[llvm] Eliminating li of 0 into arg registers of unused arguments (PR #122741)

[zhijian lin via llvm-commits]

diggerlin wrote:

I rebased the patch based on the [[SelectionDAG] Introducing a new ISD::POISON SDNode to represent the poison value in the IR](https://github.com/llvm/llvm-project/pull/125883#top),I would appreciate any feedback on it.

https://github.com/llvm/llvm-project/pull/122741