llvm dev - May 2017 - How does one match undef in tablegen?

I would like to specialise build_vector for the case when one of the
operands is undefined. How do I describe this?

This is looking for an analog of specialisations like:
def : Pat <v2i32 (build_vector i32:$x, (i32 0)),...>;
but for an undefined, rather than zero, value.

I can work around my ignorance in performDAGCombine but would prefer to add
to the existing pattern matching.

Thanks,

Jon
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I believe

def : Pat <v2i32 (build_vector i32:$x, (i32 undef)),...>;

Should work.

~Craig

On Sun, May 7, 2017 at 9:44 AM, Jon Chesterfield via llvm-dev <
llvm-dev at lists.llvm.org> wrote:
> I would like to specialise build_vector for the case when one of the
> operands is undefined. How do I describe this?
>
> This is looking for an analog of specialisations like:
> def : Pat <v2i32 (build_vector i32:$x, (i32 0)),...>;
> but for an undefined, rather than zero, value.
>
> I can work around my ignorance in performDAGCombine but would prefer to
> add to the existing pattern matching.
>
> Thanks,
>
> Jon
>
> _______________________________________________
> LLVM Developers mailing list
> llvm-dev at lists.llvm.org
> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>
>
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It does indeed. Somewhat embarrassed that I didn't try that before asking.

Thanks!

On Sun, May 7, 2017 at 5:59 PM, Craig Topper <craig.topper at gmail.com>
wrote:
> I believe
>
> def : Pat <v2i32 (build_vector i32:$x, (i32 undef)),...>;
>
> Should work.
>
> ~Craig
>
> On Sun, May 7, 2017 at 9:44 AM, Jon Chesterfield via llvm-dev <
> llvm-dev at lists.llvm.org> wrote:
>
>> I would like to specialise build_vector for the case when one of the
>> operands is undefined. How do I describe this?
>>
>> This is looking for an analog of specialisations like:
>> def : Pat <v2i32 (build_vector i32:$x, (i32 0)),...>;
>> but for an undefined, rather than zero, value.
>>
>> I can work around my ignorance in performDAGCombine but would prefer to
>> add to the existing pattern matching.
>>
>> Thanks,
>>
>> Jon
>>
>> _______________________________________________
>> LLVM Developers mailing list
>> llvm-dev at lists.llvm.org
>> http://lists.llvm.org/cgi-bin/mailman/listinfo/llvm-dev
>>
>>
>
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