[llvm] [SimplifyCFG] Use hash map to continue hoisting the common instructions (PR #78615)

[Nikita Popov via llvm-commits]

https://github.com/nikic requested changes to this pull request.

This PR is really pushing the bounds of what is appropriate to do in SimplifyCFG. The code has become quite hard to understand.

My primary concern with this implementation would be with non-determinism -- I don't think that your approach of only supporting hoisting for the first instruction with a given hash is viable (unless I am misunderstanding something).

https://github.com/llvm/llvm-project/pull/78615