llvm dev - Dec 2009 - [LLVMdev] SplitVecRes with SIGN_EXTEND_INREG unsupported

On Thu, Dec 10, 2009 at 12:46 PM, Villmow, Micah <Micah.Villmow at
amd.com> wrote:
> Eli,
>  I have a simple SplitVecRes function that implements what you mentioned,
splitting the LHS just as in BinaryOp, but passing through the RHS. The problem
is that the second operand is MVT::Other, but when casted to an VTSDNode reveals
that it is a vector length of the same size as the LHS SDValue. This causes a
split on the LHS side to work correctly, but then it fails instruction selection
because of Other. I have not been able to figure out how to split the MVT::Other
node yet, any idea how to do this?
You should be able to split the contained type with GetSplitDestVTs,
then recreate the node using SelectionDAG::getValueType(), I think.

That said, it could possibly be considered a bug in DAGCombine that
the second operand is a vector type; someone want to comment on that?

-Eli

Eli,
 I don't see how this helps with the splitting of the Other node as it
isn't the Dest that is the problem, but the second source value. Any place
in the code that I can look at on how to split a VTSDNode?

Thanks,
Micah 
> -----Original Message-----
> From: Eli Friedman [mailto:eli.friedman at gmail.com]
> Sent: Thursday, December 10, 2009 1:25 PM
> To: Villmow, Micah
> Cc: llvmdev at cs.uiuc.edu
> Subject: Re: [LLVMdev] SplitVecRes with SIGN_EXTEND_INREG unsupported
> 
> On Thu, Dec 10, 2009 at 12:46 PM, Villmow, Micah
> <Micah.Villmow at amd.com> wrote:
> > Eli,
> >  I have a simple SplitVecRes function that implements what you
> mentioned, splitting the LHS just as in BinaryOp, but passing through
> the RHS. The problem is that the second operand is MVT::Other, but when
> casted to an VTSDNode reveals that it is a vector length of the same
> size as the LHS SDValue. This causes a split on the LHS side to work
> correctly, but then it fails instruction selection because of Other. I
> have not been able to figure out how to split the MVT::Other node yet,
> any idea how to do this?
> 
> 
> You should be able to split the contained type with GetSplitDestVTs,
> then recreate the node using SelectionDAG::getValueType(), I think.
> 
> That said, it could possibly be considered a bug in DAGCombine that
> the second operand is a vector type; someone want to comment on that?
> 
> -Eli

Eli, 
 I think I was able to get it working. Thanks for the help, does this look
correct to you?

void DAGTypeLegalizer::SplitVecRes_SIGN_EXTEND_INREG(SDNode *N, SDValue &Lo,
                                         SDValue &Hi) {
  SDValue LHSLo, LHSHi;
  GetSplitVector(N->getOperand(0), LHSLo, LHSHi);
  DebugLoc dl = N->getDebugLoc();
  EVT LoVT, HiVT;
  GetSplitDestVTs(N->getValueType(1), LoVT, HiVT);

  Lo = DAG.getNode(N->getOpcode(), dl, LHSLo.getValueType(), LHSLo,
DAG.getValueType(LoVT));
  Hi = DAG.getNode(N->getOpcode(), dl, LHSHi.getValueType(), LHSHi,
DAG.getValueType(HiVT));
}


Thanks,
Micah
> -----Original Message-----
> From: llvmdev-bounces at cs.uiuc.edu [mailto:llvmdev-bounces at
cs.uiuc.edu]
> On Behalf Of Villmow, Micah
> Sent: Thursday, December 10, 2009 3:10 PM
> To: llvmdev at cs.uiuc.edu
> Subject: Re: [LLVMdev] SplitVecRes with SIGN_EXTEND_INREG unsupported
> 
> Eli,
>  I don't see how this helps with the splitting of the Other node as it
> isn't the Dest that is the problem, but the second source value. Any
> place in the code that I can look at on how to split a VTSDNode?
> 
> Thanks,
> Micah
> 
> > -----Original Message-----
> > From: Eli Friedman [mailto:eli.friedman at gmail.com]
> > Sent: Thursday, December 10, 2009 1:25 PM
> > To: Villmow, Micah
> > Cc: llvmdev at cs.uiuc.edu
> > Subject: Re: [LLVMdev] SplitVecRes with SIGN_EXTEND_INREG unsupported
> >
> > On Thu, Dec 10, 2009 at 12:46 PM, Villmow, Micah
> > <Micah.Villmow at amd.com> wrote:
> > > Eli,
> > >  I have a simple SplitVecRes function that implements what you
> > mentioned, splitting the LHS just as in BinaryOp, but passing through
> > the RHS. The problem is that the second operand is MVT::Other, but
> when
> > casted to an VTSDNode reveals that it is a vector length of the same
> > size as the LHS SDValue. This causes a split on the LHS side to work
> > correctly, but then it fails instruction selection because of Other.
> I
> > have not been able to figure out how to split the MVT::Other node
> yet,
> > any idea how to do this?
> >
> >
> > You should be able to split the contained type with GetSplitDestVTs,
> > then recreate the node using SelectionDAG::getValueType(), I think.
> >
> > That said, it could possibly be considered a bug in DAGCombine that
> > the second operand is a vector type; someone want to comment on that?
> >
> > -Eli
> 
> 
> 
> _______________________________________________
> LLVM Developers mailing list
> LLVMdev at cs.uiuc.edu         http://llvm.cs.uiuc.edu
> http://lists.cs.uiuc.edu/mailman/listinfo/llvmdev