Use multiple virtual registers in PPC CR spilling

Now that the register scavenger can support multiple spill slots, and PEI can
use virtual-register-based scavenging for multiple simultaneous registers, we
can use a virtual register for the transfer register in the CR spilling code.

This should eliminate the last place (outside of the prologue/epilogue) where
we depend on the unconditional availability of the r0 register. We will soon be
able to allocate it (in a somewhat restricted sense) as a GPR.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@178060 91177308-0d34-0410-b5e6-96231b3b80d8

lib/Target/PowerPC/PPCFrameLowering.cpp

@@ -1094,6 +1094,13 @@ PPCFrameLowering::addScavengingSpillSlot(MachineFunction &MF,
     RS->addScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
                                                        RC->getAlignment(),
                                                        false));
+
+    // These kinds of spills might need two registers.
+    if (spillsCR(MF) || spillsVRSAVE(MF))
+      RS->addScavengingFrameIndex(MFI->CreateStackObject(RC->getSize(),
+                                                         RC->getAlignment(),
+                                                         false));
+
   }
 }