Replace TargetRegisterInfo::printReg with a PrintReg class that also works without a TRI instance.

Print virtual registers numbered from 0 instead of the arbitrary
FirstVirtualRegister. The first virtual register is printed as %vreg0.
TRI::NoRegister is printed as %noreg.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123107 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/PHIElimination.cpp b/lib/CodeGen/PHIElimination.cpp
index 2ed1c38..923fa21 100644
--- a/lib/CodeGen/PHIElimination.cpp
+++ b/lib/CodeGen/PHIElimination.cpp
@@ -211,7 +211,7 @@
       IncomingReg = entry;
       reusedIncoming = true;
       ++NumReused;
-      DEBUG(dbgs() << "Reusing %reg" << IncomingReg << " for " << *MPhi);
+      DEBUG(dbgs() << "Reusing " << PrintReg(IncomingReg) << " for " << *MPhi);
     } else {
       const TargetRegisterClass *RC = MF.getRegInfo().getRegClass(DestReg);
       entry = IncomingReg = MF.getRegInfo().createVirtualRegister(RC);