[llvm] InstSimplify: strip bad TODO (NFC) (PR #92754)

[Nikita Popov via llvm-commits]

https://github.com/nikic approved this pull request.

@artagnon I think the point of this TODO is something like `shuffle(bitcast(shuffle())` where the whole sequence cancels out, e.g. because the inner shuffle is 3,2,1,0 and the outer is 6,7,4,5,2,3,0,1 on elements half as wide. There is no need for any IR rewrites in that case.

I'm fine with dropping it though, this kind of TODO often does more damage than good -- the worst PRs we get are from inexperienced contributors trying to resolve TODOs.

https://github.com/llvm/llvm-project/pull/92754