Hi,
I'm a litle bit puzzled by the TargetLowering::LowerOperation function, and what different callers of this function assumes about the returned value.
In several places it seems like it is assumed that LowerOperation can return three kinds of values:
* Something completely new.
* SDValue()
* The same SDValue as LowerOperation was called on.
However in some places, e.g. in TargetLowering::LowerOperationWrapper, it seems like it is assumed only the first two of the above cases can happen because there we do:
SDValue Res = LowerOperation(SDValue(N, 0), DAG);
if (Res.getNode())
Results.push_back(Res);
So, when LowerOperationWrapper is called from DAGTypeLegalizer::CustomLowerNode, and my target's LowerOperation returns the same SDValue as it was called on since we don't want to do anything special with this particular SDValue, then we get an assert "Potential legalization loop!" when DAGTypeLegalizer::CustomLowerNode tries to replace the SDValue with itself.
So in some cases it's ok for LowerOperation to return the same SDValue it was called on, and sometimes it's not?
Can anyone shed some light on this?
Thanks,
Mikael