Index: lib/CodeGen/MachineOperand.cpp
===================================================================
--- lib/CodeGen/MachineOperand.cpp
+++ lib/CodeGen/MachineOperand.cpp
@@ -1100,7 +1100,7 @@
           OS, cast<ExternalSymbolPseudoSourceValue>(PVal)->getSymbol());
       break;
     case PseudoSourceValue::TargetCustom:
-      llvm_unreachable("TargetCustom pseudo source values are not supported");
+      OS << "TODO(cannot print TargetCustom pseudo source values)";
       break;
     }
   }