// returns if the value was marked or not.
func (b *atomicOffAddr) Load() (uintptr, bool) {
	v := b.a.Load()
	wasMarked := false
	if v < 0 {
		wasMarked = true
		v = -v
	}
	return uintptr(v) + arenaBaseOffset, wasMarked
}

// addrRanges is a data structure holding a collection of ranges of
// address space.
//
// The ranges are coalesced eagerly to reduce the