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

[zhijian lin via llvm-commits]

diggerlin wrote:

I saw that you recently committed some AMDGPU-related test cases. Since I changed SIGN_EXTEND(POISON) and ZERO_EXTEND(POISON) to just POISON in my patch, I’ve updated the test cases accordingly. Would you be willing to help review them?  @arsenm

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