func BenchmarkDominatorsManyPred(b *testing.B)   { benchmarkDominators(b, 10000, genManyPred) }
func BenchmarkDominatorsMaxPred(b *testing.B)    { benchmarkDominators(b, 10000, genMaxPred) }
func BenchmarkDominatorsMaxPredVal(b *testing.B) { benchmarkDominators(b, 10000, genMaxPredValue) }

type blockGen func(size int) []bloc

// genLinear creates an array of blocks that succeed one another
// b_n -> [b_n+1].