diff --git a/llvm/lib/Analysis/OrderedBasicBlock.cpp b/llvm/lib/Analysis/OrderedBasicBlock.cpp
index 3cc6319..48f2a40 100644
--- a/llvm/lib/Analysis/OrderedBasicBlock.cpp
+++ b/llvm/lib/Analysis/OrderedBasicBlock.cpp
@@ -85,3 +85,27 @@
 
   return comesBefore(A, B);
 }
+
+void OrderedBasicBlock::eraseInstruction(const Instruction *I) {
+  if (LastInstFound != BB->end() && I == &*LastInstFound) {
+    if (LastInstFound == BB->begin()) {
+      LastInstFound = BB->end();
+      NextInstPos = 0;
+    } else
+      LastInstFound--;
+  }
+
+  NumberedInsts.erase(I);
+}
+
+void OrderedBasicBlock::replaceInstruction(const Instruction *Old,
+                                           const Instruction *New) {
+  auto OI = NumberedInsts.find(Old);
+  if (OI == NumberedInsts.end())
+    return;
+
+  NumberedInsts.insert({New, OI->second});
+  if (LastInstFound != BB->end() && Old == &*LastInstFound)
+    LastInstFound = New->getIterator();
+  NumberedInsts.erase(Old);
+}