//
//go:nosplit
func arenaIndex(p uintptr) arenaIdx {
	return arenaIdx((p - arenaBaseOffset) / heapArenaBytes)
}

// arenaBase returns the low address of the region covered by heap
// arena i.
func arenaBase(i arenaIdx) uintptr {
	return uintptr(i)*heapArenaBytes + arenaBaseOffset
}

type arenaIdx uint

// l1 returns the "l1" portion of an arenaIdx.
//

	for i1 := range mheap_.arenas {
		if mheap_.arenas[i1] == nil {
			continue
		}
		for i, ha := range mheap_.arenas[i1] {
			if ha == nil {
				continue
			}
			base := arenaBase(arenaIdx(i1)<<arenaL1Shift | arenaIdx(i))
			if arenaStart == 0 || base < arenaStart {
				arenaStart = base
			}
			if base+heapArenaBytes > arenaEnd {
				arenaEnd = base + heapArenaBytes
			}
		}
	}