optimize and reuse reflect call arguments allocation

Author: diegommm

vm/vm.go

@@ -40,6 +40,7 @@ type VM struct {
 	Stack        []any
 	Scopes       []*Scope
 	Variables    []any
+	reflectArgs  []reflect.Value
 	MemoryBudget uint
 	ip           int
 	memory       uint
@@ -82,6 +83,10 @@ func (vm *VM) Run(program *Program, env any) (_ any, err error) {
 	if vm.MemoryBudget == 0 {
 		vm.MemoryBudget = conf.DefaultMemoryBudget
 	}
+	if vm.reflectArgs != nil {
+		clearSlice(vm.reflectArgs)
+	}
+
 	vm.memory = 0
 	vm.ip = 0
 
@@ -336,15 +341,25 @@ func (vm *VM) Run(program *Program, env any) (_ any, err error) {
 		case OpCall:
 			fn := reflect.ValueOf(vm.pop())
 			size := arg
-			in := make([]reflect.Value, size)
-			for i := int(size) - 1; i >= 0; i-- {
-				param := vm.pop()
-				if param == nil {
-					in[i] = reflect.Zero(fn.Type().In(i))
-				} else {
-					in[i] = reflect.ValueOf(param)
+			if len(vm.reflectArgs) < size {
+				vm.reflectArgs = make([]reflect.Value, size)
+			}
+			var in []reflect.Value
+			if size > 0 {
+				in = vm.reflectArgs[:size]
+				// pop in bulk
+				stackTail := vm.Stack[len(vm.Stack)-size:]
+				vm.Stack = vm.Stack[:len(vm.Stack)-size]
+				for i := range stackTail {
+					param := stackTail[i]
+					if param == nil {
+						in[i] = reflect.Zero(fn.Type().In(i))
+					} else {
+						in[i] = reflect.ValueOf(param)
+					}
 				}
 			}
+
 			out := fn.Call(in)
 			if len(out) == 2 && out[1].Type() == errorType && !out[1].IsNil() {
 				panic(out[1].Interface().(error))