diff --git a/lib/CodeGen/SlotIndexes.cpp b/lib/CodeGen/SlotIndexes.cpp
index 277cce3..6e3fa90 100644
--- a/lib/CodeGen/SlotIndexes.cpp
+++ b/lib/CodeGen/SlotIndexes.cpp
@@ -158,6 +158,7 @@
   // resulting numbering will match what would have been generated by the
   // pass during the initial numbering of the function if the new instructions
   // had been present.
+  DEBUG(dbgs() << "\n*** Renumbering SlotIndexes ***\n");
 
   functionSize = 0;
   unsigned index = 0;
@@ -203,7 +204,10 @@
 
 // Print a SlotIndex to a raw_ostream.
 void SlotIndex::print(raw_ostream &os) const {
-  os << entry().getIndex() << "LudS"[getSlot()];
+  if (isValid())
+    os << entry().getIndex() << "LudS"[getSlot()];
+  else
+    os << "invalid";
 }
 
 // Dump a SlotIndex to stderr.