compiler: support copy()

docs/compiler.md

@@ -9,6 +9,7 @@ there are some important deviations that you need to be aware of that make it
 a dialect of Go rather than a complete port of the language:
  * `new()` is not supported, most of the time you can substitute structs with composite literals
  * `make()` is supported for maps and slices with elements of basic types
+ * `copy()` is supported only for byte slices, because of underlying `MEMCPY` opcode
  * pointers are supported only for struct literals, one can't take an address
    of an arbitrary variable
  * there is no real distinction between different integer types, all of them

pkg/compiler/analysis.go

@@ -14,7 +14,7 @@ import (
 
 var (
 	// Go language builtin functions.
-	goBuiltins = []string{"len", "append", "panic", "make"}
+	goBuiltins = []string{"len", "append", "panic", "make", "copy"}
 	// Custom builtin utility functions.
 	customBuiltins = []string{
 		"FromAddress", "Equals",

pkg/compiler/codegen.go

@@ -1295,6 +1295,44 @@ func (c *codegen) convertSyscall(expr *ast.CallExpr, api, name string) {
 	emit.Opcode(c.prog.BinWriter, opcode.NOP)
 }
 
+// emitSliceHelper emits 3 items on stack: slice, its first index, and its size.
+func (c *codegen) emitSliceHelper(e ast.Expr) {
+	if !isByteSlice(c.typeOf(e)) {
+		c.prog.Err = fmt.Errorf("copy is supported only for byte-slices")
+		return
+	}
+	var hasLowIndex bool
+	switch src := e.(type) {
+	case *ast.SliceExpr:
+		ast.Walk(c, src.X)
+		if src.High != nil {
+			ast.Walk(c, src.High)
+		} else {
+			emit.Opcode(c.prog.BinWriter, opcode.DUP)
+			emit.Opcode(c.prog.BinWriter, opcode.SIZE)
+		}
+		if src.Low != nil {
+			ast.Walk(c, src.Low)
+			hasLowIndex = true
+		} else {
+			emit.Int(c.prog.BinWriter, 0)
+		}
+	default:
+		ast.Walk(c, src)
+		emit.Opcode(c.prog.BinWriter, opcode.DUP)
+		emit.Opcode(c.prog.BinWriter, opcode.SIZE)
+		emit.Int(c.prog.BinWriter, 0)
+	}
+	if !hasLowIndex {
+		emit.Opcode(c.prog.BinWriter, opcode.SWAP)
+	} else {
+		emit.Opcode(c.prog.BinWriter, opcode.DUP)
+		emit.Opcode(c.prog.BinWriter, opcode.ROT)
+		emit.Opcode(c.prog.BinWriter, opcode.SWAP)
+		emit.Opcode(c.prog.BinWriter, opcode.SUB)
+	}
+}
+
 func (c *codegen) convertBuiltin(expr *ast.CallExpr) {
 	var name string
 	switch t := expr.Fun.(type) {
@@ -1305,6 +1343,14 @@ func (c *codegen) convertBuiltin(expr *ast.CallExpr) {
 	}
 
 	switch name {
+	case "copy":
+		// stack for MEMCPY is: dst, dst_index, src, src_index, count
+		c.emitSliceHelper(expr.Args[0])
+		c.emitSliceHelper(expr.Args[1])
+		emit.Int(c.prog.BinWriter, 3)
+		emit.Opcode(c.prog.BinWriter, opcode.ROLL)
+		emit.Opcode(c.prog.BinWriter, opcode.MIN)
+		emit.Opcode(c.prog.BinWriter, opcode.MEMCPY)
 	case "make":
 		typ := c.typeOf(expr.Args[0])
 		switch {
@@ -1412,10 +1458,10 @@ func transformArgs(fun ast.Expr, args []ast.Expr) []ast.Expr {
 			return args[1:]
 		}
 	case *ast.Ident:
-		if f.Name == "panic" {
+		switch f.Name {
+		case "panic":
 			return args[1:]
-		}
-		if f.Name == "make" {
+		case "make", "copy":
 			return nil
 		}
 	}

pkg/compiler/slice_test.go

@@ -364,3 +364,67 @@ func TestMake(t *testing.T) {
 		require.Error(t, err)
 	})
 }
+
+func TestCopy(t *testing.T) {
+	t.Run("Invalid", func(t *testing.T) {
+		src := `package foo
+		func Main() []int {
+			src := []int{3, 2, 1}
+			dst := make([]int, 2)
+			copy(dst, src)
+			return dst
+		}`
+		_, err := compiler.Compile("foo.go", strings.NewReader(src))
+		require.Error(t, err)
+	})
+	t.Run("Simple", func(t *testing.T) {
+		src := `package foo
+		func Main() []byte {
+			src := []byte{3, 2, 1}
+			dst := make([]byte, 2)
+			copy(dst, src)
+			return dst
+		}`
+		eval(t, src, []byte{3, 2})
+	})
+	t.Run("LowSrcIndex", func(t *testing.T) {
+		src := `package foo
+		func Main() []byte {
+			src := []byte{3, 2, 1}
+			dst := make([]byte, 2)
+			copy(dst, src[1:])
+			return dst
+		}`
+		eval(t, src, []byte{2, 1})
+	})
+	t.Run("LowDstIndex", func(t *testing.T) {
+		src := `package foo
+		func Main() []byte {
+			src := []byte{3, 2, 1}
+			dst := make([]byte, 2)
+			copy(dst[1:], src[1:])
+			return dst
+		}`
+		eval(t, src, []byte{0, 2})
+	})
+	t.Run("BothIndices", func(t *testing.T) {
+		src := `package foo
+		func Main() []byte {
+			src := []byte{4, 3, 2, 1}
+			dst := make([]byte, 4)
+			copy(dst[1:], src[1:3])
+			return dst
+		}`
+		eval(t, src, []byte{0, 3, 2, 0})
+	})
+	t.Run("EmptySliceExpr", func(t *testing.T) {
+		src := `package foo
+		func Main() []byte {
+			src := []byte{3, 2, 1}
+			dst := make([]byte, 2)
+			copy(dst[1:], src[:])
+			return dst
+		}`
+		eval(t, src, []byte{0, 3})
+	})
+}