public static void ComputeDominators(LBlock[] blocks)
{
BitArray[] doms = new BitArray[blocks.Length];
for (int i = 0; i < doms.Length; i++)
{
doms[i] = new BitArray(doms.Length);
}
doms[0].Set(0, true);
for (int i = 1; i < blocks.Length; i++)
{
for (int j = 0; j < blocks.Length; j++)
{
doms[i].SetAll(true);
}
}
// Compute dominators.
bool changed;
do
{
changed = false;
for (int i = 1; i < blocks.Length; i++)
{
LBlock block = blocks[i];
for (int j = 0; j < block.numPredecessors; j++)
{
LBlock pred = block.getPredecessor(j);
BitArray u = new BitArray(doms[i]);
doms[block.id].And(doms[pred.id]);
doms[block.id].Set(block.id, true);
if (!CompareBitArrays(doms[block.id], u))
{
changed = true;
}
}
}
}while (changed);
// Turn the bit vectors into lists.
for (int i = 0; i < blocks.Length; i++)
{
LBlock block = blocks[i];
List <LBlock> list = new List <LBlock>();
for (int j = 0; j < blocks.Length; j++)
{
if (doms[block.id][j])
{
list.Add(blocks[j]);
}
}
block.setDominators(list.ToArray());
}
}
public void scan(LBlock block)
{
for (var i = 0; i < block.numPredecessors; i++)
{
var pred = block.getPredecessor(i);
// Has this block already been scanned?
if (pred.loop == backedge_.loop)
{
continue;
}
pred = SkipContainedLoop(pred, backedge_.loop);
// If this assert hits, there is probably a |break| keyword.
//Debug.Assert(pred.loop == null || pred.loop == backedge_.loop);
if (pred.loop != null)
{
continue;
}
stack_.Push(pred);
}
}
private ControlType findLoopJoinAndBody(NodeBlock header, NodeBlock effectiveHeader,
out NodeBlock join, out NodeBlock body, out NodeBlock cond)
{
//Debug.Assert(effectiveHeader.lir.numSuccessors == 2);
LBlock succ1 = effectiveHeader.lir.getSuccessor(0);
LBlock succ2 = effectiveHeader.lir.getSuccessor(1);
if (succ1.loop != header.lir || succ2.loop != header.lir)
{
//Debug.Assert(succ1.loop == header.lir || succ2.loop == header.lir);
if (succ1.loop != header.lir)
{
join = graph_[succ1.id];
body = graph_[succ2.id];
}
else
{
join = graph_[succ2.id];
body = graph_[succ1.id];
}
cond = header;
// If this is a self-loop, it is more correct to decompose it
// to a do-while loop. This may not be source accurate in the
// case of something like |while (x);| but it catches many more
// source-accurate cases.
if (header == effectiveHeader &&
BlockAnalysis.GetEmptyTarget(body) == header)
{
body = null;
return(ControlType.DoWhileLoop);
}
return(ControlType.WhileLoop);
}
else
{
// Neither successor of the header exits the loop, so this is
// probably a do-while loop. For now, assume it's simple.
//Debug.Assert(header == effectiveHeader);
LBlock backedge = header.lir.backedge;
if (BlockAnalysis.GetEmptyTarget(graph_[backedge.id]) == header)
{
// Skip an empty block sitting in between the backedge and
// the condition.
//Debug.Assert(backedge.numPredecessors == 1);
backedge = backedge.getPredecessor(0);
}
//Debug.Assert(backedge.numSuccessors == 2);
succ1 = backedge.getSuccessor(0);
succ2 = backedge.getSuccessor(1);
body = header;
cond = graph_[backedge.id];
if (succ1.loop != header.lir)
{
join = graph_[succ1.id];
}
else
{
//Debug.Assert(succ2.loop != header.lir);
join = graph_[succ2.id];
}
return(ControlType.DoWhileLoop);
}
}
public void scan(LBlock block)
{
for (int i = 0; i < block.numPredecessors; i++)
{
LBlock pred = block.getPredecessor(i);
// Has this block already been scanned?
if (pred.loop == backedge_.loop)
continue;
pred = SkipContainedLoop(pred, backedge_.loop);
// If this assert hits, there is probably a |break| keyword.
//Debug.Assert(pred.loop == null || pred.loop == backedge_.loop);
if (pred.loop != null)
continue;
stack_.Push(pred);
}
}
// 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);
}