private static void WriteConditionalGotoStatement(BoundConditionalGotoStatement node, IndentedTextWriter writer)
{
writer.WriteKeyword("goto");
writer.WriteWhiteSpace();
writer.WriteIdentifier(node.Label.Name);
writer.WriteWhiteSpace();
writer.WriteKeyword(node.JumpIfTrue ? "if" : "unless");
writer.WriteWhiteSpace();
node.Condition.WriteTo(writer);
writer.WriteLine();
}
public ControlFlowGraph Build(List <BasicBlock> blocks)
{
if (!blocks.Any())
{
Connect(start, end);
}
else
{
Connect(start, blocks.First());
}
foreach (BasicBlock block in blocks)
{
foreach (var statement in block.Statements)
{
blockFromStatement.Add(statement, block);
if (statement is BoundLabelStatement labelStatement)
{
blockFromLabel.Add(labelStatement.Label, block);
}
}
}
for (int i = 0; i < blocks.Count; i++)
{
BasicBlock current = blocks[i];
var next = i == blocks.Count - 1 ? end : blocks[i + 1];
foreach (var statement in current.Statements)
{
bool isLastStatementInBlock = statement == current.Statements.Last();
switch (statement.Kind)
{
case BoundNodeKind.GotoStatement:
BoundGotoStatement gs = (BoundGotoStatement)statement;
BasicBlock toBlock = blockFromLabel[gs.Label];
Connect(current, toBlock);
break;
case BoundNodeKind.ConditionalGotoStatement:
BoundConditionalGotoStatement cgs = (BoundConditionalGotoStatement)statement;
BasicBlock themBlock = blockFromLabel[cgs.Label];
BasicBlock elseBlock = next;
BoundExpression negatedCondition = Negate(cgs.Condition);
BoundExpression thenCondition = cgs.JumpIfTrue ? cgs.Condition: negatedCondition;
BoundExpression elseCondition = cgs.JumpIfTrue ? negatedCondition: cgs.Condition;
Connect(current, themBlock, thenCondition);
Connect(current, elseBlock, elseCondition);
break;
case BoundNodeKind.ReturnStatement:
Connect(current, end);
break;
case BoundNodeKind.LabelStatement:
case BoundNodeKind.VariableDeclaration:
case BoundNodeKind.ExpressionStatement:
if (isLastStatementInBlock)
{
Connect(current, next);
}
break;
default:
throw new Exception($"Unexpected statemend: '{statement.Kind}'.");
}
}
}
ScanAgain:
foreach (BasicBlock block in blocks)
{
if (!block.Incoming.Any())
{
RemoveBlock(blocks, block);
goto ScanAgain;
}
}
blocks.Insert(0, start);
blocks.Add(end);
return(new ControlFlowGraph(start, end, blocks, branches));
}