[LLVMdev] LowerCALL (TargetLowering)

[Nikhil Patil]

Hi Evan,

On Wed, Nov 15, 2006 at 10:17 -0800, Evan Cheng wrote:
> Hi Nickhil,
> 
> The Legalizer expects lower'd call is the node that produce the same  
> number of values as the non-lowered node. That's what the assertion  
> is checking.
> 
> Take a look at the LowerCall routine for any other targets. You will  
> see that in the non-void function case, it returns a MERGE_VALUES,  
> i.e. all the results merged along with the chain.

Sorry, I don't understand. I am only trying to look at functions that
return void here (hence the RetVT == MVT::Other assertion near the end
of my function). So, I think there should be only a single result -
the SDOperand returned by the DAG.getNode(..), and I shouldn't need any
MERGE_VALUES node.

Am I missing something?

Thanks!
Nikhil

> 
> Cheers,
> 
> Evan
> On Nov 15, 2006, at 3:30 AM, Nikhil Patil wrote:
> 
> > Hi,
> >
> > I am trying to write a LowerCALL() function for my (custom) target  
> > ISA.
> > All I need to do is map a CALL instruction directly onto an SDNode  
> > that
> > takes an equal number of arguments (very much alike intrinsics, except
> > that these are custom to my target.) I do not need to implement any  
> > call
> > sequences, stack frames etc.
> >
> > I get the following assertion failure:
> >
> > llc: LegalizeDAG.cpp:834: llvm::SDOperand  
> > <unnamed>::SelectionDAGLegalize::LegalizeOp(llvm::SDOperand):  
> > Assertion `Tmp3.Val->getNumValues() == Result.Val->getNumValues()  
> > && "Lowering call/formal_arguments produced unexpected # results!"'  
> > failed.
> >
> > This is what my LowerCALL looks like:
> >
> > SDOperand MCTargetLowering::LowerCALL(SDOperand Op, SelectionDAG  
> > &DAG) {
> >     SDOperand Chain     = Op.getOperand(0);
> >     bool isVarArg       = cast<ConstantSDNode>(Op.getOperand(2))- 
> > >getValue() != 0;
> >     assert(!isVarArg);
> >     bool isTailCall     = cast<ConstantSDNode>(Op.getOperand(3))- 
> > >getValue() != 0;
> >     SDOperand Callee    = Op.getOperand(4);
> >     MVT::ValueType RetVT= Op.Val->getValueType(0);
> >     unsigned NumOps     = (Op.getNumOperands() - 5) / 2;
> >
> >     std::string Name;
> >     if (GlobalAddressSDNode *G = dyn_cast<GlobalAddressSDNode> 
> > (Callee))
> > 	Name = G->getGlobal()->getName();
> >     else if (ExternalSymbolSDNode *S =  
> > dyn_cast<ExternalSymbolSDNode>(Callee))
> > 	Name = S->getSymbol();
> >
> >     unsigned opcode = funcname_to_opc[Name];
> >     assert(opcode != 0 && "Unknown function call.");
> >
> >     std::vector<MVT::ValueType> Tys;
> >     std::vector<SDOperand> Ops;
> >
> >     for (unsigned i = 0; i != NumOps; ++i) {
> > 	SDOperand Arg = Op.getOperand(5+2*i);
> > 	Tys.push_back(Arg.getValueType());
> > 	Ops.push_back(Arg);
> >     }
> >     Tys.push_back(MVT::Other);
> >     Ops.push_back(Chain);
> >
> >     Chain = DAG.getNode(opcode, Tys, &Ops[0], Ops.size());
> >
> >     assert(RetVT == MVT::Other);
> >     return Chain;
> > }
> >
> > Everything works fine for functions with no arguments, but otherwise I
> > get this assert. Can anyone point out my mistake?
> >
> > Any help will be greatly appreciated,
> >
> > Thanks,
> > Nikhil
> > _______________________________________________
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> > LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> > http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev
> 
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