Index: include/llvm/CodeGen/MachineFunction.h
===================================================================
--- include/llvm/CodeGen/MachineFunction.h
+++ include/llvm/CodeGen/MachineFunction.h
@@ -363,6 +363,25 @@
                     int Slot, const DILocation *Loc)
         : Var(Var), Expr(Expr), Slot(Slot), Loc(Loc) {}
   };
+
+  class Delegate {
+    virtual void anchor();
+
+  public:
+    virtual ~Delegate() = default;
+    virtual void MF_HandleInsertion(const MachineInstr *MI) = 0;
+    virtual void MF_HandleRemoval(const MachineInstr *MI) = 0;
+  };
+
+private:
+  Delegate *TheDelegate = nullptr;
+
+  // Callbacks for insertion and removal.
+  void handleInsertion(const MachineInstr *MI);
+  void handleRemoval(const MachineInstr *MI);
+  friend struct ilist_traits<MachineInstr>;
+
+public:
   using VariableDbgInfoMapTy = SmallVector<VariableDbgInfo, 4>;
   VariableDbgInfoMapTy VariableDbgInfos;
 
@@ -379,6 +398,23 @@
     init();
   }
 
+  void resetDelegate(Delegate *delegate) {
+    // Ensure another delegate does not take over unless the current
+    // delegate first unattaches itself. If we ever need to multicast
+    // notifications, we will need to change to using a list.
+    assert(TheDelegate == delegate &&
+           "Only the current delegate can perform reset!");
+    TheDelegate = nullptr;
+  }
+
+  void setDelegate(Delegate *delegate) {
+    assert(delegate && !TheDelegate &&
+           "Attempted to set delegate to null, or to change it without "
+           "first resetting it!");
+
+    TheDelegate = delegate;
+  }
+
   MachineModuleInfo &getMMI() const { return MMI; }
   MCContext &getContext() const { return Ctx; }
 
Index: lib/CodeGen/MachineBasicBlock.cpp
===================================================================
--- lib/CodeGen/MachineBasicBlock.cpp
+++ lib/CodeGen/MachineBasicBlock.cpp
@@ -110,6 +110,7 @@
   // use/def lists.
   MachineFunction *MF = Parent->getParent();
   N->AddRegOperandsToUseLists(MF->getRegInfo());
+  MF->handleInsertion(N);
 }
 
 /// When we remove an instruction from a basic block list, we update its parent
@@ -118,8 +119,10 @@
   assert(N->getParent() && "machine instruction not in a basic block");
 
   // Remove from the use/def lists.
-  if (MachineFunction *MF = N->getMF())
+  if (MachineFunction *MF = N->getMF()) {
+    MF->handleRemoval(N);
     N->RemoveRegOperandsFromUseLists(MF->getRegInfo());
+  }
 
   N->setParent(nullptr);
 }
Index: lib/CodeGen/MachineFunction.cpp
===================================================================
--- lib/CodeGen/MachineFunction.cpp
+++ lib/CodeGen/MachineFunction.cpp
@@ -99,6 +99,9 @@
   llvm_unreachable("Invalid machine function property");
 }
 
+// Pin the vtable to this file.
+void MachineFunction::Delegate::anchor() {}
+
 void MachineFunctionProperties::print(raw_ostream &OS) const {
   const char *Separator = "";
   for (BitVector::size_type I = 0; I < Properties.size(); ++I) {
@@ -135,6 +138,16 @@
   init();
 }
 
+void MachineFunction::handleInsertion(const MachineInstr *MI) {
+  if (TheDelegate)
+    TheDelegate->MF_HandleInsertion(MI);
+}
+
+void MachineFunction::handleRemoval(const MachineInstr *MI) {
+  if (TheDelegate)
+    TheDelegate->MF_HandleRemoval(MI);
+}
+
 void MachineFunction::init() {
   // Assume the function starts in SSA form with correct liveness.
   Properties.set(MachineFunctionProperties::Property::IsSSA);