[llvm] [CodeGen] Don't renumber invalid domtree (PR #102427)

[David Li via llvm-commits]

david-xl wrote:

The blocks are laid out in chains. For each BuildChain, the MPDT is checked to see if tailDup can be done for the successor, and taildup will be attempted after successor selection is done. It seems that this fix will nullify MPDT on the fly which can trigger segfault later?  Taildup is not happening frequently, so perhaps recalculate it instead of nullifying it?

https://github.com/llvm/llvm-project/pull/102427