[llvm] [SLP]Improve reductions for copyables/split nodes (PR #185697)

[Pengcheng Wang via llvm-commits]

wangpc-pp wrote:

Thanks! I applied this PR locally and I can confirm that the issue of https://github.com/llvm/llvm-project/issues/184313 has been fixed!

https://github.com/llvm/llvm-project/pull/185697