1 files changed, 2 insertions, 0 deletions
diff --git a/lib/CodeGen/LiveIntervalUnion.cpp b/lib/CodeGen/LiveIntervalUnion.cpp
index d5c7bf08eb..59d48a4b64 100644
--- a/lib/CodeGen/LiveIntervalUnion.cpp
+++ b/lib/CodeGen/LiveIntervalUnion.cpp
@@ -168,6 +168,8 @@ LiveIntervalUnion::Query::firstInterference() {
       IR.VirtRegI = VirtReg->end();
   }
   findIntersection(FirstInterference);
+  assert((IR.VirtRegI == VirtReg->end() || IR.LiveUnionI.valid())
+         && "Uninitialized iterator");
   return FirstInterference;
 }