[llvm] [Transforms][Utils] Add LoopSplitUtils for iteration-space loop splitting (PR #205995)

[Ramkumar Ramachandra via llvm-commits]

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artagnon wrote:

```suggestion
  if (ICmpInst::isRelational(P))
    return ICmpInst::isSigned(P);
  if (IndAR->hasNoSignedWrap())
    return true;
  if (IndAR->hasNoUnsignedWrap())
    return false;
```

Perhaps clearer? If it's relational (ie. not eq/ne), it must have a sign.

https://github.com/llvm/llvm-project/pull/205995