[llvm-branch-commits] [llvm] AMDGPU: Replace unused permlane inputs with poison instead of undef (PR #131288)

[Matt Arsenault via llvm-branch-commits]

arsenm wrote:

> This patch is relying on an undocumented assumption that poison is _not_ propagated for all arguments of the intrinsic.

The only folding of anything for target intrinsics is done explicitly here in this function 




https://github.com/llvm/llvm-project/pull/131288