[llvm] [AMDGPU] Insert readfirstlane for uniform VGPR arguments (PR #178198)

[via llvm-commits]

Shoreshen wrote:

> ```
> /home/harald/source/llvm-project/llvm/lib/Target/M68k/GISel/M68kCallLowering.cpp
> ```

Hi @hvdijk I'm looking into it. shall I create a PR or just push the change to main??

https://github.com/llvm/llvm-project/pull/178198