[Utils] Avoid repeated hash lookups (NFC)

Author: kazutakahirata

llvm/lib/Transforms/Utils/Local.cpp

@@ -2178,11 +2178,9 @@ void llvm::insertDebugValuesForPHIs(BasicBlock *BB,
       auto V = DbgValueMap.find(VI);
       if (V != DbgValueMap.end()) {
         auto *DbgII = cast<DbgVariableIntrinsic>(V->second);
-        auto NewDI = NewDbgValueMap.find({Parent, DbgII});
-        if (NewDI == NewDbgValueMap.end()) {
-          auto *NewDbgII = cast<DbgVariableIntrinsic>(DbgII->clone());
-          NewDI = NewDbgValueMap.insert({{Parent, DbgII}, NewDbgII}).first;
-        }
+        auto [NewDI, Inserted] = NewDbgValueMap.try_emplace({Parent, DbgII});
+        if (Inserted)
+          NewDI->second = cast<DbgVariableIntrinsic>(DbgII->clone());
         DbgVariableIntrinsic *NewDbgII = NewDI->second;
         // If PHI contains VI as an operand more than once, we may
         // replaced it in NewDbgII; confirm that it is present.