We support allocating deeply immutable typed data in the Dart C API
already.
=> This CL adds a test for that.
Furthermore we hook into the already O(n) construction of
`List.unmodifiable(<list>)` and set the objects immutable bit
if all elements of `<list>` are also immutable.
=> This allows then sharing of such lists when sent across isolates.
We do this eagerly to
- avoid introducing complexity to the deep immutability check in
transitive copy algorithm
- avoids re-checking for the subgraph on every send (similar to
canonicalized bit for constants, we can simply rely on the
immutable bit)
If we ever optimized `List.unmodifiable()` (which always performs
runtime call atm) we could fold this checking into the place that copies
list elements from `<list>` to the newly allocated list.
Issue https://github.com/dart-lang/sdk/issues/51302
TEST=vm/dart{,_2}/isolates/fast_object_copy2_test
Change-Id: Ie275e65036a4c53d992804972aae741a9f5ed6dd
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/281424
Reviewed-by: Ryan Macnak <rmacnak@google.com>
Reviewed-by: Alexander Aprelev <aam@google.com>
Commit-Queue: Martin Kustermann <kustermann@google.com>
Martin Kustermann
896e535fe9