func (x ValAndOff) String() string {
	return fmt.Sprintf("val=%d,off=%d", x.Val(), x.Off())
}

// validVal reports whether the value can be used
// as an argument to makeValAndOff.
func validVal(val int64) bool {
	return val == int64(int32(val))
}

func makeValAndOff(val, off int32) ValAndOff {
	return ValAndOff(int64(val)<<32 + int64(uint32(off)))
}

func (x ValAndOff) canAdd32(off int32) bool {