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

[Matt Arsenault via llvm-commits]

================
@@ -259,53 +264,57 @@ SparcFrameLowering::getFrameIndexReference(const MachineFunction &MF, int FI,
   return true;
 }
 
-bool SparcFrameLowering::isLeafProc(MachineFunction &MF) const
-{
-
-  MachineRegisterInfo &MRI = MF.getRegInfo();
-  MachineFrameInfo    &MFI = MF.getFrameInfo();
+bool SparcFrameLowering::isLeafProc(MachineFunction &MF) const {
+  if (MF.getFrameInfo().hasCalls() || hasFP(MF) || MF.hasInlineAsm())
+    return false;
 
-  return !(MFI.hasCalls()               // has calls
-           || MRI.isPhysRegUsed(SP::L0) // Too many registers needed
-           || MRI.isPhysRegUsed(SP::O6) // %sp is used
-           || hasFP(MF)                 // need %fp
-           || MF.hasInlineAsm());       // has inline assembly
+  const MachineRegisterInfo &MRI = MF.getRegInfo();
+  for (unsigned Reg = SP::L0; Reg <= SP::L7; ++Reg)
----------------
arsenm wrote:

I think the flow is closer to correct now, though checking isPhysRegUsed in a function called by getReservedRegs is still concerning. Is there a more direct property you can check that implies these registers would be used, rather than checking if they happened to appear during selection?

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