/// <summary>
/// Group input into a set of blocks that can be later arbitraliby schufled.
/// The method adds necessary branches to make control flow between blocks
/// explicit and thus order independent.
/// </summary>
///
public static void SplitToBasicBlocks(ILBlock block, bool reducebranches = false)
{
int nextLabelIndex = 0;
List <ILNode> basicBlocks = new List <ILNode>();
ILLabel entryLabel = block.Body.FirstOrDefault() as ILLabel ?? ILLabel.Generate("Block_", nextLabelIndex++);
ILBasicBlock basicBlock = new ILBasicBlock();
basicBlocks.Add(basicBlock);
basicBlock.Body.Add(entryLabel);
block.EntryGoto = new ILExpression(GMCode.B, entryLabel);
if (block.Body.Count > 0)
{
if (block.Body[0] != entryLabel)
{
basicBlock.Body.Add(block.Body[0]);
}
for (int i = 1; i < block.Body.Count; i++)
{
ILNode lastNode = block.Body[i - 1];
ILNode currNode = block.Body[i];
// Start a new basic block if necessary
if (currNode is ILLabel ||
lastNode.IsConditionalControlFlow() ||
lastNode.IsUnconditionalControlFlow())
{
// Try to reuse the label
ILLabel label = currNode as ILLabel ?? ILLabel.Generate("Block_", nextLabelIndex++);
// Terminate the last block
if (!lastNode.IsUnconditionalControlFlow())
{
// Explicit branch from one block to other
basicBlock.Body.Add(new ILExpression(GMCode.B, label));
}
// Start the new block
basicBlock = new ILBasicBlock();
basicBlocks.Add(basicBlock);
basicBlock.Body.Add(label);
// Add the node to the basic block
if (currNode != label)
{
basicBlock.Body.Add(currNode);
}
}
else
{
basicBlock.Body.Add(currNode);
}
}
}
block.Body = basicBlocks;
if (reducebranches)
{
if (basicBlocks.Count > 0)
{
for (int i = 0; i < block.Body.Count; i++)
{
ILBasicBlock bb = block.Body[i] as ILBasicBlock;
if (bb == null)
{
continue;
}
ILLabel trueLabel;
ILLabel falseLabel;
if (bb.MatchLastAndBr(GMCode.Bf, out falseLabel, out trueLabel))
{
ILExpression bf = bb.Body[bb.Body.Count - 2] as ILExpression;
ILExpression b = bb.Body[bb.Body.Count - 1] as ILExpression;
bf.Code = GMCode.Bt;
b.Operand = falseLabel;
bf.Operand = trueLabel;
}
}
}
}
return;
}
