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

[Jay Foad via llvm-commits]

jayfoad 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.

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