Build ahead-of-time compiled snapshots and incorporate them into Android APKs (#3592)

This currently requires a local build of the engine.

Run "flutter build aot" to build an AOT snapshot.
Run "flutter build apk --profile" to build a "profile mode" APK that uses AOT.

packages/flutter_tools/lib/src/commands/build.dart

@@ -8,12 +8,14 @@ import 'dart:io';
 import '../globals.dart';
 import '../runner/flutter_command.dart';
 import 'build_apk.dart';
+import 'build_aot.dart';
 import 'build_flx.dart';
 import 'build_ios.dart';
 
 class BuildCommand extends FlutterCommand {
   BuildCommand() {
     addSubcommand(new BuildApkCommand());
+    addSubcommand(new BuildAotCommand());
     addSubcommand(new BuildCleanCommand());
     addSubcommand(new BuildIOSCommand());
     addSubcommand(new BuildFlxCommand());

packages/flutter_tools/lib/src/commands/build_aot.dart

+// Copyright 2016 The Chromium Authors. 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:async';
+import 'dart:io';
+
+import 'package:path/path.dart' as path;
+
+import '../base/process.dart';
+import '../build_configuration.dart';
+import '../globals.dart';
+import '../runner/flutter_command.dart';
+import 'run.dart';
+
+const String _kDefaultAotOutputDir = 'build/aot';
+
+// Files generated by the ahead-of-time snapshot builder.
+const List<String> kAotSnapshotFiles = const <String>[
+  'snapshot_aot_instr', 'snapshot_aot_isolate', 'snapshot_aot_rodata', 'snapshot_aot_vmisolate',
+];
+
+class BuildAotCommand extends FlutterCommand {
+  BuildAotCommand() {
+    usesTargetOption();
+    addBuildModeFlags();
+    usesPubOption();
+    argParser.addOption('output-dir', defaultsTo: _kDefaultAotOutputDir);
+  }
+
+  @override
+  final String name = 'aot';
+
+  @override
+  final String description = "Build an ahead-of-time compiled snapshot of your app's Dart code. "
+                             "(local engine builds only)";
+
+  @override
+  Future<int> runInProject() async {
+    String outputPath = buildAotSnapshot(
+      findMainDartFile(argResults['target']),
+      outputPath: argResults['output-dir']
+    );
+    if (outputPath == null)
+      return 1;
+
+    printStatus('Built $outputPath.');
+    return 0;
+  }
+}
+
+String _getSdkExtensionPath(String packagesPath, String package) {
+  Directory packageDir = new Directory(path.join(packagesPath, package));
+  return path.join(path.dirname(packageDir.resolveSymbolicLinksSync()), 'sdk_ext');
+}
+
+String buildAotSnapshot(
+  String mainPath, {
+  String outputPath: _kDefaultAotOutputDir
+}) {
+  String engineSrc = tools.engineSrcPath;
+  if (engineSrc == null) {
+    printError('AOT compilation requires --engine-src-path');
+    return null;
+  }
+
+  String engineOut = tools.getEngineArtifactsDirectory(
+      TargetPlatform.android_arm, BuildMode.profile).path;
+  String genSnapshot = path.join(engineOut, 'clang_x86', 'gen_snapshot');
+
+  Directory outputDir = new Directory(outputPath);
+  outputDir.createSync(recursive: true);
+  String vmIsolateSnapshot = path.join(outputDir.path, 'snapshot_aot_vmisolate');
+  String isolateSnapshot = path.join(outputDir.path, 'snapshot_aot_isolate');
+  String instructionsBlob = path.join(outputDir.path, 'snapshot_aot_instr');
+  String rodataBlob = path.join(outputDir.path, 'snapshot_aot_rodata');
+
+  String bindingsSrc = path.join(engineSrc, 'sky', 'engine', 'bindings');
+  String vmEntryPoints = path.join(bindingsSrc, 'dart_vm_entry_points.txt');
+  String vmEntryPointsAndroid = path.join(bindingsSrc, 'dart_vm_entry_points_android.txt');
+
+  String packagesPath = path.absolute(Directory.current.path, 'packages');
+  if (!FileSystemEntity.isDirectorySync(packagesPath)) {
+    printError('Could not find packages directory: $packagesPath\n' +
+               'Did you run `pub get` in this directory?');
+    return null;
+  }
+
+  String mojoSdkExt = _getSdkExtensionPath(packagesPath, 'mojo');
+  String mojoInternalPath = path.join(mojoSdkExt, 'internal.dart');
+
+  String skyEngineSdkExt = _getSdkExtensionPath(packagesPath, 'sky_engine');
+  String uiPath = path.join(skyEngineSdkExt, 'dart_ui.dart');
+  String vmServicePath = path.join(skyEngineSdkExt, 'dart', 'runtime', 'bin', 'vmservice', 'vmservice_io.dart');
+  String jniPath = path.join(skyEngineSdkExt, 'dart_jni', 'jni.dart');
+
+  List<String> filePaths = [
+    genSnapshot, vmEntryPoints, vmEntryPointsAndroid, mojoInternalPath, uiPath, vmServicePath, jniPath
+  ];
+  List<String> missingFiles = filePaths.where((String p) => !FileSystemEntity.isFileSync(p)).toList();
+  if (missingFiles.isNotEmpty) {
+    printError('Missing files: $missingFiles');
+    return null;
+  }
+
+  List<String> genSnapshotCmd = [
+    genSnapshot,
+    '--vm_isolate_snapshot=$vmIsolateSnapshot',
+    '--isolate_snapshot=$isolateSnapshot',
+    '--instructions_blob=$instructionsBlob',
+    '--rodata_blob=$rodataBlob',
+    '--embedder_entry_points_manifest=$vmEntryPoints',
+    '--embedder_entry_points_manifest=$vmEntryPointsAndroid',
+    '--package_root=$packagesPath',
+    '--url_mapping=dart:mojo.internal,$mojoInternalPath',
+    '--url_mapping=dart:ui,$uiPath',
+    '--url_mapping=dart:vmservice_sky,$vmServicePath',
+    '--url_mapping=dart:jni,$jniPath',
+    '--no-sim-use-hardfp',
+  ];
+
+  if (!tools.engineRelease) {
+    genSnapshotCmd.addAll([
+      '--no-checked',
+      '--conditional_directives',
+    ]);
+  }
+
+  genSnapshotCmd.add(mainPath);
+
+  printStatus('Building snapshot...');
+  runCheckedSync(genSnapshotCmd);
+
+  return outputPath;
+}

packages/flutter_tools/lib/src/commands/build_apk.dart

@@ -18,6 +18,7 @@ import '../globals.dart';
 import '../runner/flutter_command.dart';
 import '../services.dart';
 import '../toolchain.dart';
+import 'build_aot.dart';
 import 'run.dart';
 
 export '../android/android_device.dart' show AndroidDevice;
@@ -156,6 +157,9 @@ class BuildApkCommand extends FlutterCommand {
     argParser.addOption('flx',
       abbr: 'f',
       help: 'Path to the FLX file. If this is not provided, an FLX will be built.');
+    argParser.addOption('aot-path',
+      help: 'Path to the ahead-of-time compiled snapshot directory.\n'
+            'If this is not provided, an AOT snapshot will be built.');
     argParser.addOption('add-file',
       help: 'Add a file to the APK (must have the format <path/in/APK>=<local/file/path>).',
       allowMultiple: true);
@@ -217,6 +221,7 @@ class BuildApkCommand extends FlutterCommand {
       outputFile: argResults['output-file'],
       target: argResults['target'],
       flxPath: argResults['flx'],
+      aotPath: argResults['aot-path'],
       extraFiles: extraFiles,
       keystore: (argResults['keystore'] ?? '').isEmpty ? null : new ApkKeystoreInfo(
         keystore: argResults['keystore'],
@@ -401,6 +406,9 @@ bool _needsRebuild(String apkPath, String manifest) {
   return false;
 }
 
+// Returns true if the selected build mode uses ahead-of-time compilation.
+bool _isAotBuildMode(BuildMode mode) => mode == BuildMode.profile;
+
 Future<int> buildAndroid(
   TargetPlatform platform,
   BuildMode buildMode, {
@@ -411,6 +419,7 @@ Future<int> buildAndroid(
   String outputFile: _kDefaultOutputPath,
   String target,
   String flxPath,
+  String aotPath,
   Map<String, File> extraFiles,
   ApkKeystoreInfo keystore
 }) async {
@@ -458,18 +467,44 @@ Future<int> buildAndroid(
       printError('(Omit the --flx option to build the FLX automatically)');
       return 1;
     }
-
-    return _buildApk(platform, buildMode, components, flxPath, keystore, outputFile);
   } else {
-    // Find the path to the main Dart file; build the FLX.
-    String mainPath = findMainDartFile(target);
-    String localBundlePath = await flx.buildFlx(
+    // Build the FLX.
+    flxPath = await flx.buildFlx(
       toolchain,
-      mainPath: mainPath,
+      mainPath: findMainDartFile(target),
+      precompiledSnapshot: _isAotBuildMode(buildMode),
       includeRobotoFonts: false);
+  }
 
-    return _buildApk(platform, buildMode, components, localBundlePath, keystore, outputFile);
+  // Build an AOT snapshot if needed.
+  if (_isAotBuildMode(buildMode) && aotPath == null) {
+    aotPath = buildAotSnapshot(findMainDartFile(target));
+    if (aotPath == null) {
+      printError('Failed to build AOT snapshot');
+      return 1;
+    }
   }
+
+  if (aotPath != null) {
+    if (!_isAotBuildMode(buildMode)) {
+      printError('AOT snapshot can not be used in build mode $buildMode');
+      return 1;
+    }
+    if (!FileSystemEntity.isDirectorySync(aotPath)) {
+      printError('AOT snapshot does not exist: $aotPath');
+      return 1;
+    }
+    for (String aotFilename in kAotSnapshotFiles) {
+      String aotFilePath = path.join(aotPath, aotFilename);
+      if (!FileSystemEntity.isFileSync(aotFilePath)) {
+        printError('Missing AOT snapshot file: $aotFilePath');
+        return 1;
+      }
+      components.extraFiles['assets/$aotFilename'] = new File(aotFilePath);
+    }
+  }
+
+  return _buildApk(platform, buildMode, components, flxPath, keystore, outputFile);
 }
 
 Future<int> buildApk(

packages/flutter_tools/lib/src/flx.dart

@@ -245,6 +245,7 @@ ZipEntry _createFontManifest(Map<String, dynamic> manifestDescriptor,
 Future<String> buildFlx(
   Toolchain toolchain, {
   String mainPath: defaultMainPath,
+  bool precompiledSnapshot: false,
   bool includeRobotoFonts: true
 }) async {
   int result;
@@ -255,6 +256,7 @@ Future<String> buildFlx(
     snapshotPath: localSnapshotPath,
     outputPath: localBundlePath,
     mainPath: mainPath,
+    precompiledSnapshot: precompiledSnapshot,
     includeRobotoFonts: includeRobotoFonts
   );
   if (result == 0)