SYNC		// 0000000f

//
// NOP
//
//	LNOP comma // asm doesn't support the trailing comma.
//	{
//		outcode(int($1), &nullgen, 0, &nullgen);
//	}
	NOP

//	LNOP rreg comma // asm doesn't support the trailing comma.
//	{
//		outcode(int($1), &$2, 0, &nullgen);
//	}
	NOP R2

//	LNOP freg comma // asm doesn't support the trailing comma.
//	{
//		outcode(int($1), &$2, 0, &nullgen);
//	}

using newer toolchains to compile old code.

A GODEBUG setting is a `key=value` pair
that controls the execution of certain parts of a Go program.
The environment variable `GODEBUG`
can hold a comma-separated list of these settings.
For example, if a Go program is running in an environment that contains

	GODEBUG=http2client=0,http2server=0

then that Go program will disable the use of HTTP/2 by default in both

	var features []string
	for f, cmap := range featureCtx {
		if len(cmap) == len(contexts) {
			features = append(features, f)
			continue
		}
		comma := strings.Index(f, ",")
		for cname := range cmap {
			f2 := fmt.Sprintf("%s (%s)%s", f[:comma], cname, f[comma:])
			features = append(features, f2)
		}
	}

	bw := bufio.NewWriter(os.Stdout)
	defer bw.Flush()

	var required []string

	if tok != scanner.Ident {
		p.errorf("expected identifier, found %q", p.lex.Text())
		return "", "", nil, false // Might as well stop now.
	}
	word, cond = p.lex.Text(), ""
	operands = scratch[:0]
	// Zero or more comma-separated operands, one per loop.
	nesting := 0
	colon := -1
	for tok != '\n' && tok != ';' {
		// Process one operand.
		var items []lex.Token
		if cap(operands) > len(operands) {

		}

		// Canonicalize spacing in printed form.
		// First field is opcode, then tab, then arguments separated by spaces.
		// Canonicalize spaces after commas first.
		// Comma to separate argument gets a space; comma within does not.
		var buf []byte
		nest := 0
		for i := 0; i < len(printed); i++ {
			c := printed[i]
			switch c {
			case '{', '[':
				nest++
			case '}', ']':

		f.walk(n.Body, ctxSwitch, visit)
	case *ast.TypeSwitchStmt:
		f.walk(n.Init, ctxStmt, visit)
		f.walk(n.Assign, ctxStmt, visit)
		f.walk(n.Body, ctxTypeSwitch, visit)
	case *ast.CommClause:
		f.walk(n.Comm, ctxStmt, visit)
		f.walk(n.Body, ctxStmt, visit)
	case *ast.SelectStmt:
		f.walk(n.Body, ctxStmt, visit)
	case *ast.ForStmt:
		f.walk(n.Init, ctxStmt, visit)
		f.walk(&n.Cond, ctxExpr, visit)