[vm/concurrency] Ensure rehashing of maps correctly resets [_deletedKeys]

When we rehash a linked hash map, we rebuild the index but keep the
existing data array. The [_deletedKeys] specifies the number of entries in the
[_index] which were marked as deleted. The Dart code that triggers
rehashing and initializes a new [_index] didn't initialize

=> We'll fix this in the Dart code and as a precaution also in the
   transitive object copy code.

Furthermore we add a missing optimization: In the example from the bug
report we shouldn't even have attempted to re-hash, because the maps
have only primitive keys (which do not rely on identity or user-defined

=> We'll change the existing optimization to ignore deleted entries when
   determining whether a rehash is needed.

The rehashing code for Sets works differently and takes this already
into account.

Closes https://github.com/dart-lang/sdk/issues/47598


Change-Id: I3529ecbf500009ab0c72b98e6c427b8840a69371
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/219000
Reviewed-by: Alexander Aprelev <aam@google.com>
Commit-Queue: Martin Kustermann <kustermann@google.com>
4 files changed
tree: 284c06ad6ec6efe002203d1209af4512ab000e7f
  1. .dart_tool/
  2. .github/
  3. benchmarks/
  4. build/
  5. client/
  6. docs/
  7. pkg/
  8. runtime/
  9. samples/
  10. samples-dev/
  11. samples_2/
  12. sdk/
  13. tests/
  14. third_party/
  15. tools/
  16. utils/
  17. .clang-format
  18. .gitattributes
  19. .gitconfig
  20. .gitignore
  21. .gn
  22. .mailmap
  23. .packages
  24. .style.yapf
  25. .vpython
  27. BUILD.gn
  28. CHANGELOG.md
  29. codereview.settings
  31. DEPS
  34. PRESUBMIT.py
  35. README.dart-sdk
  36. README.md
  37. sdk_args.gni
  38. SECURITY.md


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