func (l *loop) nearestOuterLoop(sdom SparseTree, b *Block) *loop {
	var o *loop
	for o = l.outer; o != nil && !sdom.IsAncestorEq(o.header, b); o = o.outer {
	}
	return o
}

func loopnestfor(f *Func) *loopnest {
	po := f.postorder()
	sdom := f.Sdom()
	b2l := make([]*loop, f.NumBlocks())
	loops := make([]*loop, 0)
	visited := f.Cache.allocBoolSlice(f.NumBlocks())
	defer f.Cache.freeBoolSlice(visited)

	}
	return f.cachedSdom
}

// loopnest returns the loop nest information for f.
func (f *Func) loopnest() *loopnest {
	if f.cachedLoopnest == nil {
		f.cachedLoopnest = loopnestfor(f)
	}
	return f.cachedLoopnest
}

// invalidateCFG tells f that its CFG has changed.
func (f *Func) invalidateCFG() {
	f.cachedPostorder = nil
	f.cachedIdom = nil
	f.cachedSdom = nil