[CodeGen] Always use `printReg` to print registers in both MIR and debug
output

As part of the unification of the debug format and the MIR format,
always use `printReg` to print all kinds of registers.

Updated the tests using '_' instead of '%noreg' until we decide which
one we want to be the default one.

Differential Revision: https://reviews.llvm.org/D40421

llvm-svn: 319445
diff --git a/llvm/lib/CodeGen/ExecutionDepsFix.cpp b/llvm/lib/CodeGen/ExecutionDepsFix.cpp
index 6199067..73c4b6a 100644
--- a/llvm/lib/CodeGen/ExecutionDepsFix.cpp
+++ b/llvm/lib/CodeGen/ExecutionDepsFix.cpp
@@ -394,7 +394,7 @@
       continue;
     for (int rx : regIndices(MO.getReg())) {
       // This instruction explicitly defines rx.
-      DEBUG(dbgs() << TRI->getName(RC->getRegister(rx)) << ":\t" << CurInstr
+      DEBUG(dbgs() << printReg(RC->getRegister(rx), TRI) << ":\t" << CurInstr
                    << '\t' << *MI);
 
       if (breakDependency) {