[llvm] [polly] [SimpleLoopUnswitch] Generalize the notion of trivial unswitching (PR #193989)

[Nikita Popov via llvm-commits]

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nikic wrote:

Can you please add a `assert(!ModifiedBranch)` here, to make sure we don't bail out after doing IR modifications (which would result in incorrect change tracking). I do believe all the conditions can't fail in the cases we modify, but it's a bit fragile.

https://github.com/llvm/llvm-project/pull/193989