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// Licensed to the .NET Foundation under one or more agreements.
// The .NET Foundation licenses this file to you under the MIT license.
// See the LICENSE file in the project root for more information.
using System.Diagnostics;
using Microsoft.CodeAnalysis.CSharp.Symbols;
using Microsoft.CodeAnalysis.CSharp.Syntax;
using Microsoft.CodeAnalysis.PooledObjects;
namespace Microsoft.CodeAnalysis.CSharp
{
internal sealed partial class LocalRewriter
{
public override BoundNode VisitIfStatement(BoundIfStatement node)
{
Debug.Assert(node != null);
var stack = ArrayBuilder<(BoundIfStatement, GeneratedLabelSymbol, int)>.GetInstance();
var builder = ArrayBuilder<BoundStatement>.GetInstance();
while (true)
{
var rewrittenCondition = VisitExpression(node.Condition);
var rewrittenConsequence = VisitStatement(node.Consequence);
Debug.Assert(rewrittenConsequence is { });
// EnC: We need to insert a hidden sequence point to handle function remapping in case
// the containing method is edited while methods invoked in the condition are being executed.
if (this.Instrument && !node.WasCompilerGenerated)
{
rewrittenCondition = Instrumenter.InstrumentIfStatementCondition(node, rewrittenCondition, _factory);
}
var elseIfStatement = node.AlternativeOpt as BoundIfStatement;
BoundStatement? rewrittenAlternative = null;
if (elseIfStatement is null)
{
rewrittenAlternative = VisitStatement(node.AlternativeOpt);
}
var afterif = new GeneratedLabelSymbol("afterif");
stack.Push((node, afterif, builder.Count));
if (elseIfStatement is null && rewrittenAlternative is null)
{
// if (condition)
// consequence;
//
// becomes
//
// GotoIfFalse condition afterif;
// consequence;
// afterif:
builder.Add(new BoundConditionalGoto(rewrittenCondition.Syntax, rewrittenCondition, false, afterif));
builder.Add(rewrittenConsequence);
break;
}
else
{
// if (condition)
// consequence;
// else
// alternative;
//
// becomes
//
// GotoIfFalse condition alt;
// consequence
// goto afterif;
// alt:
// alternative;
// afterif:
var alt = new GeneratedLabelSymbol("alternative");
builder.Add(new BoundConditionalGoto(rewrittenCondition.Syntax, rewrittenCondition, false, alt));
builder.Add(rewrittenConsequence);
builder.Add(BoundSequencePoint.CreateHidden());
var syntax = (IfStatementSyntax)node.Syntax;
builder.Add(new BoundGotoStatement(syntax, afterif));
builder.Add(new BoundLabelStatement(syntax, alt));
if (rewrittenAlternative is not null)
{
builder.Add(rewrittenAlternative);
break;
}
Debug.Assert(elseIfStatement is not null);
node = elseIfStatement;
}
}
do
{
(node, var afterif, var conditionalGotoIndex) = stack.Pop();
Debug.Assert(builder[conditionalGotoIndex] is BoundConditionalGoto);
var syntax = (IfStatementSyntax)node.Syntax;
builder.Add(BoundSequencePoint.CreateHidden());
builder.Add(new BoundLabelStatement(syntax, afterif));
// add sequence point before the whole statement
if (this.Instrument && !node.WasCompilerGenerated)
{
builder[conditionalGotoIndex] = Instrumenter.InstrumentIfStatementConditionalGoto(node, builder[conditionalGotoIndex]);
}
}
while (stack.Any());
stack.Free();
return new BoundStatementList(node.Syntax, builder.ToImmutableAndFree(), node.HasErrors);
}
private static BoundStatement RewriteIfStatement(
SyntaxNode syntax,
BoundExpression rewrittenCondition,
BoundStatement rewrittenConsequence,
bool hasErrors)
{
var afterif = new GeneratedLabelSymbol("afterif");
var builder = ArrayBuilder<BoundStatement>.GetInstance();
// if (condition)
// consequence;
//
// becomes
//
// GotoIfFalse condition afterif;
// consequence;
// afterif:
builder.Add(new BoundConditionalGoto(rewrittenCondition.Syntax, rewrittenCondition, false, afterif));
builder.Add(rewrittenConsequence);
builder.Add(BoundSequencePoint.CreateHidden());
builder.Add(new BoundLabelStatement(syntax, afterif));
var statements = builder.ToImmutableAndFree();
return new BoundStatementList(syntax, statements, hasErrors);
}
}
}
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