The element map indexing system adds complexity to our element model with little benefit. Serialization already has its own indexing logic that we now reuse for entities.
Some things to note:
1) Libraries are still assigned an index. We only use that index in one place in the namer to disambiguate members. I now assign these indices as a late final field when adding the libraries to the element map.
2) The sizes of serialized files get slightly bigger since serialization indexing uses "addresses" rather than incrementing numbers for the indices. This effect is very minimal (<4MB+ for the largest programs).
3) "Late" members (constructor and generator bodies) which are created during codegen must be tracked and registered separately. Before the index was used to determine which entities were "late".
I see a very small memory improvement across all phases because of this change. There is also a small regression in runtime because the entity map queries are hash map lookups instead of list index lookups now. I think this very small regression is worth the reduced complexity in the compiler.
If we care about getting that time regression back we can add an "IndexedEntityMixin" with a late final index member that the registry would set/manage internally and would allow it to go back to tracking entities in a List. The field should be private so it would only be used for this purpose. This would only be necessary if we find the added time overhead of the map lookups to be too much.
Change-Id: Idd6d22bfc6ab61943a07feb58b35287d50e7d72e
Reviewed-on: https://dart-review.googlesource.com/c/sdk/+/326461
Reviewed-by: Mayank Patke <fishythefish@google.com>
Reviewed-by: Sigmund Cherem <sigmund@google.com>
Reviewed-by: Stephen Adams <sra@google.com>
Commit-Queue: Nate Biggs <natebiggs@google.com>
Nate Biggs
232d716474