// Copyright 2016 The Go Authors. All rights reserved.
// Use of this source code is governed by a BSD-style
// license that can be found in the LICENSE file.

package arm64

import (
	"bytes"
	"fmt"
	"internal/testenv"
	"io/ioutil"
	"os"
	"os/exec"
	"path/filepath"
	"testing"
)

// TestLarge generates a very large file to verify that large
// program builds successfully, in particular, too-far
// conditional branches are fixed.
func TestLarge(t *testing.T) {
	if testing.Short() {
		t.Skip("Skip in short mode")
	}
	testenv.MustHaveGoBuild(t)

	dir, err := ioutil.TempDir("", "testlarge")
	if err != nil {
		t.Fatalf("could not create directory: %v", err)
	}
	defer os.RemoveAll(dir)

	// generate a very large function
	buf := bytes.NewBuffer(make([]byte, 0, 7000000))
	gen(buf)

	tmpfile := filepath.Join(dir, "x.s")
	err = ioutil.WriteFile(tmpfile, buf.Bytes(), 0644)
	if err != nil {
		t.Fatalf("can't write output: %v\n", err)
	}

	// build generated file
	cmd := exec.Command(testenv.GoToolPath(t), "tool", "asm", "-o", filepath.Join(dir, "x.o"), tmpfile)
	cmd.Env = []string{"GOARCH=arm64", "GOOS=linux"}
	out, err := cmd.CombinedOutput()
	if err != nil {
		t.Errorf("Build failed: %v, output: %s", err, out)
	}
}

// gen generates a very large program, with a very far conditional branch.
func gen(buf *bytes.Buffer) {
	fmt.Fprintln(buf, "TEXT f(SB),0,$0-0")
	fmt.Fprintln(buf, "TBZ $5, R0, label")
	fmt.Fprintln(buf, "CBZ R0, label")
	fmt.Fprintln(buf, "BEQ label")
	for i := 0; i < 1<<19; i++ {
		fmt.Fprintln(buf, "MOVD R0, R1")
	}
	fmt.Fprintln(buf, "label:")
	fmt.Fprintln(buf, "RET")
}
