MachineOperand/MIParser: Do not print debug-use flag, infer it

The debug-use flag must be set exactly for uses on DBG_VALUEs.  This is
so obvious that it can be trivially inferred while parsing. This will
reduce noise when printing while omitting an information that has little
value to the user.

The parser will keep recognizing the flag for compatibility with old
`.mir` files.

Differential Revision: https://reviews.llvm.org/D53903

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@345671 91177308-0d34-0410-b5e6-96231b3b80d8

lib/CodeGen/MachineOperand.cpp

@@ -744,10 +744,10 @@ void MachineOperand::print(raw_ostream &OS, ModuleSlotTracker &MST,
       OS << "undef ";
     if (isEarlyClobber())
       OS << "early-clobber ";
-    if (isDebug())
-      OS << "debug-use ";
     if (TargetRegisterInfo::isPhysicalRegister(getReg()) && isRenamable())
       OS << "renamable ";
+    // isDebug() is exactly true for register operands of a DBG_VALUE. So we
+    // simply infer it when parsing and do not need to print it.
 
     const MachineRegisterInfo *MRI = nullptr;
     if (TargetRegisterInfo::isVirtualRegister(Reg)) {