llvm dev - Jun 2012 - [LLVMdev] [NVPTX] Backend failure in LegalizeDAG due to unimplemented expand in target lowering

On Fri, Jun 29, 2012 at 2:11 PM, Dmitry N. Mikushin <maemarcus at
gmail.com> wrote:
> Hi again,
>
> Kind people on #llvm helped me to utilize bugpoint to reduce the
> previously submitted test case. For record, it code be done with the
> following command:
>
> $ bugpoint -llc-safe test.ll
>
> The resulting IR is attached, and it is crashing in the same way. Is
> it a valid code?
Looks like a bug in the NVPTXISelLowering.cpp: it has
"setOperationAction(ISD::STORE, MVT::i1, Expand);", but the legalizer
doesn't know how to handle that.

-Eli

Thanks, for insight, Eli,

So instead of setOperationAction(ISD::STORE, MVT::i1, Expand); one
should probably do setOperationAction(ISD::STORE, MVT::i1, Custom);
and implement it in NVPTXTargetLowering::LowerOperation.

But this issue makes a good point about the code efficiency: I suspect
such expansion will be very ugly in terms of performance. Probably we
can do much better if bool would use i32 instead of i1. I don't know
how to do that, though. Is it possible?

Anyway, if this is a defect, then it's a blocker for us, and we'd much
appreciate a fix.

- D.

2012/6/29 Eli Friedman <eli.friedman at
gmail.com>:
> On Fri, Jun 29, 2012 at 2:11 PM, Dmitry N. Mikushin <maemarcus at
gmail.com> wrote:
>> Hi again,
>>
>> Kind people on #llvm helped me to utilize bugpoint to reduce the
>> previously submitted test case. For record, it code be done with the
>> following command:
>>
>> $ bugpoint -llc-safe test.ll
>>
>> The resulting IR is attached, and it is crashing in the same way. Is
>> it a valid code?
>
> Looks like a bug in the NVPTXISelLowering.cpp: it has
> "setOperationAction(ISD::STORE, MVT::i1, Expand);", but the
legalizer
> doesn't know how to handle that.
>
> -Eli

Hi Dmitry,
> So instead of setOperationAction(ISD::STORE, MVT::i1, Expand); one
> should probably do setOperationAction(ISD::STORE, MVT::i1, Custom);
> and implement it in NVPTXTargetLowering::LowerOperation.
>
> But this issue makes a good point about the code efficiency: I suspect
> such expansion will be very ugly in terms of performance. Probably we
> can do much better if bool would use i32 instead of i1. I don't know
> how to do that, though. Is it possible?
did you declare i1 to be an illegal type?  If so, you shouldn't get any
stores of i1 at this stage (you may get trunc stores to i1, but that is
different).

Ciao, Duncan.
>
> Anyway, if this is a defect, then it's a blocker for us, and we'd
much
> appreciate a fix.
>
> - D.
>
> 2012/6/29 Eli Friedman <eli.friedman at gmail.com>:
>> On Fri, Jun 29, 2012 at 2:11 PM, Dmitry N. Mikushin <maemarcus at
gmail.com> wrote:
>>> Hi again,
>>>
>>> Kind people on #llvm helped me to utilize bugpoint to reduce the
>>> previously submitted test case. For record, it code be done with
the
>>> following command:
>>>
>>> $ bugpoint -llc-safe test.ll
>>>
>>> The resulting IR is attached, and it is crashing in the same way.
Is
>>> it a valid code?
>>
>> Looks like a bug in the NVPTXISelLowering.cpp: it has
>> "setOperationAction(ISD::STORE, MVT::i1, Expand);", but the
legalizer
>> doesn't know how to handle that.
>>
>> -Eli
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