diff --git a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
--- a/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
+++ b/llvm/lib/Transforms/Utils/SimplifyCFG.cpp
@@ -1610,16 +1610,22 @@
 
   SmallVector<DominatorTree::UpdateType, 4> Updates;
 
+  SmallSetVector<BasicBlock *, 4> SuccsToUpdate;
   // Update any PHI nodes in our new successors.
   for (BasicBlock *Succ : successors(BB1)) {
     AddPredecessorToBlock(Succ, BIParent, BB1);
     if (DTU)
-      Updates.push_back({DominatorTree::Insert, BIParent, Succ});
+      SuccsToUpdate.insert(Succ);
   }
 
-  if (DTU)
-    for (BasicBlock *Succ : successors(BI))
-      Updates.push_back({DominatorTree::Delete, BIParent, Succ});
+  if (DTU) {
+    for (BasicBlock *Succ : SuccsToUpdate)
+      Updates.push_back({DominatorTree::Insert, BIParent, Succ});
+
+    Updates.push_back({DominatorTree::Delete, BIParent, BB1});
+    if (BB1 != BB2)
+      Updates.push_back({DominatorTree::Delete, BIParent, BB2});
+  }
 
   EraseTerminatorAndDCECond(BI);
   if (DTU)