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

[Ramkumar Ramachandra via llvm-commits]

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artagnon wrote:

I think the API is richer than the loop-split-test pass: could write more extensive unit tests with the API, and strip the test pass? You can use raw C11 strings, and just port the existing tests to unittests as-is, and use parseAssemblyString.

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