Add sync star benchmark cases (#36303)

dev/benchmarks/microbenchmarks/lib/language/sync_star_bench.dart

+// Copyright 2019 The Flutter 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 '../common.dart';
+
+const int _kNumIterations = 1000;
+const int _kNumWarmUp = 100;
+
+void main() {
+  assert(false, "Don't run benchmarks in checked mode! Use 'flutter run --release'.");
+
+  // Warm up lap
+  for (int i = 0; i < _kNumWarmUp; i += 1) {
+    sumIterable(generateIterableSyncStar());
+    sumIterable(generateIterableList());
+    sumIterable(Iterable<int>.generate(100, generate));
+  }
+
+  final Stopwatch watch = Stopwatch();
+  watch.start();
+  for (int i = 0; i < _kNumIterations; i += 1) {
+    sumIterable(generateIterableSyncStar());
+  }
+  final int traverseIterableSyncStar = watch.elapsedMicroseconds;
+  watch
+    ..reset()
+    ..start();
+  for (int i = 0; i < _kNumIterations; i += 1) {
+    sumIterable(generateIterableList());
+  }
+  final int traverseIterableList = watch.elapsedMicroseconds;
+  watch
+    ..reset()
+    ..start();
+  for (int i = 0; i < _kNumIterations; i += 1) {
+    sumIterable(Iterable<int>.generate(100, generate));
+  }
+  final int traverseIterableGenerated = watch.elapsedMicroseconds;
+  watch
+    ..reset()
+    ..start();
+
+  final BenchmarkResultPrinter printer = BenchmarkResultPrinter();
+  const double scale = 1000.0 / _kNumIterations;
+  printer.addResult(
+    description: 'traverseIterableSyncStar',
+    value: traverseIterableSyncStar * scale,
+    unit: 'ns per iteration',
+    name: 'traverseIterableSyncStar_iteration',
+  );
+  printer.addResult(
+    description: 'traverseIterableList',
+    value: traverseIterableList * scale,
+    unit: 'ns per iteration',
+    name: 'traverseIterableList_iteration',
+  );
+  printer.addResult(
+    description: 'traverseIterableGenerated',
+    value: traverseIterableGenerated * scale,
+    unit: 'ns per iteration',
+    name: 'traverseIterableGenerated_iteration',
+  );
+  printer.printToStdout();
+}
+
+int generate(int index) => index;
+
+// Generate an Iterable using a sync* method.
+Iterable<int> generateIterableSyncStar() sync* {
+  for (int i = 0; i < 100; i++) {
+    yield i;
+  }
+}
+
+// Generate an Iterable using a List.
+Iterable<int> generateIterableList() {
+  final List<int> items = <int>[];
+  for (int i = 0; i < 100; i++) {
+    items.add(i);
+  }
+  return items;
+}
+
+int sumIterable(Iterable<int> values) {
+  int result = 0;
+  for (int value in values) {
+    result += value;
+  }
+  return result;
+}

dev/benchmarks/microbenchmarks/lib/language/sync_star_semantics_bench.dart

+// Copyright 2019 The Flutter 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 'package:flutter/widgets.dart';
+
+import '../common.dart';
+
+const int _kNumIterations = 1000;
+const int _kNumWarmUp = 100;
+
+void main() {
+  final List<String> words = 'Lorem Ipsum is simply dummy text of the printing and'
+    'typesetting industry. Lorem Ipsum has been the industry\'s'
+    ' standard dummy text ever since the 1500s, when an unknown'
+    ' printer took a galley of type and scrambled it to make a'
+    ' type specimen book'.split(' ');
+  final List<InlineSpanSemanticsInformation> data = <InlineSpanSemanticsInformation>[];
+  for (int i = 0; i < words.length; i++) {
+    if (i.isEven) {
+      data.add(
+        InlineSpanSemanticsInformation(words[i], isPlaceholder: false),
+      );
+    } else if (i % 2 == 0) {
+      data.add(
+        InlineSpanSemanticsInformation(words[i], isPlaceholder: true),
+      );
+    }
+  }
+  print(words);
+
+  // Warm up lap
+  for (int i = 0; i < _kNumWarmUp; i += 1) {
+    combineSemanticsInfoSyncStar(data);
+    combineSemanticsInfoList(data);
+  }
+
+  final Stopwatch watch = Stopwatch();
+  watch.start();
+  for (int i = 0; i < _kNumIterations; i += 1) {
+    consumeSpan(combineSemanticsInfoSyncStar(data));
+  }
+  final int combineSemanticsInfoSyncStarTime = watch.elapsedMicroseconds;
+  watch
+    ..reset()
+    ..start();
+  for (int i = 0; i < _kNumIterations; i += 1) {
+    consumeSpan(combineSemanticsInfoList(data));
+  }
+  final int combineSemanticsInfoListTime = watch.elapsedMicroseconds;
+  watch
+    ..reset()
+    ..start();
+
+  final BenchmarkResultPrinter printer = BenchmarkResultPrinter();
+  const double scale = 1000.0 / _kNumIterations;
+  printer.addResult(
+    description: 'combineSemanticsInfoSyncStar',
+    value: combineSemanticsInfoSyncStarTime * scale,
+    unit: 'ns per iteration',
+    name: 'combineSemanticsInfoSyncStar_iteration',
+  );
+  printer.addResult(
+    description: 'combineSemanticsInfoList',
+    value: combineSemanticsInfoListTime * scale,
+    unit: 'ns per iteration',
+    name: 'combineSemanticsInfoList_iteration',
+  );
+  printer.printToStdout();
+}
+
+String consumeSpan(Iterable<InlineSpanSemanticsInformation> items) {
+  String result = '';
+  for (InlineSpanSemanticsInformation span in items) {
+    result += span.text;
+  }
+  return result;
+}
+
+
+Iterable<InlineSpanSemanticsInformation> combineSemanticsInfoSyncStar(List<InlineSpanSemanticsInformation> inputs) sync* {
+  String workingText = '';
+  String workingLabel;
+  for (InlineSpanSemanticsInformation info in inputs) {
+    if (info.requiresOwnNode) {
+      if (workingText != null) {
+        yield InlineSpanSemanticsInformation(workingText, semanticsLabel: workingLabel ?? workingText);
+        workingText = '';
+        workingLabel = null;
+      }
+      yield info;
+    } else {
+      workingText += info.text;
+      workingLabel ??= '';
+      if (info.semanticsLabel != null) {
+        workingLabel += info.semanticsLabel;
+      } else {
+        workingLabel += info.text;
+      }
+    }
+  }
+  if (workingText != null) {
+    yield InlineSpanSemanticsInformation(workingText, semanticsLabel: workingLabel);
+  } else {
+    assert(workingLabel != null);
+  }
+}
+
+Iterable<InlineSpanSemanticsInformation> combineSemanticsInfoList(List<InlineSpanSemanticsInformation> inputs) {
+  String workingText = '';
+  String workingLabel;
+  final List<InlineSpanSemanticsInformation> result = <InlineSpanSemanticsInformation>[];
+  for (InlineSpanSemanticsInformation info in inputs) {
+    if (info.requiresOwnNode) {
+      if (workingText != null) {
+        result.add(InlineSpanSemanticsInformation(workingText, semanticsLabel: workingLabel ?? workingText));
+        workingText = '';
+        workingLabel = null;
+      }
+      result.add(info);
+    } else {
+      workingText += info.text;
+      workingLabel ??= '';
+      if (info.semanticsLabel != null) {
+        workingLabel += info.semanticsLabel;
+      } else {
+        workingLabel += info.text;
+      }
+    }
+  }
+  if (workingText != null) {
+    result.add(InlineSpanSemanticsInformation(workingText, semanticsLabel: workingLabel));
+  } else {
+    assert(workingLabel != null);
+  }
+  return result;
+}

dev/devicelab/lib/tasks/microbenchmarks.dart

@@ -56,6 +56,8 @@ TaskFunction createMicrobenchmarkTask() {
       ...await _runMicrobench('lib/gestures/velocity_tracker_bench.dart'),
       ...await _runMicrobench('lib/gestures/gesture_detector_bench.dart'),
       ...await _runMicrobench('lib/stocks/animation_bench.dart'),
+      ...await _runMicrobench('lib/language/sync_star_bench.dart'),
+      ...await _runMicrobench('lib/language/sync_star_semantics_bench.dart'),
     };
 
     return TaskResult.success(allResults, benchmarkScoreKeys: allResults.keys.toList());