[clang] [llvm] [LLVM] Fix incorrect alignment on AMDGPU variadics (PR #96370)

[Matt Arsenault via llvm-commits]

arsenm wrote:

Incrementing by align is just a bug, of course the size is the real value. Whether we want to continue wasting space is another not-correctness discussion 

https://github.com/llvm/llvm-project/pull/96370