ControlFlowNode[] PrepareReverseCFG(ControlFlowNode loopHead, bool treatBackEdgesAsExits)
{
ControlFlowNode[] cfg = context.ControlFlowGraph.cfg;
ControlFlowNode[] rev = new ControlFlowNode[cfg.Length + 1];
for (int i = 0; i < cfg.Length; i++)
{
rev[i] = new ControlFlowNode {
UserIndex = i, UserData = cfg[i].UserData
};
}
ControlFlowNode exitNode = new ControlFlowNode {
UserIndex = -1
};
rev[cfg.Length] = exitNode;
for (int i = 0; i < cfg.Length; i++)
{
if (!loopHead.Dominates(cfg[i]))
{
continue;
}
// Add reverse edges for all edges in cfg
foreach (var succ in cfg[i].Successors)
{
if (loopHead.Dominates(succ) && (!treatBackEdgesAsExits || loopHead != succ))
{
rev[succ.UserIndex].AddEdgeTo(rev[i]);
}
else
{
exitNode.AddEdgeTo(rev[i]);
}
}
if (context.ControlFlowGraph.HasDirectExitOutOfContainer(cfg[i]))
{
exitNode.AddEdgeTo(rev[i]);
}
}
Dominance.ComputeDominance(exitNode, context.CancellationToken);
return(rev);
}
/// <summary>
/// Constructs a new control flow graph.
/// Each node cfg[i] has a corresponding node rev[i].
/// Edges are only created for nodes dominated by loopHead, and are in reverse from their direction
/// in the primary CFG.
/// An artificial exit node is used for edges that leave the set of nodes dominated by loopHead,
/// or that leave the block Container.
/// </summary>
/// <param name="loopHead">Entry point of the loop.</param>
/// <param name="exitNodeArity">out: The number of different CFG nodes.
/// Possible values:
/// 0 = no CFG nodes used as exit nodes (although edges leaving the block container might still be exits);
/// 1 = a single CFG node (not dominated by loopHead) was used as an exit node;
/// 2 = more than one CFG node (not dominated by loopHead) was used as an exit node.
/// </param>
/// <returns></returns>
ControlFlowNode[] PrepareReverseCFG(ControlFlowNode loopHead, out int exitNodeArity)
{
ControlFlowNode[] cfg = context.ControlFlowGraph.cfg;
ControlFlowNode[] rev = new ControlFlowNode[cfg.Length + 1];
for (int i = 0; i < cfg.Length; i++)
{
rev[i] = new ControlFlowNode {
UserIndex = i, UserData = cfg[i].UserData
};
}
ControlFlowNode nodeTreatedAsExitNode = null;
bool multipleNodesTreatedAsExitNodes = false;
ControlFlowNode exitNode = new ControlFlowNode {
UserIndex = -1
};
rev[cfg.Length] = exitNode;
for (int i = 0; i < cfg.Length; i++)
{
if (!loopHead.Dominates(cfg[i]) || isSwitch && cfg[i] != loopHead && loopContext.MatchContinue(cfg[i]))
{
continue;
}
// Add reverse edges for all edges in cfg
foreach (var succ in cfg[i].Successors)
{
// edges to outer loops still count as exits (labelled continue not implemented)
if (isSwitch && loopContext.MatchContinue(succ, 1))
{
continue;
}
if (loopHead.Dominates(succ))
{
rev[succ.UserIndex].AddEdgeTo(rev[i]);
}
else
{
if (nodeTreatedAsExitNode == null)
{
nodeTreatedAsExitNode = succ;
}
if (nodeTreatedAsExitNode != succ)
{
multipleNodesTreatedAsExitNodes = true;
}
exitNode.AddEdgeTo(rev[i]);
}
}
if (context.ControlFlowGraph.HasDirectExitOutOfContainer(cfg[i]))
{
exitNode.AddEdgeTo(rev[i]);
}
}
if (multipleNodesTreatedAsExitNodes)
{
exitNodeArity = 2; // more than 1
}
else if (nodeTreatedAsExitNode != null)
{
exitNodeArity = 1;
}
else
{
exitNodeArity = 0;
}
Dominance.ComputeDominance(exitNode, context.CancellationToken);
return(rev);
}
