// returned by text/scanner.Scanner, plus a couple of extra values.
type ScanToken rune

const (
	// Asm defines some two-character lexemes. We make up
	// a rune/ScanToken value for them - ugly but simple.
	LSH          ScanToken = -1000 - iota // << Left shift.
	RSH                                   // >> Logical right shift.
	ARR                                   // -> Used on ARM for shift type 3, arithmetic right shift.

func (p *Parser) atRegisterShift() bool {
	// ARM only.
	if !p.arch.InFamily(sys.ARM, sys.ARM64) {
		return false
	}
	// R1<<...
	if lex.IsRegisterShift(p.peek()) {
		return true
	}
	// R(1)<<...   Ugly check. TODO: Rethink how we handle ARM register shifts to be
	// less special.
	if p.peek() != '(' || len(p.input)-p.inputPos < 4 {
		return false
	}