digraph g {
    l1 [label = "Enter f()", style = filled];
    l2 [label = "2: int sum = 0"];
    l3 [label = "3: int prod = 0", style = filled];
    l4 [label = "4: while (x > 0)"];
    l5 [label = "5: sum += sum"];
    l6 [label = "6: prod *= prod", style = filled];
    l7 [label = "7: x--"];
    l9 [label = "9: log(\"sum: \" + sum)"];
    l10 [label = "10: log(\"prod: \" + prod)", style = "bold,filled"];
    // graph order
    {rank=min; l1};
    {rank=same; l2 l3 l4 l9 l10};
    {rank=max; l5 l6 l7};
    { edge [style=invis];
        l2 -> l3 -> l4 -> l9 -> l10;
        l5 -> l6 -> l7;
    }

    { // control edges
        // edge [style=invis];
        edge [color = grey];
        l1 -> {l2 l4 l9 l10};
        l1 -> l3 [color = black];
        l4 -> {l5 l7};
        l4 -> l6 [style = bold, color = black];
    }

    { // data input
        node [style=dashed];
        edge [color = grey];
        // node [style=invis];
        // edge [style=invis];
        x [label = "x = x_in"];
        l1 -> x;
        x -> {l2} [style=invis];
    }
    
    { // data edges
        edge [color=red,constraint=true];
        {l2 l5} -> {l5 l9} [color = grey]; // sum
        {l3 l6} -> {l10} [color = grey]; // prod
        {l3 l6} -> l6 [color = darkgreen];
        {x l7} -> {l4 l7} [color = grey]; // x
    }
}