[llvm] [X86][MC] Allow to specify any of the 8/16/32/64 register names interchangeably for R16-R31 (PR #73421)

[Phoebe Wang via llvm-commits]

================
@@ -817,6 +817,22 @@ MCRegister llvm::getX86SubSuperRegister(MCRegister Reg, unsigned Size,
         NO_SUB_SUPER(13, R13B)
         NO_SUB_SUPER(14, R14B)
         NO_SUB_SUPER(15, R15B)
+        NO_SUB_SUPER(16, R16B)
----------------
phoebewang wrote:

How about define a `NO_SUB_SUPERB(8)`?

https://github.com/llvm/llvm-project/pull/73421