[llvm] [AMDGPU] Split struct kernel arguments (PR #133786)

[Shilei Tian via llvm-commits]

shiltian wrote:

> it is similar to the arguments promotion IPO

which we (at least @arsenm and I) want to get rid of and want to do it right in the front end instead. :-D

However, IMO this pass is fine. We are not doing something "less optimal" in the first place and then try to correct it later, unlike the kernel argument promotion. It's hard to do this kind of reasoning in the front end.

https://github.com/llvm/llvm-project/pull/133786