internal/ethapi: optimize calculating effective price

Seems better to have this in a dedicated function, and we can also avoid
creating multiple temp bigints.

Author: fjl

internal/ethapi/api.go

@@ -1470,11 +1470,11 @@ func newRPCTransaction(tx *types.Transaction, blockHash common.Hash, blockNumber
 		// if the transaction has been mined, compute the effective gas price
 		if baseFee != nil && blockHash != (common.Hash{}) {
 			// price = min(gasTipCap + baseFee, gasFeeCap)
-			price := math.BigMin(new(big.Int).Add(tx.GasTipCap(), baseFee), tx.GasFeeCap())
-			result.GasPrice = (*hexutil.Big)(price)
+			result.GasPrice = (*hexutil.Big)(effectiveGasPrice(tx, baseFee))
 		} else {
 			result.GasPrice = (*hexutil.Big)(tx.GasFeeCap())
 		}
+
 	case types.BlobTxType:
 		al := tx.AccessList()
 		yparity := hexutil.Uint64(v.Sign())
@@ -1485,9 +1485,7 @@ func newRPCTransaction(tx *types.Transaction, blockHash common.Hash, blockNumber
 		result.GasTipCap = (*hexutil.Big)(tx.GasTipCap())
 		// if the transaction has been mined, compute the effective gas price
 		if baseFee != nil && blockHash != (common.Hash{}) {
-			// price = min(gasTipCap + baseFee, gasFeeCap)
-			price := math.BigMin(new(big.Int).Add(tx.GasTipCap(), baseFee), tx.GasFeeCap())
-			result.GasPrice = (*hexutil.Big)(price)
+			result.GasPrice = (*hexutil.Big)(effectiveGasPrice(tx, baseFee))
 		} else {
 			result.GasPrice = (*hexutil.Big)(tx.GasFeeCap())
 		}
@@ -1497,6 +1495,18 @@ func newRPCTransaction(tx *types.Transaction, blockHash common.Hash, blockNumber
 	return result
 }
 
+// effectiveGasPrice computes the transaction gas fee, based on the given basefee value.
+//
+//	price = min(gasTipCap + baseFee, gasFeeCap)
+func effectiveGasPrice(tx *types.Transaction, baseFee *big.Int) *big.Int {
+	fee := tx.GasTipCap()
+	fee = fee.Add(fee, baseFee)
+	if tx.GasTipCapIntCmp(fee) < 0 {
+		return tx.GasTipCap()
+	}
+	return fee
+}
+
 // NewRPCPendingTransaction returns a pending transaction that will serialize to the RPC representation
 func NewRPCPendingTransaction(tx *types.Transaction, current *types.Header, config *params.ChainConfig) *RPCTransaction {
 	var (