[llvm] [InstCombine] Propagate demanded elements through trivially-vectorizable intrinsics (PR #221495)

[Nikita Popov via llvm-commits]

nikic wrote:

Should subsume the code added at https://github.com/llvm/llvm-project/commit/7f5794c102a0caa350f6791e7ef541ec065d093f ? Though that one also propagates poison. Might make sense to include it here? intrinsicPropagatesPoison/propagatesPoison may be used.

https://github.com/llvm/llvm-project/pull/221495