// From Engineering a Compiler (Cooper, Torczon)
public static bool IsReducible(LBlock[] blocks)
{
// Copy the graph into a temporary mutable structure.
var rblocks = new RBlock[blocks.Length];
for (var i = 0; i < blocks.Length; i++)
{
rblocks[i] = new RBlock(i);
}
for (var i = 0; i < blocks.Length; i++)
{
var block = blocks[i];
var rblock = rblocks[i];
for (var j = 0; j < block.numPredecessors; j++)
{
rblock.predecessors.Add(rblocks[block.getPredecessor(j).id]);
}
for (var j = 0; j < block.numSuccessors; j++)
{
rblock.successors.Add(rblocks[block.getSuccessor(j).id]);
}
}
// Okay, start reducing.
var queue = new LinkedList <RBlock>(rblocks);
for (; ;)
{
var deleteQueue = new List <RBlock>();
foreach (var rblock in queue)
{
// Transformation T1, remove self-edges.
if (rblock.predecessors.Contains(rblock))
{
rblock.predecessors.Remove(rblock);
}
if (rblock.successors.Contains(rblock))
{
rblock.successors.Remove(rblock);
}
// Transformation T2, remove blocks with one predecessor,
// reroute successors' predecessors.
if (rblock.predecessors.Count == 1)
{
// Mark this node for removal since C# sucks and can't delete during iteration.
deleteQueue.Add(rblock);
var predecessor = rblock.predecessors[0];
// Delete the edge from pred -> me
predecessor.successors.Remove(rblock);
for (var i = 0; i < rblock.successors.Count; i++)
{
var successor = rblock.successors[i];
//Debug.Assert(successor.predecessors.Contains(rblock));
successor.predecessors.Remove(rblock);
if (!successor.predecessors.Contains(predecessor))
{
successor.predecessors.Add(predecessor);
}
if (!predecessor.successors.Contains(successor))
{
predecessor.successors.Add(successor);
}
}
}
}
if (deleteQueue.Count == 0)
{
break;
}
foreach (var rblock in deleteQueue)
{
queue.Remove(rblock);
}
}
// If the graph reduced to one node, it was reducible.
return(queue.Count == 1);
}
// From Engineering a Compiler (Cooper, Torczon)
public static bool IsReducible(LBlock[] blocks)
{
// Copy the graph into a temporary mutable structure.
RBlock[] rblocks = new RBlock[blocks.Length];
for (int i = 0; i < blocks.Length; i++)
rblocks[i] = new RBlock(i);
for (int i = 0; i < blocks.Length; i++)
{
LBlock block = blocks[i];
RBlock rblock = rblocks[i];
for (int j = 0; j < block.numPredecessors; j++)
rblock.predecessors.Add(rblocks[block.getPredecessor(j).id]);
for (int j = 0; j < block.numSuccessors; j++)
rblock.successors.Add(rblocks[block.getSuccessor(j).id]);
}
// Okay, start reducing.
LinkedList<RBlock> queue = new LinkedList<RBlock>(rblocks);
for (;;)
{
List<RBlock> deleteQueue = new List<RBlock>();
foreach (RBlock rblock in queue)
{
// Transformation T1, remove self-edges.
if (rblock.predecessors.Contains(rblock))
rblock.predecessors.Remove(rblock);
if (rblock.successors.Contains(rblock))
rblock.successors.Remove(rblock);
// Transformation T2, remove blocks with one predecessor,
// reroute successors' predecessors.
if (rblock.predecessors.Count == 1)
{
// Mark this node for removal since C# sucks and can't delete during iteration.
deleteQueue.Add(rblock);
RBlock predecessor = rblock.predecessors[0];
// Delete the edge from pred -> me
predecessor.successors.Remove(rblock);
for (int i = 0; i < rblock.successors.Count; i++)
{
RBlock successor = rblock.successors[i];
//Debug.Assert(successor.predecessors.Contains(rblock));
successor.predecessors.Remove(rblock);
if (!successor.predecessors.Contains(predecessor))
successor.predecessors.Add(predecessor);
if (!predecessor.successors.Contains(successor))
predecessor.successors.Add(successor);
}
}
}
if (deleteQueue.Count == 0)
break;
foreach (RBlock rblock in deleteQueue)
queue.Remove(rblock);
}
// If the graph reduced to one node, it was reducible.
return queue.Count == 1;
}
