[llvm] [IRCE] Fix '"Instruction does not dominate all uses!" after IRCE pass #63984' (PR #136505)

[Nikita Popov via llvm-commits]

https://github.com/nikic commented:

Can you please add a test case and some explanation to the PR description about what the problem is / why this fixes it?

https://github.com/llvm/llvm-project/pull/136505