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[pkg/vm] Initial work on constant operating system fields and getters.

* Add an `targetOS` argument to `pkg/vm`'s `compileToKernel`,
  that contains the target operating system's name.

* Add a new `--target-os` command line argument for all binaries
  that use `compileToKernel` for clients to provide the target
  operating system, if known.

* Add a new`"vm:platform:const"` annotation to certain field and
  getters in the Platform class.

  This annotation is used to annotate static getters and fields with
  initializers where the getter body or field initializer must evaluate
  to a constant value if the target operating system is known. This
  annotation may be used outside the Platform class and in user code.

  For example, this annotation can be used on a static `String` field
  that is initialized with one value if `Platform.isWindows` is true
  and to a different value if `Platform.isWindows` is false.

  Note: If the const functions experimental flag is disabled, then
  any annotated static methods can only contain a single expression
  whose value is returned. If it is enabled, then the static method
  is evaluated as if it is a const function with the special
  handling of annotated static fields and getters above.

* Create a VM constant evaluator that evaluates uses of static getters
  and fields marked with the above annotations when a target operating
  system is provided.

* Use the new VM constant evaluator in the unreachable code elimination
  transformer.

TEST=pkg/vm/test/transformations/platform_use_transformer
     pkg/vm/test/transformations/unreachable_code_elimination

Change-Id: Ie381de70486a767fd7b1d515fd9e6bb58c6bf090
Bug: https://github.com/dart-lang/sdk/issues/31969
Cq-Include-Trybots: luci.dart.try:pkg-linux-release-try
CoreLibraryReviewExempt: Just adding vm-specific annotations.
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/274386
Commit-Queue: Tess Strickland <sstrickl@google.com>
Reviewed-by: Chloe Stefantsova <cstefantsova@google.com>
Reviewed-by: Alexander Markov <alexmarkov@google.com>
Reviewed-by: Martin Kustermann <kustermann@google.com>
26 files changed
tree: 2502235f9963580c0d66569f314e9c50fa9e3b94
  1. .dart_tool/
  2. .github/
  3. benchmarks/
  4. build/
  5. docs/
  6. pkg/
  7. runtime/
  8. samples/
  9. sdk/
  10. tests/
  11. third_party/
  12. tools/
  13. utils/
  14. .clang-format
  15. .gitattributes
  16. .gitconfig
  17. .gitignore
  18. .gn
  19. .mailmap
  20. .style.yapf
  21. .vpython
  22. AUTHORS
  23. BUILD.gn
  24. CHANGELOG.md
  25. codereview.settings
  26. CONTRIBUTING.md
  27. DEPS
  28. LICENSE
  29. OWNERS
  30. PATENT_GRANT
  31. PRESUBMIT.py
  32. README.dart-sdk
  33. README.md
  34. sdk_args.gni
  35. SECURITY.md
  36. WATCHLISTS
README.md

Dart

A client-optimized language for fast apps on any platform

Dart is:

  • Optimized for UI: Develop with a programming language specialized around the needs of user interface creation.

  • Productive: Make changes iteratively: use hot reload to see the result instantly in your running app.

  • Fast on all platforms: Compile to ARM & x64 machine code for mobile, desktop, and backend. Or compile to JavaScript for the web.

Dart's flexible compiler technology lets you run Dart code in different ways, depending on your target platform and goals:

  • Dart Native: For programs targeting devices (mobile, desktop, server, and more), Dart Native includes both a Dart VM with JIT (just-in-time) compilation and an AOT (ahead-of-time) compiler for producing machine code.

  • Dart Web: For programs targeting the web, Dart Web includes both a development time compiler (dartdevc) and a production time compiler (dart2js).

Dart platforms illustration

License & patents

Dart is free and open source.

See LICENSE and PATENT_GRANT.

Using Dart

Visit dart.dev to learn more about the language, tools, and to find codelabs.

Browse pub.dev for more packages and libraries contributed by the community and the Dart team.

Our API reference documentation is published at api.dart.dev, based on the stable release. (We also publish docs from our beta and dev channels, as well as from the primary development branch).

Building Dart

If you want to build Dart yourself, here is a guide to getting the source, preparing your machine to build the SDK, and building.

There are more documents on our wiki.

Contributing to Dart

The easiest way to contribute to Dart is to file issues.

You can also contribute patches, as described in Contributing.