[clang] [clang][CodeGen][SPIR-V][AMDGPU] Tweak AMDGCNSPIRV ABI to allow for the correct handling of aggregates passed to kernels / functions. (PR #102776)

[Alex Voicu via cfe-commits]

https://github.com/AlexVlx commented:

> > but empirically robust and guaranteed to work as the AMDGPU BE retains handling of direct passing for legacy reasons.

I would like to get rid of that someday... 

I share the sentiment, but as far as I can see this is one of those things that has been on the way out someday for years, so it's not going to suddenly disappear. At worst, since tests cover it, if the BE goes and disallows direct passing to a kernel (for example), tests flare up and we'll have to fix it on the AMDGCNSPIRV end.

https://github.com/llvm/llvm-project/pull/102776