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using ARMeilleure.IntermediateRepresentation;
using System;
using System.Collections.Generic;
using System.Diagnostics;
namespace ARMeilleure.Translation
{
class ControlFlowGraph
{
public BasicBlock Entry { get; }
public IntrusiveList<BasicBlock> Blocks { get; }
public BasicBlock[] PostOrderBlocks { get; }
public int[] PostOrderMap { get; }
public ControlFlowGraph(BasicBlock entry, IntrusiveList<BasicBlock> blocks)
{
Entry = entry;
Blocks = blocks;
RemoveUnreachableBlocks(blocks);
HashSet<BasicBlock> visited = new HashSet<BasicBlock>();
Stack<BasicBlock> blockStack = new Stack<BasicBlock>();
PostOrderBlocks = new BasicBlock[blocks.Count];
PostOrderMap = new int[blocks.Count];
visited.Add(entry);
blockStack.Push(entry);
int index = 0;
while (blockStack.TryPop(out BasicBlock block))
{
if (block.Next != null && visited.Add(block.Next))
{
blockStack.Push(block);
blockStack.Push(block.Next);
}
else if (block.Branch != null && visited.Add(block.Branch))
{
blockStack.Push(block);
blockStack.Push(block.Branch);
}
else
{
PostOrderMap[block.Index] = index;
PostOrderBlocks[index++] = block;
}
}
}
private void RemoveUnreachableBlocks(IntrusiveList<BasicBlock> blocks)
{
HashSet<BasicBlock> visited = new HashSet<BasicBlock>();
Queue<BasicBlock> workQueue = new Queue<BasicBlock>();
visited.Add(Entry);
workQueue.Enqueue(Entry);
while (workQueue.TryDequeue(out BasicBlock block))
{
Debug.Assert(block.Index != -1, "Invalid block index.");
if (block.Next != null && visited.Add(block.Next))
{
workQueue.Enqueue(block.Next);
}
if (block.Branch != null && visited.Add(block.Branch))
{
workQueue.Enqueue(block.Branch);
}
}
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))
{
block.Next = null;
block.Branch = null;
blocks.Remove(block);
}
else
{
block.Index = index++;
}
block = nextBlock;
}
}
}
public BasicBlock SplitEdge(BasicBlock predecessor, BasicBlock successor)
{
BasicBlock splitBlock = new BasicBlock(Blocks.Count);
if (predecessor.Next == successor)
{
predecessor.Next = splitBlock;
}
if (predecessor.Branch == successor)
{
predecessor.Branch = splitBlock;
}
if (splitBlock.Predecessors.Count == 0)
{
throw new ArgumentException("Predecessor and successor are not connected.");
}
// Insert the new block on the list of blocks.
BasicBlock succPrev = successor.ListPrevious;
if (succPrev != null && succPrev != predecessor && succPrev.Next == successor)
{
// Can't insert after the predecessor or before the successor.
// Here, we insert it before the successor by also spliting another
// edge (the one between the block before "successor" and "successor").
BasicBlock splitBlock2 = new BasicBlock(splitBlock.Index + 1);
succPrev.Next = splitBlock2;
splitBlock2.Branch = successor;
splitBlock2.Operations.AddLast(new Operation(Instruction.Branch, null));
Blocks.AddBefore(successor, splitBlock2);
}
splitBlock.Next = successor;
Blocks.AddBefore(successor, splitBlock);
return splitBlock;
}
}
}
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