[Analysis] Avoid repeated hash lookups (NFC)

Author: kazutakahirata

llvm/include/llvm/Analysis/SparsePropagation.h

@@ -244,13 +244,13 @@ SparseSolver<LatticeKey, LatticeVal, KeyInfo>::getValueState(LatticeKey Key) {
 template <class LatticeKey, class LatticeVal, class KeyInfo>
 void SparseSolver<LatticeKey, LatticeVal, KeyInfo>::UpdateState(LatticeKey Key,
                                                                 LatticeVal LV) {
-  auto I = ValueState.find(Key);
-  if (I != ValueState.end() && I->second == LV)
+  auto [I, Inserted] = ValueState.try_emplace(Key);
+  if (!Inserted && I->second == LV)
     return; // No change.
 
   // Update the state of the given LatticeKey and add its corresponding LLVM
   // value to the work list.
-  ValueState[Key] = std::move(LV);
+  I->second = std::move(LV);
   if (Value *V = KeyInfo::getValueFromLatticeKey(Key))
     ValueWorkList.push_back(V);
 }