core/vm: update EIP-8024 - Missing immediate byte is now treated as 0x00 (#33614)

This PR updates the EIP-8024 implementation to match the latest spec
clarification.

---------

Co-authored-by: lightclient <lightclient@protonmail.com>

core/vm/instructions.go

@@ -973,11 +973,11 @@ func opDupN(pc *uint64, evm *EVM, scope *ScopeContext) ([]byte, error) {
 	code := scope.Contract.Code
 	i := *pc + 1
 
-	// Ensure an immediate byte exists after DUPN
+	// If the immediate byte is missing, treat as 0x00 (same convention as PUSHn).
-	if i >= uint64(len(code)) {
+	var x byte
-		return nil, &ErrInvalidOpCode{opcode: INVALID}
+	if i < uint64(len(code)) {
+		x = code[i]
 	}
-	x := code[i]
 
 	// This range is excluded to preserve compatibility with existing opcodes.
 	if x > 90 && x < 128 {
@@ -1000,11 +1000,11 @@ func opSwapN(pc *uint64, evm *EVM, scope *ScopeContext) ([]byte, error) {
 	code := scope.Contract.Code
 	i := *pc + 1
 
-	// Ensure an immediate byte exists after SWAPN
+	// If the immediate byte is missing, treat as 0x00 (same convention as PUSHn).
-	if i >= uint64(len(code)) {
+	var x byte
-		return nil, &ErrInvalidOpCode{opcode: INVALID}
+	if i < uint64(len(code)) {
+		x = code[i]
 	}
-	x := code[i]
 
 	// This range is excluded to preserve compatibility with existing opcodes.
 	if x > 90 && x < 128 {
@@ -1029,11 +1029,11 @@ func opExchange(pc *uint64, evm *EVM, scope *ScopeContext) ([]byte, error) {
 	code := scope.Contract.Code
 	i := *pc + 1
 
-	// Ensure an immediate byte exists after EXCHANGE
+	// If the immediate byte is missing, treat as 0x00 (same convention as PUSHn).
-	if i >= uint64(len(code)) {
+	var x byte
-		return nil, &ErrInvalidOpCode{opcode: INVALID}
+	if i < uint64(len(code)) {
+		x = code[i]
 	}
-	x := code[i]
 
 	// This range is excluded both to preserve compatibility with existing opcodes
 	// and to keep decode_pair’s 16-aligned arithmetic mapping valid (0–79, 128–255).

core/vm/instructions_test.go

@@ -1027,6 +1027,15 @@ func TestEIP8024_Execution(t *testing.T) {
 				1,
 			},
 		},
+		{
+			name:    "DUPN_MISSING_IMMEDIATE",
+			codeHex: "60016000808080808080808080808080808080e6",
+			wantVals: []uint64{
+				1,
+				0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+				1,
+			},
+		},
 		{
 			name:    "SWAPN",
 			codeHex: "600160008080808080808080808080808080806002e700",
@@ -1036,11 +1045,29 @@ func TestEIP8024_Execution(t *testing.T) {
 				2,
 			},
 		},
+		{
+			name:    "SWAPN_MISSING_IMMEDIATE",
+			codeHex: "600160008080808080808080808080808080806002e7",
+			wantVals: []uint64{
+				1,
+				0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+				2,
+			},
+		},
 		{
 			name:     "EXCHANGE",
 			codeHex:  "600060016002e801",
 			wantVals: []uint64{2, 0, 1},
 		},
+		{
+			name:    "EXCHANGE_MISSING_IMMEDIATE",
+			codeHex: "600060006000600060006000600060006000600060006000600060006000600060006000600060006000600060006000600060006000600060016002e8",
+			wantVals: []uint64{
+				2,
+				0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0, 0,
+				1,
+			},
+		},
 		{
 			name:    "INVALID_SWAPN_LOW",
 			codeHex: "e75b",
@@ -1092,21 +1119,6 @@ func TestEIP8024_Execution(t *testing.T) {
 			codeHex: "60016002e801", // (n,m)=(1,2), need 3 items, have 2
 			wantErr: true,
 		},
-		{
-			name:    "MISSING_IMMEDIATE_DUPN",
-			codeHex: "e6", // no operand
-			wantErr: true,
-		},
-		{
-			name:    "MISSING_IMMEDIATE_SWAPN",
-			codeHex: "e7", // no operand
-			wantErr: true,
-		},
-		{
-			name:    "MISSING_IMMEDIATE_EXCHANGE",
-			codeHex: "e8", // no operand
-			wantErr: true,
-		},
 		{
 			name:     "PC_INCREMENT",
 			codeHex:  "600060006000e80115",
@@ -1123,25 +1135,25 @@ func TestEIP8024_Execution(t *testing.T) {
 			var err error
 			for pc < uint64(len(code)) && err == nil {
 				op := code[pc]
-				switch op {
+				switch OpCode(op) {
-				case 0x00:
+				case STOP:
 					return
-				case 0x60:
+				case PUSH1:
 					_, err = opPush1(&pc, evm, scope)
-				case 0x80:
+				case DUP1:
 					dup1 := makeDup(1)
 					_, err = dup1(&pc, evm, scope)
-				case 0x56:
+				case JUMP:
 					_, err = opJump(&pc, evm, scope)
-				case 0x5b:
+				case JUMPDEST:
 					_, err = opJumpdest(&pc, evm, scope)
-				case 0x15:
+				case ISZERO:
 					_, err = opIszero(&pc, evm, scope)
-				case 0xe6:
+				case DUPN:
 					_, err = opDupN(&pc, evm, scope)
-				case 0xe7:
+				case SWAPN:
 					_, err = opSwapN(&pc, evm, scope)
-				case 0xe8:
+				case EXCHANGE:
 					_, err = opExchange(&pc, evm, scope)
 				default:
 					err = &ErrInvalidOpCode{opcode: OpCode(op)}