var genericBlocks = []blockData{
	{name: "Plain"},                  // a single successor
	{name: "If", controls: 1},        // if Controls[0] goto Succs[0] else goto Succs[1]
	{name: "Defer", controls: 1},     // Succs[0]=defer queued, Succs[1]=defer recovered. Controls[0] is call op (of memory type)
	{name: "Ret", controls: 1},       // no successors, Controls[0] value is memory result

func (t SparseTree) treestructure(b *Block) string {
	return t.treestructure1(b, 0)
}
func (t SparseTree) treestructure1(b *Block, i int) string {
	s := "\n" + strings.Repeat("\t", i) + b.String() + "->["
	for i, e := range b.Succs {
		if i > 0 {
			s += ","
		}
		s += e.b.String()
	}
	s += "]"
	if c0 := t[b.ID].child; c0 != nil {
		s += "("
		for c := c0; c != nil; c = t[c.ID].sibling {
			if c != c0 {
				s += " "

				// A variable is live on output from this block
				// if it is live on input to some successor.
				//
				// out[b] = \bigcup_{s \in succ[b]} in[s]
				newliveout.Copy(lv.blockEffects(b.Succs[0].Block()).livein)
				for _, succ := range b.Succs[1:] {
					newliveout.Or(newliveout, lv.blockEffects(succ.Block()).livein)
				}
			}

			if !be.liveout.Eq(newliveout) {
				change = true
				be.liveout.Copy(newliveout)
			}

		s += html.EscapeString(fmt.Sprintf(" [%v]", t))
	}
	for _, c := range b.ControlValues() {
		s += fmt.Sprintf(" %s", c.HTML())
	}
	if len(b.Succs) > 0 {
		s += " →" // right arrow
		for _, e := range b.Succs {
			c := e.b
			s += " " + c.HTML()
		}
	}
	switch b.Likely {
	case BranchUnlikely:
		s += " (unlikely)"
	case BranchLikely:
		s += " (likely)"

				delta := int32(normalDistance)
				if len(p.Succs) == 2 {
					if p.Succs[0].b == b && p.Likely == BranchLikely ||
						p.Succs[1].b == b && p.Likely == BranchUnlikely {
						delta = likelyDistance
					}
					if p.Succs[0].b == b && p.Likely == BranchUnlikely ||
						p.Succs[1].b == b && p.Likely == BranchLikely {
						delta = unlikelyDistance
					}
				}

		case Work:
			b := node.block

			// First, see if we're dominated by an explicit nil check.
			if len(b.Preds) == 1 {
				p := b.Preds[0].b
				if p.Kind == BlockIf && p.Controls[0].Op == OpIsNonNil && p.Succs[0].b == b {
					if ptr := p.Controls[0].Args[0]; nonNilValues[ptr.ID] == nil {
						nonNilValues[ptr.ID] = ptr
						work = append(work, bp{op: ClearPtr, ptr: ptr})
					}
				}
			}

	case b.Succs[1].Block():
		s.oneJump(b, &jumps[1][0])
		s.oneJump(b, &jumps[1][1])
	default:
		var q *obj.Prog
		if b.Likely != ssa.BranchUnlikely {
			s.oneJump(b, &jumps[1][0])
			s.oneJump(b, &jumps[1][1])
			q = s.Br(obj.AJMP, b.Succs[1].Block())
		} else {
			s.oneJump(b, &jumps[0][0])
			s.oneJump(b, &jumps[0][1])
			q = s.Br(obj.AJMP, b.Succs[0].Block())
		}
		q.Pos = b.Pos
	}
}

		if int(ID) < len(f.Cache.blocks) {
			b = &f.Cache.blocks[ID]
			b.ID = ID
		} else {
			b = &Block{ID: ID}
		}
	}
	b.Kind = kind
	b.Func = f
	b.Preds = b.predstorage[:0]
	b.Succs = b.succstorage[:0]
	b.Values = b.valstorage[:0]
	f.Blocks = append(f.Blocks, b)
	f.invalidateCFG()
	return b
}

func (f *Func) freeBlock(b *Block) {
	if b.Func == nil {

	var states map[string]bool
	for {
		change := false
		deadChange := false
		for _, b := range f.Blocks {
			var b0 *Block
			if debug > 1 {
				b0 = new(Block)
				*b0 = *b
				b0.Succs = append([]Edge{}, b.Succs...) // make a new copy, not aliasing
			}
			for i, c := range b.ControlValues() {
				for c.Op == OpCopy {
					c = c.Args[0]
					b.ReplaceControl(i, c)
				}
			}
			if rb(b) {