[CodeGen] Use DenseMapInfo<Register> to implement DenseMapInfo<TargetInstrInfo::RegSubRegPair>. NFC

Instead of casting Register to unsigned to use DenseMapInfo<unsigned>.

Author: topperc

llvm/include/llvm/CodeGen/TargetInstrInfo.h

@@ -2287,29 +2287,30 @@ class TargetInstrInfo : public MCInstrInfo {
 
 /// Provide DenseMapInfo for TargetInstrInfo::RegSubRegPair.
 template <> struct DenseMapInfo<TargetInstrInfo::RegSubRegPair> {
-  using RegInfo = DenseMapInfo<unsigned>;
+  using RegInfo = DenseMapInfo<Register>;
+  using SubRegInfo = DenseMapInfo<unsigned>;
 
   static inline TargetInstrInfo::RegSubRegPair getEmptyKey() {
     return TargetInstrInfo::RegSubRegPair(RegInfo::getEmptyKey(),
-                                          RegInfo::getEmptyKey());
+                                          SubRegInfo::getEmptyKey());
   }
 
   static inline TargetInstrInfo::RegSubRegPair getTombstoneKey() {
     return TargetInstrInfo::RegSubRegPair(RegInfo::getTombstoneKey(),
-                                          RegInfo::getTombstoneKey());
+                                          SubRegInfo::getTombstoneKey());
   }
 
   /// Reuse getHashValue implementation from
   /// std::pair<unsigned, unsigned>.
   static unsigned getHashValue(const TargetInstrInfo::RegSubRegPair &Val) {
-    std::pair<unsigned, unsigned> PairVal = std::make_pair(Val.Reg, Val.SubReg);
-    return DenseMapInfo<std::pair<unsigned, unsigned>>::getHashValue(PairVal);
+    return DenseMapInfo<std::pair<Register, unsigned>>::getHashValue(
+        std::make_pair(Val.Reg, Val.SubReg));
   }
 
   static bool isEqual(const TargetInstrInfo::RegSubRegPair &LHS,
                       const TargetInstrInfo::RegSubRegPair &RHS) {
     return RegInfo::isEqual(LHS.Reg, RHS.Reg) &&
-           RegInfo::isEqual(LHS.SubReg, RHS.SubReg);
+           SubRegInfo::isEqual(LHS.SubReg, RHS.SubReg);
   }
 };