// basic blocks. Figure out a way to make this function (or, more precisely, the user
// of this function) require only linear size & time.
func (s *stackAllocState) computeLive(spillLive [][]ID) {
	s.live = make([][]ID, s.f.NumBlocks())
	var phis []*Value
	live := s.f.newSparseSet(s.f.NumValues())
	defer s.f.retSparseSet(live)
	t := s.f.newSparseSet(s.f.NumValues())
	defer s.f.retSparseSet(t)

	t.edges = append(t.edges, Edge{f.Entry, 0})
	t.defUse = make(map[*Value][]*Value)
	t.defBlock = make(map[*Value][]*Block)
	t.latticeCells = make(map[*Value]lattice)
	t.visitedBlock = f.Cache.allocBoolSlice(f.NumBlocks())
	defer f.Cache.freeBoolSlice(t.visitedBlock)

	// build it early since we rely heavily on the def-use chain later
	t.buildDefUses()

	// pick up either an edge or SSA value from worklist, process it
	for {

	paxSchilyXattr = "SCHILY.xattr."

	// Keywords for GNU sparse files in a PAX extended header.
	paxGNUSparse          = "GNU.sparse."
	paxGNUSparseNumBlocks = "GNU.sparse.numblocks"
	paxGNUSparseOffset    = "GNU.sparse.offset"
	paxGNUSparseNumBytes  = "GNU.sparse.numbytes"
	paxGNUSparseMap       = "GNU.sparse.map"
	paxGNUSparseName      = "GNU.sparse.name"