commit 719c0a91dc401bc53ff49e8e085b086c5168a46a
author Tess Strickland <sstrickl@google.com> Mon Jun 26 09:27:59 2023 +0000
committer Commit Queue <dart-scoped@luci-project-accounts.iam.gserviceaccount.com> Mon Jun 26 09:27:59 2023 +0000
tree 8392f231411869560821bbcbacfd6b75d1752468
parent 06e099884b46f23761b6ce351384aee6df204a97

[vm] Remove UntaggedField::type_test_cache_.

This field is now only used when reloading to check assignability
during `ProgramReloadContext::ReloadPhase4CommitFinish()` (via
`PostCommit()` -> `InvalidateWorld()` -> `InvalidateFields`).

However, the method `DeoptimizeDependentCode()` is called near the
start of the actual reloading process in `Reload` prior to the
commit/rollback phases. This calls `DeoptimizeTypeTestingStubs()`, which
walks the heap and resets the contents of all `SubtypeTestCaches`
(`STC`s).

That means that the `STC` information isn't actually kept between
different reloads, so all this does is cause a number of `STC` objects
to be allocated during reload whose backing arrays are not used
post-reload for anything and so are unnecessary garbage.

That, and the creation of the `STC`s during `InvalidateFields` creates
all-input `STC`s, as they don't just check assignability to a given field type but also for checking elements of `RecordTypes`. That means
the per-field `STC`s contain way more information needed to check for
valid assignments to the corresponding field type, even if the `STC`
was used between reloads.

This CL removes the unnecessary field and changes `InvalidateFields`
so that the `STC`s used during reload are instead lazily allocated once
per `FieldInvalidator` object and now both the `STC` and its backing
array are now garbage post-field invalidation.

TEST=reload ci

Change-Id: I3ffa199551ba69f0afd4eba6303c6ff73d7473a3
Cq-Include-Trybots: luci.dart.try:vm-reload-linux-debug-x64-try,vm-reload-linux-release-x64-try,vm-reload-rollback-linux-debug-x64-try,vm-reload-rollback-linux-release-x64-try,vm-aot-linux-debug-x64-try,vm-aot-linux-product-x64-try,vm-aot-linux-release-x64-try,vm-linux-release-x64-try,vm-linux-debug-x64-try,vm-aot-dwarf-linux-product-x64-try
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/311220
Commit-Queue: Tess Strickland <sstrickl@google.com>
Reviewed-by: Martin Kustermann <kustermann@google.com>