diff --git a/llvm/include/llvm/CodeGen/LiveRangeEdit.h b/llvm/include/llvm/CodeGen/LiveRangeEdit.h
--- a/llvm/include/llvm/CodeGen/LiveRangeEdit.h
+++ b/llvm/include/llvm/CodeGen/LiveRangeEdit.h
@@ -134,7 +134,7 @@
       : Parent(parent), NewRegs(newRegs), MRI(MF.getRegInfo()), LIS(lis),
         VRM(vrm), TII(*MF.getSubtarget().getInstrInfo()), TheDelegate(delegate),
         FirstNew(newRegs.size()), DeadRemats(deadRemats) {
-    MRI.setDelegate(this);
+    MRI.addDelegate(this);
   }
 
   ~LiveRangeEdit() override { MRI.resetDelegate(this); }
diff --git a/llvm/include/llvm/CodeGen/MachineRegisterInfo.h b/llvm/include/llvm/CodeGen/MachineRegisterInfo.h
--- a/llvm/include/llvm/CodeGen/MachineRegisterInfo.h
+++ b/llvm/include/llvm/CodeGen/MachineRegisterInfo.h
@@ -17,6 +17,7 @@
 #include "llvm/ADT/BitVector.h"
 #include "llvm/ADT/IndexedMap.h"
 #include "llvm/ADT/PointerUnion.h"
+#include "llvm/ADT/SmallPtrSet.h"
 #include "llvm/ADT/SmallVector.h"
 #include "llvm/ADT/StringSet.h"
 #include "llvm/ADT/iterator_range.h"
@@ -56,11 +57,15 @@
     virtual ~Delegate() = default;
 
     virtual void MRI_NoteNewVirtualRegister(Register Reg) = 0;
+    virtual void MRI_NotecloneVirtualRegister(Register NewReg,
+                                              Register SrcReg) {
+      MRI_NoteNewVirtualRegister(NewReg);
+    }
   };
 
 private:
   MachineFunction *MF;
-  Delegate *TheDelegate = nullptr;
+  SmallPtrSet<Delegate *, 1> TheDelegates;
 
   /// True if subregister liveness is tracked.
   const bool TracksSubRegLiveness;
@@ -154,19 +159,28 @@
 
   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;
+    // delegate first unattaches itself.
+    assert(TheDelegates.count(delegate) &&
+           "Only an existing delegate can perform reset!");
+    TheDelegates.erase(delegate);
   }
 
-  void setDelegate(Delegate *delegate) {
-    assert(delegate && !TheDelegate &&
-           "Attempted to set delegate to null, or to change it without "
+  void addDelegate(Delegate *delegate) {
+    assert(delegate && !TheDelegates.count(delegate) &&
+           "Attempted to add null delegate, or to change it without "
            "first resetting it!");
 
-    TheDelegate = delegate;
+    TheDelegates.insert(delegate);
+  }
+
+  void noteNewVirtualRegister(Register Reg) {
+    for (auto *TheDelegate : TheDelegates)
+      TheDelegate->MRI_NoteNewVirtualRegister(Reg);
+  }
+
+  void noteCloneVirtualRegister(Register NewReg, Register SrcReg) {
+    for (auto *TheDelegate : TheDelegates)
+      TheDelegate->MRI_NotecloneVirtualRegister(NewReg, SrcReg);
   }
 
   //===--------------------------------------------------------------------===//
diff --git a/llvm/lib/CodeGen/MachineRegisterInfo.cpp b/llvm/lib/CodeGen/MachineRegisterInfo.cpp
--- a/llvm/lib/CodeGen/MachineRegisterInfo.cpp
+++ b/llvm/lib/CodeGen/MachineRegisterInfo.cpp
@@ -48,6 +48,7 @@
   RegAllocHints.reserve(256);
   UsedPhysRegMask.resize(NumRegs);
   PhysRegUseDefLists.reset(new MachineOperand*[NumRegs]());
+  TheDelegates.clear();
 }
 
 /// setRegClass - Set the register class of the specified virtual register.
@@ -162,8 +163,7 @@
   // New virtual register number.
   Register Reg = createIncompleteVirtualRegister(Name);
   VRegInfo[Reg].first = RegClass;
-  if (TheDelegate)
-    TheDelegate->MRI_NoteNewVirtualRegister(Reg);
+  noteNewVirtualRegister(Reg);
   return Reg;
 }
 
@@ -172,8 +172,7 @@
   Register Reg = createIncompleteVirtualRegister(Name);
   VRegInfo[Reg].first = VRegInfo[VReg].first;
   setType(Reg, getType(VReg));
-  if (TheDelegate)
-    TheDelegate->MRI_NoteNewVirtualRegister(Reg);
+  noteCloneVirtualRegister(Reg, VReg);
   return Reg;
 }
 
@@ -189,8 +188,7 @@
   // FIXME: Should we use a dummy register class?
   VRegInfo[Reg].first = static_cast<RegisterBank *>(nullptr);
   setType(Reg, Ty);
-  if (TheDelegate)
-    TheDelegate->MRI_NoteNewVirtualRegister(Reg);
+  noteNewVirtualRegister(Reg);
   return Reg;
 }