From d16ef536530c8881d3662acffc1943a3bb5217d5 Mon Sep 17 00:00:00 2001
From: Evgeniy Stratonikov <evgeniy@nspcc.ru>
Date: Tue, 16 Feb 2021 16:45:06 +0300
Subject: [PATCH] compiler: support ellipsis for append of non-byte slices

NeoVM lacks opcode for array append, thus some
kind of loop is needed for this.
---
 pkg/compiler/codegen.go    | 30 ++++++++++++++++++++++++++----
 pkg/compiler/slice_test.go | 17 +++++++++++++++++
 2 files changed, 43 insertions(+), 4 deletions(-)

diff --git a/pkg/compiler/codegen.go b/pkg/compiler/codegen.go
index 53b0cd1d9..0d4f59a17 100644
--- a/pkg/compiler/codegen.go
+++ b/pkg/compiler/codegen.go
@@ -1635,10 +1635,32 @@ func (c *codegen) convertBuiltin(expr *ast.CallExpr) {
 		} else {
 			emit.Instruction(c.prog.BinWriter, opcode.JMPIFNOT, []byte{2 + 2})
 			emit.Opcodes(c.prog.BinWriter, opcode.DROP, opcode.NEWARRAY0)
-			for _, e := range expr.Args[1:] {
-				emit.Opcodes(c.prog.BinWriter, opcode.DUP)
-				ast.Walk(c, e)
-				emit.Opcodes(c.prog.BinWriter, opcode.APPEND)
+			if expr.Ellipsis.IsValid() {
+				ast.Walk(c, expr.Args[1])                    // x y
+				emit.Opcodes(c.prog.BinWriter, opcode.PUSH0) // x y cnt=0
+				start := c.newLabel()
+				c.setLabel(start)
+				emit.Opcodes(c.prog.BinWriter, opcode.PUSH2, opcode.PICK) // x y cnt x
+				emit.Opcodes(c.prog.BinWriter, opcode.PUSH2, opcode.PICK) // x y cnt x y
+				emit.Opcodes(c.prog.BinWriter, opcode.DUP, opcode.SIZE)   // x y cnt x y len(y)
+				emit.Opcodes(c.prog.BinWriter, opcode.PUSH3, opcode.PICK) // x y cnt x y len(y) cnt
+				after := c.newLabel()
+				emit.Jmp(c.prog.BinWriter, opcode.JMPEQL, after)          // x y cnt x y
+				emit.Opcodes(c.prog.BinWriter, opcode.PUSH2, opcode.PICK, // x y cnt x y cnt
+					opcode.PICKITEM, // x y cnt x y[cnt]
+					opcode.APPEND,   // x=append(x, y[cnt]) y cnt
+					opcode.INC)      // x y cnt+1
+				emit.Jmp(c.prog.BinWriter, opcode.JMPL, start)
+				c.setLabel(after)
+				for i := 0; i < 4; i++ { // leave x on stack
+					emit.Opcodes(c.prog.BinWriter, opcode.DROP)
+				}
+			} else {
+				for _, e := range expr.Args[1:] {
+					emit.Opcodes(c.prog.BinWriter, opcode.DUP)
+					ast.Walk(c, e)
+					emit.Opcodes(c.prog.BinWriter, opcode.APPEND)
+				}
 			}
 		}
 	case "panic":
diff --git a/pkg/compiler/slice_test.go b/pkg/compiler/slice_test.go
index 4e3e9b82c..37f163b38 100644
--- a/pkg/compiler/slice_test.go
+++ b/pkg/compiler/slice_test.go
@@ -181,6 +181,23 @@ var sliceTestCases = []testCase{
 			stackitem.NewBigInteger(big.NewInt(5)),
 		},
 	},
+	{
+		"int slice, append slice",
+		`package foo
+			func getByte() byte { return 0x80 }
+			func Main() []int {
+				x := []int{1}
+				y := []int{2, 3}
+				x = append(x, y...)
+				x = append(x, y...)
+				return x
+			}`,
+		[]stackitem.Item{
+			stackitem.Make(1),
+			stackitem.Make(2), stackitem.Make(3),
+			stackitem.Make(2), stackitem.Make(3),
+		},
+	},
 	{
 		"declare compound slice",
 		`package foo