[llvm] [AMDGPU] Use 32-bit SGPR to save/restore of SCC (PR #68367)

[Jay Foad via llvm-commits]

https://github.com/jayfoad requested changes to this pull request.

SIFixSGPRCopies is supposed to fix "illegal" VGPR->SGPR copies. Apparently it also fixes VGPR<->SCC copies. But I do not think it should touch SGPR<->SCC copies. Those are perfectly legal and will be handled by SIInstrInfo::copyPhysReg.

So a better fix would be to teach fixSCCCopies not to touch SGPR<->SCC copies.

https://github.com/llvm/llvm-project/pull/68367