Merge pull request #2128 from nspcc-dev/vm-update-int

Some VM optimizations

pkg/compiler/codegen.go

@@ -2097,20 +2097,17 @@ func (c *codegen) resolveFuncDecls(f *ast.File, pkg *types.Package) {
 func (c *codegen) writeJumps(b []byte) ([]byte, error) {
 	ctx := vm.NewContext(b)
 	var offsets []int
-	for op, _, err := ctx.Next(); err == nil && ctx.IP() < len(b); op, _, err = ctx.Next() {
+	for op, param, err := ctx.Next(); err == nil && ctx.IP() < len(b); op, param, err = ctx.Next() {
 		switch op {
 		case opcode.JMP, opcode.JMPIFNOT, opcode.JMPIF, opcode.CALL,
 			opcode.JMPEQ, opcode.JMPNE,
 			opcode.JMPGT, opcode.JMPGE, opcode.JMPLE, opcode.JMPLT:
 		case opcode.TRYL:
-			nextIP := ctx.NextIP()
+			_, err := c.replaceLabelWithOffset(ctx.IP(), param)
-			catchArg := b[nextIP-8:]
-			_, err := c.replaceLabelWithOffset(ctx.IP(), catchArg)
 			if err != nil {
 				return nil, err
 			}
-			finallyArg := b[nextIP-4:]
+			_, err = c.replaceLabelWithOffset(ctx.IP(), param[4:])
-			_, err = c.replaceLabelWithOffset(ctx.IP(), finallyArg)
 			if err != nil {
 				return nil, err
 			}
@@ -2118,10 +2115,7 @@ func (c *codegen) writeJumps(b []byte) ([]byte, error) {
 			opcode.JMPEQL, opcode.JMPNEL,
 			opcode.JMPGTL, opcode.JMPGEL, opcode.JMPLEL, opcode.JMPLTL,
 			opcode.CALLL, opcode.PUSHA, opcode.ENDTRYL:
-			// we can't use arg returned by ctx.Next() because it is copied
+			offset, err := c.replaceLabelWithOffset(ctx.IP(), param)
-			nextIP := ctx.NextIP()
-			arg := b[nextIP-4:]
-			offset, err := c.replaceLabelWithOffset(ctx.IP(), arg)
 			if err != nil {
 				return nil, err
 			}

pkg/smartcontract/convertor.go

@@ -17,7 +17,7 @@ func ParameterFromStackItem(i stackitem.Item, seen map[stackitem.Item]bool) Para
 			Type:  IntegerType,
 			Value: i.Value().(*big.Int).Int64(),
 		}
-	case *stackitem.Bool:
+	case stackitem.Bool:
 		return Parameter{
 			Type:  BoolType,
 			Value: i.Value().(bool),

pkg/vm/context.go

@@ -97,9 +97,9 @@ func (c *Context) NextIP() int {
 	return c.nextip
 }
 
-// Next returns the next instruction to execute with its parameter if any. After
+// Next returns the next instruction to execute with its parameter if any.
-// its invocation the instruction pointer points to the instruction being
+// The parameter is not copied and shouldn't be written to. After its invocation
-// returned.
+// the instruction pointer points to the instruction being returned.
 func (c *Context) Next() (opcode.Opcode, []byte, error) {
 	var err error
 
@@ -171,8 +171,7 @@ func (c *Context) Next() (opcode.Opcode, []byte, error) {
 	if err != nil {
 		return instr, nil, err
 	}
-	parameter := make([]byte, numtoread)
+	parameter := c.prog[c.nextip : c.nextip+numtoread]
-	copy(parameter, c.prog[c.nextip:c.nextip+numtoread])
 	c.nextip += numtoread
 	return instr, parameter, nil
 }

pkg/vm/json_test.go

@@ -195,7 +195,7 @@ func compareItems(t *testing.T, a, b stackitem.Item) {
 			require.Equal(t, val, ac.Value().(*big.Int).Int64())
 		case *stackitem.ByteArray:
 			require.Equal(t, val, bigint.FromBytes(ac.Value().([]byte)).Int64())
-		case *stackitem.Bool:
+		case stackitem.Bool:
 			if ac.Value().(bool) {
 				require.Equal(t, val, int64(1))
 			} else {
@@ -208,6 +208,28 @@ func compareItems(t *testing.T, a, b stackitem.Item) {
 		p, ok := b.(*stackitem.Pointer)
 		require.True(t, ok)
 		require.Equal(t, si.Position(), p.Position()) // there no script in test files
+	case *stackitem.Array, *stackitem.Struct:
+		require.Equal(t, a.Type(), b.Type())
+
+		as := a.Value().([]stackitem.Item)
+		bs := a.Value().([]stackitem.Item)
+		require.Equal(t, len(as), len(bs))
+
+		for i := range as {
+			compareItems(t, as[i], bs[i])
+		}
+
+	case *stackitem.Map:
+		require.Equal(t, a.Type(), b.Type())
+
+		as := a.Value().([]stackitem.MapElement)
+		bs := a.Value().([]stackitem.MapElement)
+		require.Equal(t, len(as), len(bs))
+
+		for i := range as {
+			compareItems(t, as[i].Key, bs[i].Key)
+			compareItems(t, as[i].Value, bs[i].Value)
+		}
 	default:
 		require.Equal(t, a, b)
 	}

pkg/vm/ref_counter.go

@@ -5,15 +5,19 @@ import (
 )
 
 // refCounter represents reference counter for the VM.
-type refCounter struct {
+type refCounter int
-	items map[stackitem.Item]int
+
-	size  int
+type (
-}
+	rcInc interface {
+		IncRC() int
+	}
+	rcDec interface {
+		DecRC() int
+	}
+)
 
 func newRefCounter() *refCounter {
-	return &refCounter{
+	return new(refCounter)
-		items: make(map[stackitem.Item]int),
-	}
 }
 
 // Add adds an item to the reference counter.
@@ -21,14 +25,12 @@ func (r *refCounter) Add(item stackitem.Item) {
 	if r == nil {
 		return
 	}
-	r.size++
+	*r++
 
-	switch item.(type) {
+	irc, ok := item.(rcInc)
-	case *stackitem.Array, *stackitem.Struct, *stackitem.Map:
+	if !ok || irc.IncRC() > 1 {
-		if r.items[item]++; r.items[item] > 1 {
 		return
 	}
-
 	switch t := item.(type) {
 	case *stackitem.Array, *stackitem.Struct:
 		for _, it := range item.Value().([]stackitem.Item) {
@@ -39,7 +41,6 @@ func (r *refCounter) Add(item stackitem.Item) {
 			r.Add(t.Value().([]stackitem.MapElement)[i].Value)
 		}
 	}
-	}
 }
 
 // Remove removes item from the reference counter.
@@ -47,17 +48,12 @@ func (r *refCounter) Remove(item stackitem.Item) {
 	if r == nil {
 		return
 	}
-	r.size--
+	*r--
 
-	switch item.(type) {
+	irc, ok := item.(rcDec)
-	case *stackitem.Array, *stackitem.Struct, *stackitem.Map:
+	if !ok || irc.DecRC() > 0 {
-		if r.items[item] > 1 {
-			r.items[item]--
 		return
 	}
-
-		delete(r.items, item)
-
 	switch t := item.(type) {
 	case *stackitem.Array, *stackitem.Struct:
 		for _, it := range item.Value().([]stackitem.Item) {
@@ -68,5 +64,4 @@ func (r *refCounter) Remove(item stackitem.Item) {
 			r.Remove(t.Value().([]stackitem.MapElement)[i].Value)
 		}
 	}
-	}
 }

pkg/vm/ref_counter_test.go

@@ -10,24 +10,34 @@ import (
 func TestRefCounter_Add(t *testing.T) {
 	r := newRefCounter()
 
-	require.Equal(t, 0, r.size)
+	require.Equal(t, 0, int(*r))
 
 	r.Add(stackitem.Null{})
-	require.Equal(t, 1, r.size)
+	require.Equal(t, 1, int(*r))
 
 	r.Add(stackitem.Null{})
-	require.Equal(t, 2, r.size) // count scalar items twice
+	require.Equal(t, 2, int(*r)) // count scalar items twice
 
 	arr := stackitem.NewArray([]stackitem.Item{stackitem.NewByteArray([]byte{1}), stackitem.NewBool(false)})
 	r.Add(arr)
-	require.Equal(t, 5, r.size) // array + 2 elements
+	require.Equal(t, 5, int(*r)) // array + 2 elements
 
 	r.Add(arr)
-	require.Equal(t, 6, r.size) // count only array
+	require.Equal(t, 6, int(*r)) // count only array
 
 	r.Remove(arr)
-	require.Equal(t, 5, r.size)
+	require.Equal(t, 5, int(*r))
 
 	r.Remove(arr)
-	require.Equal(t, 2, r.size)
+	require.Equal(t, 2, int(*r))
+}
+
+func BenchmarkRefCounter_Add(b *testing.B) {
+	a := stackitem.NewArray(nil)
+	rc := newRefCounter()
+
+	b.ResetTimer()
+	for i := 0; i < b.N; i++ {
+		rc.Add(a)
+	}
 }

pkg/vm/stackitem/item.go

@@ -2,7 +2,6 @@ package stackitem
 
 import (
 	"bytes"
-	"encoding/binary"
 	"encoding/hex"
 	"encoding/json"
 	"errors"
@@ -90,45 +89,23 @@ func mkInvConversion(from Item, to Type) error {
 func Make(v interface{}) Item {
 	switch val := v.(type) {
 	case int:
-		return &BigInteger{
+		return (*BigInteger)(big.NewInt(int64(val)))
-			value: big.NewInt(int64(val)),
-		}
 	case int64:
-		return &BigInteger{
+		return (*BigInteger)(big.NewInt(val))
-			value: big.NewInt(val),
-		}
 	case uint8:
-		return &BigInteger{
+		return (*BigInteger)(big.NewInt(int64(val)))
-			value: big.NewInt(int64(val)),
-		}
 	case uint16:
-		return &BigInteger{
+		return (*BigInteger)(big.NewInt(int64(val)))
-			value: big.NewInt(int64(val)),
-		}
 	case uint32:
-		return &BigInteger{
+		return (*BigInteger)(big.NewInt(int64(val)))
-			value: big.NewInt(int64(val)),
-		}
 	case uint64:
-		b := make([]byte, 8)
+		return (*BigInteger)(new(big.Int).SetUint64(val))
-		binary.BigEndian.PutUint64(b, val)
-		bigInt := big.NewInt(0)
-		bigInt.SetBytes(b)
-		return &BigInteger{
-			value: bigInt,
-		}
 	case []byte:
-		return &ByteArray{
+		return NewByteArray(val)
-			value: val,
-		}
 	case string:
-		return &ByteArray{
+		return NewByteArray([]byte(val))
-			value: []byte(val),
-		}
 	case bool:
-		return &Bool{
+		return Bool(val)
-			value: val,
-		}
 	case []Item:
 		return &Array{
 			value: val,
@@ -207,6 +184,7 @@ func convertPrimitive(item Item, typ Type) (Item, error) {
 // Struct represents a struct on the stack.
 type Struct struct {
 	value []Item
+	rc
 }
 
 // NewStruct returns an new Struct object.
@@ -330,7 +308,7 @@ func (i *Struct) Clone() (*Struct, error) {
 }
 
 func (i *Struct) clone(limit *int) (*Struct, error) {
-	ret := &Struct{make([]Item, len(i.value))}
+	ret := &Struct{value: make([]Item, len(i.value))}
 	for j := range i.value {
 		*limit--
 		if *limit < 0 {
@@ -402,9 +380,7 @@ func (i Null) Convert(typ Type) (Item, error) {
 }
 
 // BigInteger represents a big integer on the stack.
-type BigInteger struct {
+type BigInteger big.Int
-	value *big.Int
-}
 
 // NewBigInteger returns an new BigInteger object.
 func NewBigInteger(value *big.Int) *BigInteger {
@@ -420,19 +396,22 @@ func NewBigInteger(value *big.Int) *BigInteger {
 			panic(errTooBigInteger)
 		}
 	}
-	return &BigInteger{
+	return (*BigInteger)(value)
-		value: value,
+}
-	}
+
+// Big casts i to the big.Int type.
+func (i *BigInteger) Big() *big.Int {
+	return (*big.Int)(i)
 }
 
 // Bytes converts i to a slice of bytes.
 func (i *BigInteger) Bytes() []byte {
-	return bigint.ToBytes(i.value)
+	return bigint.ToBytes(i.Big())
 }
 
 // TryBool implements Item interface.
 func (i *BigInteger) TryBool() (bool, error) {
-	return i.value.Sign() != 0, nil
+	return i.Big().Sign() != 0, nil
 }
 
 // TryBytes implements Item interface.
@@ -442,7 +421,7 @@ func (i *BigInteger) TryBytes() ([]byte, error) {
 
 // TryInteger implements Item interface.
 func (i *BigInteger) TryInteger() (*big.Int, error) {
-	return i.value, nil
+	return i.Big(), nil
 }
 
 // Equals implements Item interface.
@@ -453,12 +432,12 @@ func (i *BigInteger) Equals(s Item) bool {
 		return false
 	}
 	val, ok := s.(*BigInteger)
-	return ok && i.value.Cmp(val.value) == 0
+	return ok && i.Big().Cmp(val.Big()) == 0
 }
 
 // Value implements Item interface.
 func (i *BigInteger) Value() interface{} {
-	return i.value
+	return i.Big()
 }
 
 func (i *BigInteger) String() string {
@@ -468,7 +447,7 @@ func (i *BigInteger) String() string {
 // Dup implements Item interface.
 func (i *BigInteger) Dup() Item {
 	n := new(big.Int)
-	return &BigInteger{n.Set(i.value)}
+	return (*BigInteger)(n.Set(i.Big()))
 }
 
 // Type implements Item interface.
@@ -481,103 +460,95 @@ func (i *BigInteger) Convert(typ Type) (Item, error) {
 
 // MarshalJSON implements the json.Marshaler interface.
 func (i *BigInteger) MarshalJSON() ([]byte, error) {
-	return json.Marshal(i.value)
+	return json.Marshal(i.Big())
 }
 
 // Bool represents a boolean Item.
-type Bool struct {
+type Bool bool
-	value bool
-}
 
 // NewBool returns an new Bool object.
-func NewBool(val bool) *Bool {
+func NewBool(val bool) Bool {
-	return &Bool{
+	return Bool(val)
-		value: val,
-	}
 }
 
 // Value implements Item interface.
-func (i *Bool) Value() interface{} {
+func (i Bool) Value() interface{} {
-	return i.value
+	return bool(i)
 }
 
 // MarshalJSON implements the json.Marshaler interface.
-func (i *Bool) MarshalJSON() ([]byte, error) {
+func (i Bool) MarshalJSON() ([]byte, error) {
-	return json.Marshal(i.value)
+	return json.Marshal(bool(i))
 }
 
-func (i *Bool) String() string {
+func (i Bool) String() string {
 	return "Boolean"
 }
 
 // Dup implements Item interface.
-func (i *Bool) Dup() Item {
+func (i Bool) Dup() Item {
-	return &Bool{i.value}
+	return i
 }
 
 // TryBool implements Item interface.
-func (i *Bool) TryBool() (bool, error) { return i.value, nil }
+func (i Bool) TryBool() (bool, error) { return bool(i), nil }
 
 // Bytes converts Bool to bytes.
-func (i *Bool) Bytes() []byte {
+func (i Bool) Bytes() []byte {
-	if i.value {
+	if i {
 		return []byte{1}
 	}
 	return []byte{0}
 }
 
 // TryBytes implements Item interface.
-func (i *Bool) TryBytes() ([]byte, error) {
+func (i Bool) TryBytes() ([]byte, error) {
 	return i.Bytes(), nil
 }
 
 // TryInteger implements Item interface.
-func (i *Bool) TryInteger() (*big.Int, error) {
+func (i Bool) TryInteger() (*big.Int, error) {
-	if i.value {
+	if i {
 		return big.NewInt(1), nil
 	}
 	return big.NewInt(0), nil
 }
 
 // Equals implements Item interface.
-func (i *Bool) Equals(s Item) bool {
+func (i Bool) Equals(s Item) bool {
 	if i == s {
 		return true
 	} else if s == nil {
 		return false
 	}
-	val, ok := s.(*Bool)
+	val, ok := s.(Bool)
-	return ok && i.value == val.value
+	return ok && i == val
 }
 
 // Type implements Item interface.
-func (i *Bool) Type() Type { return BooleanT }
+func (i Bool) Type() Type { return BooleanT }
 
 // Convert implements Item interface.
-func (i *Bool) Convert(typ Type) (Item, error) {
+func (i Bool) Convert(typ Type) (Item, error) {
 	return convertPrimitive(i, typ)
 }
 
 // ByteArray represents a byte array on the stack.
-type ByteArray struct {
+type ByteArray []byte
-	value []byte
-}
 
 // NewByteArray returns an new ByteArray object.
 func NewByteArray(b []byte) *ByteArray {
-	return &ByteArray{
+	return (*ByteArray)(&b)
-		value: b,
-	}
 }
 
 // Value implements Item interface.
 func (i *ByteArray) Value() interface{} {
-	return i.value
+	return []byte(*i)
 }
 
 // MarshalJSON implements the json.Marshaler interface.
 func (i *ByteArray) MarshalJSON() ([]byte, error) {
-	return json.Marshal(hex.EncodeToString(i.value))
+	return json.Marshal(hex.EncodeToString(*i))
 }
 
 func (i *ByteArray) String() string {
@@ -586,10 +557,10 @@ func (i *ByteArray) String() string {
 
 // TryBool implements Item interface.
 func (i *ByteArray) TryBool() (bool, error) {
-	if len(i.value) > MaxBigIntegerSizeBits/8 {
+	if len(*i) > MaxBigIntegerSizeBits/8 {
 		return false, errTooBigInteger
 	}
-	for _, b := range i.value {
+	for _, b := range *i {
 		if b != 0 {
 			return true, nil
 		}
@@ -598,21 +569,21 @@ func (i *ByteArray) TryBool() (bool, error) {
 }
 
 // TryBytes implements Item interface.
-func (i *ByteArray) TryBytes() ([]byte, error) {
+func (i ByteArray) TryBytes() ([]byte, error) {
-	return i.value, nil
+	return i, nil
 }
 
 // TryInteger implements Item interface.
-func (i *ByteArray) TryInteger() (*big.Int, error) {
+func (i ByteArray) TryInteger() (*big.Int, error) {
-	if len(i.value) > MaxBigIntegerSizeBits/8 {
+	if len(i) > MaxBigIntegerSizeBits/8 {
 		return nil, errTooBigInteger
 	}
-	return bigint.FromBytes(i.value), nil
+	return bigint.FromBytes(i), nil
 }
 
 // Equals implements Item interface.
 func (i *ByteArray) Equals(s Item) bool {
-	if len(i.value) > MaxByteArrayComparableSize {
+	if len(*i) > MaxByteArrayComparableSize {
 		panic(errTooBigComparable)
 	}
 	if i == s {
@@ -624,15 +595,16 @@ func (i *ByteArray) Equals(s Item) bool {
 	if !ok {
 		return false
 	}
-	if len(val.value) > MaxByteArrayComparableSize {
+	if len(*val) > MaxByteArrayComparableSize {
 		panic(errTooBigComparable)
 	}
-	return bytes.Equal(i.value, val.value)
+	return bytes.Equal(*i, *val)
 }
 
 // Dup implements Item interface.
 func (i *ByteArray) Dup() Item {
-	return &ByteArray{slice.Copy(i.value)}
+	ba := slice.Copy(*i)
+	return (*ByteArray)(&ba)
 }
 
 // Type implements Item interface.
@@ -646,6 +618,7 @@ func (i *ByteArray) Convert(typ Type) (Item, error) {
 // Array represents a new Array object.
 type Array struct {
 	value []Item
+	rc
 }
 
 // NewArray returns a new Array object.
@@ -746,6 +719,7 @@ type MapElement struct {
 // if need be.
 type Map struct {
 	value []MapElement
+	rc
 }
 
 // NewMap returns new Map object.
@@ -861,7 +835,7 @@ func (i *Map) Drop(index int) {
 // key.
 func IsValidMapKey(key Item) error {
 	switch key.(type) {
-	case *Bool, *BigInteger:
+	case Bool, *BigInteger:
 		return nil
 	case *ByteArray:
 		size := len(key.Value().([]byte))
@@ -1045,20 +1019,16 @@ func (p *Pointer) Position() int {
 }
 
 // Buffer represents represents Buffer stack item.
-type Buffer struct {
+type Buffer []byte
-	value []byte
-}
 
 // NewBuffer returns a new Buffer object.
 func NewBuffer(b []byte) *Buffer {
-	return &Buffer{
+	return (*Buffer)(&b)
-		value: b,
-	}
 }
 
 // Value implements Item interface.
 func (i *Buffer) Value() interface{} {
-	return i.value
+	return []byte(*i)
 }
 
 // String implements fmt.Stringer interface.
@@ -1073,7 +1043,7 @@ func (i *Buffer) TryBool() (bool, error) {
 
 // TryBytes implements Item interface.
 func (i *Buffer) TryBytes() ([]byte, error) {
-	return i.value, nil
+	return *i, nil
 }
 
 // TryInteger implements Item interface.
@@ -1093,7 +1063,7 @@ func (i *Buffer) Dup() Item {
 
 // MarshalJSON implements the json.Marshaler interface.
 func (i *Buffer) MarshalJSON() ([]byte, error) {
-	return json.Marshal(hex.EncodeToString(i.value))
+	return json.Marshal(hex.EncodeToString(*i))
 }
 
 // Type implements Item interface.
@@ -1107,12 +1077,12 @@ func (i *Buffer) Convert(typ Type) (Item, error) {
 	case BufferT:
 		return i, nil
 	case ByteArrayT:
-		return NewByteArray(slice.Copy(i.value)), nil
+		return NewByteArray(slice.Copy(*i)), nil
 	case IntegerT:
-		if len(i.value) > MaxBigIntegerSizeBits/8 {
+		if len(*i) > MaxBigIntegerSizeBits/8 {
 			return nil, errTooBigInteger
 		}
-		return NewBigInteger(bigint.FromBytes(i.value)), nil
+		return NewBigInteger(bigint.FromBytes(*i)), nil
 	default:
 		return nil, mkInvConversion(i, typ)
 	}
@@ -1120,7 +1090,7 @@ func (i *Buffer) Convert(typ Type) (Item, error) {
 
 // Len returns length of Buffer value.
 func (i *Buffer) Len() int {
-	return len(i.value)
+	return len(*i)
 }
 
 // DeepCopy returns new deep copy of the provided item.
@@ -1162,17 +1132,14 @@ func deepCopy(item Item, seen map[Item]Item) Item {
 		}
 		return m
 	case *BigInteger:
-		bi := new(big.Int).SetBytes(it.value.Bytes())
+		bi := new(big.Int).Set(it.Big())
-		if it.value.Sign() == -1 {
+		return (*BigInteger)(bi)
-			bi.Neg(bi)
-		}
-		return NewBigInteger(bi)
 	case *ByteArray:
-		return NewByteArray(slice.Copy(it.value))
+		return NewByteArray(slice.Copy(*it))
 	case *Buffer:
-		return NewBuffer(slice.Copy(it.value))
+		return NewBuffer(slice.Copy(*it))
-	case *Bool:
+	case Bool:
-		return NewBool(it.value)
+		return it
 	case *Pointer:
 		return NewPointerWithHash(it.pos, it.script, it.hash)
 	case *Interop:

pkg/vm/stackitem/item_test.go

@@ -15,67 +15,67 @@ var makeStackItemTestCases = []struct {
 }{
 	{
 		input:  int64(3),
-		result: &BigInteger{value: big.NewInt(3)},
+		result: (*BigInteger)(big.NewInt(3)),
 	},
 	{
 		input:  int16(3),
-		result: &BigInteger{value: big.NewInt(3)},
+		result: (*BigInteger)(big.NewInt(3)),
 	},
 	{
 		input:  3,
-		result: &BigInteger{value: big.NewInt(3)},
+		result: (*BigInteger)(big.NewInt(3)),
 	},
 	{
 		input:  uint8(3),
-		result: &BigInteger{value: big.NewInt(3)},
+		result: (*BigInteger)(big.NewInt(3)),
 	},
 	{
 		input:  uint16(3),
-		result: &BigInteger{value: big.NewInt(3)},
+		result: (*BigInteger)(big.NewInt(3)),
 	},
 	{
 		input:  uint32(3),
-		result: &BigInteger{value: big.NewInt(3)},
+		result: (*BigInteger)(big.NewInt(3)),
 	},
 	{
 		input:  uint64(3),
-		result: &BigInteger{value: big.NewInt(3)},
+		result: (*BigInteger)(big.NewInt(3)),
 	},
 	{
 		input:  big.NewInt(3),
-		result: &BigInteger{value: big.NewInt(3)},
+		result: (*BigInteger)(big.NewInt(3)),
 	},
 	{
 		input:  []byte{1, 2, 3, 4},
-		result: &ByteArray{value: []byte{1, 2, 3, 4}},
+		result: NewByteArray([]byte{1, 2, 3, 4}),
 	},
 	{
 		input:  []byte{},
-		result: &ByteArray{value: []byte{}},
+		result: NewByteArray([]byte{}),
 	},
 	{
 		input:  "bla",
-		result: &ByteArray{value: []byte("bla")},
+		result: NewByteArray([]byte("bla")),
 	},
 	{
 		input:  "",
-		result: &ByteArray{value: []byte{}},
+		result: NewByteArray([]byte{}),
 	},
 	{
 		input:  true,
-		result: &Bool{value: true},
+		result: Bool(true),
 	},
 	{
 		input:  false,
-		result: &Bool{value: false},
+		result: Bool(false),
 	},
 	{
-		input:  []Item{&BigInteger{value: big.NewInt(3)}, &ByteArray{value: []byte{1, 2, 3}}},
+		input:  []Item{(*BigInteger)(big.NewInt(3)), NewByteArray([]byte{1, 2, 3})},
-		result: &Array{value: []Item{&BigInteger{value: big.NewInt(3)}, &ByteArray{value: []byte{1, 2, 3}}}},
+		result: &Array{value: []Item{(*BigInteger)(big.NewInt(3)), NewByteArray([]byte{1, 2, 3})}},
 	},
 	{
 		input:  []int{1, 2, 3},
-		result: &Array{value: []Item{&BigInteger{value: big.NewInt(1)}, &BigInteger{value: big.NewInt(2)}, &BigInteger{value: big.NewInt(3)}}},
+		result: &Array{value: []Item{(*BigInteger)(big.NewInt(1)), (*BigInteger)(big.NewInt(2)), (*BigInteger)(big.NewInt(3))}},
 	},
 }
 
@@ -281,18 +281,18 @@ var equalsTestCases = map[string][]struct {
 			result: false,
 		},
 		{
-			item1:  NewArray([]Item{&BigInteger{big.NewInt(1)}, &BigInteger{big.NewInt(2)}, &BigInteger{big.NewInt(3)}}),
+			item1:  NewArray([]Item{(*BigInteger)(big.NewInt(1)), (*BigInteger)(big.NewInt(2)), (*BigInteger)(big.NewInt(3))}),
-			item2:  NewArray([]Item{&BigInteger{big.NewInt(1)}, &BigInteger{big.NewInt(2)}, &BigInteger{big.NewInt(3)}}),
+			item2:  NewArray([]Item{(*BigInteger)(big.NewInt(1)), (*BigInteger)(big.NewInt(2)), (*BigInteger)(big.NewInt(3))}),
 			result: false,
 		},
 		{
-			item1:  NewArray([]Item{&BigInteger{big.NewInt(1)}}),
+			item1:  NewArray([]Item{(*BigInteger)(big.NewInt(1))}),
 			item2:  NewBigInteger(big.NewInt(1)),
 			result: false,
 		},
 		{
-			item1:  NewArray([]Item{&BigInteger{big.NewInt(1)}, &BigInteger{big.NewInt(2)}, &BigInteger{big.NewInt(3)}}),
+			item1:  NewArray([]Item{(*BigInteger)(big.NewInt(1)), (*BigInteger)(big.NewInt(2)), (*BigInteger)(big.NewInt(3))}),
-			item2:  NewArray([]Item{&BigInteger{big.NewInt(1)}, &BigInteger{big.NewInt(2)}, &BigInteger{big.NewInt(4)}}),
+			item2:  NewArray([]Item{(*BigInteger)(big.NewInt(1)), (*BigInteger)(big.NewInt(2)), (*BigInteger)(big.NewInt(4))}),
 			result: false,
 		},
 	},
@@ -441,7 +441,7 @@ var marshalJSONTestCases = []struct {
 		result: []byte(`"010203"`),
 	},
 	{
-		input:  &Array{value: []Item{&BigInteger{value: big.NewInt(3)}, &ByteArray{value: []byte{1, 2, 3}}}},
+		input:  &Array{value: []Item{(*BigInteger)(big.NewInt(3)), NewByteArray([]byte{1, 2, 3})}},
 		result: []byte(`[3,"010203"]`),
 	},
 	{
@@ -459,8 +459,8 @@ func TestMarshalJSON(t *testing.T) {
 		switch testCase.input.(type) {
 		case *BigInteger:
 			actual, err = testCase.input.(*BigInteger).MarshalJSON()
-		case *Bool:
+		case Bool:
-			actual, err = testCase.input.(*Bool).MarshalJSON()
+			actual, err = testCase.input.(Bool).MarshalJSON()
 		case *ByteArray:
 			actual, err = testCase.input.(*ByteArray).MarshalJSON()
 		case *Array:
@@ -532,7 +532,9 @@ func TestDeepCopy(t *testing.T) {
 		t.Run(tc.name, func(t *testing.T) {
 			actual := DeepCopy(tc.item)
 			require.Equal(t, tc.item, actual)
+			if tc.item.Type() != BooleanT {
 				require.False(t, actual == tc.item)
+			}
 		})
 	}
 

pkg/vm/stackitem/json.go

@@ -110,18 +110,18 @@ func toJSON(data []byte, seen map[Item]sliceNoPointer, item Item) ([]byte, error
 		data = append(data, '}')
 		seen[item] = sliceNoPointer{start, len(data)}
 	case *BigInteger:
-		if it.value.CmpAbs(big.NewInt(MaxAllowedInteger)) == 1 {
+		if it.Big().CmpAbs(big.NewInt(MaxAllowedInteger)) == 1 {
 			return nil, fmt.Errorf("%w (MaxAllowedInteger)", ErrInvalidValue)
 		}
-		data = append(data, it.value.String()...)
+		data = append(data, it.Big().String()...)
 	case *ByteArray, *Buffer:
 		raw, err := itemToJSONString(it)
 		if err != nil {
 			return nil, err
 		}
 		data = append(data, raw...)
-	case *Bool:
+	case Bool:
-		if it.value {
+		if it {
 			data = append(data, "true"...)
 		} else {
 			data = append(data, "false"...)
@@ -288,12 +288,12 @@ func toJSONWithTypes(item Item, seen map[Item]bool) (interface{}, error) {
 		}
 		value = arr
 		delete(seen, item)
-	case *Bool:
+	case Bool:
-		value = it.value
+		value = bool(it)
 	case *Buffer, *ByteArray:
 		value = base64.StdEncoding.EncodeToString(it.Value().([]byte))
 	case *BigInteger:
-		value = it.value.String()
+		value = it.Big().String()
 	case *Map:
 		if seen[item] {
 			return "", ErrRecursive

pkg/vm/stackitem/reference.go

@@ -0,0 +1,15 @@
+package stackitem
+
+type rc struct {
+	count int
+}
+
+func (r *rc) IncRC() int {
+	r.count++
+	return r.count
+}
+
+func (r *rc) DecRC() int {
+	r.count--
+	return r.count
+}

pkg/vm/stackitem/serialization.go

@@ -103,9 +103,9 @@ func (w *serContext) serialize(item Item) error {
 		data := t.Value().([]byte)
 		w.appendVarUint(uint64(len(data)))
 		w.data = append(w.data, data...)
-	case *Bool:
+	case Bool:
 		w.data = append(w.data, byte(BooleanT))
-		if t.Value().(bool) {
+		if t {
 			w.data = append(w.data, 1)
 		} else {
 			w.data = append(w.data, 0)

pkg/vm/vm.go

@@ -105,7 +105,6 @@ func NewWithTrigger(t trigger.Type) *VM {
 		Invocations:    make(map[util.Uint160]int),
 	}
 
-	vm.refs.items = make(map[stackitem.Item]int)
 	initStack(&vm.istack, "invocation", nil)
 	vm.estack = newStack("evaluation", &vm.refs)
 	return vm
@@ -520,7 +519,7 @@ func (v *VM) execute(ctx *Context, op opcode.Opcode, parameter []byte) (err erro
 		if errRecover := recover(); errRecover != nil {
 			v.state = FaultState
 			err = newError(ctx.ip, op, errRecover)
-		} else if v.refs.size > MaxStackSize {
+		} else if v.refs > MaxStackSize {
 			v.state = FaultState
 			err = newError(ctx.ip, op, "stack is too big")
 		}

pkg/vm/vm_test.go

@@ -415,7 +415,7 @@ func TestStackLimit(t *testing.T) {
 	require.NoError(t, vm.Step(), "failed to initialize static slot")
 	for i := range expected {
 		require.NoError(t, vm.Step())
-		require.Equal(t, expected[i].size, vm.refs.size, "i: %d", i)
+		require.Equal(t, expected[i].size, int(vm.refs), "i: %d", i)
 	}
 }
 
@@ -829,7 +829,7 @@ func getTestFuncForVM(prog []byte, result interface{}, args ...interface{}) func
 	if result != nil {
 		f = func(t *testing.T, v *VM) {
 			require.Equal(t, 1, v.estack.Len())
-			require.Equal(t, stackitem.Make(result), v.estack.Pop().value)
+			require.Equal(t, stackitem.Make(result).Value(), v.estack.Pop().Value())
 		}
 	}
 	return getCustomTestFuncForVM(prog, f, args...)
@@ -1761,7 +1761,7 @@ func TestPACK_UNPACK_MaxSize(t *testing.T) {
 	vm.estack.PushVal(len(elements))
 	runVM(t, vm)
 	// check reference counter = 1+1+1024
-	assert.Equal(t, 1+1+len(elements), vm.refs.size)
+	assert.Equal(t, 1+1+len(elements), int(vm.refs))
 	assert.Equal(t, 1+1+len(elements), vm.estack.Len()) // canary + length + elements
 	assert.Equal(t, int64(len(elements)), vm.estack.Peek(0).Value().(*big.Int).Int64())
 	for i := 0; i < len(elements); i++ {
@@ -1784,7 +1784,7 @@ func TestPACK_UNPACK_PACK_MaxSize(t *testing.T) {
 	vm.estack.PushVal(len(elements))
 	runVM(t, vm)
 	// check reference counter = 1+1+1024
-	assert.Equal(t, 1+1+len(elements), vm.refs.size)
+	assert.Equal(t, 1+1+len(elements), int(vm.refs))
 	assert.Equal(t, 2, vm.estack.Len())
 	a := vm.estack.Peek(0).Array()
 	assert.Equal(t, len(elements), len(a))
@@ -1959,7 +1959,7 @@ func testCLEARITEMS(t *testing.T, item stackitem.Item) {
 	v.estack.PushVal(item)
 	runVM(t, v)
 	require.Equal(t, 2, v.estack.Len())
-	require.EqualValues(t, 2, v.refs.size) // empty collection + it's size
+	require.EqualValues(t, 2, int(v.refs)) // empty collection + it's size
 	require.EqualValues(t, 0, v.estack.Pop().BigInt().Int64())
 }