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Relax block ordering constraints (#1535)

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* Relax block ordering constraints

Before `block.Next` had to follow `block.ListNext`, now it does not.
Instead `CodeGenerator` will now emit the necessary jump instructions
to ensure control flow.

This makes control flow and block order modifications easier. It also
eliminates some simple cases of redundant branches.

* Set PPTC version
This commit is contained in:
FICTURE7 2020-09-12 19:32:53 +04:00 • committed by GitHub
parent 3d055da5fc
commit 36ec1bc6c0
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11 changed files with 164 additions and 174 deletions
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94
ARMeilleure/Translation/ControlFlowGraph.cs
View file

@ -8,47 +8,48 @@ 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;
Entry = entry;
Blocks = blocks;
RemoveUnreachableBlocks(blocks);
HashSet<BasicBlock> visited = new HashSet<BasicBlock>();
Stack<BasicBlock> blockStack = new Stack<BasicBlock>();
var visited = new HashSet<BasicBlock>();
var 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))
bool visitedNew = false;
for (int i = 0; i < block.SuccessorCount; i++)
{
blockStack.Push(block);
blockStack.Push(block.Next);
BasicBlock succ = block.GetSuccessor(i);
if (visited.Add(succ))
{
blockStack.Push(block);
blockStack.Push(succ);
visitedNew = true;
break;
}
}
else if (block.Branch != null && visited.Add(block.Branch))
{
blockStack.Push(block);
blockStack.Push(block.Branch);
}
else
if (!visitedNew)
{
PostOrderMap[block.Index] = index;
@ -59,26 +60,24 @@ namespace ARMeilleure.Translation
private void RemoveUnreachableBlocks(IntrusiveList<BasicBlock> blocks)
{
HashSet<BasicBlock> visited = new HashSet<BasicBlock>();
Queue<BasicBlock> workQueue = new Queue<BasicBlock>();
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.");
if (block.Next != null && visited.Add(block.Next))
for (int i = 0; i < block.SuccessorCount; i++)
{
workQueue.Enqueue(block.Next);
}
BasicBlock succ = block.GetSuccessor(i);
if (block.Branch != null && visited.Add(block.Branch))
{
workQueue.Enqueue(block.Branch);
if (visited.Add(succ))
{
workQueue.Enqueue(succ);
}
}
}
@ -93,8 +92,10 @@ namespace ARMeilleure.Translation
if (!visited.Contains(block))
{
block.Next = null;
block.Branch = null;
while (block.SuccessorCount > 0)
{
block.RemoveSuccessor(index: block.SuccessorCount - 1);
}
blocks.Remove(block);
}
@ -112,14 +113,12 @@ namespace ARMeilleure.Translation
{
BasicBlock splitBlock = new BasicBlock(Blocks.Count);
if (predecessor.Next == successor)
for (int i = 0; i < predecessor.SuccessorCount; i++)
{
predecessor.Next = splitBlock;
}
if (predecessor.Branch == successor)
{
predecessor.Branch = splitBlock;
if (predecessor.GetSuccessor(i) == successor)
{
predecessor.SetSuccessor(i, splitBlock);
}
}
if (splitBlock.Predecessors.Count == 0)
@ -127,26 +126,7 @@ namespace ARMeilleure.Translation
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(OperationHelper.Operation(Instruction.Branch, null));
Blocks.AddBefore(successor, splitBlock2);
}
splitBlock.Next = successor;
splitBlock.AddSuccessor(successor);
Blocks.AddBefore(successor, splitBlock);