if !typ.manual() {
		throw("manual span allocation called with non-manually-managed type")
	}
	return h.allocSpan(npages, typ, 0)
}

// setSpans modifies the span map so [spanOf(base), spanOf(base+npage*pageSize))
// is s.
func (h *mheap) setSpans(base, npage uintptr, s *mspan) {
	p := base / pageSize
	ai := arenaIndex(base)
	ha := h.arenas[ai.l1()][ai.l2()]
	for n := uintptr(0); n < npage; n++ {