[llvm] [Transforms][Utils] Reject unsafe iteration spaces in LoopSplitUtils (PR #214272)

[Ashutosh Nema via llvm-commits]

nema-ashutosh wrote:

Split the patch into three independent PRs:
  #214272 - refuse iteration spaces that wrap or saturate at the type extreme (original)
  #214453 - handle live-outs not defined in the loop
  #214452 - default the pass to innermost loops, with -loop-split-outer for top-level

https://github.com/llvm/llvm-project/pull/214272