func BuiltinIdx(name string, abi int) int {
	i, ok := builtinMap[name]
	if !ok {
		return -1
	}
	if buildcfg.Experiment.RegabiWrappers && builtins[i].abi != abi {
		return -1
	}
	return i
}

//go:generate go run mkbuiltin.go

var builtinMap map[string]int

func init() {
	builtinMap = make(map[string]int, len(builtins))
	for i, b := range builtins {
		builtinMap[b.name] = i
	}

	n.Fun = typecheck(n.Fun, ctxExpr|ctxType|ctxCallee)

	l := n.Fun

	if l.Op() == ir.ONAME && l.(*ir.Name).BuiltinOp != 0 {
		l := l.(*ir.Name)
		if n.IsDDD && l.BuiltinOp != ir.OAPPEND {
			base.Errorf("invalid use of ... with builtin %v", l)
		}

		// builtin: OLEN, OCAP, etc.
		switch l.BuiltinOp {
		default:
			base.Fatalf("unknown builtin %v", l)

		n = n.(*ir.ParenExpr).X
	}

	switch n.Op() {
	default:
		ir.Dump("typecheck", n)
		base.Fatalf("typecheck %v", n.Op())
		panic("unreachable")

	case ir.ONAME:
		n := n.(*ir.Name)
		if n.BuiltinOp != 0 {
			if top&ctxCallee == 0 {
				base.Errorf("use of builtin %v not in function call", n.Sym())
				n.SetType(nil)
				return n
			}
			return n
		}
		if top&ctxAssign == 0 {