[llvm] Reland "[Support] Assert that DomTree nodes share parent"" (PR #102782)

[Alexis Engelke via llvm-commits]

aengelke wrote:

Thanks @dyung for the reproducer, that was very helpful -- reduced further to a test case. I now was able to track it down to SLPVectorize and made a (imho) uncontroversial change to fix it.

>  Sorry for reverting, but it's better to revert and then investigate.

Sure, nothing to be sorry about! :)

https://github.com/llvm/llvm-project/pull/102782