Martin Kustermann
20fc102287
Currently we have 3 different string types (JS Strings, OneByteString and TwoByteString)s. There's some advantages to this, mainly that if strings are used purely inside Dart we have more control over optimizing them. But it does come with some issues * Operations on mixture of strings are slow * We get JS strings from outside (in DevTools e.g. websocket messages) * Any kind of DOM interaction requires copying strings * Regular expression matches can result in O(N*N) instead of O(N) * Encoding of string literals/constants is terrible, high size overhead * ... Now that there's a standardized way to access JS strings (via the `js-string` builtin spec) and this standard is finalized and enabled in Chrome & Firefox it makes sense for us to switch to it. It reduces app size: * Smaller size: hello world -25%, flute -5.5% * Faster startup The performance changes are nuanced, some workloads will improve significantly, some workloads will regress. Improvements will come especially in cases where strings are concatenated (due to JS not actually allocating new strings in this case). That impacts e.g. string interpolations, string buffer, json-to-string encoding, ... Regressions will come especially for cases where we have to construct strings from bytes (e.g. in utf8 decoder, utf8+json decoder) - mainly due to having to go through an intermediary `WasmArray<WasmI16>` to allocate strings. Also in cases where we access individual char codes from the strings. There's some follow-up improvements we can do, but it's better to not iterate on this CL even longer but get it landed. This CL will make the benchmarking system use `--require-js-string-builtin` as well as most of test CI (in `pkg/dart2wasm/tool/compile_benchmark`) Though we run some configurations via overriding with `--no-require-js-string-builtin` (in `tools/bots/test_matrix.json`) Issue https://github.com/flutter/flutter/issues/159400#issuecomment-2538593980 Issue https://github.com/dart-lang/sdk/issues/59699 TEST=ci Change-Id: I238ac65efe092de569da870f23134f889ac929f9 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/392903 Reviewed-by: Slava Egorov <vegorov@google.com> Reviewed-by: Lasse Nielsen <lrn@google.com> Commit-Queue: Martin Kustermann <kustermann@google.com>
This package hosts VM specific Dart code and helper scripts.