[LLVMdev] Inserting nodes into SelectionDAG (X86)

[Dan Gohman]

On Jun 29, 2009, at 9:00 AM, Artjom Kochtchi wrote:


>
> Sorry to ask again, but I still can't get it right.
>
> The following code compiles and runs, but produces no instructions:
>  Ops.push_back(DAG.getRegister(X86::EAX, MVT::i32));
>  Ops.push_back(DAG.getConstant(1, MVT::i32));
>  DAG.getNode(ISD::ADD, DAG.getVTList(MVT::i32), &Ops[0], Ops.size());

To read the value of a physical register, a CopyFromReg node is
needed.

>
> I reckon that has something to do with the fact that I am not using  
> the
> Chain object. But as soon as I try to chain that node, llc tells me  
> that I
> have the wrong number of operands:
>  Ops.push_back(Chain);
>  Ops.push_back(DAG.getRegister(X86::EAX, MVT::i32));
>  Ops.push_back(DAG.getConstant(1, MVT::i32));
>  Chain = DAG.getNode(ISD::ADD, DAG.getVTList(MVT::Other, MVT::i32),
> &Ops[0], Ops.size());
>
> Isn't that the way how it is supposed to work?

ADD does not use a chain, so there's no chain operand, or
MVT::Other result for it in an ADD node.

Dan