diff --git a/llvm/include/llvm/CodeGen/TargetRegisterInfo.h b/llvm/include/llvm/CodeGen/TargetRegisterInfo.h
--- a/llvm/include/llvm/CodeGen/TargetRegisterInfo.h
+++ b/llvm/include/llvm/CodeGen/TargetRegisterInfo.h
@@ -23,6 +23,7 @@
 #include "llvm/IR/CallingConv.h"
 #include "llvm/MC/LaneBitmask.h"
 #include "llvm/MC/MCRegisterInfo.h"
+#include "llvm/MC/Register.h"
 #include "llvm/Support/ErrorHandling.h"
 #include "llvm/Support/MachineValueType.h"
 #include "llvm/Support/MathExtras.h"
@@ -267,46 +268,41 @@
   /// isStackSlot() first.
   ///
   static bool isStackSlot(unsigned Reg) {
-    return int(Reg) >= (1 << 30);
+    return Register::isStackSlot(Reg);
   }
 
   /// Compute the frame index from a register value representing a stack slot.
   static int stackSlot2Index(unsigned Reg) {
-    assert(isStackSlot(Reg) && "Not a stack slot");
-    return int(Reg - (1u << 30));
+    return Register::stackSlot2Index(Reg);
   }
 
   /// Convert a non-negative frame index to a stack slot register value.
   static unsigned index2StackSlot(int FI) {
-    assert(FI >= 0 && "Cannot hold a negative frame index.");
-    return FI + (1u << 30);
+    return Register::index2StackSlot(FI);
   }
 
   /// Return true if the specified register number is in
   /// the physical register namespace.
   static bool isPhysicalRegister(unsigned Reg) {
-    assert(!isStackSlot(Reg) && "Not a register! Check isStackSlot() first.");
-    return int(Reg) > 0;
+    return Register::isPhysicalRegister(Reg);
   }
 
   /// Return true if the specified register number is in
   /// the virtual register namespace.
   static bool isVirtualRegister(unsigned Reg) {
-    assert(!isStackSlot(Reg) && "Not a register! Check isStackSlot() first.");
-    return int(Reg) < 0;
+    return Register::isVirtualRegister(Reg);
   }
 
   /// Convert a virtual register number to a 0-based index.
   /// The first virtual register in a function will get the index 0.
   static unsigned virtReg2Index(unsigned Reg) {
-    assert(isVirtualRegister(Reg) && "Not a virtual register");
-    return Reg & ~(1u << 31);
+    return Register::virtReg2Index(Reg);
   }
 
   /// Convert a 0-based index to a virtual register number.
   /// This is the inverse operation of VirtReg2IndexFunctor below.
   static unsigned index2VirtReg(unsigned Index) {
-    return Index | (1u << 31);
+    return Register::index2VirtReg(Index);
   }
 
   /// Return the size in bits of a register from class RC.
diff --git a/llvm/include/llvm/MC/Register.h b/llvm/include/llvm/MC/Register.h
--- a/llvm/include/llvm/MC/Register.h
+++ b/llvm/include/llvm/MC/Register.h
@@ -21,29 +21,84 @@
 public:
   Register(unsigned Val = 0): Reg(Val) {}
 
+  // Register numbers can represent physical registers, virtual registers, and
+  // sometimes stack slots. The unsigned values are divided into these ranges:
+  //
+  //   0           Not a register, can be used as a sentinel.
+  //   [1;2^30)    Physical registers assigned by TableGen.
+  //   [2^30;2^31) Stack slots. (Rarely used.)
+  //   [2^31;2^32) Virtual registers assigned by MachineRegisterInfo.
+  //
+  // Further sentinels can be allocated from the small negative integers.
+  // DenseMapInfo<unsigned> uses -1u and -2u.
+
+  /// isStackSlot - Sometimes it is useful the 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.
+  ///
+  /// Note that isVirtualRegister() and isPhysicalRegister() cannot handle stack
+  /// slots, so if a variable may contains a stack slot, always check
+  /// isStackSlot() first.
+  ///
+  static bool isStackSlot(unsigned Reg) {
+    return int(Reg) >= (1 << 30);
+  }
+
+  /// Compute the frame index from a register value representing a stack slot.
+  static int stackSlot2Index(unsigned Reg) {
+    assert(isStackSlot(Reg) && "Not a stack slot");
+    return int(Reg - (1u << 30));
+  }
+
+  /// Convert a non-negative frame index to a stack slot register value.
+  static unsigned index2StackSlot(int FI) {
+    assert(FI >= 0 && "Cannot hold a negative frame index.");
+    return FI + (1u << 30);
+  }
+
+  /// Return true if the specified register number is in
+  /// the physical register namespace.
+  static bool isPhysicalRegister(unsigned Reg) {
+    assert(!isStackSlot(Reg) && "Not a register! Check isStackSlot() first.");
+    return int(Reg) > 0;
+  }
+
+  /// Return true if the specified register number is in
+  /// the virtual register namespace.
+  static bool isVirtualRegister(unsigned Reg) {
+    assert(!isStackSlot(Reg) && "Not a register! Check isStackSlot() first.");
+    return int(Reg) < 0;
+  }
+
+  /// Convert a virtual register number to a 0-based index.
+  /// The first virtual register in a function will get the index 0.
+  static unsigned virtReg2Index(unsigned Reg) {
+    assert(isVirtualRegister(Reg) && "Not a virtual register");
+    return Reg & ~(1u << 31);
+  }
+
+  /// Convert a 0-based index to a virtual register number.
+  /// This is the inverse operation of VirtReg2IndexFunctor below.
+  static unsigned index2VirtReg(unsigned Index) {
+    return Index | (1u << 31);
+  }
+
   /// Return true if the specified register number is in the virtual register
   /// namespace.
   bool isVirtual() const {
-    return int(Reg) < 0;
+    return isVirtualRegister(Reg);
   }
 
   /// Return true if the specified register number is in the physical register
   /// namespace.
   bool isPhysical() const {
-    return int(Reg) > 0;
+    return isPhysicalRegister(Reg);
   }
 
   /// Convert a virtual register number to a 0-based index. The first virtual
   /// register in a function will get the index 0.
   unsigned virtRegIndex() const {
-    assert(isVirtual() && "Not a virtual register");
-    return Reg & ~(1u << 31);
-  }
-
-  /// Convert a 0-based index to a virtual register number.
-  /// This is the inverse operation of VirtReg2IndexFunctor below.
-  static Register index2VirtReg(unsigned Index) {
-    return Register(Index | (1u << 31));
+    return virtReg2Index(Reg);
   }
 
   operator unsigned() const {