[vm] Improvements in the BitField API.

If no position is specified, then the bitfield starts at bit 0.

The default size for bool BitFields is 1 instead of the remaining
bits in the container.

If the size of the value type is smaller than the remaining bits
in the container, then the size of the value type is used as
the default size instead.

If a signed value is used in a non-sign-extended BitField, only
the magnitude of the value is stored, not the sign bit. This means
the actual size of the bitfield may be one less than the requested
size in this case.

If the requested size of the bitfield is larger than the size of the
value type, a compile-time error is thrown. (For signed types, the
requested size is allowed to be the size of the entire value, even if
only the magnitude bits are stored.)

Rework uses of BitFields to avoid using separate constants for
bit positions/sizes except for macro-defined bitfields (which now
are universally bool, and so size 1).

TEST=vm/cc/BitFields_Defaults

Change-Id: I40711c929d2e5165ce40823772beb49e8cfdb820
Cq-Include-Trybots: luci.dart.try:vm-aot-dwarf-linux-product-x64-try,vm-aot-linux-debug-x64c-try,vm-aot-linux-release-x64-try,vm-aot-mac-release-arm64-try,vm-aot-linux-release-simarm_x64-try
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/381644
Reviewed-by: Ryan Macnak <rmacnak@google.com>
Commit-Queue: Tess Strickland <sstrickl@google.com>
16 files changed
tree: 82f3b286151710444edb91fb82c3bf65996f3977
  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. AUTHORS
  22. BUILD.gn
  23. CHANGELOG.md
  24. codereview.settings
  25. CONTRIBUTING.md
  26. DEPS
  27. LICENSE
  28. OWNERS
  29. PATENT_GRANT
  30. PRESUBMIT.py
  31. README.dart-sdk
  32. README.md
  33. sdk.code-workspace
  34. sdk_args.gni
  35. sdk_packages.yaml
  36. SECURITY.md
  37. WATCHLISTS
README.md

Dart

An approachable, portable, and productive language for high-quality apps on any platform

Dart is:

  • Approachable: Develop with a strongly typed programming language that is consistent, concise, and offers modern language features like null safety and patterns.

  • Portable: Compile to ARM, x64, or RISC-V machine code for mobile, desktop, and backend. Compile to JavaScript or WebAssembly for the web.

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

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 in our repo at docs.

Contributing to Dart

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

You can also contribute patches, as described in Contributing.

Roadmap

Future plans for Dart are included in the combined Dart and Flutter roadmap on the Flutter wiki.