[llvm] [SPARC] Preserve liveins after leaf register remapping (PR #213359)

[Matt Arsenault via llvm-commits]

https://github.com/arsenm commented:

It seems to me what this should be doing is moving the isLeafProc call into getReservedRegs so the reserved registers are correct up front, instead of hacking around it by updating live-ins lists. This will need to do something else to replace the isPhysRegUsed checks 

https://github.com/llvm/llvm-project/pull/213359