diff --git a/llvm/include/llvm/CodeGen/LiveIntervals.h b/llvm/include/llvm/CodeGen/LiveIntervals.h
--- a/llvm/include/llvm/CodeGen/LiveIntervals.h
+++ b/llvm/include/llvm/CodeGen/LiveIntervals.h
@@ -431,7 +431,7 @@
     /// Remove value numbers and related live segments starting at position
     /// \p Pos that are part of any liverange of physical register \p Reg or one
     /// of its subregisters.
-    void removePhysRegDefAt(unsigned Reg, SlotIndex Pos);
+    void removePhysRegDefAt(MCRegister Reg, SlotIndex Pos);
 
     /// Remove value number and related live segments of \p LI and its subranges
     /// that start at position \p Pos.
diff --git a/llvm/include/llvm/CodeGen/VirtRegMap.h b/llvm/include/llvm/CodeGen/VirtRegMap.h
--- a/llvm/include/llvm/CodeGen/VirtRegMap.h
+++ b/llvm/include/llvm/CodeGen/VirtRegMap.h
@@ -98,9 +98,9 @@
 
     /// returns the physical register mapped to the specified
     /// virtual register
-    Register getPhys(Register virtReg) const {
+    MCRegister getPhys(Register virtReg) const {
       assert(virtReg.isVirtual());
-      return Virt2PhysMap[virtReg.id()];
+      return MCRegister::from(Virt2PhysMap[virtReg.id()]);
     }
 
     /// creates a mapping for the specified virtual register to
diff --git a/llvm/lib/CodeGen/InlineSpiller.cpp b/llvm/lib/CodeGen/InlineSpiller.cpp
--- a/llvm/lib/CodeGen/InlineSpiller.cpp
+++ b/llvm/lib/CodeGen/InlineSpiller.cpp
@@ -881,7 +881,7 @@
     // FoldMI does not define this physreg. Remove the LI segment.
     assert(MO->isDead() && "Cannot fold physreg def");
     SlotIndex Idx = LIS.getInstructionIndex(*MI).getRegSlot();
-    LIS.removePhysRegDefAt(Reg, Idx);
+    LIS.removePhysRegDefAt(Reg.asMCReg(), Idx);
   }
 
   int FI;
diff --git a/llvm/lib/CodeGen/LiveIntervals.cpp b/llvm/lib/CodeGen/LiveIntervals.cpp
--- a/llvm/lib/CodeGen/LiveIntervals.cpp
+++ b/llvm/lib/CodeGen/LiveIntervals.cpp
@@ -1037,7 +1037,8 @@
 
       // For physregs, only update the regunits that actually have a
       // precomputed live range.
-      for (MCRegUnitIterator Units(Reg, &TRI); Units.isValid(); ++Units)
+      for (MCRegUnitIterator Units(Reg.asMCReg(), &TRI); Units.isValid();
+           ++Units)
         if (LiveRange *LR = getRegUnitLI(*Units))
           updateRange(*LR, *Units, LaneBitmask::getNone());
     }
@@ -1683,7 +1684,7 @@
   }
 }
 
-void LiveIntervals::removePhysRegDefAt(unsigned Reg, SlotIndex Pos) {
+void LiveIntervals::removePhysRegDefAt(MCRegister Reg, SlotIndex Pos) {
   for (MCRegUnitIterator Unit(Reg, TRI); Unit.isValid(); ++Unit) {
     if (LiveRange *LR = getCachedRegUnit(*Unit))
       if (VNInfo *VNI = LR->getVNInfoAt(Pos))
diff --git a/llvm/lib/CodeGen/LiveRangeEdit.cpp b/llvm/lib/CodeGen/LiveRangeEdit.cpp
--- a/llvm/lib/CodeGen/LiveRangeEdit.cpp
+++ b/llvm/lib/CodeGen/LiveRangeEdit.cpp
@@ -316,7 +316,7 @@
       if (Reg && MOI->readsReg() && !MRI.isReserved(Reg))
         ReadsPhysRegs = true;
       else if (MOI->isDef())
-        LIS.removePhysRegDefAt(Reg, Idx);
+        LIS.removePhysRegDefAt(Reg.asMCReg(), Idx);
       continue;
     }
     LiveInterval &LI = LIS.getInterval(Reg);
diff --git a/llvm/lib/CodeGen/RegAllocGreedy.cpp b/llvm/lib/CodeGen/RegAllocGreedy.cpp
--- a/llvm/lib/CodeGen/RegAllocGreedy.cpp
+++ b/llvm/lib/CodeGen/RegAllocGreedy.cpp
@@ -2866,7 +2866,7 @@
     // Get the current assignment.
     Register OtherPhysReg = Register::isPhysicalRegister(OtherReg)
                                 ? OtherReg
-                                : VRM->getPhys(OtherReg);
+                                : Register(VRM->getPhys(OtherReg));
     // Push the collected information.
     Out.push_back(HintInfo(MBFI->getBlockFreq(Instr.getParent()), OtherReg,
                            OtherPhysReg));
diff --git a/llvm/lib/CodeGen/RegisterCoalescer.h b/llvm/lib/CodeGen/RegisterCoalescer.h
--- a/llvm/lib/CodeGen/RegisterCoalescer.h
+++ b/llvm/lib/CodeGen/RegisterCoalescer.h
@@ -14,6 +14,8 @@
 #ifndef LLVM_LIB_CODEGEN_REGISTERCOALESCER_H
 #define LLVM_LIB_CODEGEN_REGISTERCOALESCER_H
 
+#include "llvm/CodeGen/Register.h"
+
 namespace llvm {
 
 class MachineInstr;
@@ -28,10 +30,10 @@
 
     /// The register that will be left after coalescing. It can be a
     /// virtual or physical register.
-    unsigned DstReg = 0;
+    Register DstReg;
 
     /// The virtual register that will be coalesced into dstReg.
-    unsigned SrcReg = 0;
+    Register SrcReg;
 
     /// The sub-register index of the old DstReg in the new coalesced register.
     unsigned DstIdx = 0;
@@ -92,10 +94,10 @@
 
     /// Return the register (virtual or physical) that will remain
     /// after coalescing.
-    unsigned getDstReg() const { return DstReg; }
+    Register getDstReg() const { return DstReg; }
 
     /// Return the virtual register that will be coalesced away.
-    unsigned getSrcReg() const { return SrcReg; }
+    Register getSrcReg() const { return SrcReg; }
 
     /// Return the subregister index that DstReg will be coalesced into, or 0.
     unsigned getDstIdx() const { return DstIdx; }
diff --git a/llvm/lib/CodeGen/RegisterCoalescer.cpp b/llvm/lib/CodeGen/RegisterCoalescer.cpp
--- a/llvm/lib/CodeGen/RegisterCoalescer.cpp
+++ b/llvm/lib/CodeGen/RegisterCoalescer.cpp
@@ -173,7 +173,7 @@
     SmallVector<MachineInstr*, 8> DeadDefs;
 
     /// Virtual registers to be considered for register class inflation.
-    SmallVector<unsigned, 8> InflateRegs;
+    SmallVector<Register, 8> InflateRegs;
 
     /// The collection of live intervals which should have been updated
     /// immediately after rematerialiation but delayed until
@@ -285,7 +285,7 @@
     /// number if it is not zero. If DstReg is a physical register and the
     /// existing subregister number of the def / use being updated is not zero,
     /// make sure to set it to the correct physical subregister.
-    void updateRegDefsUses(unsigned SrcReg, unsigned DstReg, unsigned SubIdx);
+    void updateRegDefsUses(Register SrcReg, Register DstReg, unsigned SubIdx);
 
     /// If the given machine operand reads only undefined lanes add an undef
     /// flag.
@@ -1246,9 +1246,9 @@
                                                 MachineInstr *CopyMI,
                                                 bool &IsDefCopy) {
   IsDefCopy = false;
-  unsigned SrcReg = CP.isFlipped() ? CP.getDstReg() : CP.getSrcReg();
+  Register SrcReg = CP.isFlipped() ? CP.getDstReg() : CP.getSrcReg();
   unsigned SrcIdx = CP.isFlipped() ? CP.getDstIdx() : CP.getSrcIdx();
-  unsigned DstReg = CP.isFlipped() ? CP.getSrcReg() : CP.getDstReg();
+  Register DstReg = CP.isFlipped() ? CP.getSrcReg() : CP.getDstReg();
   unsigned DstIdx = CP.isFlipped() ? CP.getSrcIdx() : CP.getDstIdx();
   if (Register::isPhysicalRegister(SrcReg))
     return false;
@@ -1700,7 +1700,7 @@
   }
 }
 
-void RegisterCoalescer::updateRegDefsUses(unsigned SrcReg, unsigned DstReg,
+void RegisterCoalescer::updateRegDefsUses(Register SrcReg, Register DstReg,
                                           unsigned SubIdx) {
   bool DstIsPhys = Register::isPhysicalRegister(DstReg);
   LiveInterval *DstInt = DstIsPhys ? nullptr : &LIS->getInterval(DstReg);
@@ -1942,7 +1942,7 @@
       if (Changed) {
         deleteInstr(CopyMI);
         if (Shrink) {
-          unsigned DstReg = CP.isFlipped() ? CP.getSrcReg() : CP.getDstReg();
+          Register DstReg = CP.isFlipped() ? CP.getSrcReg() : CP.getDstReg();
           LiveInterval &DstLI = LIS->getInterval(DstReg);
           shrinkToUses(&DstLI);
           LLVM_DEBUG(dbgs() << "\t\tshrunk:   " << DstLI << '\n');
@@ -2034,8 +2034,8 @@
 }
 
 bool RegisterCoalescer::joinReservedPhysReg(CoalescerPair &CP) {
-  unsigned DstReg = CP.getDstReg();
-  unsigned SrcReg = CP.getSrcReg();
+  Register DstReg = CP.getDstReg();
+  Register SrcReg = CP.getSrcReg();
   assert(CP.isPhys() && "Must be a physreg copy");
   assert(MRI->isReserved(DstReg) && "Not a reserved register");
   LiveInterval &RHS = LIS->getInterval(SrcReg);
@@ -2132,7 +2132,7 @@
     LLVM_DEBUG(dbgs() << "\t\tRemoving phys reg def of "
                       << printReg(DstReg, TRI) << " at " << CopyRegIdx << "\n");
 
-    LIS->removePhysRegDefAt(DstReg, CopyRegIdx);
+    LIS->removePhysRegDefAt(DstReg.asMCReg(), CopyRegIdx);
     // Create a new dead def at the new def location.
     for (MCRegUnitIterator UI(DstReg, TRI); UI.isValid(); ++UI) {
       LiveRange &LR = LIS->getRegUnit(*UI);
@@ -2393,14 +2393,15 @@
   bool isPrunedValue(unsigned ValNo, JoinVals &Other);
 
 public:
-  JoinVals(LiveRange &LR, unsigned Reg, unsigned SubIdx, LaneBitmask LaneMask,
-           SmallVectorImpl<VNInfo*> &newVNInfo, const CoalescerPair &cp,
+  JoinVals(LiveRange &LR, Register Reg, unsigned SubIdx, LaneBitmask LaneMask,
+           SmallVectorImpl<VNInfo *> &newVNInfo, const CoalescerPair &cp,
            LiveIntervals *lis, const TargetRegisterInfo *TRI, bool SubRangeJoin,
            bool TrackSubRegLiveness)
-    : LR(LR), Reg(Reg), SubIdx(SubIdx), LaneMask(LaneMask),
-      SubRangeJoin(SubRangeJoin), TrackSubRegLiveness(TrackSubRegLiveness),
-      NewVNInfo(newVNInfo), CP(cp), LIS(lis), Indexes(LIS->getSlotIndexes()),
-      TRI(TRI), Assignments(LR.getNumValNums(), -1), Vals(LR.getNumValNums()) {}
+      : LR(LR), Reg(Reg), SubIdx(SubIdx), LaneMask(LaneMask),
+        SubRangeJoin(SubRangeJoin), TrackSubRegLiveness(TrackSubRegLiveness),
+        NewVNInfo(newVNInfo), CP(cp), LIS(lis), Indexes(LIS->getSlotIndexes()),
+        TRI(TRI), Assignments(LR.getNumValNums(), -1),
+        Vals(LR.getNumValNums()) {}
 
   /// Analyze defs in LR and compute a value mapping in NewVNInfo.
   /// Returns false if any conflicts were impossible to resolve.
diff --git a/llvm/lib/CodeGen/VirtRegMap.cpp b/llvm/lib/CodeGen/VirtRegMap.cpp
--- a/llvm/lib/CodeGen/VirtRegMap.cpp
+++ b/llvm/lib/CodeGen/VirtRegMap.cpp
@@ -104,7 +104,7 @@
     return false;
   if (Hint.isVirtual())
     Hint = getPhys(Hint);
-  return getPhys(VirtReg) == Hint;
+  return Register(getPhys(VirtReg)) == Hint;
 }
 
 bool VirtRegMap::hasKnownPreference(Register VirtReg) {
diff --git a/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp b/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp
--- a/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZInstrInfo.cpp
@@ -1196,7 +1196,7 @@
     if (RC == &SystemZ::VR32BitRegClass || RC == &SystemZ::VR64BitRegClass) {
       Register Reg = MI.getOperand(I).getReg();
       Register PhysReg = Register::isVirtualRegister(Reg)
-                             ? (VRM ? VRM->getPhys(Reg) : Register())
+                             ? (VRM ? Register(VRM->getPhys(Reg)) : Register())
                              : Reg;
       if (!PhysReg ||
           !(SystemZ::FP32BitRegClass.contains(PhysReg) ||
@@ -1242,7 +1242,8 @@
     else {
       Register DstReg = MI.getOperand(0).getReg();
       Register DstPhys =
-          (Register::isVirtualRegister(DstReg) ? VRM->getPhys(DstReg) : DstReg);
+          (Register::isVirtualRegister(DstReg) ? Register(VRM->getPhys(DstReg))
+                                               : DstReg);
       Register SrcReg = (OpNum == 2 ? MI.getOperand(1).getReg()
                                     : ((OpNum == 1 && MI.isCommutable())
                                            ? MI.getOperand(2).getReg()
diff --git a/llvm/lib/Target/SystemZ/SystemZRegisterInfo.cpp b/llvm/lib/Target/SystemZ/SystemZRegisterInfo.cpp
--- a/llvm/lib/Target/SystemZ/SystemZRegisterInfo.cpp
+++ b/llvm/lib/Target/SystemZ/SystemZRegisterInfo.cpp
@@ -109,8 +109,9 @@
 
         auto tryAddHint = [&](const MachineOperand *MO) -> void {
           Register Reg = MO->getReg();
-          Register PhysReg =
-            Register::isPhysicalRegister(Reg) ? Reg : VRM->getPhys(Reg);
+          Register PhysReg = Register::isPhysicalRegister(Reg)
+                                 ? Reg
+                                 : Register(VRM->getPhys(Reg));
           if (PhysReg) {
             if (MO->getSubReg())
               PhysReg = getSubReg(PhysReg, MO->getSubReg());
diff --git a/llvm/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp b/llvm/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp
--- a/llvm/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp
+++ b/llvm/lib/Target/WebAssembly/WebAssemblyRegStackify.cpp
@@ -595,7 +595,7 @@
   if (IsDead) {
     LLVM_DEBUG(dbgs() << " - Deleting original\n");
     SlotIndex Idx = LIS.getInstructionIndex(Def).getRegSlot();
-    LIS.removePhysRegDefAt(WebAssembly::ARGUMENTS, Idx);
+    LIS.removePhysRegDefAt(MCRegister::from(WebAssembly::ARGUMENTS), Idx);
     LIS.removeInterval(Reg);
     LIS.RemoveMachineInstrFromMaps(Def);
     Def.eraseFromParent();