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
@@ -823,12 +823,13 @@
 
   /// updateDbgUsersToReg - Update a collection of DBG_VALUE instructions
   /// to refer to the designated register.
-  void updateDbgUsersToReg(Register Reg,
-                           ArrayRef<MachineInstr*> Users) const {
+  void updateDbgUsersToReg(Register OldReg, Register NewReg,
+                           ArrayRef<MachineInstr *> Users) const {
     for (MachineInstr *MI : Users) {
-      assert(MI->isDebugInstr());
-      assert(MI->getOperand(0).isReg());
-      MI->getOperand(0).setReg(Reg);
+      assert(MI->isDebugValue());
+      assert(MI->hasDebugOperandForReg(OldReg));
+      for (auto &Op : MI->getDebugOperandsForReg(OldReg))
+        Op.setReg(NewReg);
     }
   }
 
diff --git a/llvm/lib/CodeGen/MachineCopyPropagation.cpp b/llvm/lib/CodeGen/MachineCopyPropagation.cpp
--- a/llvm/lib/CodeGen/MachineCopyPropagation.cpp
+++ b/llvm/lib/CodeGen/MachineCopyPropagation.cpp
@@ -734,7 +734,8 @@
       // Update matching debug values, if any.
       assert(MaybeDead->isCopy());
       Register SrcReg = MaybeDead->getOperand(1).getReg();
-      MRI->updateDbgUsersToReg(SrcReg, CopyDbgUsers[MaybeDead]);
+      Register DestReg = MaybeDead->getOperand(0).getReg();
+      MRI->updateDbgUsersToReg(DestReg, SrcReg, CopyDbgUsers[MaybeDead]);
 
       MaybeDead->eraseFromParent();
       Changed = true;