[llvm] [RegisterCoalescer] Clear instructions not recorded in `ErasedInstrs` but erased (PR #79820)

[Quentin Colombet via llvm-commits]

https://github.com/qcolombet commented:

Sorry guys I'm late to the party.
Finally got time to look closer.
Ultimately I think the issue is we try to maintain a global state whereas the local and non-local worklist are not shared.

In this patch, I feel we are trying to reconstruct which list has been effectively modified and update the other one accordingly.

All in all, I think the complexity is not worth it.
Instead I would recommend that we stop being smart with ErasedInstrs and just remove that call to remove.

If the memory consumption is indeed a problem with ErasedInstrs growing, we can revisit.

@arsenm @DianQK what do you think?

https://github.com/llvm/llvm-project/pull/79820