[llvm] [VirtRegMap] Store MCRegister in Virt2PhysMap. (PR #108775)

[Matt Arsenault via llvm-commits]

================
@@ -49,7 +48,7 @@ class TargetInstrInfo;
     /// it; even spilled virtual registers (the register mapped to a
     /// spilled register is the temporary used to load it from the
     /// stack).
-    IndexedMap<Register, VirtReg2IndexFunctor> Virt2PhysMap;
+    IndexedMap<MCRegister, VirtReg2IndexFunctor> Virt2PhysMap;
----------------
arsenm wrote:

If the key is a virtual register, this should still be Register 

https://github.com/llvm/llvm-project/pull/108775