/// <summary>
/// Removes unused, non-effectful instructions and basic block
/// parameters from a flow graph.
/// </summary>
/// <param name="graph">The flow graph to transform.</param>
/// <returns>A transformed flow graph.</returns>
public override FlowGraph Apply(FlowGraph graph)
{
// This transform simply builds a set of live values and
// then deletes everything that's not.
// Compute the live values.
var liveValues = ComputeLiveValues(graph);
// Compute the set of dead values.
var deadValues = new HashSet <ValueTag>(graph.ValueTags);
deadValues.ExceptWith(liveValues);
// Delete everything that's not live.
return(graph.RemoveDefinitions(deadValues));
}
