Use IKG for restarts, use IKG with ProtectedFileByteStore. (#12953)

* Use IKG for restarts, use IKG with ProtectedFileByteStore.

* Fix comment, add end of file newline.

* Remove unused import

packages/flutter_tools/lib/src/build_info.dart

@@ -205,3 +205,9 @@ String getAssetBuildDirectory() {
 String getIosBuildDirectory() {
   return fs.path.join(getBuildDirectory(), 'ios');
 }
+
+/// Returns directory used by incremental compiler (IKG - incremental kernel
+/// generator) to store cached intermediate state.
+String getIncrementalCompilerByteStoreDirectory() {
+  return fs.path.join(getBuildDirectory(), 'ikg_byte_store');
+}

packages/flutter_tools/lib/src/compile.dart

@@ -60,7 +60,8 @@ Future<String> compile(
     {String sdkRoot,
     String mainPath,
     bool linkPlatformKernelIn : false,
-    List<String> extraFrontEndOptions}) async {
+    List<String> extraFrontEndOptions,
+    String incrementalCompilerByteStorePath}) async {
   final String frontendServer = artifacts.getArtifactPath(
     Artifact.frontendServerSnapshotForEngineDartSdk
   );
@@ -76,6 +77,13 @@ Future<String> compile(
   ];
   if (!linkPlatformKernelIn)
     command.add('--no-link-platform');
+  if (incrementalCompilerByteStorePath != null) {
+    command.addAll(<String>[
+      '--incremental',
+      '--byte-store',
+      incrementalCompilerByteStorePath]);
+    fs.directory(incrementalCompilerByteStorePath).createSync(recursive: true);
+  }
   if (extraFrontEndOptions != null)
     command.addAll(extraFrontEndOptions);
   command.add(mainPath);

packages/flutter_tools/lib/src/devfs.dart

@@ -5,7 +5,6 @@
 import 'dart:async';
 import 'dart:convert' show BASE64, UTF8;
 
-import 'package:flutter_tools/src/artifacts.dart';
 import 'package:json_rpc_2/json_rpc_2.dart' as rpc;
 
 import 'asset.dart';
@@ -446,11 +445,6 @@ class DevFS {
       // that isModified does not reset last check timestamp because we
       // want to report all modified files to incremental compiler next time
       // user does hot reload.
-      // TODO(aam): Remove this logic once we switch to using incremental
-      // compiler for full application compilation when doing full restart.
-      if (fullRestart && generator != null && content is DevFSFileContent) {
-        content = DevFSFileContent.clone(content);
-      }
       if (content.isModified || (bundleDirty && archivePath != null)) {
         dirtyEntries[deviceUri] = content;
         numBytes += content.size;
@@ -480,11 +474,11 @@ class DevFS {
       // host and result of compilation is single kernel file.
       filesUris.forEach(dirtyEntries.remove);
       printTrace('Compiling dart to kernel with ${invalidatedFiles.length} updated files');
-      final String compiledBinary = fullRestart
-        ? await compile(
-              sdkRoot: artifacts.getArtifactPath(Artifact.flutterPatchedSdkPath),
-              mainPath: mainPath)
-        : await generator.recompile(mainPath, invalidatedFiles);
+      if (fullRestart) {
+        generator.reset();
+      }
+      final String compiledBinary =
+          await generator.recompile(mainPath, invalidatedFiles);
       if (compiledBinary != null && compiledBinary.isNotEmpty)
         dirtyEntries.putIfAbsent(
           Uri.parse(target + '.dill'),

packages/flutter_tools/lib/src/flx.dart

@@ -71,6 +71,7 @@ Future<Null> build({
   if (!precompiledSnapshot && previewDart2) {
     final String kernelBinaryFilename = await compile(
       sdkRoot: artifacts.getArtifactPath(Artifact.flutterPatchedSdkPath),
+      incrementalCompilerByteStorePath: fs.path.absolute(getIncrementalCompilerByteStoreDirectory()),
       mainPath: fs.file(mainPath).absolute.path
     );
     kernelContent = new DevFSFileContent(fs.file(kernelBinaryFilename));

packages/flutter_tools/lib/src/run_hot.dart

@@ -353,9 +353,20 @@ class HotRunner extends ResidentRunner {
     // TODO(aam): Add generator reset logic once we switch to using incremental
     // compiler for full application recompilation on restart.
     final bool updatedDevFS = await _updateDevFS(fullRestart: true);
-    _resetDirtyAssets();
-    if (!updatedDevFS)
+    if (!updatedDevFS) {
+      for (FlutterDevice device in flutterDevices) {
+        if (device.generator != null)
+          device.generator.reject();
+      }
       return new OperationResult(1, 'DevFS synchronization failed');
+    }
+    _resetDirtyAssets();
+    for (FlutterDevice device in flutterDevices) {
+      // VM must have accepted the kernel binary, there will be no reload
+      // report, so we let incremental compiler know that source code was accepted.
+      if (device.generator != null)
+        device.generator.accept();
+    }
     // Check if the isolate is paused and resume it.
     for (FlutterDevice device in flutterDevices) {
       for (FlutterView view in device.views) {