core: filter out txs with invalid signatures as soon as possible

Once we detect an invalid transaction during recovering signatures, we should
directly exclude this transaction to avoid validating the signatures hereafter.

This should optimize the validations times of transactions with invalid signatures
to only one time.

core/tx_pool.go

@@ -781,16 +781,22 @@ func (pool *TxPool) addTxs(txs []*types.Transaction, local, sync bool) []error {
 			knownTxMeter.Mark(1)
 			continue
 		}
+		// Exclude transactions with invalid signatures as soon as
+		// possible and cache senders in transactions before
+		// obtaining lock
+		_, err := types.Sender(pool.signer, tx)
+		if err != nil {
+			errs[i] = ErrInvalidSender
+			invalidTxMeter.Mark(1)
+			continue
+		}
 		// Accumulate all unknown transactions for deeper processing
 		news = append(news, tx)
 	}
 	if len(news) == 0 {
 		return errs
 	}
-	// Cache senders in transactions before obtaining lock (pool.signer is immutable)
-	for _, tx := range news {
-		types.Sender(pool.signer, tx)
-	}
+
 	// Process all the new transaction and merge any errors into the original slice
 	pool.mu.Lock()
 	newErrs, dirtyAddrs := pool.addTxsLocked(news, local)