[llvm] [AMDGPU] Add function attribute to control TBUFFER combining (PR #156454)

[Piotr Sobczak via llvm-commits]

piotrAMD wrote:

> > This attribute is false by default, so TBUFFER combining is disabled for all bit-widths unless explicitly enabled.
> 
> I am not completely up to speed on this, but I thought combining dword loads into multi-dword loads was always OK, because bounds checking checks each dword individually. Hopefully @piotrAMD will correct me if I am wrong.

Typed buffer loads are not range-checked per dword, they are range-checked "all or nothing".

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