shift
-      ;;
-
-    -O4 | --optimization-level=4)
-      DART2WASM_ARGS+=(${OPT_FLAGS_L4[@]})
-      RUN_BINARYEN=1
-      shift
-      ;;
-
     --extra-compiler-option=--platform=*)
       PLATFORM_FILENAME="${1#--extra-compiler-option=--platform=}"
       shift
       ;;
 
-    --enable-deferred-loading | --extra-compiler-option=--enable-deferred-loading)
-      MULTI_MODULE=1
-      DART2WASM_ARGS+=("--enable-deferred-loading")
-      shift
-      ;;
-
-    --extra-compiler-option=--enable-multi-module-stress-test-mode)
-      MULTI_MODULE=1
-      DART2WASM_ARGS+=("--enable-multi-module-stress-test-mode")
-      shift
-      ;;
-
     --extra-compiler-option=--no-js-compatibility)
       PLATFORM_FILENAME="$BIN_DIR/dart2wasm_platform.dill"
       DART2WASM_ARGS+=("--no-js-compatibility")
@@ -243,9 +192,9 @@ COMPILER_GZIP_SIZE=0
 
 function run_compiler() {
   if [ $RUN_SRC -eq 1 ]; then
-    dart2wasm_command=("$DART" "${VM_ARGS[@]}" "$DART2WASM_SRC" "$LIBRARIES_JSON_ARG" "${DART2WASM_ARGS[@]}" "$DART_FILE" "$OUTPUT_FILE")
+    dart2wasm_command=("$DART" "${VM_ARGS[@]}" "$DART2WASM_SRC" "$LIBRARIES_JSON_ARG" "${DART2WASM_ARGS[@]}" "--phases=cfe,tfa,codegen" "$DART_FILE" "$OUTPUT_FILE")
   else
-    dart2wasm_command=("$DART_AOT_RUNTIME" "${VM_ARGS[@]}" "$DART2WASM_AOT_SNAPSHOT" "$PLATFORM_ARG" "${DART2WASM_ARGS[@]}" "$DART_FILE" "$OUTPUT_FILE")
+    dart2wasm_command=("$DART_AOT_RUNTIME" "${VM_ARGS[@]}" "$DART2WASM_AOT_SNAPSHOT" "$PLATFORM_ARG" "${DART2WASM_ARGS[@]}" "--phases=cfe,tfa,codegen" "$DART_FILE" "$OUTPUT_FILE")
   fi
 
   if [ -n "$COMPILE_BENCHMARK_BASE_NAME" ]; then
@@ -257,17 +206,11 @@ function run_compiler() {
     MJS_SIZE=$SIZE
     MJS_GZIP_SIZE=$GZIP_SIZE
 
-    if [ $MULTI_MODULE -eq 1 ]; then
-      for OUTPUT_FILE in "${OUTPUT_FILE%.wasm}"*.wasm; do
-        measure_size $OUTPUT_FILE
-        (( COMPILER_SIZE+=$SIZE ))
-        (( COMPILER_GZIP_SIZE+=$GZIP_SIZE ))
-      done
-    else
+    for OUTPUT_FILE in "${OUTPUT_FILE%.wasm}"*.wasm; do
       measure_size $OUTPUT_FILE
-      COMPILER_SIZE=$SIZE
-      COMPILER_GZIP_SIZE=$GZIP_SIZE
-    fi
+      (( COMPILER_SIZE+=$SIZE ))
+      (( COMPILER_GZIP_SIZE+=$GZIP_SIZE ))
+    done
   else
     "${dart2wasm_command[@]}"
   fi
@@ -278,43 +221,24 @@ BINARYEN_MEMORY=0
 BINARYEN_SIZE=0
 BINARYEN_GZIP_SIZE=0
 
-function run_binaryen_single() {
-  OUTPUT_FILE="$1"
-  shift
-
-  if [ $GENERATE_SOURCE_MAP -eq 1 ]; then
-    SOURCE_MAP_FLAGS=("-ism" "${OUTPUT_FILE}.map" "-osm" "${OUTPUT_FILE}.map")
+function run_binaryen() {
+  if [ $RUN_SRC -eq 1 ]; then
+    opt_command=("$DART" "${VM_ARGS[@]}" "$DART2WASM_SRC" "$LIBRARIES_JSON_ARG" "${DART2WASM_ARGS[@]}" "--phases=opt" "--wasm-opt=$BINARYEN" "$OUTPUT_FILE" "$OUTPUT_FILE")
+  else
+    opt_command=("$DART_AOT_RUNTIME" "${VM_ARGS[@]}" "$DART2WASM_AOT_SNAPSHOT" "$PLATFORM_ARG" "${DART2WASM_ARGS[@]}" "--phases=opt" "--wasm-opt=$BINARYEN" "$OUTPUT_FILE" "$OUTPUT_FILE")
   fi
-
-  binaryen_command=("$BINARYEN" "${ADDITIONAL_BINARYEN_FLAGS[@]}" "$@" "${SOURCE_MAP_FLAGS[@]}" "$OUTPUT_FILE" -o "$OUTPUT_FILE")
   if [ -n "$COMPILE_BENCHMARK_BASE_NAME" ]; then
     # If we're measuring run each binaryen command sequentially.
-    measure ${binaryen_command[@]}
+    measure "${opt_command[@]}"
     BINARYEN_TIME=$(echo "$BINARYEN_TIME + $TIME" | bc)
     BINARYEN_MEMORY=$(($BINARYEN_MEMORY > $MEMORY ? $BINARYEN_MEMORY : $MEMORY ))
     measure_size $OUTPUT_FILE
     BINARYEN_SIZE=$(echo "$BINARYEN_SIZE + $SIZE" | bc)
     BINARYEN_GZIP_SIZE=$(echo "$BINARYEN_GZIP_SIZE + $GZIP_SIZE" | bc)
-  else
-    ${binaryen_command[@]} &
-  fi
-}
-
-function run_binaryen() {
-  if [ $MULTI_MODULE -eq 1 ]; then
-    # Iterate over all matching wasm files and optimize them concurrently in
-    # different processes.
-    for OUTPUT_FILE in "${OUTPUT_FILE%.wasm}"*.wasm; do
-      run_binaryen_single "$OUTPUT_FILE" "${BINARYEN_FLAGS_DEFERRED_LOADING[@]}"
-    done
-  else
-    run_binaryen_single "$OUTPUT_FILE" "${BINARYEN_FLAGS[@]}"
-  fi
-  wait
-
-  if [ -n "$COMPILE_BENCHMARK_BASE_NAME" ]; then
     MAX_MEMORY=$(($COMPILER_MEMORY > $BINARYEN_MEMORY ? $COMPILER_MEMORY : $BINARYEN_MEMORY ))
     TOTAL_TIME=$(echo "$COMPILER_TIME + $BINARYEN_TIME" | bc)
+  else
+    "${opt_command[@]}"
   fi
 }
 
diff --git a/pkg/dartdev/lib/src/commands/compile.dart b/pkg/dartdev/lib/src/commands/compile.dart
index b34bf8ac90b..5eb20e7aa02 100644
--- a/pkg/dartdev/lib/src/commands/compile.dart
+++ b/pkg/dartdev/lib/src/commands/compile.dart
@@ -723,86 +723,6 @@ class CompileWasmCommand extends CompileSubcommandCommand {
   static const String commandName = 'wasm';
   static const String help = 'Compile Dart to a WebAssembly/WasmGC module.';
 
-  // The unique place where we store various flags for dart2wasm & binaryen.
-  //
-  // Other uses (e.g. pkg/dart2wasm/tool/compile_benchmark) will grep in this
-  // file for the flags. So please keep the formatting.
-
-  final List<String> binaryenFlags = _flagList('''
-      --enable-gc
-      --enable-reference-types
-      --enable-multivalue
-      --enable-exception-handling
-      --enable-nontrapping-float-to-int
-      --enable-sign-ext
-      --enable-bulk-memory
-      --enable-threads
-
-      --no-inline=*<noInline>*
-
-      --closed-world
-      --traps-never-happen
-      --type-unfinalizing
-      -Os
-      --type-ssa
-      --gufa
-      -Os
-      --type-merging
-      -Os
-      --type-finalizing
-      --minimize-rec-groups
-    '''); // end of binaryenFlags
-
-  final List<String> binaryenFlagsDeferredLoading = _flagList('''
-      --enable-gc
-      --enable-reference-types
-      --enable-multivalue
-      --enable-exception-handling
-      --enable-nontrapping-float-to-int
-      --enable-sign-ext
-      --enable-bulk-memory
-      --enable-threads
-
-      --no-inline=*<noInline>*
-
-      --traps-never-happen
-      -Os
-    '''); // end of binaryenFlagsDeferredLoading
-
-  final List<String> optimizationLevel0Flags = _flagList('''
-      --no-inlining
-      --no-minify
-    '''); // end of optimizationLevel0Flags
-
-  final List<String> optimizationLevel1Flags = _flagList('''
-      --inlining
-      --no-minify
-    '''); // end of optimizationLevel1Flags
-
-  final List<String> optimizationLevel2Flags = _flagList('''
-      --inlining
-      --minify
-    '''); // end of optimizationLevel2Flags
-
-  final List<String> optimizationLevel3Flags = _flagList('''
-      --inlining
-      --minify
-      --omit-implicit-checks
-    '''); // end of optimizationLevel3Flags
-
-  final List<String> optimizationLevel4Flags = _flagList('''
-      --inlining
-      --minify
-      --omit-implicit-checks
-      --omit-bounds-checks
-    '''); // end of optimizationLevel4Flags
-
-  static List<String> _flagList(String lines) => lines
-      .split('\n')
-      .map((line) => line.trim())
-      .where((line) => line.isNotEmpty)
-      .toList();
-
   CompileWasmCommand({bool verbose = false})
       : super(commandName, help, verbose) {
     argParser
@@ -857,6 +777,14 @@ class CompileWasmCommand extends CompileSubcommandCommand {
         valueHelp: 'page count',
         hide: !verbose,
       )
+      ..addMultiOption('phases',
+          help: 'Specifies which phases of the dart2wasm compiler to run. Each '
+              'phase will emit a partial result that is then the input to the '
+              'next phase.',
+          allowed: ['cfe', 'tfa', 'codegen', 'opt'],
+          defaultsTo: ['cfe', 'tfa', 'codegen', 'opt'],
+          hide: !verbose,
+          splitCommas: true)
       ..addMultiOption(
         'extra-compiler-option',
         abbr: 'E',
@@ -872,13 +800,6 @@ class CompileWasmCommand extends CompileSubcommandCommand {
         allowed: ['0', '1', '2', '3', '4'],
         defaultsTo: '1',
         valueHelp: 'level',
-        allowedHelp: {
-          '0': optimizationLevel0Flags.join(' '),
-          '1': optimizationLevel1Flags.join(' '),
-          '2': optimizationLevel2Flags.join(' '),
-          '3': optimizationLevel3Flags.join(' '),
-          '4': optimizationLevel4Flags.join(' '),
-        },
         hide: !verbose,
       )
       ..addFlag(
@@ -964,43 +885,23 @@ class CompileWasmCommand extends CompileSubcommandCommand {
       }
     }
 
-    final isDeferredLoading = args.flag('enable-deferred-loading');
-    // Used in testing to force multiple modules.
-    final isMultiStressTestMode = extraCompilerOptions
-        .any((e) => e.contains('enable-multi-module-stress-test'));
-    final isMultiModule = isDeferredLoading || isMultiStressTestMode;
-    final optimizationLevel = int.parse(args.option('optimization-level')!);
-
-    final runWasmOpt =
-        optimizationLevel >= 1 && path.extension(outputFile) == '.wasm';
-
-    if (runWasmOpt && !checkArtifactExists(sdk.wasmOpt)) {
-      return 255;
+    int? optimizationLevel;
+    List<String> phases = args.multiOption('phases');
+    if (args.wasParsed('phases')) {}
+    if (args.option('optimization-level') != null) {
+      optimizationLevel = int.tryParse(args.option('optimization-level')!);
+      if (optimizationLevel == null) {
+        usageException(
+            'Error: The --optimization-level flag must specify a number!');
+      }
+      if (optimizationLevel == 0) {
+        if (!args.wasParsed('phases')) {
+          // Don't add the opt phase.
+          phases.removeLast();
+        }
+      }
     }
 
-    void handleOverride(List<String> flags, String name, bool? value) {
-      // If no override provided, default to what -O implies.
-      if (value == null) return;
-
-      flags.removeWhere((option) => option == '--no-$name');
-      flags.removeWhere((option) => option == '--$name');
-
-      // Explicitly use the flag value, irrespective of -O settings.
-      value ? flags.add('--$name') : flags.add('--no-$name');
-    }
-
-    final optimizationFlags = (switch (optimizationLevel) {
-      0 => optimizationLevel0Flags,
-      1 => optimizationLevel1Flags,
-      2 => optimizationLevel2Flags,
-      3 => optimizationLevel3Flags,
-      4 => optimizationLevel4Flags,
-      _ => throw 'unreachable',
-    })
-        .toList();
-    handleOverride(optimizationFlags, 'minify',
-        args.wasParsed('minify') ? args.flag('minify') : null);
-
     final generateSourceMap = args.flag('source-maps');
     final enabledExperiments = args.enabledExperiments;
     final dart2wasmCommand = [
@@ -1013,20 +914,19 @@ class CompileWasmCommand extends CompileSubcommandCommand {
       if (args.flag('print-kernel')) '--print-kernel',
       if (args.flag(enableAssertsOption.flag)) '--${enableAssertsOption.flag}',
       if (!generateSourceMap) '--no-source-maps',
-      if (isDeferredLoading) '--enable-deferred-loading',
+      if (optimizationLevel != null) '--optimization-level=$optimizationLevel',
+      if (args.flag('minify')) '--minify',
+      if (args.flag('strip-wasm')) '--strip-wasm',
+      if (args.flag('enable-deferred-loading')) '--enable-deferred-loading',
       for (final define in defines) '-D$define',
       if (maxPages != null) ...[
         '--import-shared-memory',
         '--shared-memory-max-pages=$maxPages',
       ],
+      '--phases=${phases.join(",")}',
+      '--wasm-opt=${sdk.wasmOpt}',
       ...enabledExperiments.map((e) => '--enable-experiment=$e'),
-
-      // First we pass flags based on the optimization level.
-      ...optimizationFlags,
-
-      // Then we pass any extra compiler flags through.
       ...extraCompilerOptions,
-
       sourcePath,
       outputFile,
     ];
@@ -1042,102 +942,16 @@ class CompileWasmCommand extends CompileSubcommandCommand {
       return compileErrorExitCode;
     }
 
-    final bool strip = args.flag('strip-wasm');
-
     // When running in dry run mode there will not be any file emitted.
     final isDryRun = extraCompilerOptions.any((e) => e.contains('dry-run'));
 
     if (isDryRun) return 0;
 
-    if (runWasmOpt) {
-      if (isMultiModule) {
-        // Iterate over all matching wasm files and optimize them concurrently
-        // in different processes.
-        final outputFiles = await _listMultiWasmModules(
-            path.dirname(outputFile), outputFileBasename);
-        final futures = <Future<int>>[];
-        for (final f in outputFiles) {
-          final baseFileName = path.setExtension(f.path, '');
-          futures.add(optimize(baseFileName, f.path,
-              deferredLoadingEnabled: true,
-              generateSourceMap: generateSourceMap,
-              strip: strip));
-        }
-        final exitCode = (await Future.wait(futures))
-            .firstWhere((r) => r != 0, orElse: () => 0);
-        if (exitCode != 0) return exitCode;
-      } else {
-        final exitCode = await optimize(outputFileBasename, outputFile,
-            deferredLoadingEnabled: false,
-            generateSourceMap: generateSourceMap,
-            strip: strip);
-        if (exitCode != 0) return exitCode;
-      }
-    }
-
     final mjsFile = '$outputFileBasename.mjs';
     log.stdout(
         "Generated wasm module '$outputFile', and JS init file '$mjsFile'.");
     return 0;
   }
-
-  Future<List<File>> _listMultiWasmModules(
-      String outputDir, String outputFileBasename) async {
-    final files = <File>[];
-    final outputFiles = await Directory(outputDir).list().toList();
-    // When multiple modules are produced from wasm (e.g. with deferred
-    // loading), the compiler emits files:
-    // - basename.wasm (main module)
-    // - basename_module{1...N}.wasm (extra modules)
-    for (final f in outputFiles) {
-      if (f is! File) continue;
-      if (!path.split(f.path).last.startsWith(outputFileBasename)) continue;
-      if (path.extension(f.path) != '.wasm') continue;
-
-      files.add(f);
-    }
-    return files;
-  }
-
-  Future<int> optimize(String outputFileBasename, String outputFile,
-      {required bool deferredLoadingEnabled,
-      required bool generateSourceMap,
-      required bool strip}) async {
-    final unoptFile = '$outputFileBasename.unopt.wasm';
-    File(outputFile).renameSync(unoptFile);
-
-    final unoptSourceMapFile = '$outputFileBasename.unopt.wasm.map';
-    if (generateSourceMap) {
-      File('$outputFile.map').renameSync(unoptSourceMapFile);
-    }
-
-    final flags = [
-      ...(deferredLoadingEnabled
-          ? binaryenFlagsDeferredLoading
-          : binaryenFlags),
-      if (!strip) '-g',
-      if (generateSourceMap) ...[
-        '-ism',
-        unoptSourceMapFile,
-        '-osm',
-        '$outputFile.map'
-      ]
-    ];
-
-    if (verbose) {
-      log.stdout('Optimizing output with: ${sdk.wasmOpt} $flags');
-    }
-    final processResult = Process.runSync(
-      sdk.wasmOpt,
-      [...flags, '-o', outputFile, unoptFile],
-    );
-    if (processResult.exitCode != 0) {
-      log.stderr('Error: Wasm compilation failed while optimizing output');
-      log.stderr(processResult.stderr);
-      return compileErrorExitCode;
-    }
-    return 0;
-  }
 }
 
 abstract class CompileSubcommandCommand extends DartdevCommand {