Index: llvm/lib/Transforms/Utils/Local.cpp
===================================================================
--- llvm/lib/Transforms/Utils/Local.cpp
+++ llvm/lib/Transforms/Utils/Local.cpp
@@ -2228,7 +2228,8 @@
   SmallSetVector<BasicBlock *, 8> DeadBlockSet;
   for (Function::iterator I = ++F.begin(), E = F.end(); I != E; ++I) {
     auto *BB = &*I;
-    if (Reachable.count(BB))
+    //skip reachable basic blocks
+    if (Reachable.find(BB)!=Reachable.end())
       continue;
     DeadBlockSet.insert(BB);
   }
@@ -2250,12 +2251,8 @@
       LVI->eraseBlock(BB);
     BB->dropAllReferences();
   }
-  for (Function::iterator I = ++F.begin(); I != F.end();) {
-    auto *BB = &*I;
-    if (Reachable.count(BB)) {
-      ++I;
-      continue;
-    }
+
+  for (auto *BB : DeadBlockSet) {
     if (DTU) {
       // Remove the terminator of BB to clear the successor list of BB.
       if (BB->getTerminator())
@@ -2263,9 +2260,8 @@
       new UnreachableInst(BB->getContext(), BB);
       assert(succ_empty(BB) && "The successor list of BB isn't empty before "
                                "applying corresponding DTU updates.");
-      ++I;
     } else {
-      I = F.getBasicBlockList().erase(I);
+      BB->eraseFromParent();
     }
   }