[llvm] [AMDGPU] Split the true16 fcopysign pattern by uniformity (PR #226898)

[Shilei Tian via llvm-commits]

https://github.com/shiltian approved this pull request.

LGTM, though I wonder if we could do something to avoid all these updates. That would be nice.

CC @broxigarchen 

https://github.com/llvm/llvm-project/pull/226898