[llvm-dev] How does one match undef in tablegen?

[Craig Topper via llvm-dev]

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
>
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