BaseChunkIdx + 64,
			},
			inUse: []AddrRange{
				MakeAddrRange(PageBase(BaseChunkIdx, 0), PageBase(BaseChunkIdx+1, 0)),
				MakeAddrRange(PageBase(BaseChunkIdx+2, 0), PageBase(BaseChunkIdx+3, 0)),
				MakeAddrRange(PageBase(BaseChunkIdx+4, 0), PageBase(BaseChunkIdx+5, 0)),
				MakeAddrRange(PageBase(BaseChunkIdx+6, 0), PageBase(BaseChunkIdx+7, 0)),
				MakeAddrRange(PageBase(BaseChunkIdx+8, 0), PageBase(BaseChunkIdx+9, 0)),

	// First range.
	a.Add(MakeAddrRange(512, 1024))
	validateAddrRanges(t, &a,
		MakeAddrRange(512, 1024),
	)

	// Coalesce up.
	a.Add(MakeAddrRange(1024, 2048))
	validateAddrRanges(t, &a,
		MakeAddrRange(512, 2048),
	)

	// Add new independent range.
	a.Add(MakeAddrRange(4096, 8192))
	validateAddrRanges(t, &a,
		MakeAddrRange(512, 2048),
		MakeAddrRange(4096, 8192),
	)

	// Coalesce down.

		needMin = haveMax
	}

	// Avoid a panic from indexing one past the last element.
	chunksBase := uintptr(unsafe.Pointer(&s.chunks[0]))
	have := makeAddrRange(chunksBase+haveMin*scSize, chunksBase+haveMax*scSize)
	need := makeAddrRange(chunksBase+needMin*scSize, chunksBase+needMax*scSize)

	// Subtract any overlap from rounding. We can't re-map memory because
	// it'll be zeroed.
	need = need.subtract(have)

	// platforms with a segmented address space, that is, on platforms
	// where arenaBaseOffset != 0.
	base, limit offAddr
}

// makeAddrRange creates a new address range from two virtual addresses.
//
// Throws if the base and limit are not in the same memory segment.
func makeAddrRange(base, limit uintptr) addrRange {
	r := addrRange{offAddr{base}, offAddr{limit}}
	if (base-arenaBaseOffset >= base) != (limit-arenaBaseOffset >= limit) {

}

// AddrRange is a wrapper around addrRange for testing.
type AddrRange struct {
	addrRange
}

// MakeAddrRange creates a new address range.
func MakeAddrRange(base, limit uintptr) AddrRange {
	return AddrRange{makeAddrRange(base, limit)}
}

// Base returns the virtual base address of the address range.
func (a AddrRange) Base() uintptr {
	return a.addrRange.base.addr()
}

		rzSize := computeRZlog(span.elemsize)
		span.elemsize -= rzSize
		span.largeType.Size_ = span.elemsize
		rzStart := span.base() + span.elemsize
		span.userArenaChunkFree = makeAddrRange(span.base(), rzStart)
		asanpoison(unsafe.Pointer(rzStart), span.limit-rzStart)
		asanunpoison(unsafe.Pointer(span.base()), span.elemsize)
	}

	if rate := MemProfileRate; rate > 0 {
		c := getMCache(mp)

	if end > p.end {
		p.end = end
	}
	// Note that [base, limit) will never overlap with any existing
	// range inUse because grow only ever adds never-used memory
	// regions to the page allocator.
	p.inUse.add(makeAddrRange(base, limit))

	// A grow operation is a lot like a free operation, so if our
	// chunk ends up below p.searchAddr, update p.searchAddr to the
	// new address, just like in free.