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

[Quentin Dian via llvm-commits]

DianQK wrote:

> 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?

I agree. `ErasedInstrs` makes maintenance complicated. I would be concerned that this issue would reappear again due to some sort of input. I think there is a need to redesign a solution.

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