[MCRegInfo] Add sub_and_superregs_inclusive iterator range.

[fhahn]

ping

[paquette]

I don't suppose it's possible to add a testcase for this somehow? Not sure if there's any infrastructure for that.

Because it's tested by D70450, and this is pretty small, I think it's fine to go in as is.

llvm/include/llvm/MC/MCRegisterInfo.h

public:
 
   /// Return an iterator range over all super-registers of \p Reg, including \p
   /// Reg.
   iterator_range<mc_superreg_iterator>
   superregs_inclusive(MCRegister Reg) const {
     return make_range({Reg, this}, mc_superreg_iterator::end());
   }
 
+  /// Return an iterator range over all sub- and super-registers of \p Reg,
+  /// including \p Reg.
+  detail::concat_range<const MCPhysReg, iterator_range<mc_subreg_iterator>,
+                       iterator_range<mc_superreg_iterator>>
+  sub_and_superregs_inclusive(MCRegister Reg) const {
+    return concat<const MCPhysReg>(subregs_inclusive(Reg), superregs(Reg));
+  }
+
   // These iterators are allowed to sub-class DiffListIterator and access
   // internal list pointers.
   friend class MCSubRegIterator;
   friend class MCSubRegIndexIterator;
   friend class MCSuperRegIterator;
   friend class MCRegUnitIterator;
   friend class MCRegUnitMaskIterator;
   friend class MCRegUnitRootIterator;