defer f.Cache.freeBlockSlice(fromID)
	for _, v := range f.Blocks {
		fromID[v.ID] = v
	}
	idom := make([]*Block, maxBlockID)

	// Step 1. Carry out a depth first search of the problem graph. Number
	// the vertices from 1 to n as they are reached during the search.
	n := f.dfsOrig(entry, succFn, semi, vertex, label, parent)

	for i := n; i >= 2; i-- {
		w := vertex[i]

		// step2 in TOPLAS paper