core/types: optimize modernSigner.Equal (#32971)

Equal is called every time the transaction sender is accessed,
even when the sender is cached, so it is worth optimizing.

---------

Co-authored-by: Felix Lange <fjl@twurst.com>

core/types/transaction_signing.go

@@ -20,7 +20,6 @@ import (
 	"crypto/ecdsa"
 	"errors"
 	"fmt"
-	"maps"
 	"math/big"
 
 	"github.com/ethereum/go-ethereum/common"
@@ -183,18 +182,31 @@ type Signer interface {
 // modernSigner is the signer implementation that handles non-legacy transaction types.
 // For legacy transactions, it defers to one of the legacy signers (frontier, homestead, eip155).
 type modernSigner struct {
-	txtypes map[byte]struct{}
+	txtypes txtypeSet
 	chainID *big.Int
 	legacy  Signer
 }
 
+// txtypeSet is a bitmap for transaction types.
+type txtypeSet [2]uint64
+
+func (v *txtypeSet) set(txType byte) {
+	v[txType/64] |= 1 << (txType % 64)
+}
+
+func (v *txtypeSet) has(txType byte) bool {
+	if txType >= byte(len(v)*64) {
+		return false
+	}
+	return v[txType/64]&(1<<(txType%64)) != 0
+}
+
 func newModernSigner(chainID *big.Int, fork forks.Fork) Signer {
 	if chainID == nil || chainID.Sign() <= 0 {
 		panic(fmt.Sprintf("invalid chainID %v", chainID))
 	}
 	s := &modernSigner{
 		chainID: chainID,
-		txtypes: make(map[byte]struct{}, 4),
 	}
 	// configure legacy signer
 	switch {
@@ -205,19 +217,19 @@ func newModernSigner(chainID *big.Int, fork forks.Fork) Signer {
 	default:
 		s.legacy = FrontierSigner{}
 	}
-	s.txtypes[LegacyTxType] = struct{}{}
+	s.txtypes.set(LegacyTxType)
 	// configure tx types
 	if fork >= forks.Berlin {
-		s.txtypes[AccessListTxType] = struct{}{}
+		s.txtypes.set(AccessListTxType)
 	}
 	if fork >= forks.London {
-		s.txtypes[DynamicFeeTxType] = struct{}{}
+		s.txtypes.set(DynamicFeeTxType)
 	}
 	if fork >= forks.Cancun {
-		s.txtypes[BlobTxType] = struct{}{}
+		s.txtypes.set(BlobTxType)
 	}
 	if fork >= forks.Prague {
-		s.txtypes[SetCodeTxType] = struct{}{}
+		s.txtypes.set(SetCodeTxType)
 	}
 	return s
 }
@@ -228,7 +240,7 @@ func (s *modernSigner) ChainID() *big.Int {
 
 func (s *modernSigner) Equal(s2 Signer) bool {
 	other, ok := s2.(*modernSigner)
-	return ok && s.chainID.Cmp(other.chainID) == 0 && maps.Equal(s.txtypes, other.txtypes) && s.legacy.Equal(other.legacy)
+	return ok && s.chainID.Cmp(other.chainID) == 0 && s.txtypes == other.txtypes && s.legacy.Equal(other.legacy)
 }
 
 func (s *modernSigner) Hash(tx *Transaction) common.Hash {
@@ -236,8 +248,7 @@ func (s *modernSigner) Hash(tx *Transaction) common.Hash {
 }
 
 func (s *modernSigner) supportsType(txtype byte) bool {
-	_, ok := s.txtypes[txtype]
-	return ok
+	return s.txtypes.has(txtype)
 }
 
 func (s *modernSigner) Sender(tx *Transaction) (common.Address, error) {

core/types/transaction_signing_test.go

@@ -25,6 +25,7 @@ import (
 	"github.com/ethereum/go-ethereum/common"
 	"github.com/ethereum/go-ethereum/crypto"
 	"github.com/ethereum/go-ethereum/params"
+	"github.com/ethereum/go-ethereum/params/forks"
 	"github.com/ethereum/go-ethereum/rlp"
 )
 
@@ -188,3 +189,14 @@ func createTestLegacyTxInner() *LegacyTx {
 		Data:     nil,
 	}
 }
+
+func Benchmark_modernSigner_Equal(b *testing.B) {
+	signer1 := newModernSigner(big.NewInt(1), forks.Amsterdam)
+	signer2 := newModernSigner(big.NewInt(1), forks.Amsterdam)
+
+	for b.Loop() {
+		if !signer1.Equal(signer2) {
+			b.Fatal("expected signers to be equal")
+		}
+	}
+}