[llvm] [AMDGPU] Add function attribute to disable TBUFFER combine (PR #156454)

[Harrison Hao via llvm-commits]

harrisonGPU wrote:

> > > This is not a robust feature design, it is hacking out a singular transformation. You need to define a semantic meaning, have the default be conservatively correct
> > 
> > 
> > Hi, Matt, I don't know how to define a semantic meaning, could you please give me some suggestions?
> 
> Is this the same as relaxed-buffer-oob-mod?

I think it is not same as relaxed-buffer-oob-mod, this attribute is aims to the Vulkan semantics for typed-buffers and unbound vertex attributes, where if any component is out of bounds, the entire result must return zero.So the attribute is not enabling relaxed OOB handling, but instead enforcing
the stricter API-level semantics which prohibit TBUFFER combine.

https://github.com/llvm/llvm-project/pull/156454