span.ensureSwept()

	offset := uintptr(p) - span.base()
	kind := s.kind

	lock(&span.speciallock)

	// Find splice point, check for existing record.
	iter, exists := span.specialFindSplicePoint(offset, kind)
	if !exists {
		// Splice in record, fill in offset.
		s.offset = uint16(offset)
		s.next = *iter
		*iter = s
		spanHasSpecials(span)
	}

	unlock(&span.speciallock)