[llvm-dev] RFC: Exposing TargetTransformInfo factories from TargetMachine

[Hal Finkel via llvm-dev]

On 12/15/2017 01:22 AM, Sanjoy Das via llvm-dev wrote:
> Hi all,
>
> I'd like to be able to use TargetTransformInfo to make architecture
> specific code generation decisions from the XLA LLVM IR emitter[0].
> However, we don't have a great way to do this today --
> TargetTransformInfo is wrapped in a TargetIRAnalysis and getting the
> TargetTransformInfo out of it requires something like:
>
>    FunctionAnalysisManager DummyFAM;
>    TTI = TIRA.run(F, DummyFAM);
>    return *TTI;
>
> which isn't ideal.
>
> Given that all in-tree backends have a factory function to directly
> construct a TargetTransformInfo implementation anyway, what do you
> think about exposing said factory function from the TargetMachine
> subclasses directly?  Something conceptually like this
> https://reviews.llvm.org/D41268 but for all backends and will less
> std::function?

Are there reasons why we might not want to do this? Other options we 
should consider?

  -Hal

>
> [0]:  XLA is a machine learning focussed linear algebra compiler
> https://www.tensorflow.org/performance/xla/ that uses LLVM for its CPU
> and GPU backends.
>
> -- Sanjoy
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-- 
Hal Finkel
Lead, Compiler Technology and Programming Languages
Leadership Computing Facility
Argonne National Laboratory