[llvm] [CodeGen] Utilizing register units based liveIns tracking in MBB (PR #129847)

[Jay Foad via llvm-commits]

jayfoad wrote:

> > will be transformed into :
> > liveins: $vgpr0_lo16, $vgpr0_hi16, $vgpr4, $vgpr5_hi16
> > Does it make sense, along the line of my doubts just mentioned above?
> 
> This is the whole point, re-encode the live-ins in terms of register units

I think @vg0204's suggestion here was to store the liveins as a minimal covering set of physregs. This has some of the advantages of storing them as regunits, but without needing to implement serialization/deserialization of regunits themselves in MIR.

https://github.com/llvm/llvm-project/pull/129847