depth      int32 // depth in dominator tree (root=0, its children=1, etc.)
}

func makeLCArange(f *Func) *lcaRange {
	dom := f.Idom()

	// Build tree
	blocks := make([]lcaRangeBlock, f.NumBlocks())
	for _, b := range f.Blocks {
		blocks[b.ID].b = b
		if dom[b.ID] == nil {
			continue // entry or unreachable
		}
		parent := dom[b.ID].ID
		blocks[b.ID].parent = parent

//	  CMPQ ...
//	  JLT loop
func loopRotate(f *Func) {
	loopnest := f.loopnest()
	if loopnest.hasIrreducible {
		return
	}
	if len(loopnest.loops) == 0 {
		return
	}

	idToIdx := f.Cache.allocIntSlice(f.NumBlocks())
	defer f.Cache.freeIntSlice(idToIdx)
	for i, b := range f.Blocks {
		idToIdx[b.ID] = i
	}

	// Set of blocks we're moving, by ID.
	move := map[ID]struct{}{}

	live, order = liveValues(f, reachable)
	f.Cache.freeValueSlice(order)
	return
}

// ReachableBlocks returns the reachable blocks in f.
func ReachableBlocks(f *Func) []bool {
	reachable := make([]bool, f.NumBlocks())
	reachable[f.Entry.ID] = true
	p := make([]*Block, 0, 64) // stack-like worklist
	p = append(p, f.Entry)
	for len(p) > 0 {
		// Pop a reachable block
		b := p[len(p)-1]
		p = p[:len(p)-1]