Ideal graphs dumped after GCM contain duplicated nodes and edges. This leads to duplication in edge tooltips (sea of nodes views, see sea.png) and node input lists (control-flow graph view, see cfg.png), and adds unnecessary overhead to the graph files.

To reproduce the issue:

1. Run IGV
2. Run $ java -Xbatch -XX:PrintIdealGraphLevel=1
3. Open any 'Final Code' graph
4. Look at edge tooltips in the sea of nodes view or node input lists in the control-flow graph view.