Fix braino in dominator tree walk.

git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@123338 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/lib/CodeGen/LiveDebugVariables.cpp b/lib/CodeGen/LiveDebugVariables.cpp
index 1e2dba2..fc6275f 100644
--- a/lib/CodeGen/LiveDebugVariables.cpp
+++ b/lib/CodeGen/LiveDebugVariables.cpp
@@ -405,7 +405,7 @@
     SlotIndex Start = Todo.pop_back_val();
     MachineBasicBlock *MBB = LIS.getMBBFromIndex(Start);
     SlotIndex Stop = LIS.getMBBEndIdx(MBB);
-    LocMap::iterator I = locInts.find(Idx);
+    LocMap::iterator I = locInts.find(Start);
 
     // Limit to VNI's live range.
     bool ToEnd = true;