protected override BoundStatement RewriteWhileStatement(BoundWhileStatement node)
{
// while <condition>
// <bode>
//
// ----->
//
// goto continue
// <body>
// continue:
// gotoTrue <condition> body
// Break
//
var gotoContinue = new BoundGotoStatment(node.ContinueLabel);
var bodyLabelStatement = new BoundLabelStatement(node.BodyLabel);
var continueLabelStatement = new BoundLabelStatement(node.ContinueLabel);
var gotoTrue = new BoundConditionalGotoStatment(node.BodyLabel, node.Condition);
var breakLabelStatement = new BoundLabelStatement(node.BreakLabel);
var result = new BoundBlockStatemnet(ImmutableArray.Create <BoundStatement>(
gotoContinue,
bodyLabelStatement,
node.Body,
continueLabelStatement,
gotoTrue,
breakLabelStatement
));
return(RewriteStatement(result));
}
protected override BoundStatement RewriteIfStatement(BoundIfStatement node)
{
if (node.ElseStatement == null)
{
// if <condition>
// <then>
//
// ---->
//
// gotoFalse <condition> end
// <then>
// end:
var endLabel = GenerateLabel();
var gotoFalse = new BoundConditionalGotoStatment(endLabel, node.Condition, false);
var endLabelStatement = new BoundLabelStatement(endLabel);
var result = new BoundBlockStatemnet(ImmutableArray.Create <BoundStatement>(gotoFalse, node.ThenStatement, endLabelStatement));
return(RewriteStatement(result));
}
else
{
// if <condition>
// <then>
// else
// <else>
//
// ---->
//
// gotoFalse <condition> else
// <then>
// goto end
// else:
// <else>
// end:
var elseLabel = GenerateLabel();
var endLabel = GenerateLabel();
var gotoFalse = new BoundConditionalGotoStatment(elseLabel, node.Condition, false);
var gotoEndStatement = new BoundGotoStatment(endLabel);
var elseLabelStatement = new BoundLabelStatement(elseLabel);
var endLabelStatement = new BoundLabelStatement(endLabel);
var result = new BoundBlockStatemnet(ImmutableArray.Create <BoundStatement>(
gotoFalse,
node.ThenStatement,
gotoEndStatement,
elseLabelStatement,
node.ElseStatement,
endLabelStatement
));
return(RewriteStatement(result));
}
}
protected override BoundStatement RewriteForStatement(BoundForStatement node)
{
// for <var> = <lower> to <upper>
// <body>
//
// ---->
//
// {
// var <var> = <lower>
// while (<var> <= <upper>)
// {
// <body>
// <var> = <var> + 1
// }
// }
var variableDeclaration = new BoundVeriableDeclaration(node.Variable, node.LowerBound);
var variableExpression = new BoundVariableExpression(node.Variable);
var upperBoundSybmle = new VariableSymble("upperBound", true, typeof(int));
var upperBoundDeclaration = new BoundVeriableDeclaration(upperBoundSybmle, node.UpperBound);
var condition = new BoundBinaryExpression(
variableExpression,
BoundBinaryOperator.Bind(SyntaxKind.LessOrEqualToken, typeof(int), typeof(int)),
new BoundVariableExpression(upperBoundSybmle)
);
var increment = new BoundExpressionStatemnet(
new BoundAssignmentExpression(
node.Variable,
new BoundBinaryExpression(
variableExpression,
BoundBinaryOperator.Bind(SyntaxKind.PlusToken, typeof(int), typeof(int)),
new BoundLiteralExpression(1)
)
)
);
var whileBody = new BoundBlockStatemnet(ImmutableArray.Create <BoundStatement>(node.Body, increment));
var whileStatement = new BoundWhileStatement(condition, whileBody);
var result = new BoundBlockStatemnet(ImmutableArray.Create <BoundStatement>(
variableDeclaration, upperBoundDeclaration, whileStatement));
return(RewriteStatement(result));
}
protected override BoundStatement RewriteWhileStatement(BoundWhileStatement node)
{
// while <condition>
// <bode>
//
// ----->
//
// goto check
// continue:
// <body>
// check:
// gotoTrue <condition> continue
// end:
//
var continueLabel = GenerateLabel();
var checkLabel = GenerateLabel();
var endLabel = GenerateLabel();
var gotoCheck = new BoundGotoStatment(checkLabel);
var continueLabelStatement = new BoundLabelStatement(continueLabel);
var checkLabelStatement = new BoundLabelStatement(checkLabel);
var gotoTrue = new BoundConditionalGotoStatment(continueLabel, node.Condition);
var endLabelStatement = new BoundLabelStatement(endLabel);
var result = new BoundBlockStatemnet(ImmutableArray.Create <BoundStatement>(
gotoCheck,
continueLabelStatement,
node.Body,
checkLabelStatement,
gotoTrue,
endLabelStatement
));
return(RewriteStatement(result));
}
protected override BoundStatement RewriteForStatement(BoundForStatement node)
{
// for <var> = <lower> to <upper> by <incriment>
// <body>
//
// ---->
//
// {
// var <var> = <lower>
// while (<var> <= <upper>)
// {
// <body>
// continue:
// <var> = <var> + 1
// }
// }
var variableDeclaration = new BoundVeriableDeclaration(node.Variable, node.LowerBound);
var variableExpression = new BoundVariableExpression(node.Variable);
var upperBoundSybmle = new LocalVariableSymbol("upperBound", true, TypeSymbol.Int);
var upperBoundDeclaration = new BoundVeriableDeclaration(upperBoundSybmle, node.UpperBound);
var condition = new BoundBinaryExpression(
variableExpression,
BoundBinaryOperator.Bind(SyntaxKind.LessOrEqualToken, TypeSymbol.Int, TypeSymbol.Int),
new BoundVariableExpression(upperBoundSybmle)
);
var Ittertator = node.Itterator;
var Operator = SyntaxKind.PlusToken;
if (Ittertator == null)
{
Ittertator = new BoundLiteralExpression(1);
}
var continueLabelStatement = new BoundLabelStatement(node.ContinueLabel);
var increment = new BoundExpressionStatemnet(
new BoundAssignmentExpression(
node.Variable,
new BoundBinaryExpression(
variableExpression,
BoundBinaryOperator.Bind(Operator, TypeSymbol.Int, TypeSymbol.Int),
Ittertator
)
)
);
var whileBody = new BoundBlockStatemnet(ImmutableArray.Create <BoundStatement>(
node.Body,
continueLabelStatement,
increment)
);
var whileStatement = new BoundWhileStatement(condition, whileBody, node.BodyLabel, node.BreakLabel, GenerateLabel());
var result = new BoundBlockStatemnet(ImmutableArray.Create <BoundStatement>(
variableDeclaration,
upperBoundDeclaration,
whileStatement));
return(RewriteStatement(result));
}
public Evaluator(BoundBlockStatemnet root, Dictionary <VariableSymble, object> variables)
{
_root = root;
_variables = variables;
}
private object EvaluateStatement(BoundBlockStatemnet body)
{
var labeleToIndex = new Dictionary <BoundLabel, int>();
for (var i = 0; i < body.Statements.Length; i++)
{
if (body.Statements[i] is BoundLabelStatement l)
{
labeleToIndex.Add(l.Label, i + 1);
}
}
var index = 0;
while (index < body.Statements.Length)
{
var s = body.Statements[index];
switch (s.Kind)
{
case BoundNodeKind.VariableDeclaration:
EvaluateVariableDeclaration((BoundVeriableDeclaration)s);
index++;
break;
case BoundNodeKind.ExpressionStatement:
EvaluateExpressiontatement((BoundExpressionStatemnet)s);
index++;
break;
case BoundNodeKind.GotoStatment:
var gs = (BoundGotoStatment)s;
index = labeleToIndex[gs.Label];
break;
case BoundNodeKind.ConditionalGotoStatment:
var cgs = (BoundConditionalGotoStatment)s;
var condition = (bool)EvaluateExpression(cgs.Condition);
if (condition == cgs.JumpIfTrue)
{
index = labeleToIndex[cgs.Label];
}
else
{
index++;
}
break;
case BoundNodeKind.LabelStatement:
index++;
break;
case BoundNodeKind.ReturnStatement:
var rs = (BoundReturnStatement)s;
_lastValue = rs.Expression == null ? null : EvaluateExpression(rs.Expression);
return(_lastValue);
default:
throw new Exception($"Unexpected node {s.Kind}");
}
}
return(_lastValue);
}
