public override void Emit(CodeGen cg)
{
Slot list = cg.GetLocalTmp(typeof(List));
cg.EmitCall(typeof(Ops), "MakeList", Type.EmptyTypes);
list.EmitSet(cg);
// first loop: how many For; initialize labels/slots
int iFors = 0;
foreach (ListCompIter iter in iters)
{
if (iter is ListCompFor)
{
iFors++;
}
}
Label[] continueTargets = new Label[iFors];
Slot[] enumerators = new Slot[iFors];
int jIters = iters.Length;
Label[] exitTargets = new Label[jIters];
for (int i = 0; i < iFors; i++)
{
continueTargets[i] = cg.DefineLabel();
enumerators[i] = cg.GetLocalTmp(typeof(IEnumerator));
}
for (int i = 0; i < jIters; i++)
{
exitTargets[i] = cg.DefineLabel();
}
// second loop: before emiting item
iFors = jIters = 0;
foreach (ListCompIter iter in iters)
{
if (iter is ListCompFor)
{
ListCompFor cfor = iter as ListCompFor;
cfor.list.Emit(cg);
cg.EmitCall(typeof(Ops), "GetEnumerator");
enumerators[iFors].EmitSet(cg);
cg.MarkLabel(continueTargets[iFors]);
enumerators[iFors].EmitGet(cg);
cg.EmitCall(typeof(IEnumerator), "MoveNext", Type.EmptyTypes);
cg.Emit(OpCodes.Brfalse, exitTargets[jIters]);
enumerators[iFors].EmitGet(cg);
cg.EmitCall(typeof(IEnumerator).GetProperty("Current").GetGetMethod());
cfor.lhs.EmitSet(cg);
iFors++;
}
else if (iter is ListCompIf)
{
ListCompIf cif = iter as ListCompIf;
cg.EmitTestTrue(cif.test);
cg.Emit(OpCodes.Brfalse, exitTargets[jIters]);
}
jIters++;
}
// append the item
list.EmitGet(cg);
this.item.Emit(cg);
cg.EmitCall(typeof(List), "Append");
// third loop: in reverse order
iFors = continueTargets.Length - 1;
jIters = iters.Length - 1;
while (jIters >= 0)
{
ListCompIter iter = iters[jIters];
if (iter is ListCompFor)
{
cg.Emit(OpCodes.Br, continueTargets[iFors]);
cg.FreeLocalTmp(enumerators[iFors]);
iFors--;
}
cg.MarkLabel(exitTargets[jIters]);
jIters--;
}
list.EmitGet(cg);
cg.FreeLocalTmp(list);
}
public virtual void PostWalk(ListCompFor node)
{
}
// ListCompFor
public override bool Walk(ListCompFor node)
{
node.lhs.Walk(define);
return(true);
}
// ListCompFor
public virtual bool Walk(ListCompFor node)
{
return(true);
}