Stephen Adams
d8b7ec5163
On a per output-unit basis, repeated large strings are shared via a `string$` pool. TODOs: - don't do it with strings passed to JS() code (they might need to be property accesses). - tweak thresholds, using different thresholds for slow/run-once code. Change-Id: Ib14245d9d428e52fb2ca23f34fa533de97fa2208 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/136304 Reviewed-by: Joshua Litt <joshualitt@google.com> Commit-Queue: Stephen Adams <sra@google.com>
120 lines
2.9 KiB
Dart
120 lines
2.9 KiB
Dart
// Copyright (c) 2020, the Dart project authors. Please see the AUTHORS file
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// for details. All rights reserved. Use of this source code is governed by a
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// BSD-style license that can be found in the LICENSE file.
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// @dart = 2.7
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import "package:expect/expect.dart";
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import 'package:compiler/src/constants/values.dart' show StringConstantValue;
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import 'package:compiler/src/js_backend/string_reference.dart'
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show StringReference, StringReferenceResource, StringReferenceFinalizerImpl;
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import 'package:compiler/src/js/js.dart' show prettyPrint;
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void test(List<String> strings, String expected, {bool minified: false}) {
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var finalizer =
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StringReferenceFinalizerImpl(minified, shortestSharedLength: 5);
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for (var string in strings) {
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finalizer.addCode(StringReference(StringConstantValue(string)));
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}
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StringReferenceResource resource = StringReferenceResource();
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finalizer.registerStringReferenceResource(resource);
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finalizer.finalize();
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Expect.equals(expected.trim(), prettyPrint(resource).trim());
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}
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extension on List<String> {
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// TODO(42122): Remove when analyzer doesn't think `*` is unused.
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// ignore: unused_element
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List<String> operator *(int count) {
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return List.filled(count, this).expand((list) => list).toList();
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}
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}
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void main() {
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// No strings yields an empty pool.
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test([], '0');
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// Single occurrence strings are not pooled.
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test(
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['Yellow', 'Blue', 'Crimson'],
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'0',
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);
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// Repeated strings that are long enough are pooled.
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test(
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['Yellow', 'Blue', 'Blue', 'Crimson', 'Crimson'],
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r'''
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var string$ = {
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Crimso: "Crimson"
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}''',
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);
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// Readable property names have identical stretches compressed-out.
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var greets = [
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'Greetings Bob Smith',
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'Great work!',
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'Greetings Alice',
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'Greetings Bob Henry'
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];
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test(
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greets * 2,
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r'''
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var string$ = {
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Great_: "Great work!",
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GreetiA: "Greetings Alice",
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GreetiBH: "Greetings Bob Henry",
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GreetiBS: "Greetings Bob Smith"
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}''',
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);
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// Non-identifiers are replaced with '_' if that is unambiguous.
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test(
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['xylograph', '!pingpong'] * 2,
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r'''
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var string$ = {
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_pingp: "!pingpong",
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xylogr: "xylograph"
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}''',
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);
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final strings1 = [
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...['a xylograph'] * 2,
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...['a !pingpong'] * 4,
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...['a %percent'] * 6,
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];
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// Multiple discriminating non-identifier characters are replaced with an
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// escape, which causes a potentially ambiguous non-escape to be escaped.
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test(
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strings1,
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r'''
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var string$ = {
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a_x21pin: "a !pingpong",
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a_x25per: "a %percent",
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a_x78ylo: "a xylograph"
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}''',
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);
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// Minified version keeps the strings in the same order as unminified, and
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// tries to allocate the same minified name.
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const minified1 = r'''
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var string$ = {
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l: "a !pingpong",
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o: "a %percent",
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n: "a xylograph"
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}''';
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final strings2 = [
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...['a xylograph'] * 20, // now most frequent.
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...strings1
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];
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test(strings1, minified1, minified: true);
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test(strings2, minified1, minified: true);
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}
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