Martin Kustermann
9b11bf4da9
Some wasm engines have started to optimize the `js-string` builtin
proposal (e.g. V8) and those that haven't yet are probaly going to
do soon.
So we can start taking advantage of it in dart2wasm.
=> We make use of them in the JS<->Dart string copy code.
=> This will also provide a better baseline when evaluating whether
switching to JS stringes entirely makes sense.
A somewhat unrelated (but necessary for this CL) change is to tighten
the types we use in `@pragma('wasm:import')` and
`@pragma('wasm:export')` in some cases:
We should only use 'pure' wasm types (i.e. not wasm struct / function
types we define for dart classes & functions) and mostly non-composed
types in import/exports as the `--closed-world` optimizations from
binaryen rely on that (and error otherwise).
Overall this leads to significant improvements in Dart<->JS
string copies.
The `WasmDataTransfer.*{From,To}BrowserString` benchmarks
improve something between 50-100%.
Change-Id: I2048113c462ecb2047402c0616d2b3b1f45773f5
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/400641
Commit-Queue: Martin Kustermann <kustermann@google.com>
Reviewed-by: Slava Egorov <vegorov@google.com>
35 lines
1.1 KiB
Dart
35 lines
1.1 KiB
Dart
// Copyright (c) 2024, 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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import 'dart:js_interop';
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import 'package:expect/expect.dart';
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main() async {
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final String oneByteString = makeLongString('012345789');
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final String twoByteString = makeLongString('01234中6789');
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Expect.equals(oneByteString, roundTrip(oneByteString));
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Expect.equals(twoByteString, roundTrip(twoByteString));
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}
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/// Ensure we make a very long string, ensuring that we'll also hit slow paths
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/// in the string copy implementation.
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String makeLongString(String string) {
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while (string.length < 1024 * 1024) {
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string = string + string;
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}
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return string;
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}
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/// Copies the string to JS and back again to a dart internal String.
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String roundTrip(String dartString) {
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final JSString jsString = dartString.toJS;
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// Using string interpolation will force conversion to internal string (vs
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// `JSStringImpl`)
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final string = 'A${jsString.toDart}Z';
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return string.substring(1, string.length - 1);
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}
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