[CodeGen] Print stack object references as %(fixed-)stack.0 in both MIR and debug output

Work towards the unification of MIR and debug output by printing
`%stack.0` instead of `<fi#0>`, and `%fixed-stack.0` instead of
`<fi#-4>` (supposing there are 4 fixed stack objects).

Only debug syntax is affected.

Differential Revision: https://reviews.llvm.org/D41027

llvm-svn: 320827
diff --git a/llvm/lib/CodeGen/MIRPrinter.cpp b/llvm/lib/CodeGen/MIRPrinter.cpp
index 8cc9ad2..7c4e098 100644
--- a/llvm/lib/CodeGen/MIRPrinter.cpp
+++ b/llvm/lib/CodeGen/MIRPrinter.cpp
@@ -758,13 +758,8 @@
   assert(ObjectInfo != StackObjectOperandMapping.end() &&
          "Invalid frame index");
   const FrameIndexOperand &Operand = ObjectInfo->second;
-  if (Operand.IsFixed) {
-    OS << "%fixed-stack." << Operand.ID;
-    return;
-  }
-  OS << "%stack." << Operand.ID;
-  if (!Operand.Name.empty())
-    OS << '.' << Operand.Name;
+  MachineOperand::printStackObjectReference(OS, Operand.ID, Operand.IsFixed,
+                                            Operand.Name);
 }
 
 void MIPrinter::printOffset(int64_t Offset) {