[PATCH] D93860: [SLP] delete unused pairwise reduction option

[Sanjay Patel via Phabricator via llvm-commits]

spatel created this revision.
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SLP tries to model 2 forms of vector reductions: pairwise and splitting. From the cost model code comments, those are defined using an example as:

  /// Pairwise:
  ///  (v0, v1, v2, v3)
  ///  ((v0+v1), (v2+v3), undef, undef)
  /// Split:
  ///  (v0, v1, v2, v3)
  ///  ((v0+v2), (v1+v3), undef, undef)

I don't know the full history of this functionality, but it was partly added back in D29402 <https://reviews.llvm.org/D29402>. There are apparently no users at this point (no regression tests change). X86 might have managed to work-around the need for this through cost model and codegen improvements.

Removing this code makes it easier to continue the work that was started in D87416 <https://reviews.llvm.org/D87416> / D88193 <https://reviews.llvm.org/D88193>. The alternative -- if there is some target that is silently using this option -- is to move this logic into LoopUtils. We have related/duplicate functionality there via llvm::createTargetReduction().


https://reviews.llvm.org/D93860

Files:
  llvm/lib/Transforms/Vectorize/SLPVectorizer.cpp

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