diff --git a/llvm/include/llvm/CodeGen/Register.h b/llvm/include/llvm/CodeGen/Register.h
--- a/llvm/include/llvm/CodeGen/Register.h
+++ b/llvm/include/llvm/CodeGen/Register.h
@@ -40,10 +40,6 @@
   /// 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 MCRegister::isStackSlot(Reg);
   }
@@ -69,8 +65,7 @@
   /// 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 Reg & MCRegister::VirtualRegFlag;
+    return Reg & MCRegister::VirtualRegFlag && !isStackSlot(Reg);
   }
 
   /// Convert a virtual register number to a 0-based index.
diff --git a/llvm/include/llvm/MC/MCRegister.h b/llvm/include/llvm/MC/MCRegister.h
--- a/llvm/include/llvm/MC/MCRegister.h
+++ b/llvm/include/llvm/MC/MCRegister.h
@@ -46,9 +46,6 @@
   /// register. StackSlot values do not exist in the MC layer, see
   /// Register::isStackSlot() for the more information on them.
   ///
-  /// 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 !(Reg & VirtualRegFlag) &&
            uint32_t(Reg & ~VirtualRegFlag) >= FirstStackSlot;
@@ -57,8 +54,8 @@
   /// 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 Reg >= FirstPhysicalReg && !(Reg & VirtualRegFlag);
+    return Reg >= FirstPhysicalReg && !(Reg & VirtualRegFlag) &&
+           !isStackSlot(Reg);
   }
 
   /// Return true if the specified register number is in the physical register