The Ideal Graph Visualizer is a tool developed to help examine the intermediate representation of C2 which is commonly referred to as the "ideal graph". It was developed in collaboration with the University of Linz in Austria and is included in HotSpot's repository since that was the primary target of the tool. The tool itself is fairly general with only a few modules that contain C2 specific elements.
The tool is built on top of the NetBeans platform. For details about building and running it, see the README file in the tool's source directory. Papers describing the main ideas behind the tool are available at Publications.