Jens Johansen
e491bc5d86
This CL updates the frontend_server to allow specifying what dill file to initialize from. Normally, it tries to initialize from the same dill file as is the output. This is fine in many cases (e.g. flutter run always says it should output to build/app.dill): The first time it compiles everything, subsequent times (across restarts) it only recompiles what's needed. When running tests, however, the output is in a temporary directory, so it doesn't work across restarts. The startup time for tests is always rather high, because it always has to recompile everything. This CL updates the frontend_server to allow specifying what dill file to initialize from. Flutter can thus save the compiled test file in a centralized location (e.g. build/test.dill) and load from that across restarts. Plumbing this into flutter yields the following result, when running a single test (the one automatically created when creating a new flutter project): Before: ~5.5 seconds Now, first run: ~5.5 second (unchanged) Now, subsequent runs: ~3.4 seconds Approximate breakdown: Startup cost (e.g. if there's no test directory): ~ 800 ms Starting up the actual frontend server: ~150 ms Reading source from old dill, loading all relevant files and invalidating source: ~ 300 ms Compiling everything (or, rather, nothing as it's all from the dill at this point): ~ 650 ms Serializing: ~ 250 ms Copying files: ~ 50 ms Running the actual test: ~1100 ms Total: ~3300 ms `time flutter test --local-engine=host_debug --preview-dart-2` says ~3.4 seconds... To compare, --no-preview-dart-2 takes ~2.2 seconds, so dart2 still has a (significantly) higher startup cost. Moves the needle on https://github.com/flutter/flutter/issues/15767. Change-Id: I36a2d05bc76e0193d369df42eb3b9f08416dd78f Reviewed-on: https://dart-review.googlesource.com/51820 Reviewed-by: Kevin Millikin <kmillikin@google.com> Reviewed-by: Vyacheslav Egorov <vegorov@google.com> Commit-Queue: Jens Johansen <jensj@google.com>
Dart Kernel
Dart Kernel is a small high-level language derived from Dart. It is designed for use as an intermediate format for whole-program analysis and transformations, and as a frontend for codegen and execution backends.
The kernel language has in-memory representations in Dart and C++, and can be serialized as binary or text.
Both the kernel language and its implementations are unstable and are under development.
This package contains the Dart part of the implementation and contains:
- A transformable IR for the kernel language
- A frontend based on the analyzer
- Serialization of kernel code
Note: The APIs in this package are in an early state; developers should be careful about depending on this package. In particular, there is no semver contract for release versions of this package. Please depend directly on individual versions.
Getting Kernel
Checkout the repository and run pub get:
git clone https://github.com/dart-lang/kernel
cd kernel
pub get
Command-Line Tool
Run tool/dartk.dart from the command-line to convert between .dart files
and the serialized binary and textual formats.
dartk expects the .dill extension for files in the binary format.
The textual format has no preferred extension right now.
Example commands:
dartk foo.dart # print text IR for foo.dart
dartk foo.dart -ofoo.dill # write binary IR for foo.dart to foo.dill
dartk foo.dill # print text IR for binary file foo.dill
Pass the --link or -l flag to link all transitive dependencies into one file:
dartk myapp.dart -ppackages -l -omyapp.dill # Bundle everything.
dartk myapp.dill # Print it back out in a (very, very long) textual format.
See ast.dart for the in-memory IR, or binary.md for a description of the binary format. For now, the textual format is very ad-hoc and cannot be parsed back in.
Testing
If you plan to make changes to kernel, get a checkout of the Dartk SDK and run:
tool/regenerate_dill_files.dart --sdk <path to SDK checkout>
pub run test
Linking
Linking from binary files is not yet implemented. In order to compile a whole program, currently everything must be compiled from source at once.