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
@@ -101,8 +101,9 @@
   /// first member of the pair being non-zero. If the hinted register is
   /// virtual, it means the allocator should prefer the physical register
   /// allocated to it if any.
-  IndexedMap<std::pair<Register, SmallVector<Register, 4>>,
-             VirtReg2IndexFunctor> RegAllocHints;
+  IndexedMap<std::pair<unsigned, SmallVector<Register, 4>>,
+             VirtReg2IndexFunctor>
+      RegAllocHints;
 
   /// PhysRegUseDefLists - This is an array of the head of the use/def list for
   /// physical registers.
@@ -818,27 +819,25 @@
   /// getRegAllocationHint - Return the register allocation hint for the
   /// specified virtual register. If there are many hints, this returns the
   /// one with the greatest weight.
-  std::pair<Register, Register>
-  getRegAllocationHint(Register VReg) const {
+  std::pair<unsigned, Register> getRegAllocationHint(Register VReg) const {
     assert(VReg.isVirtual());
     Register BestHint = (RegAllocHints[VReg.id()].second.size() ?
                          RegAllocHints[VReg.id()].second[0] : Register());
-    return std::pair<Register, Register>(RegAllocHints[VReg.id()].first,
-                                         BestHint);
+    return {RegAllocHints[VReg.id()].first, BestHint};
   }
 
   /// getSimpleHint - same as getRegAllocationHint except it will only return
   /// a target independent hint.
   Register getSimpleHint(Register VReg) const {
     assert(VReg.isVirtual());
-    std::pair<Register, Register> Hint = getRegAllocationHint(VReg);
+    std::pair<unsigned, Register> Hint = getRegAllocationHint(VReg);
     return Hint.first ? Register() : Hint.second;
   }
 
   /// getRegAllocationHints - Return a reference to the vector of all
   /// register allocation hints for VReg.
-  const std::pair<Register, SmallVector<Register, 4>>
-  &getRegAllocationHints(Register VReg) const {
+  const std::pair<unsigned, SmallVector<Register, 4>> &
+  getRegAllocationHints(Register VReg) const {
     assert(VReg.isVirtual());
     return RegAllocHints[VReg];
   }
diff --git a/llvm/lib/CodeGen/CalcSpillWeights.cpp b/llvm/lib/CodeGen/CalcSpillWeights.cpp
--- a/llvm/lib/CodeGen/CalcSpillWeights.cpp
+++ b/llvm/lib/CodeGen/CalcSpillWeights.cpp
@@ -157,7 +157,7 @@
   unsigned NumInstr = 0; // Number of instructions using LI
   SmallPtrSet<MachineInstr *, 8> Visited;
 
-  std::pair<Register, Register> TargetHint = MRI.getRegAllocationHint(LI.reg());
+  std::pair<unsigned, Register> TargetHint = MRI.getRegAllocationHint(LI.reg());
 
   if (LI.isSpillable()) {
     Register Reg = LI.reg();
diff --git a/llvm/lib/CodeGen/TargetRegisterInfo.cpp b/llvm/lib/CodeGen/TargetRegisterInfo.cpp
--- a/llvm/lib/CodeGen/TargetRegisterInfo.cpp
+++ b/llvm/lib/CodeGen/TargetRegisterInfo.cpp
@@ -424,8 +424,8 @@
     SmallVectorImpl<MCPhysReg> &Hints, const MachineFunction &MF,
     const VirtRegMap *VRM, const LiveRegMatrix *Matrix) const {
   const MachineRegisterInfo &MRI = MF.getRegInfo();
-  const std::pair<Register, SmallVector<Register, 4>> &Hints_MRI =
-    MRI.getRegAllocationHints(VirtReg);
+  const std::pair<unsigned, SmallVector<Register, 4>> &Hints_MRI =
+      MRI.getRegAllocationHints(VirtReg);
 
   SmallSet<Register, 32> HintedRegs;
   // First hint may be a target hint.
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
@@ -116,10 +116,10 @@
 }
 
 bool VirtRegMap::hasKnownPreference(Register VirtReg) const {
-  std::pair<unsigned, unsigned> Hint = MRI->getRegAllocationHint(VirtReg);
-  if (Register::isPhysicalRegister(Hint.second))
+  std::pair<unsigned, Register> Hint = MRI->getRegAllocationHint(VirtReg);
+  if (Hint.second.isPhysical())
     return true;
-  if (Register::isVirtualRegister(Hint.second))
+  if (Hint.second.isVirtual())
     return hasPhys(Hint.second);
   return false;
 }
diff --git a/llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp b/llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp
--- a/llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp
+++ b/llvm/lib/Target/ARM/ARMBaseRegisterInfo.cpp
@@ -338,7 +338,7 @@
     SmallVectorImpl<MCPhysReg> &Hints, const MachineFunction &MF,
     const VirtRegMap *VRM, const LiveRegMatrix *Matrix) const {
   const MachineRegisterInfo &MRI = MF.getRegInfo();
-  std::pair<Register, Register> Hint = MRI.getRegAllocationHint(VirtReg);
+  std::pair<unsigned, Register> Hint = MRI.getRegAllocationHint(VirtReg);
 
   unsigned Odd;
   switch (Hint.first) {
@@ -391,7 +391,7 @@
 void ARMBaseRegisterInfo::updateRegAllocHint(Register Reg, Register NewReg,
                                              MachineFunction &MF) const {
   MachineRegisterInfo *MRI = &MF.getRegInfo();
-  std::pair<Register, Register> Hint = MRI->getRegAllocationHint(Reg);
+  std::pair<unsigned, Register> Hint = MRI->getRegAllocationHint(Reg);
   if ((Hint.first == ARMRI::RegPairOdd || Hint.first == ARMRI::RegPairEven) &&
       Hint.second.isVirtual()) {
     // If 'Reg' is one of the even / odd register pair and it's now changed
diff --git a/llvm/tools/llvm-reduce/deltas/ReduceVirtualRegisters.cpp b/llvm/tools/llvm-reduce/deltas/ReduceVirtualRegisters.cpp
--- a/llvm/tools/llvm-reduce/deltas/ReduceVirtualRegisters.cpp
+++ b/llvm/tools/llvm-reduce/deltas/ReduceVirtualRegisters.cpp
@@ -23,7 +23,7 @@
   for (unsigned I = 0, E = MRI.getNumVirtRegs(); I != E; ++I) {
     Register Reg = Register::index2VirtReg(I);
 
-    const std::pair<Register, SmallVector<Register, 4>> &Hints =
+    const std::pair<unsigned, SmallVector<Register, 4>> &Hints =
         MRI.getRegAllocationHints(Reg);
     if (Hints.second.empty())
       continue;