/// <summary>
/// Attempt to undo the if / do-while pattern that many compilers emit when
/// compiling while loops.
/// </summary>
/// <remarks>
/// </remarks>
private AbsynWhile TryRewriteGuardedDoWhile(AbsynIf ifStm)
{
if (ifStm.Then.Count == 1 && ifStm.Then[0] is AbsynDoWhile doWhile)
{
var ifCond = ifStm.Condition;
var doCond = doWhile.Condition;
if (cmp.Equals(ifCond, doCond))
{
// Pattern 1
return(new AbsynWhile(doCond, doWhile.Body));
}
var ifCondBin = ifStm.Condition as BinaryExpression;
var doCondBin = doWhile.Condition as BinaryExpression;
if (ifCondBin == null || doCondBin == null)
{
return(null);
}
if (ifCondBin.Operator == Operator.Ne &&
ifCondBin.Right is Constant ifConst && ifConst.IsZero &&
doCondBin.Operator == Operator.Gt)
{
if (cmp.Equals(ifCondBin.Left, doCondBin.Left))
{
// Flip the condition.
var condNew = new BinaryExpression(Operator.Lt, PrimitiveType.Bool, doCondBin.Right, doCondBin.Left);
return(new AbsynWhile(condNew, doWhile.Body));
}
}
}
return(null);
}
private void WriteIf(AbsynIf ifs)
{
writer.WriteKeyword("if");
writer.Write(" (");
WriteExpression(ifs.Condition);
writer.Write(")");
writer.Terminate();
WriteIndentedStatements(ifs.Then, false);
if (ifs.Else != null && ifs.Else.Count > 0)
{
writer.Indent();
writer.WriteKeyword("else");
if (IsSingleIfStatement(ifs.Else, out AbsynIf elseIf))
{
writer.Write(" ");
WriteIf(elseIf);
}
else
{
writer.Terminate();
WriteIndentedStatements(ifs.Else, false);
}
}
}
private bool IsSingleIfStatement(List <AbsynStatement> stms, out AbsynIf elseIf)
{
elseIf = null;
if (stms.Count != 1)
{
return(false);
}
elseIf = stms[0] as AbsynIf;
return(elseIf != null);
}
private AbsynIf EmitIfCondition(Expression exp, Conditional cond, AbsynStatementEmitter emitter)
{
if (cond is IfElse || cond is IfThenElse)
{
exp = exp.Invert();
}
AbsynIf ifStm = new AbsynIf();
ifStm.Condition = exp;
emitter.EmitStatement(ifStm);
return(ifStm);
}
private bool HasSingleIfThenElseStatement(List <AbsynStatement> stms)
{
if (stms.Count == 0)
{
return(false);
}
AbsynIf ifStm = stms[0] as AbsynIf;
if (ifStm == null)
{
return(false);
}
return(ifStm.Then.Count > 0 && ifStm.Else.Count > 0);
}
public AbsynStatement VisitIf(AbsynIf ifStm)
{
for (int i = 0; i < ifStm.Then.Count; ++i)
{
ifStm.Then[i] = ifStm.Then[i].Accept(this);
}
for (int i = 0; i < ifStm.Else.Count; ++i)
{
ifStm.Else[i] = ifStm.Else[i].Accept(this);
}
if (ifStm.Then.Count == 0 && ifStm.Else.Count > 0)
{
ifStm.Condition = ifStm.Condition.Invert();
ifStm.Then.AddRange(ifStm.Else);
ifStm.Else.Clear();
}
return(ifStm);
}
public void VisitIf(AbsynIf ifs)
{
writer.Indent();
WriteIf(ifs);
}
public void VisitIf(AbsynIf ifStm)
{
stms.Add(ifStm);
}
public bool VisitIf(AbsynIf ifStm)
{
RemoveRedundantReturn(ifStm.Then);
RemoveRedundantReturn(ifStm.Else);
return(false);
}
public void VisitIf(AbsynIf ifs)
{
InnerFormatter.Indent();
WriteIf(ifs);
}
//$TODO: .NET 5 output parameter is non-null if the method returns true.
private bool IsSingleIfStatement(List <AbsynStatement> stms, out AbsynIf elseIf)
{
elseIf = default !;
