protected override BoundStatement RewriteWhileStatement(BoundWhileStatement node)
{
// while <condition>
// body
//
// --> becomes
//
// goto check
// continue:
// <body>
// check:
// gotoTrue <condition> continue
// end:
var continueLabel = GenerateLabel();
var checkLabel = GenerateLabel();
var endLabel = GenerateLabel();
var gotoLabel = GenerateLabel();
var gotoCheck = new BoundGoToStatement(checkLabel);
var continueLabelStatement = new BoundLabelStatement(continueLabel);
var checkLabelStatement = new BoundLabelStatement(checkLabel);
var ebdLabelStatement = new BoundLabelStatement(endLabel);
var gotoTrue = new BoundConditionalGotoStatement(continueLabel, node.Condition);
var endLabelStatement = new BoundLabelStatement(endLabel);
var result = new BoundBlockStatement(ImmutableArray.Create <BoundStatement>(
gotoCheck,
continueLabelStatement,
node.Body,
checkLabelStatement,
gotoTrue,
endLabelStatement
));
return(RewriteStatement(result));
}
protected override BoundStatement RewriteIfStatement(BoundIfStatement node)
{
if (node.ElseStatement == null)
{
// if <condition>
// <then>
//
// --> becomes
//
// gotoIfFalse <condition> end
// <then>
// end:
var endLabel = GenerateLabel();
var gotoFalse = new BoundConditionalGotoStatement(endLabel, node.Condition, false);
var endLabelStatement = new BoundLabelStatement(endLabel);
var result = new BoundBlockStatement(ImmutableArray.Create <BoundStatement>(gotoFalse, node.ThenStatement, endLabelStatement));
return(RewriteStatement(result));
}
else
{
// if <condition>
// <then>
// else
// <else>
//
// --> becomes
//
// gotoIfFalse <condition> else
// <then>
// goto end
// else:
// <else>
// end:
var elseLabel = GenerateLabel();
var endLabel = GenerateLabel();
var gotoFalse = new BoundConditionalGotoStatement(elseLabel, node.Condition, false);
var gotoEndStatement = new BoundGoToStatement(endLabel);
var elseLabelStatement = new BoundLabelStatement(elseLabel);
var endLabelStatement = new BoundLabelStatement(endLabel);
var result = new BoundBlockStatement(ImmutableArray.Create <BoundStatement>(
gotoFalse,
node.ThenStatement,
gotoEndStatement,
elseLabelStatement,
node.ElseStatement,
endLabelStatement
));
return(RewriteStatement(result));
}
}
private void EmitGoToStatement(BoundGoToStatement statement)
{
this.instructions.Add(new TransientUnconditionalGoToInstruction(statement.Label, statement.Syntax.GoToToken.Range));
}
