public static (ControlFlowGraph, string) Decompile(ControlFlowGraph graph)
{
if (graph == null)
{
throw new ArgumentNullException(nameof(graph));
}
foreach (var head in graph.GetDfsPostOrder())
{
var(trueChild, falseChild) = graph.GetBinaryChildren(head);
if (!trueChild.HasValue || !falseChild.HasValue)
{
continue;
}
int after = -1;
var then = -1;
// Func<string> vis = () => graph.ToVis().AddPointer("head", head).AddPointer("after", after).AddPointer("then", then).ToString(); // For VS Code debug visualisation
var parents0 = graph.Parents(trueChild.Value);
var parents1 = graph.Parents(falseChild.Value);
if (parents0.Length == 1)
{
var grandChildren = graph.Children(trueChild.Value);
if (grandChildren.Length == 1 && grandChildren[0] == falseChild.Value)
{
then = trueChild.Value;
after = falseChild.Value;
}
}
else if (parents1.Length == 1)
{
var grandChildren = graph.Children(falseChild.Value);
if (grandChildren.Length == 1 && grandChildren[0] == trueChild.Value)
{
then = falseChild.Value;
after = trueChild.Value;
}
}
if (after == -1 || then == -1 || after == head)
{
continue;
}
var condition = then == falseChild.Value ? Emit.Negation(graph.Nodes[head]) : graph.Nodes[head];
var newNode = Emit.If(condition, graph.Nodes[then]);
return(graph.RemoveNode(then).ReplaceNode(head, newNode), Description);
}
return(graph, null);
}
public static (ControlFlowGraph, string) Decompile(ControlFlowGraph graph)
{
if (graph == null)
{
throw new ArgumentNullException(nameof(graph));
}
foreach (var head in graph.GetDfsPostOrder())
{
var(trueChild, falseChild) = graph.GetBinaryChildren(head);
if (!trueChild.HasValue || !falseChild.HasValue)
{
continue;
}
var left = trueChild.Value;
var right = falseChild.Value;
// Func<string> vis = () => graph.ToVis().AddPointer("head", head).AddPointer("after", after).AddPointer("left", left).AddPointer("right", right).ToString(); // For VS Code debug visualisation
var leftParents = graph.Parents(left);
var rightParents = graph.Parents(right);
var leftChildren = graph.Children(left);
var rightChildren = graph.Children(right);
if (leftParents.Length != 1 || rightParents.Length != 1) // Branches of an if can't be jump destinations from elsewhere
{
continue;
}
bool isRegularIfThenElse =
leftChildren.Length == 1 && rightChildren.Length == 1 &&
leftChildren[0] == rightChildren[0];
bool isTerminalIfThenElse = leftChildren.Length == 0 && rightChildren.Length == 0;
if (!isRegularIfThenElse && !isTerminalIfThenElse)
{
continue;
}
var after = isRegularIfThenElse ? leftChildren[0] : -1;
if (after == head)
{
continue;
}
var newNode = Emit.IfElse(
graph.Nodes[head],
graph.Nodes[left],
graph.Nodes[right]);
var updated = graph;
if (isRegularIfThenElse)
{
updated = updated.AddEdge(head, after, CfgEdge.True);
}
return(updated
.RemoveNode(left)
.RemoveNode(right)
.ReplaceNode(head, newNode), Description);
}
return(graph, null);
}