// 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 '}', ']':
				nest--
			case ',':

					p.errorf("invalid addressing modes for third operand to %s instruction, must be register", op)
					return
				}
				prog.RegTo2 = a[2].Reg
			case arch.IsARM64TBL(op):
				// one of its inputs does not fit into prog.Reg.
				prog.From = a[0]
				prog.AddRestSource(a[1])
				prog.To = a[2]
			case arch.IsARM64CASP(op):
				prog.From = a[0]
				prog.To = a[1]