[llvm] [AMDGPU][True16][CodeGen] readfirstlane for vgpr16 copy to sgpr32 (PR #118037)

[Brox Chen via llvm-commits]

broxigarchen wrote:

After investigation, we still need this patch for true16 mode. Updated and trimed this patch and updated the lit test for review

https://github.com/llvm/llvm-project/pull/118037