/*
* 处理leftValue,需要将变量对应在局部变量区的位置压入栈中
* add的结果是保存在栈上
*/
public override object VisitLeftValue([NotNull] CMMParser.LeftValueContext context)
{
if (context.ChildCount == 1)
{
//只定义成了identifier,将identifier对应的索引地址压栈
if (!curLocalVariablesTable.ContainsKey(context.GetChild(0).GetText()))
{
throw new VariableNotFountException(context.GetChild(0).GetText(), context);
}
curLocalVariablesTable.TryGetValue(context.GetChild(0).GetText(), out int addr);
IntermediateCode code = new IntermediateCode(addr, InstructionType.push, context.Start.Line);
codes.Add(code);
}
else
{
// 定义成数组的那种形式a[i]
if (!curLocalVariablesTable.ContainsKey(context.GetChild(0).GetText()))
{
throw new VariableNotFountException(context.GetChild(0).GetText(), context);
}
curLocalVariablesTable.TryGetValue(context.GetChild(0).GetText(), out int addr);
// 把基地址也push到操作栈上
IntermediateCode code0 = new IntermediateCode(addr, InstructionType.push, context.Start.Line);
Visit(context.expression());
// 使用add指令，获得addr+expression，add指令使得这个值已经压入栈中
IntermediateCode code1 = new IntermediateCode(InstructionType.add, context.expression().Start.Line);
codes.Add(code0);
codes.Add(code1);
}
return(null);
}
/// <summary>
/// Visit a parse tree produced by <see cref="CMMParser.leftValue"/>.
/// <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 VisitLeftValue([NotNull] CMMParser.LeftValueContext context)
{
return(VisitChildren(context));
}
/// <summary>
/// Exit a parse tree produced by <see cref="CMMParser.leftValue"/>.
/// <para>The default implementation does nothing.</para>
/// </summary>
/// <param name="context">The parse tree.</param>
public virtual void ExitLeftValue([NotNull] CMMParser.LeftValueContext context)
{
}
