[llvm] [VPlan] Simplify reverse(reverse(x)) -> x (PR #199057)

[Mel Chen via llvm-commits]

Mel-Chen wrote:

> @Mel-Chen in future I think we can probably extend such a pass like this to also handle more involved patterns like `reverse(binop(reverse(x))) -> binop(x)`

I’ve previously put together a list of planned simplification rules for reverse and wanted to share it https://github.com/llvm/llvm-project/issues/203206. Feel free to correct the issue if you spot any mistakes.

https://github.com/llvm/llvm-project/pull/199057