case lex.LSH:
		op = 0
	case lex.RSH:
		op = 1
	case lex.ARR:
		op = 2
	case lex.ROT:
		// following instructions on ARM64 support rotate right
		// AND, ANDS, TST, BIC, BICS, EON, EOR, ORR, MVN, ORN
		op = 3
	}
	tok := p.next()
	str := tok.String()
	var count int16
	switch tok.ScanToken {
	case scanner.Ident:
		if p.arch.Family == sys.ARM64 {

		rt := int(p.To.Reg)
		if r == 0 {
			r = rt
		}
		x, y := immrot2a(uint32(c.instoffset))
		var as2 obj.As
		switch p.As {
		case AADD, ASUB, AORR, AEOR, ABIC:
			as2 = p.As // ADD, SUB, ORR, EOR, BIC
		case ARSB:
			as2 = AADD // RSB -> RSB/ADD pair
		case AADC:
			as2 = AADD // ADC -> ADC/ADD pair
		case ASBC:
			as2 = ASUB // SBC -> SBC/SUB pair
		case ARSC:

			o1 |= 1 << 10
		} else {
			o1 |= 3 << 10
		}
		o1 |= ((uint32(v) & 0x1FF) << 12) | (uint32(p.To.Reg&31) << 5) | uint32(p.From.Reg&31)

	case 24: /* mov/mvn Rs,Rd -> add $0,Rs,Rd or orr Rs,ZR,Rd */
		rf := int(p.From.Reg)
		rt := int(p.To.Reg)
		if rf == REGSP || rt == REGSP {
			if p.As == AMVN || p.As == AMVNW {
				c.ctxt.Diag("illegal SP reference\n%v", p)
			}