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using ARMeilleure.IntermediateRepresentation;
using System;
using System.Collections.Generic;
using System.Diagnostics;
namespace ARMeilleure.Translation
{
class ControlFlowGraph
{
private BasicBlock[] _postOrderBlocks;
private int[] _postOrderMap;
public int LocalsCount { get; private set; }
public BasicBlock Entry { get; private set; }
public IntrusiveList<BasicBlock> Blocks { get; }
public BasicBlock[] PostOrderBlocks => _postOrderBlocks;
public int[] PostOrderMap => _postOrderMap;
public ControlFlowGraph(BasicBlock entry, IntrusiveList<BasicBlock> blocks, int localsCount)
{
Entry = entry;
Blocks = blocks;
LocalsCount = localsCount;
Update();
}
public Operand AllocateLocal(OperandType type)
{
Operand result = Operand.Factory.Local(type);
result.NumberLocal(++LocalsCount);
return result;
}
public void UpdateEntry(BasicBlock newEntry)
{
newEntry.AddSuccessor(Entry);
Entry = newEntry;
Blocks.AddFirst(newEntry);
Update();
}
public void Update()
{
RemoveUnreachableBlocks(Blocks);
var visited = new HashSet<BasicBlock>();
var blockStack = new Stack<BasicBlock>();
Array.Resize(ref _postOrderBlocks, Blocks.Count);
Array.Resize(ref _postOrderMap, Blocks.Count);
visited.Add(Entry);
blockStack.Push(Entry);
int index = 0;
while (blockStack.TryPop(out BasicBlock block))
{
bool visitedNew = false;
for (int i = 0; i < block.SuccessorsCount; i++)
{
BasicBlock succ = block.GetSuccessor(i);
if (visited.Add(succ))
{
blockStack.Push(block);
blockStack.Push(succ);
visitedNew = true;
break;
}
}
if (!visitedNew)
{
PostOrderMap[block.Index] = index;
PostOrderBlocks[index++] = block;
}
}
}
private void RemoveUnreachableBlocks(IntrusiveList<BasicBlock> blocks)
{
var visited = new HashSet<BasicBlock>();
var workQueue = new Queue<BasicBlock>();
visited.Add(Entry);
workQueue.Enqueue(Entry);
while (workQueue.TryDequeue(out BasicBlock block))
{
Debug.Assert(block.Index != -1, "Invalid block index.");
for (int i = 0; i < block.SuccessorsCount; i++)
{
BasicBlock succ = block.GetSuccessor(i);
if (visited.Add(succ))
{
workQueue.Enqueue(succ);
}
}
}
if (visited.Count < blocks.Count)
{
// Remove unreachable blocks and renumber.
int index = 0;
for (BasicBlock block = blocks.First; block != null;)
{
BasicBlock nextBlock = block.ListNext;
if (!visited.Contains(block))
{
while (block.SuccessorsCount > 0)
{
block.RemoveSuccessor(index: block.SuccessorsCount - 1);
}
blocks.Remove(block);
}
else
{
block.Index = index++;
}
block = nextBlock;
}
}
}
public BasicBlock SplitEdge(BasicBlock predecessor, BasicBlock successor)
{
BasicBlock splitBlock = new(Blocks.Count);
for (int i = 0; i < predecessor.SuccessorsCount; i++)
{
if (predecessor.GetSuccessor(i) == successor)
{
predecessor.SetSuccessor(i, splitBlock);
}
}
if (splitBlock.Predecessors.Count == 0)
{
throw new ArgumentException("Predecessor and successor are not connected.");
}
splitBlock.AddSuccessor(successor);
Blocks.AddBefore(successor, splitBlock);
return splitBlock;
}
}
}
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