| commit | 0d0e302c3dd078ca4173c616b2ea98708ff2db7a | [log] [tgz] |
|---|---|---|
| author | Nate Biggs <natebiggs@google.com> | Thu Jul 24 11:07:58 2025 -0700 |
| committer | dart-internal-monorepo <dart-internal-monorepo@dart-ci-internal.iam.gserviceaccount.com> | Thu Jul 24 11:10:38 2025 -0700 |
| tree | 7e6910d48424309c7128f6f6dbc1cdeaa038790a | |
| parent | b222322deb22b8035b054e87c547c1b642eb0e83 [diff] |
[dart2wasm] Generate br_table for some switch statements. Often switches over enums are exhaustive or nearly exhaustive. The current generator uses identity for the enum values which requires iterating over each value to compare it to the test expression. So each time the switch body is entered is an O(n) operation (where is n is the # of case expressions). This now generates a br_table using the index of the enum and jumps directly to the correct clause, effectively an O(1) operation. A similar approach is taken for switches over an integer range. If the range of case expresison values is close in size to the # of values, it is advantageous to normalize the range around 0 and treat the values themselves as table indices. This approach will also save code size when the index range is dense as the br_table is more compact than the identity/br_if checks. For sparse ranges this may produce a bit more code though only on the order of a few bytes per value in the range. I've added a denseness heuristic to decide when to revert to the current strategy to avoid the code size penalty. Golem benchmark: https://golem.corp.goog/Comparison?repository=dart#targetA%3Ddart2wasm-O2-d8%3BmachineTypeA%3Dlinux-x64%3BrevisionA%3D117402%3BpatchA%3Dnatebiggs-dart2wasm-switch-tables3%3BtargetB%3Ddart2wasm-O2-d8%3BmachineTypeB%3Dlinux-x64%3BrevisionB%3D117401%3BpatchB%3DNone See 100% improvement in SwitchFSM.int and 90% improvement in SwitchFSM.enum. Change-Id: Ie29e8fd59ef6235044ba5b4a4af04023d702ce57 Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/441760 Reviewed-by: Ömer Ağacan <omersa@google.com> Commit-Queue: Nate Biggs <natebiggs@google.com> https://dart.googlesource.com/sdk/+/2254755d65a4b8c9bcce6489de9dee5233ac3077
Monorepo is:
With depot_tools installed and on your path, create a directory for your monorepo checkout and run these commands to create a gclient solution in that directory:
mkdir monorepo cd monorepo gclient config --unmanaged https://dart.googlesource.com/monorepo gclient sync -D
This gives you a checkout in the monorepo directory that contains:
monorepo/ DEPS - the DEPS used for this gclient checkout commits.json - the pinned commits for Dart, flutter/engine, and flutter/flutter tools/ - scripts used to create monorepo DEPS engine/src/ - the flutter/buildroot repo flutter/ - the flutter/engine repo out/ - the build directory, where Flutter engine builds are created third_party/ - Flutter dependencies checked out by DEPS dart/ - the Dart SDK checkout. third_party - Dart dependencies, also used by Flutter flutter/ - the flutter/flutter repo
Flutter's instructions for building the engine are at Compiling the engine
They can be followed closely, with a few changes:
goma_ctl ensure_start is sufficient.Example build commands that work on linux:
MONOREPO_PATH=$PWD if [[ ! $PATH =~ (^|:)$MONOREPO_PATH/flutter/bin(:|$) ]]; then PATH=$MONOREPO_PATH/flutter/bin:$PATH fi export GOMA_DIR=$(dirname $(command -v gclient))/.cipd_bin goma_ctl ensure_start pushd engine/src flutter/tools/gn --goma --no-prebuilt-dart-sdk --unoptimized --full-dart-sdk autoninja -C out/host_debug_unopt popd
The Flutter commands used to build and run apps will use the locally built Flutter engine and Dart SDK, instead of the one downloaded by the Flutter tool, if the --local-engine option is provided.
For example, to build and run the Flutter spinning square sample on the web platform,
MONOREPO_PATH=$PWD cd flutter/examples/layers flutter --local-engine=host_debug_unopt \ -d chrome run widgets/spinning_square.dart cd $MONOREPO_PATH
To build for desktop, specify the desktop platform device in flutter run as -d macos or -d linux or -d windows. You may also need to run the command
flutter create --platforms=windows,macos,linux
on existing apps, such as sample apps. New apps created with flutter create already include these support files. Details of desktop support are at Desktop Support for Flutter
Tests in the Flutter source tree can be run with the flutter test command, run in the directory of a package containing tests. For example:
MONOREPO_PATH=$PWD cd flutter/packages/flutter flutter test --local-engine=host_debug_unopt cd $MONOREPO_PATH
Please file an issue or email the dart-engprod team with any problems with or questions about using monorepo.
We will update this documentation to address them.
flutter commands may download the engine and Dart SDK files for the configured channel, even though they will be using the local engine and its SDK.gclient sync needs to be run in an administrator session, because some installed dependencies create symlinks.