llvm dev - Jun 2012 - [LLVMdev] legalization of truncating stores in LegalizeDAG.cpp

In LegalizeDAG.cpp, truncating stores are custom-lowered in line 1314-1317:


1314         case TargetLowering::Custom:
1315           ReplaceNode(SDValue(Node, 0),
1316                       TLI.LowerOperation(SDValue(Node, 0), DAG));
1317           break;


Is there a reason it doesn't check whether the SDValue returned from
TargetLowering::LowerOperation is null before it replaces the original node with
the returned node? The return value is checked everywhere else
TLI.LowerOperation is called (line 937, for example).

937         Tmp1 = TLI.LowerOperation(Tmp3, DAG);
938         if (Tmp1.getNode()) {
939           Tmp3 = Tmp1;
940           Tmp4 = Tmp1.getValue(1);
941         }
942         break;

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Hi Akira,

On 01/06/12 02:27, Hatanaka, Akira wrote:
> In LegalizeDAG.cpp, truncating stores are custom-lowered in line 1314-1317:
>
> 1314         case TargetLowering::Custom:
> 1315           ReplaceNode(SDValue(Node, 0),
> 1316                       TLI.LowerOperation(SDValue(Node, 0), DAG));
> 1317           break;
>
> Is there a reason it doesn't check whether the SDValue returned from
> TargetLowering::LowerOperation is null before it replaces the original node
with
> the returned node? The return value is checked everywhere else
> TLI.LowerOperation is called (line 937, for example).
>
>
> 937         Tmp1 = TLI.LowerOperation(Tmp3, DAG);
> 938         if (Tmp1.getNode()) {
> 939           Tmp3 = Tmp1;
> 940           Tmp4 = Tmp1.getValue(1);
> 941         }
> 942         break;
probably it's just an oversight, because no backend needed it.  LegalizeDAG
is
unfortunately full of code like this.

Ciao, Duncan.

Hi Duncan,

It seems that none of the current targets custom-lower truncating stores.

When I added code to do custom-lowering in the Mips backend, the original
node gets removed if LowerOperation returns SDValue(). This resulted in an
assertion raised when DAGCombiner::visitTokenFactor was executed.

I will add code in LegalizeDAG.cpp to check the returned value later.

On Fri, Jun 1, 2012 at 12:59 AM, Duncan Sands <baldrick at free.fr> wrote:
> Hi Akira,
>
> On 01/06/12 02:27, Hatanaka, Akira wrote:
> > In LegalizeDAG.cpp, truncating stores are custom-lowered in line
> 1314-1317:
> >
> > 1314         case TargetLowering::Custom:
> > 1315           ReplaceNode(SDValue(Node, 0),
> > 1316                       TLI.LowerOperation(SDValue(Node, 0), DAG));
> > 1317           break;
> >
> > Is there a reason it doesn't check whether the SDValue returned
from
> > TargetLowering::LowerOperation is null before it replaces the original
> node with
> > the returned node? The return value is checked everywhere else
> > TLI.LowerOperation is called (line 937, for example).
> >
> >
> > 937         Tmp1 = TLI.LowerOperation(Tmp3, DAG);
> > 938         if (Tmp1.getNode()) {
> > 939           Tmp3 = Tmp1;
> > 940           Tmp4 = Tmp1.getValue(1);
> > 941         }
> > 942         break;
>
> probably it's just an oversight, because no backend needed it.
>  LegalizeDAG is
> unfortunately full of code like this.
>
> Ciao, Duncan.
> _______________________________________________
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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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