[llvm] [AMDGPU][True16] added Pre-RA hint to improve copy elimination (PR #103366)

[Brox Chen via llvm-commits]

broxigarchen wrote:

> What if you added CostPerUse to the high halves of the registers?

Thanks Matt I will try this. I will lower the priortiy of this PR since the upstreaming of the other true16 changes will be more urgent

https://github.com/llvm/llvm-project/pull/103366