/*
* 处理if语句
*/
public override object VisitIfStatement([NotNull] CMMParser.IfStatementContext context)
{
// 查看expression的结果
Visit(context.expression());
IntermediateCode code0 = new IntermediateCode(0, InstructionType.push, context.expression().Start.Line);
codes.Add(code0);
// 比较expression的结果和0的关系,等于0的话就跳转走,code1的目的地址待回填
IntermediateCode code1 = new IntermediateCode(InstructionType.je, context.expression().Stop.Line);
codes.Add(code1);
if (context.codeBlock() != null)
{
Visit(context.codeBlock());
}
IntermediateCode code3 = new IntermediateCode(InstructionType.j, context.codeBlock().Stop.Line);
codes.Add(code3);
// 条件不符合的情况应该执行的代码行号为addr0,回填一下
int addr0 = codes.Count;
code1.setOperant(addr0);
List <IntermediateCode> needToAddFinishAddrCodes = new List <IntermediateCode>();
needToAddFinishAddrCodes.Add(code3);
// 每个else语句都执行一下
if (context.elseClause() != null)
{
foreach (CMMParser.ElseClauseContext ctx in context.elseClause())
{
if (ctx.ifStatement() == null)
{
Visit(ctx.codeBlock());
IntermediateCode code = new IntermediateCode(InstructionType.j, ctx.codeBlock().Stop.Line);
needToAddFinishAddrCodes.Add(code);
codes.Add(code);
}
else
{
Visit(ctx.ifStatement());
}
}
}
foreach (IntermediateCode c in needToAddFinishAddrCodes)
{
c.operant = codes.Count;
}
return(null);
}
/// <summary>
/// Visit a parse tree produced by <see cref="CMMParser.ifStatement"/>.
/// <para>
/// The default implementation returns the result of calling <see cref="AbstractParseTreeVisitor{Result}.VisitChildren(IRuleNode)"/>
/// on <paramref name="context"/>.
/// </para>
/// </summary>
/// <param name="context">The parse tree.</param>
/// <return>The visitor result.</return>
public virtual Result VisitIfStatement([NotNull] CMMParser.IfStatementContext context)
{
return(VisitChildren(context));
}
/// <summary>
/// Exit a parse tree produced by <see cref="CMMParser.ifStatement"/>.
/// <para>The default implementation does nothing.</para>
/// </summary>
/// <param name="context">The parse tree.</param>
public virtual void ExitIfStatement([NotNull] CMMParser.IfStatementContext context)
{
}
