[llvm] [DAG] Make RAUW skip instances where operand is the replacement node (PR #212724)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm commented:

This is a quite a lot of code to handle an edge case that shouldn't really happen. Is there any chance of fixing the combine code to not rely on this broken intermediate state?

https://github.com/llvm/llvm-project/pull/212724