return nil, nil
	}
	if build.Default.GOOS != "linux" && build.Default.GOOS != "darwin" {
		return nil, nil
	}

	// Find assembly files to work on.
	var sfiles []string
	for _, fname := range pass.OtherFiles {
		if strings.HasSuffix(fname, ".s") && pass.Pkg.Path() != "runtime" {
			sfiles = append(sfiles, fname)
		}
	}

	for _, fname := range sfiles {
		content, tf, err := analysisutil.ReadFile(pass, fname)

	// syntax and type information
	Fset         *token.FileSet // file position information; Run may add new files
	Files        []*ast.File    // the abstract syntax tree of each file
	OtherFiles   []string       // names of non-Go files of this package
	IgnoredFiles []string       // names of ignored source files in this package
	Pkg          *types.Package // type information about the package

	Name: "buildtag",
	Doc:  Doc,
	Run:  runBuildTag,
}

func runBuildTag(pass *analysis.Pass) (interface{}, error) {
	for _, f := range pass.Files {
		checkGoFile(pass, f)
	}
	for _, name := range pass.OtherFiles {
		if err := checkOtherFile(pass, name); err != nil {
			return nil, err
		}
	}
	for _, name := range pass.IgnoredFiles {
		if strings.HasSuffix(name, ".go") {

	Run:  runDirective,
}

func runDirective(pass *analysis.Pass) (interface{}, error) {
	for _, f := range pass.Files {
		checkGoFile(pass, f)
	}
	for _, name := range pass.OtherFiles {
		if err := checkOtherFile(pass, name); err != nil {
			return nil, err
		}
	}
	for _, name := range pass.IgnoredFiles {
		if strings.HasSuffix(name, ".go") {

	Run:  runBuildTag,
}

func runBuildTag(pass *analysis.Pass) (interface{}, error) {
	for _, f := range pass.Files {
		checkGoFile(pass, f)
	}
	for _, name := range pass.OtherFiles {
		if err := checkOtherFile(pass, name); err != nil {
			return nil, err
		}
	}
	for _, name := range pass.IgnoredFiles {
		if strings.HasSuffix(name, ".go") {