diff --git a/llvm/include/llvm/CodeGen/RDFRegisters.h b/llvm/include/llvm/CodeGen/RDFRegisters.h
index 7eed0b4e1e7b..dcce190f0f30 100644
--- a/llvm/include/llvm/CodeGen/RDFRegisters.h
+++ b/llvm/include/llvm/CodeGen/RDFRegisters.h
@@ -116,9 +116,7 @@ struct RegisterRef {
   static constexpr bool isUnitId(unsigned Id) {
     return Register::isVirtualRegister(Id);
   }
-  static constexpr bool isMaskId(unsigned Id) {
-    return Register::isStackSlot(Id);
-  }
+  static constexpr bool isMaskId(unsigned Id) { return Register(Id).isStack(); }
 
   static constexpr RegisterId toUnitId(unsigned Idx) {
     return Idx | MCRegister::VirtualRegFlag;
@@ -147,7 +145,7 @@ struct PhysicalRegisterInfo {
   }
 
   const uint32_t *getRegMaskBits(RegisterId R) const {
-    return RegMasks.get(Register::stackSlot2Index(R));
+    return RegMasks.get(Register(R).stackSlotIndex());
   }
 
   bool alias(RegisterRef RA, RegisterRef RB) const;
@@ -160,7 +158,7 @@ struct PhysicalRegisterInfo {
   }
 
   const BitVector &getMaskUnits(RegisterId MaskId) const {
-    return MaskInfos[Register::stackSlot2Index(MaskId)].Units;
+    return MaskInfos[Register(MaskId).stackSlotIndex()].Units;
   }
 
   std::set<RegisterId> getUnits(RegisterRef RR) const;
diff --git a/llvm/include/llvm/CodeGen/Register.h b/llvm/include/llvm/CodeGen/Register.h
index ad05368bea6a..b5ffe079de12 100644
--- a/llvm/include/llvm/CodeGen/Register.h
+++ b/llvm/include/llvm/CodeGen/Register.h
@@ -36,25 +36,12 @@ public:
   static_assert(std::numeric_limits<decltype(Reg)>::max() >= 0xFFFFFFFF,
                 "Reg isn't large enough to hold full range.");
 
-  /// isStackSlot - Sometimes it is useful to be able to store a non-negative
-  /// frame index in a variable that normally holds a register. isStackSlot()
-  /// returns true if Reg is in the range used for stack slots.
-  ///
-  /// FIXME: remove in favor of member.
-  static constexpr bool isStackSlot(unsigned Reg) {
+  /// Return true if this is a stack slot.
+  constexpr bool isStack() const {
     return MCRegister::FirstStackSlot <= Reg &&
            Reg < MCRegister::VirtualRegFlag;
   }
 
-  /// Return true if this is a stack slot.
-  constexpr bool isStack() const { return isStackSlot(Reg); }
-
-  /// Compute the frame index from a register value representing a stack slot.
-  static int stackSlot2Index(Register Reg) {
-    assert(Reg.isStack() && "Not a stack slot");
-    return int(Reg.id() - MCRegister::FirstStackSlot);
-  }
-
   /// Convert a non-negative frame index to a stack slot register value.
   static Register index2StackSlot(int FI) {
     assert(FI >= 0 && "Cannot hold a negative frame index.");
diff --git a/llvm/lib/CodeGen/InlineSpiller.cpp b/llvm/lib/CodeGen/InlineSpiller.cpp
index 302dd37ff3d6..3834a6d7a355 100644
--- a/llvm/lib/CodeGen/InlineSpiller.cpp
+++ b/llvm/lib/CodeGen/InlineSpiller.cpp
@@ -1285,8 +1285,7 @@ void InlineSpiller::spillAll() {
 void InlineSpiller::spill(LiveRangeEdit &edit) {
   ++NumSpilledRanges;
   Edit = &edit;
-  assert(!Register::isStackSlot(edit.getReg()) &&
-         "Trying to spill a stack slot.");
+  assert(!edit.getReg().isStack() && "Trying to spill a stack slot.");
   // Share a stack slot among all descendants of Original.
   Original = VRM.getOriginal(edit.getReg());
   StackSlot = VRM.getStackSlot(Original);
diff --git a/llvm/lib/CodeGen/RDFRegisters.cpp b/llvm/lib/CodeGen/RDFRegisters.cpp
index 7ce00a66b3ae..b8d54cadc07f 100644
--- a/llvm/lib/CodeGen/RDFRegisters.cpp
+++ b/llvm/lib/CodeGen/RDFRegisters.cpp
@@ -263,7 +263,7 @@ void PhysicalRegisterInfo::print(raw_ostream &OS, RegisterRef A) const {
   } else {
     assert(A.isMask());
     // RegMask SS flag is preserved by idx().
-    unsigned Idx = Register::stackSlot2Index(A.idx());
+    unsigned Idx = Register(A.idx()).stackSlotIndex();
     const char *Fmt = Idx < 0x10000 ? "%04x" : "%08x";
     OS << "M#" << format(Fmt, Idx);
   }