[vm, bytecode] Generate bytecode per package in fronend_server incremental compiles.

flutter/examples/flutter_gallery$ flutter test --local-engine host_debug -v | grep took
              First run -> Second run (initialize from dill file)
AST             11539ms ->  6837ms
Bytecode before 32790ms -> 26665ms
Bytecode after  15435ms -> 11111ms

Change-Id: If1088f86a583170c9f3690778a5b8e2fd4b48ace
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/118341
Commit-Queue: Ryan Macnak <rmacnak@google.com>
Reviewed-by: Alexander Markov <alexmarkov@google.com>

pkg/vm/lib/frontend_server.dart

@@ -33,10 +33,12 @@ import 'package:vm/kernel_front_end.dart'
     show
         asFileUri,
         compileToKernel,
-        parseCommandLineDefines,
         convertFileOrUriArgumentToUri,
-        createFrontEndTarget,
         createFrontEndFileSystem,
+        createFrontEndTarget,
+        forEachPackage,
+        packageFor,
+        parseCommandLineDefines,
         runWithFrontEndCompilerContext,
         setVMEnvironmentDefines,
         writeDepfile;
@@ -341,6 +343,7 @@ class FrontendCompiler implements CompilerInterface {
     compilerOptions.bytecode = options['gen-bytecode'];
     final BytecodeOptions bytecodeOptions = new BytecodeOptions(
         enableAsserts: options['enable-asserts'],
+        emitSourceFiles: options['embed-source-text'],
         environmentDefines: environmentDefines)
       ..parseCommandLineFlags(options['bytecode-options']);
 
@@ -549,6 +552,59 @@ class FrontendCompiler implements CompilerInterface {
     }
   }
 
+  bool _elementsIdentical(List a, List b) {
+    if (a.length != b.length) return false;
+    for (int i = 0; i < a.length; i++) {
+      if (!identical(a[i], b[i])) return false;
+    }
+    return true;
+  }
+
+  final _packageLibraries = new Expando();
+  final _packageBytes = new Expando();
+
+  void _writePackage(Component component, String package,
+      List<Library> libraries, IOSink sink) {
+    final canCache = libraries.isNotEmpty &&
+        _compilerOptions.bytecode &&
+        errors.isEmpty &&
+        package != "main";
+
+    if (canCache) {
+      var cachedLibraries = _packageLibraries[libraries.first];
+      if ((cachedLibraries != null) &&
+          _elementsIdentical(cachedLibraries, libraries)) {
+        sink.add(_packageBytes[libraries.first]);
+        return;
+      }
+    }
+
+    Component partComponent = component;
+    if (_compilerOptions.bytecode && errors.isEmpty) {
+      generateBytecode(partComponent,
+          options: _bytecodeOptions,
+          libraries: libraries,
+          coreTypes: _generator.getCoreTypes(),
+          hierarchy: _generator.getClassHierarchy());
+
+      if (_options['drop-ast']) {
+        partComponent = createFreshComponentWithBytecode(partComponent);
+      }
+    }
+
+    final byteSink = new ByteSink();
+    final BinaryPrinter printer = new LimitedBinaryPrinter(byteSink,
+        (lib) => packageFor(lib) == package, false /* excludeUriToSource */);
+    printer.writeComponentFile(partComponent);
+
+    final bytes = byteSink.builder.takeBytes();
+    sink.add(bytes);
+    if (canCache) {
+      _packageLibraries[libraries.first] = libraries;
+      _packageBytes[libraries.first] = bytes;
+    }
+  }
+
   @override
   Future<Null> recompileDelta({String entryPoint}) async {
     final String boundaryKey = new Uuid().generateV4();
@@ -564,8 +620,21 @@ class FrontendCompiler implements CompilerInterface {
       transformer.transform(deltaProgram);
     }
     final compiledSources = deltaProgram.uriToSource.keys;
-    deltaProgram = await _generateBytecodeIfNeeded(deltaProgram);
-    await writeDillFile(deltaProgram, _kernelBinaryFilename);
+
+    if (_compilerOptions.bytecode) {
+      final IOSink sink = new File(_kernelBinaryFilename).openWrite();
+      await runWithFrontEndCompilerContext(
+          _mainSource, _compilerOptions, deltaProgram, () async {
+        await forEachPackage(deltaProgram,
+            (String package, List<Library> libraries) async {
+          _writePackage(deltaProgram, package, libraries, sink);
+        });
+      });
+      await sink.close();
+    } else {
+      await writeDillFile(deltaProgram, _kernelBinaryFilename);
+    }
+
     _outputStream.writeln(boundaryKey);
     await _outputDependenciesDelta(compiledSources);
     _outputStream

pkg/vm/lib/kernel_front_end.dart

@@ -595,28 +595,6 @@ Future writeOutputSplitByPackages(
   BytecodeOptions bytecodeOptions,
   bool dropAST: false,
 }) async {
-  // Package sharing: make the encoding not depend on the order in which parts
-  // of a package are loaded.
-  component.libraries.sort((Library a, Library b) {
-    return a.importUri.toString().compareTo(b.importUri.toString());
-  });
-  component.computeCanonicalNames();
-  for (Library lib in component.libraries) {
-    lib.additionalExports.sort((Reference a, Reference b) {
-      return a.canonicalName.toString().compareTo(b.canonicalName.toString());
-    });
-  }
-
-  final packagesSet = new Set<String>();
-  for (Library lib in component.libraries) {
-    packagesSet.add(packageFor(lib));
-  }
-  packagesSet.remove('main');
-  packagesSet.remove(null);
-
-  final List<String> packages = packagesSet.toList();
-  packages.add('main'); // Make sure main package is last.
-
   if (bytecodeOptions.showBytecodeSizeStatistics) {
     BytecodeSizeStatistics.reset();
   }
@@ -629,31 +607,24 @@ Future writeOutputSplitByPackages(
         new ClassHierarchy(component, onAmbiguousSupertypes: (cls, a, b) {});
   }
 
+  final packages = new List<String>();
   await runWithFrontEndCompilerContext(source, compilerOptions, component,
       () async {
-    for (String package in packages) {
+    await forEachPackage(component,
+        (String package, List<Library> libraries) async {
+      packages.add(package);
       final String filename = '$outputFileName-$package.dilp';
       final IOSink sink = new File(filename).openWrite();
 
-      final main = component.mainMethod;
-      final problems = component.problemsAsJson;
-      if (package != 'main') {
-        component.mainMethod = null;
-        component.problemsAsJson = null;
-      }
-
       Component partComponent = component;
       if (genBytecode) {
-        final List<Library> libraries = component.libraries
-            .where((lib) => packageFor(lib) == package)
-            .toList();
-        generateBytecode(component,
+        generateBytecode(partComponent,
             options: bytecodeOptions,
             libraries: libraries,
             hierarchy: hierarchy);
 
         if (dropAST) {
-          partComponent = createFreshComponentWithBytecode(component);
+          partComponent = createFreshComponentWithBytecode(partComponent);
         }
       }
 
@@ -661,11 +632,8 @@ Future writeOutputSplitByPackages(
           (lib) => packageFor(lib) == package, false /* excludeUriToSource */);
       printer.writeComponentFile(partComponent);
 
-      component.mainMethod = main;
-      component.problemsAsJson = problems;
-
       await sink.close();
-    }
+    });
   });
 
   if (bytecodeOptions.showBytecodeSizeStatistics) {
@@ -692,6 +660,47 @@ String packageFor(Library lib) {
   return 'main';
 }
 
+Future<Null> forEachPackage<T>(Component component,
+    T action(String package, List<Library> libraries)) async {
+  // Package sharing: make the encoding not depend on the order in which parts
+  // of a package are loaded.
+  component.libraries.sort((Library a, Library b) {
+    return a.importUri.toString().compareTo(b.importUri.toString());
+  });
+  component.computeCanonicalNames();
+  for (Library lib in component.libraries) {
+    lib.additionalExports.sort((Reference a, Reference b) {
+      return a.canonicalName.toString().compareTo(b.canonicalName.toString());
+    });
+  }
+
+  final packages = new Map<String, List<Library>>();
+  for (Library lib in component.libraries) {
+    packages.putIfAbsent(packageFor(lib), () => new List<Library>()).add(lib);
+  }
+  if (packages.containsKey(null)) {
+    packages.remove(null);
+  }
+  if (packages.containsKey('main')) {
+    // Make sure main package is last.
+    packages['main'] = packages.remove('main');
+  }
+
+  for (String package in packages.keys) {
+    final main = component.mainMethod;
+    final problems = component.problemsAsJson;
+    if (package != 'main') {
+      component.mainMethod = null;
+      component.problemsAsJson = null;
+    }
+
+    await action(package, packages[package]);
+
+    component.mainMethod = main;
+    component.problemsAsJson = problems;
+  }
+}
+
 String _escapePath(String path) {
   return path.replaceAll('\\', '\\\\').replaceAll(' ', '\\ ');
 }