[llvm] [AMDGPU] Handle non-register operands for S_SUB/ADD_U64_PSEUDO (PR #86104)

[Pierre van Houtryve via llvm-commits]

Pierre-vh wrote:

> > Missing test
> 
> How can I test ISel pseudo expansion? I didn't find the tests for it

This somewhat depends on https://github.com/llvm/llvm-project/pull/79553, we currently don't emit those pseudos so it can't be tested. Either that patch needs to add a test for it, or this whole patch should be merged with it 

https://github.com/llvm/llvm-project/pull/86104