diff --git a/lib/CodeGen/MachineCombiner.cpp b/lib/CodeGen/MachineCombiner.cpp
index 0c6efff..f51b482 100644
--- a/lib/CodeGen/MachineCombiner.cpp
+++ b/lib/CodeGen/MachineCombiner.cpp
@@ -231,6 +231,8 @@
     // Get the first instruction that uses MO
     MachineRegisterInfo::reg_iterator RI = MRI->reg_begin(MO.getReg());
     RI++;
+    if (RI == MRI->reg_end())
+      continue;
     MachineInstr *UseMO = RI->getParent();
     unsigned LatencyOp = 0;
     if (UseMO && BlockTrace.isDepInTrace(*Root, *UseMO)) {