I have a branch doing that (https://github.com/petrochenkov/rust/tree/cstore) and would like to notify others about it to avoid stepping on each other's toes (not sure this is the right place).
Removing the lock wasn't the original goal, but it kinda happened naturally after the crate loader was turned into an internal detail of the resolver.
The [WIP] commit needs some serious cleanup, but I hope to do it in some of the next days and make a PR.
I think this is a good place. cc @WG-parallel-rustc
(and that sounds great, thanks!)
@Vadim Petrochenkov very cool!
PR submitted - https://github.com/rust-lang/rust/pull/65625.