private void AddAbnormalEdges(ControlFlowGraph graph)
{
if (graph.SubGraphs.Count == 0)
{
return;
}
// Since exception handlers make it possible to transfer control to the handler block
// at any time, we have these "abnormal edges" from each node in the try block
// to the first node in the handler block (or filter block).
// First, add the initial abnormal handler edges from every try-start to the handler-start (or filter start).
// This allows us to do some more dominator-magic, where we can just infer the handler body based
// on the nodes dominated by the handler node.
foreach (var subGraph in graph.SubGraphs.OrderBy(x => x.Nodes.Count))
{
var ehFrame = (EHFrame)subGraph.UserData[EHFrame.EHFrameProperty];
// Find the try entry node.
var tryEntry = GetNode(graph, (long)ehFrame.TryStart);
tryEntry.UserData[ControlFlowGraph.TryStartProperty] = ehFrame;
// Find the handler entry node.
var handlerEntry = GetNode(graph, (long)ehFrame.HandlerAddress);
handlerEntry.UserData[ControlFlowGraph.HandlerStartProperty] = ehFrame;
// Add initial abnormal edge.
if (ehFrame.Type != EHType.FILTER)
{
// Jump straight to the handler entry.
AddAbnormalEdge(graph, tryEntry, ehFrame, handlerEntry);
}
else
{
// Jump to the filter entry.
var filterEntry = GetNode(graph, (long)ehFrame.FilterAddress);
filterEntry.UserData[ControlFlowGraph.FilterStartProperty] = ehFrame;
AddAbnormalEdge(graph, tryEntry, ehFrame, filterEntry);
// Connect all terminators of the filter block to the handler entry.
foreach (var terminator in FindReachableReturnNodes(filterEntry))
{
AddAbnormalEdge(graph, terminator, ehFrame, handlerEntry);
}
}
}
// Obtain dominator info.
var dominatorInfo = new DominatorInfo(graph.Entrypoint);
// Add all handler nodes to the cluster, and add abnormal edges for each try node to the handler start node.
var handlerExits = new Dictionary <EHFrame, ICollection <Node> >();
foreach (var subGraph in graph.SubGraphs.OrderBy(x => x.Nodes.Count))
{
var ehFrame = (EHFrame)subGraph.UserData[EHFrame.EHFrameProperty];
var tryEntry = GetNode(graph, (long)ehFrame.TryStart);
var handlerEntry = GetNode(graph, (long)ehFrame.HandlerAddress);
// Determine the handler exits.
var handlerBody = CollectHandlerNodes(handlerEntry, dominatorInfo.GetDominatedNodes(handlerEntry));
foreach (var handlerNode in handlerBody)
{
subGraph.Nodes.Add(handlerNode);
}
handlerExits.Add(ehFrame, new HashSet <Node>(handlerBody.Where(x => x.OutgoingEdges.Count == 0)));
// Add for each node in the try block an abnormal edge.
var tryBody = new HashSet <Node>(subGraph.Nodes.Except(handlerBody));
foreach (var node in tryBody.Where(n =>
!n.UserData.ContainsKey(ControlFlowGraph.TopMostEHProperty) && n != tryEntry))
{
AddAbnormalEdge(graph, node, ehFrame, handlerEntry);
}
// Register EH boundaries in the sub graph.
subGraph.UserData[ControlFlowGraph.TryBlockProperty] = tryBody;
subGraph.UserData[ControlFlowGraph.HandlerBlockProperty] = handlerBody;
if (ehFrame.Type == EHType.FILTER)
{
var filterEntry = GetNode(graph, (long)ehFrame.FilterAddress);
subGraph.UserData[ControlFlowGraph.FilterStartProperty] = filterEntry;
}
}
// Since a LEAVE instruction might not directly transfer control to the referenced instruction,
// but rather transfer control to a finally block first, we have to add edges to these nodes
// as well.
foreach (var node in graph.Nodes)
{
if (node.SubGraphs.Count > 0)
{
// Check if the node ends with a LEAVE.
var block = GetUserData <ILBasicBlock>(node, ILBasicBlock.BasicBlockProperty);
if (block == null)
{
continue;
}
var last = block.Instructions[block.Instructions.Count - 1];
if (last.OpCode.Code == ILCode.LEAVE)
{
// Find the frame we're jumping out of.
var ehFrame = last.ProgramState.EHStack.Peek();
// Add for each handler exit an edge to the referenced instruction.
foreach (var exit in handlerExits[ehFrame])
{
var edge = CreateEdge(exit, node.OutgoingEdges.First().Target, ControlFlowGraph.EndFinallyConditionLabel);
exit.UserData[ControlFlowGraph.TopMostEHProperty] = ehFrame;
graph.Edges.Add(edge);
}
}
}
}
}
private void AddFallThroughEdge(ControlFlowGraph graph, Node node, long nextOffset)
{
node.OutgoingEdges.Add(GetNode(graph, nextOffset));
}
