[llvm] [DA] Rewrite BanerjeeMIV test with safe APInt interval arithmetic (PR #207662)

[Ruoyu Qiu via llvm-commits]

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cabbaken wrote:

Agreed.
Here it works as a fallback. A backedge count is semantically an unsigned iteration count, so the fallback zero-extends it. Sign extension is used only when signed non-negativity is known, because that preserves more symbolic relationships.

https://github.com/llvm/llvm-project/pull/207662