[llvm] [LLVM][Transforms] Correct LoopSimplify unique block placement. (PR #105538)

[Tim Besard via llvm-commits]

maleadt wrote:

Is this something we want? I'm also somewhat concerned that there's tests that will fail when merging this; is there a way to (locally or not) get some additional coverage for this change?

Pinging some people who recently worked on LoopSimplify: @nikic @fhahn

https://github.com/llvm/llvm-project/pull/105538