compiler: allow to emit opcodes directly

pkg/compiler/analysis.go

@@ -288,7 +288,8 @@ func isSyscall(fun *funcScope) bool {
 	if fun.selector == nil || fun.pkg == nil || !isInteropPath(fun.pkg.Path()) {
 		return false
 	}
-	return fun.pkg.Name() == "neogointernal" && strings.HasPrefix(fun.name, "Syscall")
+	return fun.pkg.Name() == "neogointernal" && (strings.HasPrefix(fun.name, "Syscall") ||
+		strings.HasPrefix(fun.name, "Opcode"))
 }
 
 const interopPrefix = "github.com/nspcc-dev/neo-go/pkg/interop"

pkg/compiler/codegen.go

@@ -939,7 +939,7 @@ func (c *codegen) Visit(node ast.Node) ast.Visitor {
 					c.emittedEvents[name] = append(c.emittedEvents[name], params)
 				}
 			}
-			c.convertSyscall(n)
+			c.convertSyscall(f, n)
 		default:
 			emit.Call(c.prog.BinWriter, opcode.CALLL, f.label)
 		}
@@ -1530,18 +1530,27 @@ func (c *codegen) getByteArray(expr ast.Expr) []byte {
 	}
 }
 
-func (c *codegen) convertSyscall(expr *ast.CallExpr) {
+func (c *codegen) convertSyscall(f *funcScope, expr *ast.CallExpr) {
 	for _, arg := range expr.Args[1:] {
 		ast.Walk(c, arg)
 	}
-	c.emitReverse(len(expr.Args) - 1)
 	tv := c.typeAndValueOf(expr.Args[0])
-	syscall := constant.StringVal(tv.Value)
-	emit.Syscall(c.prog.BinWriter, syscall)
+	name := constant.StringVal(tv.Value)
+	if strings.HasPrefix(f.name, "Syscall") {
+		c.emitReverse(len(expr.Args) - 1)
+		emit.Syscall(c.prog.BinWriter, name)
 
-	// This NOP instruction is basically not needed, but if we do, we have a
-	// one to one matching avm file with neo-python which is very nice for debugging.
-	emit.Opcodes(c.prog.BinWriter, opcode.NOP)
+		// This NOP instruction is basically not needed, but if we do, we have a
+		// one to one matching avm file with neo-python which is very nice for debugging.
+		emit.Opcodes(c.prog.BinWriter, opcode.NOP)
+	} else {
+		op, err := opcode.FromString(name)
+		if err != nil {
+			c.prog.Err = fmt.Errorf("invalid opcode: %s", op)
+			return
+		}
+		emit.Opcodes(c.prog.BinWriter, op)
+	}
 }
 
 // emitSliceHelper emits 3 items on stack: slice, its first index, and its size.

pkg/compiler/syscall_test.go

@@ -92,3 +92,29 @@ func TestSyscallInGlobalInit(t *testing.T) {
 	require.NoError(t, v.Run())
 	require.Equal(t, []byte{1, 2}, v.Estack().Pop().Value())
 }
+
+func TestOpcode(t *testing.T) {
+	t.Run("1 argument", func(t *testing.T) {
+		src := `package foo
+		import "github.com/nspcc-dev/neo-go/pkg/interop/neogointernal"
+		func abs(a int) int {
+			return neogointernal.Opcode1("ABS", a).(int)
+		}
+		func Main() int {
+			return abs(-42)
+		}`
+		eval(t, src, big.NewInt(42))
+	})
+	t.Run("2 arguments", func(t *testing.T) {
+		src := `package foo
+		import "github.com/nspcc-dev/neo-go/pkg/interop/neogointernal"
+		func add3(a, b, c int) int {
+			return neogointernal.Opcode2("SUB", a,
+				neogointernal.Opcode2("SUB", b, c).(int)).(int)
+		}
+		func Main() int {
+			return add3(53, 12, 1)
+		}`
+		eval(t, src, big.NewInt(42))
+	})
+}

pkg/interop/neogointernal/opcode.go

@@ -0,0 +1,11 @@
+package neogointernal
+
+// Opcode1 emits opcode with 1 argument.
+func Opcode1(op string, arg interface{}) interface{} {
+	return nil
+}
+
+// Opcode2 emits opcode with 2 arguments.
+func Opcode2(op string, arg1, arg2 interface{}) interface{} {
+	return nil
+}